How to Use Diodes to Drop Voltage
- 1). Set the multimeter for voltage reading and measure the resting output voltage of the power supply. Compare this voltage to the desired circuit voltage. For example, if the supply outputs 12.7 volts and the circuit is rated 9 volts, the difference is 3.7 volts.
- 2). Set the multimeter for diode check and measure the forward drop of the diodes. Most silicon diodes will measure approximately .7 volt.
- 3). Divide the desired voltage drop by the measured forward drop per diode. Round up to the next whole number. In the example given, 3.7 volts divided by .7 volt equals 5.29; rounded up, it's 6. This number indicates how many diodes to connect to the circuit.
- 4). Connect the calculated number of diodes in series and forward biased. Solder all connections.
- 5). Connect the diode string in series forward biased between the power supply and the circuit.
