Project 45: Motion Detector
This project involves building a motion detector which senses movement by monitoring the amount of light entering the Cadmium Sulfide Cell.
The component connections are as follows.
1-13-40, 3-24, 14-105, 23-106, 25-45-107, 42-43
The connection from 1 to 13 to 40 connects the left terminal of LED 1, to the left terminal of the Cds cell, to the positive terminal of a battery with a long yellow wire and a short white wire.
The connection between 3 and 24 connects the right terminal of LED 1, to the collector terminal of of the Q3 NPN transistor with a small white wire.
The connection between 14 and 105 connects the right terminal of the Cds cell, to the left terminal of the control with a medium sized red wire.
The connection between 23 and 106 connects the base terminal of the Cds cell, to the middle terminal of the control with a medium sized blue wire.
The connection from 25 to 45 to 107 connects the emitter terminal of the Q3 NPN transistor, to the negative terminal of a battery, to the right terminal of the control with a medium length blue wire and a short white wire.
And finally the connection between 42 and 43 connects the negative terminal of a battery, to a positive terminal of a battery with a small white wire.
Once all the connections have been made upon turning the control counterclockwise, the LED gradually turns on. By setting the control to around 7 and waving your hand in front of the Cds Cell, the light dims as the Cds is covered partially, and brightens as you move your hand away.
To see the motion detector in action please click here
In this circuit The transistor acts as a switch, with the base current supplied through the Cadmium sulfide cell. LED 1 is connected to the collector in the transistor and lights if the transistor is on and goes out if the transistor is off.
Light enters the cell, the base current flows into the transistor turning it on, and LED 1 illuminates. If no light reaches the transistor there is no base current and the transistor is off so LED 1 does not light.
This was one of my favorite projects in my making process portfolio because the sensor reacted to the environment around it, and I thought that was very interesting. This project has more similarities to the electronic candle in terms of components, and was fairly simple to create.
Sources: Maxitronix Electronic Lab Owners Manual