This is a blog mostly about tech by Damian Eads and Ed Rosten. We generally like open source and standards, Linux, C++, machine learning, computer vision and full stack hacking from discrete passives to distributed systems.
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Death and the penguin 
Hi there,
on the Nutrogena face mask – if I connect a triac between the pins on the board that fire the LEDs and connect the base of the triac a standard 555 timer circuit will this work? and are there any resistors I will need to add? I am just trying to recreate the basic functionality. Sorry I dropped out of Elec Eng in year 2 and can’t remember much circuit theory anymore!
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What’s the purpose of the 555? To time the 6 minutes? If so I’d recommend you use an Attiny or similar chip (you can program one from an arduino). It’s tricky to get long time periods accurate on a 555.
You don’t want a TRIAC though, you need a MOSFET or a BJT. Once triggered, a TRIAC will continue to conduct until something external cuts the current. So, once it’s on it won’t switch off again until you remove the battery. You won’t need a base resistor for the MOSFET if you use that.
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Thanks @edrosten. Sorry for delay in responding this got caught in junk. The timing does not have to be super accurate but thanks for the tip on the processor option. Sounds like MOSFET is the easiest option I will go with that.
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