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TOPIC: Wiring an illuminated AV switch?

Wiring an illuminated AV switch? 1 week 6 days ago #85800

  • axelstriker
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Hello all,

I would like to use an illuminated switch on my upcoming (first) build, with the LED only on when the saber is on. I'm using a 3.7V 18650 battery, NBv4 soundboard, NECree RGB LED, and this red AV switch from TCSS:

Forward voltage 2.0V, runs at 20mA.

I am trying to calculate the resistor that I know I need, but I have no background in electronics (I have been teaching myself a LOT of basic material preparing for this build), so I want to check with people who KNOW what they're doing. I know that the resistor will be dependent on the amount of power available at that point in the circuit, but I also can't find a decent tutorial on where to wire the thing; most tutorials use nonilluminated switches, or don't use resistors, like the TCSS one on youtube.

Any advice I can get on wiring this switch and choosing the right resistor would be much appreciated!
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Wiring an illuminated AV switch? 6 days 9 hours ago #86130

  • EJT
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You could just buy the DynaOhm variable resistor from TCSS for less than three bucks, and put it inline with the power lead for the LED. Then you don't have to think about it.

But to answer your question, if you are starting with 3.7V, that voltage is divided between the LED (the forward voltage) and the resistor. Since you know you will have a 2V drop across your LED, that means you need to plan to have a 1.7V drop across your resistor (3.7 - 2.0 = 1.7). The voltage across a resistor is equal to the current times the resistance, or V = IR (Ohm's Law). Since you know you want 1.7V across your resistor, and since you know you want the current through the LED (and the resistor) to be 20mA (which is the same as 0.020 A), this means your V = IR equation is 1.7V = 0.020A * R. Solving for R, you have R = 1.7V / 0.020A = 85 ohms.

I hope that helps.
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Wiring an illuminated AV switch? 6 days 5 hours ago #86151

  • Jas-Ot
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Dyna ohm will make it dimmer than if you use a proper resistor.

Close counts in resistors, you may not always find exactly the right resistor that you calculate you need. Most electronics can take a range of voltage safely. That led in the switch might be rated 2v, but it may operate perfectly fine as 2.2v.

If you can't the the perfect resistor, use the closest one you can find.

In this case an 82ohm 1/4watt will be what you want.
Last Edit: 6 days 5 hours ago by Jas-Ot.
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