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How to Make a Pulsating Switch

A switch is an electronic device that has two states. In the electrical "on" position, current is able to flow between the two electrodes, but in the electrically "off" position, there is no connection between the electrodes and current does not flow. In some circuits, it is necessary to produce pulsating switches, and these can be useful in the timing of electrical signals. Although slow, pulsating switches can be purchased, they can also be made with laboratory equipment.

Things You'll Need

DC power supply
Avalanche photodiode
Oscilloscope
Pulsed laser

Instructions

- 1
  Connect the positive terminal of the DC power supply to the positive terminal of the avalanche photodiode. Connect the negative terminal of the DC power supply to the negative terminal of the photodiode.
- 2
  Connect the output of the photodiode to one of the oscilloscope inputs. Oscilloscopes have two inputs, and these are labeled "A" and "B." Switch on the appropriate input by pressing the "A" or "B" button.
- 3
  Align the pulsed laser onto the active area of the avalanche photodiode. Switch on the DC power supply and set the voltage to the level specified by the photodiode specifications. If the laser is well-aligned, the avalanche photodiode should pulsate. Adjust the volts/division and time/division on the oscilloscope in order to visualize the signal.

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