SCOTT! SH

EQU I PMENT

SCHOOLS SCIENCE

RESEARCH CENTRE

April 1983Bulletin No135

S.S.S.E.R.C. Bulletin No 135 April 1983

ADDRESS LIST

SSSERC, 103 Broughton Street, Edinburgh, EH1 3RZ. Tel. 031 556 2184.

Armon Electronics Ltd., Cottrel House, 53-63 Wembley Hill Road, Wembley, Middlesex, HA9 8BHTel. 01 902 4321.

Artec(I for E)Ltd., Salewheel House, Ribchester, Preston, Lancs. PR33XL. Tel. (0254) 84215.

Bettix Ltd., Dunbar Road, New MaIden, Surrey KT3 3RG. Tel. 01 9428701.

J. Bull (Electrical) Ltd., 34-36 America Lane, Haywards Heath, Sussex RH1 6 3QU. Tel. (0444) 454563).

Cambion Electronics Products Ltd., Cambion Works, Castleton, S30 2WR. Tel. (0433)2081.

Camlab Ltd., Nuffield Road, Cambridge CB4 1TH. TeL. (0223) 62222.

Coast-Air Ltd., Long Spring, Porter’s Wood, Valley Road Industrial Estate, St. Albans, Herts. AL3 6NQ.Tel. (0727) 61669.

Griffin and George Ltd., Ledson Road, Wythenshawe, Manchester M23 9NP. Tel. 041 248 5680.

Harburn Hobbies, 67 Elm Row, Edinburgh EH74AQ. Tel. 031 5563233.

Philip Harris Ltd., 34-36 Strathmore House, Town Centre, East Kilbride. Tel. (03552) 34983/4.

Irwin-Desman Ltd., 294 Purley Way, Croydon, CR9 4QL. Tel. 01 6866441.

Industrial and Biological Electronics Ltd., 12 Royal Terrace, Glasgow G3 7NY. Tel. 041 332 1077.

Lascar Electronics Ltd., Module House, Whiteparish, Salisbury, Wiltshire SP5 2SJ. Tel. (07948) 567.

Limrose Electronics Ltd., Aerial Road, LIay Industrial Estate, Wrexham LL12 OTU. Tel. (097 883) 5555.

Magnet ApplicationsLtd., 323 City Road, London ECIV iLL.

Model Flight Accessories Ltd., Como Drills, Mill Lane, Deal Kent. Tel. (0304) 612734.

RS Components Ltd., P0 Box 427, 13-17 Epworth Street, London EC2P 2HA. Tel. 01 253 1222.

Scoonie Hobbies, 91 Sinclair Street, Kirkcaldy, Fife. Tel. (0592) 51792.

Scottcomms, 23 Morton Street, Portobello, Edinburgh EH15. Tel. 031 6572430.

Sinclair Research Ltd., Unit F, Broad Lane, Cottenham, Cambs. CB44SW.

STEM Ltd., STEM Walton Unit, 65 Walton Lane, Liverpool L4 4HG. Tel. (051 207)1869.

Technomatic Ltd., 17 Burnley Road, London NW1O2ED. Tel. 01 452 1500.

Unilab Ltd., Clarendon Road, Blackburn, Lancs BB1 9TA. Tel. (0254) 57643/4.

Watford Electronics, 33/34 Cardiff Road, Watford, Herts. Tel. (0923) 40588.

© SSSERC 1983.(Copyright is held to be waived only for bona-fide educational uses within Scottish schoois and colleges in currentmembership of SSSERC.)

Exciting times?

INTRODUCTION development are concerned that the exam plars containthe right level of detail on apparatus, experimentalprocedure and safety. To this end information on theseaspects will form part of each examplar package.

Not all science teachers would agree with us but fromhere we see an interesting period ahead. Then perhaps,as semi-detached observers, we see just a little more ofthe game. We do see a number of areas opening up forexploitation by imaginative science teachers.

In the areas of electronics, computer interfacing andcontrol lie tremendous possibilities. Many of these areon a hidden, rather than an overt, agenda. They includechances to introduce all pupils to the real world ofmaking and doing; for the use of electronics as a vehiclefor teaching the principles of engineerinq and design;to introduce some overdue changes in earninglteaching styles and finally, yet another opportunity forbridge building to other areas of the curriculum mostnotably technical education.

The debate on these ends, and inevitably about themeans, rages politely and quietly on mostly behind thescenes. It will be interesting to note the outcome. We atSSSERC hope for radical initiatives and not only fromthose outwith the present school system.

We can also only hope that these opportunities donot slip from the grasp of Scottish teachers. A preoccupation with the ways of doing things rather thanwith the actual achievement of objectives could let thathappen. We must all cross our fingers and ferventlywish that the following cynical comment, overheardrecently, does not become a reality:

‘When people say that Britain is at the forefront of aparticular technological development, what they reallymean is that it will be imported from Japan next week.”

The other areas of opportunity were touched on in the‘Opinion” section of Bulletin 134. Current developments in the Munn-Dunning science programmeshould offer imaginative teachers opportunities toexercise more discretion on course content and learningstyle.

We are currently looking at the first of the draftmaterials which will eventually be sent out to Regionaland Island Authorities as the “National CoreExam plars” for foundation science.

Some of this material is nicely open-ended withoutbeing too ambitiously so. We even see, at the optionstages, some possibility of simple project work. Add tothat the opportunity to choose material from examplarsand to mix it with material of one’s own and thepossibilities really open up. The distribution arrangements themselves have been designed to allowmaximum flexibility in that rewrites, substitution andaddition of individual modules should be possible.

SSSERC has been commissioned to look at thisnational material as part of the overall production anddistribution arrangements. All of those involved in the

It seems foolish therefore to provide such detail inthese columns when it will eventually reach schoolsdirectly. We would wish to applaud and encourage theelements of flexibility in the course. it would indeed beunfortunate if the national examplar materials becamean ossified course in the same way that the ISCworksheets became the Si, S2 course in many schools.To this end our own ‘Foundation Science Notes” willcontinue to be a source of “extras”. They willconcentrate on ideas for apparatus and practicalactivities which can be used to augment the nationailyproduced examplars. As before, we would be pleased toreceive suitable ideas or designs from teachers ortechnicians.

Balance in the Bulletin

Way back, in Bulletin 86, we were foolish enough tobrag about our success in achieving a subject balance inthis publication. Of late we have found this almostimpossible to obtain. Given the pressure from microelectronics and Munn-Dunning referred to earlier, thisis hardly surprising. In fact we now have an informationlog jam. Ironic isn’t it with all the current talk about‘IT’! We have a great deal of material competing forlimited space and unequal clamour for certain types ofhelp. Add to that the phased production of FoundationScience examplars and you will see part of our robIem.

Our main problem is the same as that of manyscience teachers. Too much is happening at once.When SSSERC was set up 17 years ago it had to dealwith problems arising out of one major curricularupheaval. At present the Centre staff (= 3 scientific, 2technical plus a secretary) are facing demand caused bytwo separate major upheavals.

So, bear with us please if this issue seems to you toophysical, although we would hope that the notes oninterfacing the ‘beeb’ would be of interest to all.Strictly subject minded biologists and chemists arepromised more next time around. Foundation corematerial on “Environment” and “Healthy Bodies” iscoming onto our desks! Also on the way, althougn alittle further off is the prospect of one extra member ofstaff at SSSERC... Exciting times?

Safety Notes

Spectrum - faulty power supplies

We have been informed by Griffin and George Ltd.,that certain Sinclair ZX Spectrums may have beensupplied with mains adaptor power supplies whichcould be faulty. Under certain conditions, this faultcould be dangerous. You only need to check yourequipment if you have received a 16k or 48k ZXSpectrum since 1st January, 1982.

Examine the mains acaptor carefully. If the lead toconnect it to the Spectrum is black and white, please dothe following:

—if necessary switch off the mains supply anddisconnect from the socket—remove any plug which you may have fitted—package the mains adaptor for postal dispatch—DO NOT INCLUDE THE COMPUTER ITSELFNOR THE HANDBOOK, TV CASSETTE LEADSNOR THE HORIZONS TAPE—send the mains adaptor only to:Sinclair Research Ltd., at the address on the insidefront cover of this bulletin.—ensure that your name and address is included in acovering letter. You will receive a new adaptor byreturn.—your postage costs will be reimbursed if yourequest this in your covering letter.

It is not necessary to send back adaptors with red/black-leads. The problem does not extend to any mainsadaptor power supplies which have been included withZX printers or ZX81 ‘s at any time.

Griffin and George apologise for any inconveniencewhich this may cause. For any furTher information youare advised to contact your local Griffin Office (i.e. forScotland this means Manchester I)

Foundation Science Notes

Wind power - a Savonius rotor

The section on Energy in Foundation Science invitespupils to examine some potential sources of renewableenergy, two of them being wave and windpower. Analternative ‘windmill’ to those shown in the twoexemplars received here, is the Savonius rotorApologies to those who follow the good life’ or havevisited the Centre for Alternative Technology at thatfamous quarry near Machynylleth in Powys. They willknow much not only about Savonius rotors and otherwind and water driven generators, but will also beconversant with other arts ranging from fish farmingand composting to construction of methane generatingtoilets!

The traditional Savonius rotor as built by thealternative technologists consists of the two halves of alarge oil drum (sliced vertically down a diameter)welded together so as to always present one open ‘windbucket’ regardless of the wind’s direction. Described

the construction of a miniature generator usingdetergent or squash bottles in place of oilFig. 1

Fig. 1.

The two halves can simply be stapelled together anda shaft extension from a length of stiff plastic tubingcaught between the staples. This is slipped onto thespindle of a IV, motor/generator held vertically in aclamp. An alternative procedure is to mount the plasticrotor in a slot cut in a small piece of blockboard intowhich a hole of diameter just smaller than that of thespindle has been drilled. (Fig 2). This provides apushfit for the motor spindle. A drill size 43 was foundto be satisfactory for the Orbit series 305-505 and a 42or 41 for the Mabuchi motors.

here isplasticdrums.

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U

2

Another problem is that of ensuring that ‘the blowerused generates a tube of air with cross section areagreater than that of the rotors. This difficulty increasesif the Savonius rotor size is increased or if aconventional windmill or propellor with long vanes is tobe used. If however they are used outside in realwind this objection disappears! Some models ofhairdryer have a relatively wider nozzle and hence amore diffuse blow than others. The Boots headway’500W hairdryer selling at £5.45 seems to be adequatefor the purpose.

For use as a model in schools the Savonius rotor hassome advantages over the traditional long vaned rotoror windmill type which rotates in the vertical plane on ahorizontal axis:

- the simplicity and cheapness of construction

- its compactness not only aids storage but makes iteasier to cover the whole rotor with artificial wind. Itis less easy to make a large windmill rotor turn andgenerate power

- its robustness.

A further aspect of this demonstration is that it canbe easily extended. Pupils could easily investigate theeffect on performance of varying the size of and shapesof rotors. The wooden boss fixing permits rotors to befitted rapidly. Further a friendly competition to producethe highest output current could provide muchmotivation.

Fig. 2.

Many schools will possess old stock of Orbit motors(which, unfortunately, are no longer available) but thealternative presently back in the Hobby shops seems tobe the Mabuchi range. Both types of motor, Orbit (305,405 and 505) and the Mabuchi 1 1i..41/ volt type were

found to be satisfactory. For those without a convenienthobby shop three sources which will send motors bypost are given Harburn Hobbies, Model FlightAccessories and Scoonie Hobbies. Their addresses andthat of John Bull Electrical referred to in the TradeNews are given on the inside front cover. With a small60mm high rotor cut from a squeezy liquid detergentbottle of diameter 60mm the following similar outputswere obtained. Clearly dimensions are not critical.

hard

3OmA lOOmA

The voltage measured across the generator varied fromO.1V to 0.2V. Increasing the size of the rotors with anyof these motor sizes did not greatly affect the output. Infact larger rotors were found to be more difficult to startrotating.

Whilst the Savonius rotor has the advantage of notrequiring to be faced into the wind before it operates, itmust clearly be less efficient than more conventionaldesigns. It does prove difficult to start if the two lobesof the rotor happen to be stationary in the eclipsedposition. (Fig. 3a) Producing rotors more the shape ofan aerofoil reduces this problem and perhaps as aninteresting aside demonstrates the principle of lift onan aerofoil. IFig. 3b).

Such rotors are easily constructed from 20 gaugealuminium sheet. Again sizes are not critical. A heightof 70mm and width (unfolded) of 150mm was found tobe satisfactory. Sharp edges and corners should besmoothed even though the speed and momentum ofsuch wind driven rotors is unlikely to cause injury. Afurther development is to make the aerofoils solid’ bytaping on a piece of stiff paper or card as in Figs. 4(a)and 4(b).

bc’

P’tor

mouth blown(gently)

vacuum hairdryercleaner

As an aid to fitting the card,the aluminium sheet and

lOOmA 50-6OmA card can each have a vertical slot cut at their mid pointso that they interlock at the centre. (Fig. 5).

3

Biology Notes

_______

UV lamp spares

Some years ago we recommended an inexpensive UVlamp for use in CSYS Biology. The main use for thislamp was in detecting ‘quenching’ of short wave UV bynucleic acid bases on chromatograms. (Unit 3

3(). (P/-0tto “Chemistry of the Living Cell”). The lamp at that timewas supplied by European Instruments Ltd. as a‘Quartray Shortwave’ ElOl.

We have recently been informed that EuropeanInstruments no longer sell this model nor do they stockspares. However we have now traced the

r0tct,omanufacturers of the lamp. They are Coast-Air Ltd.They still keep spare bulbs for the lamp (tyoe no.0Z4 SW) at about £5 each. They make a wide range otUV equipment and their catalogue certainly bearsinspection.

Constant volume dispensersF (b) (Pl

—

There is a particularly frequent need in biology andand in chemistry (biochemistry?) to dispense equalvolumes of reagents into large numbers of test tubes.For example, in enzyme studies and in vitamin Cexperiments with DCPIP etc. It was partly because ofthis need that the d-i-y dispenser described in Bulletins73 and 74 was designed. Some rather nice, inexpensive,dispensing containers are now coming onto the market.The attention of biologists is thus drawn to the

te description of one range of such dispensers from Bettixrade News” section.featuredintheT

* * *

Physics Notes

F. J.. -

Some laser experiments

Optical transmission of an audio signal

This can quickly be achieved by stretching clingtilmacross a loudspeaker cone and letting the laser beam

___________________________________________

glance off the clingfilm (Fig. 1). The loudspeaker isdriven by a signal generator.

The lightbeam sweeps across the photodevice at thefrequency of the audio signal. We used a T1L78phototransistor as our detector. The T1L78 is an infrared detector, but it is sensitive to a helium neon laser.We used it because we had it to hand. The TIL78 can be

____________________________________________

obtained from Technomaticat 55p.

Other photodevices we nave usea wit i tile laser are2N5777 photodarlingtons and RS 305 434 lightactivated switches. The former device operatedF1. £ (E/eic*trov — ot to satisfactorily for 6 months heavy usage beforebecoming insensitive. The latter device becameinsensitive after a few minutes.

4

hotjc.€, fl.. c...i

The phototransistor can be wired up to give either ananalogue or a digital output and.monitored on a CRC(Figs. 2 & 3). We mounted the phototransistor at theback of an empty 35mm film can to mask stray light(Bulletin 133, p.11).

CR0

Ok

TIL7to CR0

q6o\J

D tL

R ,icLo.te. .±p± frc’. totst11, eo-k naL cfrv OO-.’/ Fj. 3.

//fl-t

!fecio

T;L78

F. 2.

The system works best at frequencies of around1kHz. We were however able to transmit a signal of20kHz.

Ref lection of f water waves

This is a variation of the last experiment. Circularwater waves were produced in a Petri dish of diameter5’/2 “. The waves were generated by a loudspeaker thatwas clamped about 1cm above the surface and centredover the Petri dish. A U-shape of wire, l2xl6xl2mm,attached to the central cone of the speaker with Britfix,dipped into the surface to do the generating (Fig. 4).We used 0.6mm copper wire.

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(7 irn

30 c.rn >k

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00 cn

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TIL 78

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F. 4

The laser beam was directed at the side of the Petridish so as to glance onto the waves (Fig. 5). As thereflected beam swept across the photodevice it waspossible to obtain a signal of the frequency of thesource.

What was also obtained at about 8kHz was a clearinterference pattern on a screen placed next to thephotodevice, the water surface acting like a reflectiongrating. The wavelength of the water waves was of theorder of 1 or 2 millimetres.

We will stop this article here as it seems that a lot ofopen ended project work could stem from thetechniques described. In particular the techniquesshould make possible the study of a variety of highfrequency surface waves and also enable the accuratemeasurement of wavelengths and frequencies of thesewaves.

On a point of safety, t will have been noted by somethat we have not specifically mentioned laser goggles.A more relaxed view is currently taken on the need forthese. Certainly we would not think them necessary forexperiments of this type using typical school laserswhose power output is of the order of 0.5mWproviding that due care is taken in setting up theexperiment to avoid the possibility of direct laser lightentering the eyes.

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Have you read?

Interfacing Notes

In an attempt to get on top of the information beingpublished on interfacing in periodicals we haveproduced a reading list of articles on interfacing. Thelist gives you the title, author, journal and date, plus abrief description of the articie. It is divided into sectionsbased on models of microcomputer. The first list covers1982. The second list, soon to be prepared, will coverthe first few months of 1983 and is due out April/May.The list will be automatically posted to members of theScience Interfacing Register.

Copies of the first list are available from SSSERC.1

The second list is to be printed by SMDP. We have stillto arrange its distribution.

Much of the compilation of the reading list is beingdone by Miss Janet Hughes of Montrose Academy. Weare very grateful for this help from Janet and we aresure that many of us will find this service very helpful.

Interfacing with the BBC Model B

Ti, remainder of these notes is taken up by the firstof a series of articles on the ‘Beeb’ model B. V\’ith theBBC microcomputer looking set to become one of the 2.commonest models in schools we thought it would behelpful to provide information on d-i-y interfacing assoon as possible. The model B has a number of featureswhich make it relatively simple to interface toexperiments or for control applications. Some of thesefeatures are explored and exploited in the articles wewill publish.

User port - BBC model B

Part 1 Input and output

The BC model B contains an interface chip knownas the 6522 ve satile interface adapter (VIA). The userport gives you access to one-half of the VlA (figure 1).The other half is reserved for use by a printer.

This article describes ways of connecting peripheraldevices, such as breadboard experiments, to the userport and outlines how to control the 8-bit I/O lines.

Connecting to the user port

The user port has a 20-way plug. Of these twentypins, eight are commoned to system ground, OV, andtwo are commoned to the + 5V rail. The other ten pinsare for input/output signals. It is handy to have aconnecting system to link up the user port to adistribution board with 4mm sockets (Figure 2). Onemethod of constructing such a board is outlined below.It is based on the circuit diagram in p503 of the BBC

User guide”.

Insert twelve 4mm sockets into a boardapproximately 21cm long. A neat arrangement ofthe type illustrated uses half sections of rectangular drainpipe.

Colour code and label the sockets as shown (Fig. 2).

OV black÷5V red

Connect 20-way Speedblock” ribbon cable to a20-way cable mounting socket AS 467 289, £2.09.Suitable assembly tools should be used for thisoperation. They are the R.S. Components commonframe RS 468 197, £3.00, and special insert RS 468232, £3.16. Assembly instructions are suppliedwith the common frame. Assembly is not a difficultoperation.If you chance your luck and do without theassembly tools you run the risk of applying toogreat a pressure to the device and severing leads.

AS Components Ltd., seli Speedbloc” ribboncable in 20m lengths. A reel of 20-way cable,RS 357 867, costs £26.20. If your needs are lessextravagant than 20m reels then WatfordElectronics supply 20-way grey ribbon cabe at 25pper foot.

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3. Wireupthefreeendoftheribboncabletothe4mm Pages (Edinburgh) having heard that it was becomingsockets. The user port pins are shown labelled in difficult to rnuire. Two out of the three mainFigure 3. Seven CV and one 5V wires should be merchants we contacted still stock rectangular plasticsnipped off, drainpipe.

UBM -do not stock it.StockistsPDM -4 m at £9.37Plum Center (sic! formerly ‘Mariey’) - 2.5m at £7.24.

I A different connector system that is well worth

3m at £8.70.

P57 c”, p c.zcs considering uses a 12-way quick connect blockI (RS 423 576), £2.30, which has strong spring grips forwires (Fig. 4). This connector system is useful whenlinking a breadboard circuit to the user port.

Software control

Operation of the user port is governed by several3. Ll€ Pt COflflCiOY15 8-bit and 16-bit reisters in the VIA. The registers arecontrolled by ‘writing’ operations wnich ‘set’ or

4. Make a strain relief device to grip the ribbon cable ‘reset’ the bits within them. When we write a 1 into ato the plastic drainpipe. Two bolts and a metal or bit, that bit is said to be ‘set’. When we write a 0 into aplastic strip will do. bit, that bit is said to be cleared or ‘reset’. For example

the instruction:5. Plug the ribbon cable into the user port and switch

?&FE6O = &C4n power to the computer. Each of the lines shouldbe tested using the programs listed in the secondhalf of this article. A high impedance voltmeter writes a 1 into bits 2, 6 and 7 of the I/O register B. The

such as a digital meter or CRC should be used to bit pattern of this register looks like this:

measure potential.7 6 5 4 3 2 1 0 bit number

Rectangular plastic drainpipe can be obtained fromplumber’s merchants. We tried three out of the Yellow [J 1 0 0 0 i 0 0 bit pattern of

&FE6O

8

plcshc

rn,t,.x±tr

You have to be fluent in three number systems,hexadecimal, decimal and binary, in this game.

Therefore you should have to hand a conversion tableup to decimal 255.

The VIA registers have addresses and areaddressable just as though they were locations inmemory (Table 1). By ‘addressable’ we mean that theycan be written to or read. There are some exceptions tothis which we need not go into in this article.

Registers are very different from memory locations.The latter are passive beasts whereas the former areactive. Each register bit controls a logic gate. or a series

of logic gates, within the VIA microprocessor. Thussetting the bit pattern of a register is like controlling agigantic signal box, routing and rerouting signals. Eachregister has 256 different switching combinations. Thewhole set of registers in the VIA has thus an immensenumber of modes of operation which perhaps is thereason why the ‘BBC User Guide’ does not evenattempt to explain its working.

We will conclude this article with a description of justtwo of the VIA registers, Input/Output RegisterB (IORB) and Data Direction . Register B (UDRB).These two registers operate the 8-bit port B, the 8-bit,parallel, bidirectional, data lines on the user port.

DescriptionWrite Read

Output Regiter BOutput Regi ,ter A

Data Direction Register BData Direction Register A

Timer 1 Low-Order Timer 1 Low-OrderLatches Counter

Timer 1 High-Order CounterTimer 1 Low-Order Latches

2O-t’

cWe cJa.f,

2 - k) 7’.cLc C,1p€t blcc.k

sIJt. ft’ L)IrS

tc2 c/keccz[ duce..s

Relative.address

Register

BASEBASE + 1BASE + 2BASE ± 3BASE + 4

BASE + 5BASE + 6BASE + 7BASE + 8

Hexaddress

&FE6D&FE61&FE62&FE63&FE64

& F E65& F E66&FE67&FE68

& F E69&FE6A

&FE6B&FE6C&FE6D

&FE6E&FE6F

IORBORA

D DR BDDRATIC-L

TiC-HT1L-LTi L-HT2C-L

Input Register BInput Register A

BASE -,- 9 T2C-HBASE+iO SRBASE + 11 ACRBASE + 12 PCRBASE + 13 IFR

BASE + 14 IERBASE + 15 ORA

Timer 1 High-Order LatchesTimer 2 Low Order rimer 2 Low-Order

Latches CounterTimer 2 High-Order Counter

Shift RegisterAuxiliary Control RegisterPeripheral Control Register

Interrupt Flag RegisterInterrupt Enable Register

as register 1, but without handshake

Table 1. VIA Registers

9

Data Direction Register B instruction bit pattern

This register configures each of the 8 I/O lines forinput to the computer, or output from the computer.

Rules: set bit (=1)- outputclear bit ( =0)- input

The bits are set or cleared by. write instructions toDDRB at address &FE62. The 8-bit I/O lines are calledPBO. FBi PB7. The ‘PB’ stands for peripheralport B.

Examples:

1. Configure all 8 lines PBO to PB7 for input.(Therefore write 0 into all 8 bits of &FL62).

instruction bit pattern of &FE6276543210

?&FE62=&00 oIoIoioooIoIoj2. Configure all 8 lines PBO to PB7 for output.

(Therefore write 1 into all 8 bits of &FE62)

bit pattern of &FE6210

Ti765432

3. Con ilgure lines PBO to PB5 for output.(Therefore write 1 into bits 0 to 5 of &FE62)

instruction bit pattern of &FE6276543210

?&FE62=&3F I0Iolii Ii i 11111or

?&FE62 = 63

You can write both hexadecimal and decimalnumbers to addresses. It is probably simpler convertingfrom binary to hex than from binary to decimal. Wetend to use hex more often for this reason.

Output

We will assume in this section that all 8 I/O lineshave been configured as output lines.

Each line is made high or low by setting trieappropriate bit in the Input JOutput Register B (IORB).

Rules set bit ( = 1) output highclear bit ( = 0) output low

The bits are set or cleared by write instructions to ORBat address &FE6O.

Example:

Set data lines PBO, PB2, PB4and PB6 high.(Therefore write 1 into bits, O2,4 and 6of &FE6O)

76543210?&FE6O=&55 I01I0I1I0l110h1

or?&FE6O = 85

We have now covered sufficient ground to be able toconstruct a program to test the labelling of the 8-bitdata lines. PBO to PB7, in the user port connectorsystem.

1’) F.=iFFREM all data lines made out.pLit

REFEA4u INFUTX5kj REM X can be any inteer80 REM between 0 and 25570 tFE5.r=X80 REM data lines set hiqh or law90 REM accordina tci va.iue of X

100 UNTIL FALSE

Program 1

To set the data lines PBO, FBi PB7 high one atatirnemakeXi.2,4.8.16.32,64and 128.

We would prefer to see the above program written ina more comprehensible style.

10 Bi’SE=FEbi)20 IOR8=biSE30 DDR8=B8E+240 DDRE1=fFF50 REPEATo INPUTX70 “IOREi=X80 UNTIL FiLSE

Program 2

This style features

1. Naming registers according to their initials ratherthan according to their addresses.

2. Referencing the registers to the base address of theVIA (Table 1).

One of the attractive aspects of programming theBBC micro is the ability of giving a numeric variable orconstant almost any name you fancy. Therefore wemake use of this facility in our programs and call theVIA registers after their own names. It is simplerworking with ORB, DDRB, and PCR than &FE6O,&FE62 and &FE6C. The only catch is that certain labelsmay be misinterpreted by the computer. For example ifyou call the Interrupt Flag Register FR the computerinterprets this as IF R. We get round this snag withanother name. FLAGS does.

instruction

?&FE62 = &FF

10

-4-5\J + 5V

Each one of the 8-bit I/O tines is designed to sink acurrent up to lOmA or source a current up to imA ordrive one TTL load. In practice then you would notattempt to use the I/O lines as a current source (exceptfor the case of driving one TTL load). Two arrangements for controlling an l.e.d. are shown in Figure 5.

We prefer version (b) for two reasons. One, there is achiasmus in the logic of version (a). This is not so in (b).Two, the 7404 buffers the VIA.

We suggest you control eight l.e.d.s from the userport. They can be quickly assembled on prototypeboard. This will make manifest one of the principalfeatures of 8-bit data lines, the fact that you areprocessing data in parallel. Each single softwareinstruction operates eight different devicessi m i It an eo us ly.

By way of example you can send a rippling effectalong the eight l.e.d.s using program 3.

Input

The bits in the Input/Output Register B (IORB) areset or cleared by incoming signals according to thefollowing rules

P3o t.e.cL.

0 ffOIL

cLr\Jj o TTL otecjice

c.ktrfvl± Led.

till? 7404

REPEATREAD X?IOREXY=V + 1T=TIMEF:EPEA T

uNTILTIME::T+5UNTILY=18

RESTOREUNTIL FALSE

DATAtFF, tFE, t,:FD &FEi, tF7 tEFDATAtDF, iBF, t7F, &FF, &7F, itBFDATAt:DF. &EF, tF7, &FB. &FD. &FE

Rules: input high bit set ( = 1)input low bit cleared ( 0)

Program 3.

27c ft ‘fk 7404

Lj;

170P\

PSc. 0—

P130 Led..

0 Oh

c-r-r-ftt

()

P80

5.

sk5

b)

BA5E=t’FEoOI ORE1= BASEDDRB=E’ASE+2‘?DDRB=tFF

REPEAT

1020

4(:i

5i)

70

901 oo1 101201 0141)150

170160171..)

11

Input signals are sensed by read instructions on IORB 7 6 5 4 3 2 1 0ataddress&FE6O. IORB= OIOL1 ololojol 01

We can input a high or low signal to the 8-bit I/O The instructionlines by either connecting the line to the + 5V rail via a ?IORB = ?cIORB) OR &20ikO resistor or by directly connecting the line to ground

sets bit 5 and leaves the other seven bits unaffected(Fig. 6).

76543210ORB 1b[cldelt Ig hI

0OR&20 01011 otolololol

I kO ?(IORB) OR &20 a I b 1 j d I e g I h

p P3o -P7 2. Output a 0 on PB2 and PB3. Leave the other six I/O

lines undisturbed.

The instruction is

?IORB = ?(IORB)AND&F3

IORB albdejfg

AND &F3 1 1 1 1 0 [i 1 j iJThe software for configuring the 8-bit I/O lines for

input and sensing whether they are high or low is ?(IORBIAND &F3 ra b I c I d 0 LTT11) BASE FE6L) 3. Wait until PB1 goes ow20 IORB=EiASE

The nstructions areDDREi=EiASE÷240 DDRB=05j X=7IQRB iio REPEAT) PRINTX 110 X=?(IORP>AND2

120 UNTILX=0Program 4.

1C PF:INT’PBl low

The value of X depends on the state of all eight linesPBO to PB7 because as mentioned above we are in the Program b.business of processing data in parallel. For example itX=l92thenPBOtoPB4arelowandPB5toPB7are IORB [ajbjcdjefjghjhigh

_________________________

AND2 Lolooloolol 1 oj76543210

_____________

ORB = 1 I 1 0 I 0 I 0 I 01 ?(IORB) AND2 I o I I o I 0 0 0 g j 0 ILogical masking

Model train controlThe technique for operating a single. or several 1/u

lines, but not tnem all, is known as logical masking. The above mentioned ideas are embodied in thisSome examples will illustrate the technique. example of control. The example illustrates

Examples 1. parallel processing of data2. bi-directionai data lines1. Output a 1 on PBS. Leave the other seven I/C lines3. logical maskingundisturbed.4. software control of hardware

The instruction 5. power boosting with hardware

?IORB = &20 The layout is a single length of track (Fig. 7. Thetrain is controlled to run up and down ;t (preferably

will not do. It sets bit 5, but clears the other seven, without falling off the ends’)

12

An external 6V smoothed d.c. supply should be used tooperate the relays in the circuits below.

t-.k

—-e.€c( 5’tC*

connec.t€cL to P8‘-e& s..j,t.k

Lonre.de4 t PB3

1. Data direction register B

pin function

ri€L nc’rwcLLy o’€S)tcJ cJoS€S L)iE

F3. 7

I/o

PBO current polarityPB1 current on /offPB2 sensing SWAPB3 sensing SWB

to set bits Oand 1 high.

2. Reverse polarity control

Outputoutputinputinput

3. On/offcontrol

Rs 3 b2.

IORB

76543210

state of train

R5 3-9 33 DIL -ee{-€Jcy ect -to 5);-ak

off rcvl ../l)/

sw swa

Use instruction

?DDRB = 3

*0 r€U€rS

I f tc sly

Sc.c,8

I I I I 0 reverse

I I 1 forward

-1- (,V

PS

OkBcio

ORB train

76543210

I I I I I °I loft

I I I I 1 on

13

software instructions

4. Sensing position of train

Position B on track

o’J

?IORB = 0

?IORB = 1

?IORB = 2

?IORB = 3

off

EEZIJ off

L_LJ_L_LJL2J on reverse

on forward

software instructions RE PEAT

Z = ?(IORB)ANDS

UNTIL 8

REM Z = 8swtch is open

REM Z = 0 switch is closed

Assembling these deas we can put the train intoperpetual motion with the following program.

10 SE=&FE6O20 IORB=BPtSE30 DDF:Ef=SASE÷240 7DDRE=50 REPEAT60 PROC+erward70 PRO1revere80 UNTIL FALSE90 END

100

110 DEFPRDCforward120 X3:8PR0CjoLirney130 ENDPRDC141)150 DEFPROCr ever se

160 X2: Y4 F’ROCjourney170 ENDF[0C180190 DEFFR0Cjournev200 ?IURB=X210 REPEAl221) Z=2(10R8 ANDY230 UNTILZ >Y240 ENDPROC

Program 6.

The train should nitially be placed on the trackbetween A and B pointing towards B, The program canbe stopped by pressing ESCAPE. However to stop thetrain you will have to disconnect power from the track

This program has been developed further to cause agradual acceleration and deceleration at the start andfinish of each journey. This is achieved by pulsing thecurrent with a varying mark space ratio.

JI I IoHJ

I I I I I ii

t-eecl sIc,k

9

kO

o PS3

SwB

IORB SWB

76943210

mJIiI 1 II open

JJJLm closed

14

8ASE=tFE60I ORB=EASEDDRB=BASE+2?DDRB=3PROCdisplavINF’UT”hov many journeys” • NFDRI=1TON

PRDCdi api auPRINT”Train for Hither”PROCf orardPRDCdi p1aiPRINT:PRINT”Train for Thither”F’ROCr ever seNEXT I

PROLdi api avPRINT’ journeys’ end”END

DEFPPOC for war dA3 E)1: C=8: PROC journeyENDPROC

DEFPROCr ever soPi2 B’0 C4: PROC journey

ENDPROC

DEFPROC journeyF’ROCaccei orationREPEAT

Z=7 (IORB.’ ANDCUNTILZ

PROCdecei erati onTIfl=TIMEREPEAT

UNTIL TIME::TIN+200ENOPROC

:so

41042’43o

45u4é3u

4704E)490500510 2IORB=A520 ENDPROC530

540 DEFPROCdece1 erati on

550 FORT=1TO25560 ?IORB=A570 DELAY=T580 REPEAT590 DELAY=DELAY+1aOO UNTIL DELAy::25

610 ?IORB=Ei620 DELAY=1630 REPEAT

680

DELAYDELAY+ 1UNTIL DELAy::T

NE X TTENDPROC

690 DEFPROCdi splay700 CLS710 row8720 REPEAT PRINT730 UNTIL VPOS=row740 ENDPROC

Program 7

Regular readers of the Bulletin will be wellaccustomed to remarks made tongue in cheek, not tomention faded metaphors. We would at this point in thestory, like to draw your attention to a form of movementwell beloved of setters of SEB examinations, namelyacceleration from rest, followed by constant velocity,followed by deceleration to rest.Questions on this pattern of movement are normallyset in a completely abstract fashion, devoid of anymeans of relating to observation and measurement.Now the train under control of the above programfollows this pattern of movement, which of course couldbe observed and analysed.

Control lines

Two of the four VIA control lines are accessible at theuser port, CB1 and CB2. They have many functions andthey differ from the 8-bit I/O lines in many ways. Someof their features are listed below.

1. The control lines are used singly, not in parallel.2. They can be used to sense transitions as opposed

to logic levels.3. They give access to the VIA timers.4. They can generate interrupts.5. CB2can be used to transmit 8-bit data, in or out,

in serial form.

Their mode of operation is controlled by the bitpattern setting of two special registers, the AuxiliaryControl Register (ACR) and the Peripheral ControlRegister (PCR). Details of this can be found in Section2.4 of ‘6502 Interfacing’.

640650860670

i2)

4)

67’)8)

1 :11)12131 4o15018)170181 9n

21220

24025026u

280290

310

340350360

DEFPROCacce1 orationFORT=25T0 1 STEP-i

?IORB=ADELAYREPEAT

DELAY=DELAY±1UNTIL DELAY>25

?IORB=BDELAy=1REPEAT

DELAY=DELAY + 1UNTIL DELAY>T

NEXTT

15

We will conclude this article with two programlistings, one program being used to wait for a positivetransition on CB1, the other to output pulses on CB2.

Wait for a positive transition on CB1

BASE=&FE6OI ORE=BASEPCR=BASE÷ 12FLAGS=BASE+ 13REM set bit 4 of PCR to detect

REM a positi’ie transition on CEll

?PCR=&10REM wait for a positive transitionX=? (FLAGS) AND&1OIFXOTHEN9OELSEPRINT”+ve transition”REM clear flag in IFRREM by reading IOREiZ=?IDREi

140 ENDProgram 8.

You will have to use a debounced switch to check thisprogram’s operation.

Output pulses on CB2

10 BASE=t.:FE6O20 PCR=EiASE÷1230 REPEAT40 ?PCR=&E050 ?PCR=tC060 UNTIL FALSE

Program 9.

The pulses should be viewed on a CR0 since thefrequency lies between 300 and 400 Hz. The effect isjittery since the Basic program is continuallyinterrupted by machine language programs whichservice housekeeping tasks.

There will be other articles in future Bulletinscontinuing the story of BBC interfacing.

Surplus Equipment Offer

The following items of equipment are offered forsale, subject to the conditions laid down in Bulletin 116.Items with numbers less than 236 have alreadyappeared in previous bulletin issues. Details of theseitems can be found in the relevant issue (number givenin list). Items 236 to 240 are new stock. Because of thesmall number of new items we do not intend to hold aballot. All of the items below are therefore offered on afirst-come, first-served basis.

In addition to the listed items we also have stocks ofswitches. capacitors, other small components and arange of general chemistry/biology items. This latterstock comprises soda glass test tubes, plastic soecimencontainers, rubber bungs, tubing and filter paoer, etc.Stocks of any particular item are fairly small but let usknow your requirements and we will try to mee’ them.

Item 84 Bulletin 125 Photographic Fixer

Item 89 Bulletin 125 Dry cells 1 ‘/2V

Item 165 Bulletin 129 Bimetallic strip. 30cm 40pItem 176 Bulletin 132 Impact adhesive, 1/21 tin 75pItem 178 Bulletin 132 Bromide paper, WSG4,

16.5 x 21.6cm, box 100sheets £5.00

Item 179 Bulletin 132 As above but WSG2. 20.3x 25cm, box 100 sheet3 £6.00As above but WSG1, 20.3x 25cm, box 100 sheets £6.0035mm b/w film, 60-8CASAin cans of 1000’ £5.00

Item 185 Bulletin 132 35mm colour neg. film,100ASA 61m in can

Item 205 Bulletin 132 Kodak multipurposedeveloper for papers.51 bottle £3.00

Ilfospeed paper developer,51 bottle £3.50Ilfospeed fixer, 51 bottle £2.50Milliammeter, centrezero £3.50

Item 212 Bulletin 132 Large wirewound potentiometer, 25W,8R 80p

12V motor by Smiths, doubleended, 2 “spindles £2.50J24’ 12V power supp’y £3.50

BC1 07/ BC1 08 transistors 5p

Item 223 Bulletin 133 Time clock and set switchby Smiths, mains, £3.50Bromide paper, WSG2,16.5x 21.6cm, box 100 sheets £5.00As above but WSG1 and 30.5x 40.6cm. box 100 sheets £6.00Veribrom Fl, size as lastitem, box 100 sheets £12.00

Item 231 Bulletin 133 35mm colour slide filmEktachrome, per cassette 60p

Item 234 Bulletin 133 Polaroid land film, perpack £1.50

Item 235 Bulletin 133 6V lantern battery, springterminals 70p

Item 236 Photographic paper, Kodak bromide,WSG3, 16.5 x 21cm (61/2 x 8½”). box oflOOsheets £5.00

102030405060708090

100110120130

30pper box

£1.50 per 24£8.00 per gross

Item 180 Bulletin 132

Item 183 Bulletin 132

£10.00

Item 206 Bulletin 132

Item 207 Bulletin 132Item 209 Bulletin 132

Item 215 Bulletin 133

Item 216Item 221Item 222

Bulletin 133Bulletin 133Bulletin 133 Speakerlm crop hone

insert 30p

Item 226 Bulletin 133

Item 227 Bulletin 133

Item 230 Bulletin 133

16

Item 23 Black and white 35mm film, liford FP4cine, 125 ASA, 200’ in can £6.00

Item 23 Photographic timer, 0-60s (0-6s x 10) £6.00Item 23 Colour slide film, 120 size, Ektachrome

16OASA, (artificial light -tungsten) 7OpItem 24) Prismatic com pass, hand bearing type

by Stanley of London, each £7.00

Display Laboratory

Thos of you who have visited SSSERC will know ourdistinct.ve Victorian premises. Many will also knowthat th building, from time to time, reminds us of itsage. Tie last major reminder was when the displaylaboratory ceiling fell down in 1982. We are nowpleasec to announce that repairs, redecoration andreorganisation are virtually complete. The display areais thus again open for business. Teachers coming toEdinbugh are welcome to visit us, 9 a.m. to 5 p.m.every v’eekday and 9 a.m. to 1 p.m. on the first twoSaturd.ys of every month (excepting national holidayweeker is).

We give below some indication of the type ofequipment which will beon display during the next twoto three months. However, because we also run suchexhibitions on a national basis, on occasion some itemsmay be out of the Centre. If you are coming to see somespecific item it is always wise to telephone us first.

At pesent the display is organised around threethemes.

a) Mici )electronics, interfacing and simple control

A v.riety of demonstrations is set up using aselectic•n from the following:

Appi II; BBC model B; Pet; Vic 20; ZX81 and ZXSpec rum.

b) Foundation Science

A grJwing collection of d-i-y items is on display,includi. g our versions of items from National Examplarmateri Is as well as SSSERC suggestions for additionalor optimal activities. These include experiments onaltern’tive energy; materials testing, health and

fitness and human behaviour.

c) New commercial apparatus

A cc lection of the newer items from a variety ofmanufrcturers or suppliers. This currently comprises:

i) i) Laboratory apparatus, for example -

The new range of microscopes from Philip Harris.Three models, ‘Junior, intermediate’ andAdvanced’.

Dispensing containers from Bettix Ltd. (See“Trade News”).

From Griffin and George we have a number ofitems including -

- the Ohaus ‘Brainweigh’dual range electronicbalance B3000D.

- the minimag’ magnetic stirrer- new chemistry and physics power supplies- pressure sensor/transducer- digital meter and accessories.

ii) Electronics apparatus and microprocessor tutor!demonstrators

- ‘Experimental Electronics Kit’ (for primary)from Cambion

- part of the ‘Micropippa’ range from IrwinDesman

- ‘Digital Electronics Units’, Griffin and George- Digital Logic Kits - STEM board and mini-

board’ by STEM

Out on evaluation but due back soon are:

- ‘Microprocessor Tutor/Demonstrator MkIl’,Philip Harris

- ‘Microprofessor’ from Philip Harris- ‘Microprocessor Tutor Kit’ by Limrose- ‘One-bit Microprocessor’ from Unilab.

Trade News

Bourdon Gauges

It is interesting to watch how equipment comes ontothe market in surges. We mentioned in Bulletin 134 thesplendid looking Bourdon gauge with 6” dial fromArtec. The same firm now stock a range of inexpensivegauges with 1 ¾” dials at £4.90 each. There is of coursea penalty to pay for investing such a tiny sum of moneyin a pressure gauge. The scales are marked in bars andIbfin2 and the pointer indicates zero at normalatmospheric pressure. The latter snag can be overcomeby removing the meter from its case and redirecting thepointer to read 1 atmosphere. This operation isstraightforward. The pointer is friction held on thespindle and can be orised off by careful levering. Thegauge ranges available are 0 to 1.6 bar, 0 to 4 bar and 0to 10 bar.

Digital multimeters

The March ‘83 edition of “Wireless World” carriesadverts for eleven different models of digitalmultimeter costing under £40. It is obvious thatinexpensive digital multimeters are now widelyavailable. We have bought and used three models.Unfortunately the performance of our samples has beendisappointing. The details are given below.

17

1. Metertech, model no. 3T

18 ranges, made in Taiwan, supplied by Industrialand Biological Electronics Ltd. at £43.50 plus VAT.

- performs well.

2. Lascar, model DP2O1O

20 ranges and diode test, made in England, suppliedby Lascar Electronics Ltd. at £27.40, available also inkit form at £23.62.

- the instrument has to be calibrated by a multiturntrimming potentiometer on delivery. Ours hasdeveloped an intermittent fault that reduces readingsby 10% of their true value.

3. Hung Chang, model 6010

28 ranges, made in Korea, supplied by ArmonElectronics Ltd. at £29.95.

- meter has developed an intermittent switch faultpreventing it measuring current or voltage. Armon saythey will replace faulty meters within one year ofpurchase.

Whilst we cannot condemn cheap digital multimetersas a whole, based on a sample of three there is acautionary tale in this. The market does seem to becatch as catch can at the moment. It does seemsignificant that AS Components have had severemanufacturing difficulties with their “slimline meterintroduced in November ‘82 and discontinued in March83.

Will you let us know of your experiences please? Wewill be better placed to offer advice if we have a largersample to go on.

Finally, a feature to which we should draw yourattention is that digital multimeters are sometimesavailable from local firms in the electronics trade. Forexample in our own case Scotcomms of Portobello haveat present a small batch of ARC digital multitesters,model KD-200, at £29.95. This model features auto-ranging and bipolarity making it very easy to use andensuring that’witching perhaps a weak point in suchmeters is kept toa minimum.

Magnets

We recently obtained a catalogue on permanentmagnets from a firm called Magnet Applications Ltd.Some of their items, with prices, are shown below:

- rectangular ferrites12 x 7.7 x 6mm20.5x7.7x6mm42x 25x 6mm

-circular ferrites12 x 6mm

Other items of interest are:

1. Lattam magnets which are manufactured intoblocks and used where sheer strength is noreimportant than direct pull.

2. Flexible magnets which are produced by loadng asuitable elastomer such as rubber with a frritepowder. The resulting mix can be manufactured intosheet, ribbon or strip. Flexor ribbon is available a 89pper metre.

3. Placor magnetic sheet which is obtainer bybonding flexor sheet on to steel sheet. This prod u;es athin magnetic sheet which is almost rigid.

Motors

Besides the usual sources of electric motors refrredto in the article on Windpower in Foundation ScenceNotes” one cheap source is John Bull (Electrical) Ltd.Their battery motors are intended to operate at vol agesabove 1 volt but not above 12V. The type most akin tothe old Orbit series or to the Mabuchi 1 1/2V to 41/2Vmotors found in hobby shops, is their BM8 which sellsat 60p. Postage and packing is 60p extra for odersunder £12.00. This motor is in fact made by Mabuchi,but has a number of differences to the Ma[uchireferred to above. The John Bull motor ha: nomounting bracket nor external terminals. The pasticend cap may be prised off and leads soldered ft thecontacts at the end of the copper brushes. A fu-therslight disadvantage is that these leads are most Easilybrought out through the same end as the spindi€ andwould require to be taped to the motor body.

John Bull also makes available a sample kit ci oneeach of six sizes of motors for £2.95 plus 60p p&p Theidea is that you can identify the motor most suitabi fora particular task and order it. Discounts are avaiablefor quantity, 10% for 10-49 of any one motor and higherdiscount for larger quantity. A number of accessuriessuch as switches, reversing switches, speed controllersare also available.

Dispensing containers

These have been coming on to the market from avariety of suppliers over the last year or two. Ourattention was recently drawn to one relativelyinexpensive source of these. Bettix Ltd. actuallymanufacture such dispensing containers. These Bettixcontainers are designed to dispense measured amountsof liquid by a single handed operation.

2Ox8mm29.6 x 9.5mm

- alnico 600 bar magnets

25p each29p each

round barsquarebar lO3x6x6mm £2.53each

3Ox6mm 46p each

7p eachl2p each20p each

lOp each

18

available with main chambers of 100;250500cm3and 1and 2 litres. Guide prices for thesE per 100 are £9;13;£18 and £30 respectively. The only Sr’ag is that to obtainthese dispensers at such competitive prices meansmeeting the Bettix minimum order conditions of £50per order

‘Stick-off’ labels

Self adhesive labels guaranteed to wash of t in warmwater have obvious advantages. Such labels areavailable from Camlab. The sizes range from 25 x 25 to76 x 32mm at prices from £5 to £16 per carton. Eachcarton contains 2.500 labels on a dispenser reel. It isclaimed that these labels can be used with a typewriteras well as felt-tip or ballpoint pens and that they willwithstand periods in fridges or freezers withoutaffecting the wash-off’ facility.

Stop press - Olympus HSC

Fig. 1.

In use the double chambered dispenser is gentlysqueezed, transferring liquid from the main chamber tothe smaller, dispensing chamber. The cap is thenremoved and the measured amount dispensed.Dispensing chamber sizes of 5cm3 upwards are

We have just been informed that due to a frustratedexoort order Griffin and George are offering the OlympusHSC ‘H grade microscope at a special price. Triis modelcatalogue number MJA-500-F is reduced from £148 to£105 whilst these current stocks last. At this price the HSCoffers exceptional value for money to anyone looking foran ‘H’ grade/A’ level microscope.

THE SCOTTISH ASSOCIATIONFOR

BIOLOGICAL EDUCATION

SIXTH ANNUAL SYMPOSIUM MAY 14TH 1983

at THE COUNTRYSIDE COMMISSION FOR SCOTLAND, BATTLEBY, PERTH

SYMPOSIUM COMMENCES 9.30 a.m.

Programme includes:

Presidential address by Professor W.D.P. Stewart, F.R.S. of theUniversity of Dundee.

Illustrated talk on the Work of the Countryside Commission for Scotlandby the Deputy Director, Mr T. Huxley.

Lecture by Dr 0. Lilley of the Department of Biochemistry, University of Dundee,on ‘Recombinant DNA Practice and Potential’.

Colloquy: H.M.l.s Mr H. McLaren, Dr S. Milne, Dr J. Jackson,Implementation of Munn-Dunning Development Programme.

Fee for Symposium, including lunch and morning coffee, £5.50.

Please send cheques, or request detailed programme to:

Gordon Swann, Hon. Secretary, S.A.B.E.,1 Dovecot Road,Edinburgh EH12 7LF.Tel. 031-334 4769, at work 031-443 7111, Extn. 220.

S.S.S.E.R.C.

CONTENTS Bulletin 135 April 1983

Page

Introduction —exciting times? 1—balance in the bulletin 1

Safety Notes —ZX Spectrum power supplies 2

Foundation Science Notes —a Savonius rotor 2

Biology Notes —UV lamp spares 4—dispenser hint 4

Physics Notes —some laser experiments 4Interfacing Notes —have you read? 7

—user port BBC model B 7

Surplus Equipment Offer 16

Display Laboratory 17

Trade News 17