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How to Control Servos From LED Power

Controlling a servo with Light Emitting Diode (LED) power involves using a light dependent switch to control a relay which is connected to the servo. The LED can be used to transmit switching information to the servo. This configuration separates the power system for the diode from the power system from the servo. In the world of robotics, this configuration can be used to address limited space and control issues depending on the size of the robot design.

Things You'll Need

Light dependant resistor
2 resistors
1 NPN transistor
1 power relay
12 volt battery

Instructions

- 1
  Connect one terminal of resistor 1, and the emitter terminal of the transistor to the negative terminal of the battery. Connect the second terminal of resistor 1 to the first terminal of resistor 2. Connect the second terminal of resistor 2 to the base terminal of the transistor. Connect one terminal of the LDR to the second terminal of Resistor 1. Next connect the collector terminal of the transistor to the negative terminal of the relay control. Connect the second terminal of the LDR, and the positive terminal of the relay control to the positive terminal of the battery.
- 2
  Shine LED light on the LDR, and the servo should activate. Remove the LED light and the servo should stop. This should be tested in a room with low light. Another way to set this up is to use an IR pair instead of the LDR and LED seperately.
- 3
  Adjusting the LED frequency will change the speed and power of the servo up to the switching limit of the relay. The LED "On" and "Off" frequency will generate a pulse width modulation signal at the servo. To switch at higher frequencies, the relay would have to be replaced by a power transistor.

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