School of Physics and Astronomy How to make a dark detecting torch Chris Staddon – Senior...
5
School of Physics and Astronomy How to make a dark detecting torch Chris Staddon – Senior Experimental Officer & Outreach Officer Michael Forrester – Student Helper Modified from: www.evilmadscientist.com/article.php/nightlight
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School of Physics and Astronomy The Mid-point needs 1.8 V to switch on 0.6 V transistor +1.2 V LED ratio of voltages = ratio of resistances so 1.8 / 3.0 = LDR / ( 2k4+LDR ) How it Works
Transcript of School of Physics and Astronomy How to make a dark detecting torch Chris Staddon – Senior...
School of Physics and Astronomy
How to make a dark detecting torchChris Staddon – Senior Experimental Officer &
Outreach Officer
Michael Forrester – Student Helper
Acknowledgements:
Modified from: www.evilmadscientist.com/article.php/nightlight
School of Physics and Astronomy
Potential Divider CircuitThe Potential (Voltage) is shared between the resistances
LDRLight - low resistanceDark - high resistance
School of Physics and Astronomy
The Mid-point needs 1.8 V
to switch on
0.6 V transistor +1.2 V LED
ratio of voltages
= ratio of resistances
so 1.8 / 3.0
= LDR / (2k4+LDR)
How it Works
School of Physics and Astronomy
Components • 1 x Prepared four-way terminal block (Choc block)
• 1 x Prepared battery clip
• 1 x LED (Light Emitting Diode – red)
• 1 x Transistor
• 1 x Resistor
• 2 x Prepared wires (red and black
Battery supplied separately
School of Physics and Astronomy
Now build your torch !
