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Trying to make a small momentary touch switch with CR1220 button cell battery...

deusx33

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...But I am an uneducated buffoon when it comes to EE.

I'm wanting to use a 3V lithium CR1220 button cell battery to power a cheapie 3V 5mW red laser diode rated for 20mA.

Here's my shopping list:

Lasers: https://www.amazon.com/gp/product/B0166JFLES/ref=ox_sc_act_title_2?smid=A28JUS3SJ1A0RV&th=1
Battery breakout: https://www.adafruit.com/product/1868
Battery: https://www.amazon.com/gp/product/B06XQ1C5TN/ref=ox_sc_act_title_1?smid=A3AKWD07R3ZO85&psc=1

I'd like the switch to be a momentary touch switch. I've seen this done with LEDs, and the shopping list is:
1k ohm resistor
BC 547 or BC 548 transistor
(example video:
)

I guess I'm trying to figure out if I can do something very much like that video, but with the laser instead of the LED? Would I need a different resistor?


Thanks folks. I'll post photos when it's all done!
 



Cyparagon

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A low power red laser diode is electrically very similar to 5mm GaAsP LEDs. A drop-in replacement would be fine as far as I can see.
 

deusx33

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Thank you. So just a 1k ohm resistor is OK? That laser diode is 20mA current at 3V
 

Cyparagon

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1k is acting as the current limiting resistor here. So it won't pass 20mA. More like 1/2mA by my calculations. This is enough to make the laser diode glow, but may not be enough to lase. It depends on what you're actually trying to do here. You may need to drop the resistor value to 22ohm or even lower to get full current.

This circuit is just designed to demonstrate the operation of the transistor, not the light emitter.
 

deusx33

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1k is acting as the current limiting resistor here. So it won't pass 20mA. More like 1/2mA by my calculations. This is enough to make the laser diode glow, but may not be enough to lase. It depends on what you're actually trying to do here. You may need to drop the resistor value to 22ohm or even lower to get full current.

This circuit is just designed to demonstrate the operation of the transistor, not the light emitter.
Thanks. Basically, I'm trying to have the diode lase as brightly as possible when the user bridges the contacts. By dropping the resistor value, do I run into an issue with the transistor I'm trying to use?
 




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