The Optoisolator is a great way to keep your circuit protected from unwanted surges or noises. This component is isolated on each side so you can use different voltages without damaging your circuit. Optoisolators use light to transfer signals with an LED (usually IR) and a photodiode. There are several types to choose from such as an SCR ( AC voltage), TRIAC ( AC voltage) , Darlington ( DC voltage ), and Transistor (DC voltage) . I will be using a Transistor type to demonstrate a simple circuit .


I used the 1.5 volt battery for the 4N35 input because that was within the max range of the forward voltage and was enough for the tactile switch to be turned on as well. The 300 ohm resistor had to be used to offset the current that goes into the 4N35 for the internal LED. The 9 volt battery was chosen for the red LED because it is a blinking one and it actually has a voltage range of 3.5 to 14 volts. Since it’s a blinking LED it has an internal resistor. You can use different voltages to effect the blinking rate along with the resistance if you wanted specific timing.


The parts :

  1. BKGS-830-ND - Breadboard

    2. 438-1049-ND - Jumper Pack

    3. 450-1650-ND - Tactile Switch

    4. CF14JT300RCT-ND- 300 OHM Resistor

    5. 4N35-ND - Optoisolator

    6.P646-ND - 1.5 Volt Battery AA

    7. 36-2461-ND - AA Battery Holder

    8. 1497-1453-ND - Red LED

    9.P687-ND - 9 Volt Battery

    10.BH9VW - ND - 9 Volt Battery Holder.
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