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Controlling led strip with a uC

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24ariel3:
Hi,
I want to control a 12V 100mA led strip with a microcontroller, what is the best way to do it, darlington transistor, MOSFET or other way?

Thanks

macboy:
NPN transistor: emitter to ground, collector to the - side of the LED strip. LED strip + connected to 12 V supply +. Connect 1 kOhm resistor from micro output pin to NPN base pin. Output high = LED On.  12 V and micro (5 V?) must have their ground (-) connected together.   Use any 'jellybean' NPN like 2N2222, 2N3904, BC547, any of them can handle 100 mA when saturated.

24ariel3:
What about voltage drop over the npn, won't it make the led strip abit dimmer?
(The uC is 3.3V)

macboy:
Drop will be equal to VCE(sat) at 100 mA, which should be around 0.35 V.
If that is a problem, then you can replace the NPN with a small logic-level N-channel MOSFET, as long as the output voltage of the micro is higher than the turn-on threshold of the MOSFET, and keep the RDSON low (like < 1 ohm) to minimize voltage drop. Something like BSH103 would work. They cost more than a simple NPN, and its a SMT part.

24ariel3:
Mosfet sound good.

What about SSR or is it an overkill?
When to consider to use SSR?

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