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5v control of a 12V circuit

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Encuana

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I've been looking for a way to control 12V with a 5V source, to control some LED strips with an MCU. Obviously the MCU isn't powerful enough to directly control the strips, but there is a problem that outcasts relays. I want to use hyper blinking (my word for rapidly turning on and off) to control the brightness of the LED's. A relay simply wouldn't be fast enough, since I'm looking for "blinks" in terms of 50Hz to 1000Hz.
I've come op with two solutions myself, but I'd like to hear some opinions on my ideas.

First of, I want to use a simple converter that makes 12V out of 5V. I worry though that the component will have a delay too big that will mess up my blinking. Also, I worry that my power source (a USB charger so far) will be too weak once its voltage has been upped. The converters I've found so far have an output of about 165 mA, if I stay at prices fun enough for a little project like this. I wonder if this is enough to power, say, 150 LED's at a time.

The second solution I figured uses a transistor. This would allow me to use a full 12V 500mA source to power the LED's, like they should be, and shouldn't have any lag or delay. I just wonder a transistor used to control a 12V current can be controlled by a 5V signal, which would come from my MCU. If this works, I'd definitely prefer this option.

Hope you guys can give me some advice!
 

crutschow

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You can use a MOSFET transistor to control the LEDs from an external 12V source (such as a wall-wart).
Use a logic-level type N-MOSFET as a low-side switch (12V to LEDs to MOSFET drain with MOSFET source to common [ground]).
The MOSFET will turn on when the gate is at 5V and off when gate is at 0V (you may need a 10k resistor from gate to source to insure the gate is at 0V with no input).
 

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Encuana

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You can use a MOSFET transistor to control the LEDs from an external 12V source (such as a wall-wart).
Use a logic-level type N-MOSFET as a low-side switch (12V to LEDs to MOSFET drain with MOSFET source to common [ground]).
The MOSFET will turn on when the gate is at 5V and off when gate is at 0V (you may need a 10k resistor from gate to source to insure the gate is at 0V with no input).

Thanks for the tip!
I never heard of any MOSFET before so my search whas rather a self-teaching than a shop and buy, but in the end I got these MOSFET's. I put the source to the 12V ground, the drain to the LED's which then connect to the positive 12V source. I put a resistor between the gate and the source to pull the gate down, but I shortly tested without and that worked as well. I connected the gate to the positive 5V source but had to link the 5V and 12V grounds to make it work. In the end it does though, and I've got my LED's blinking at 500Hz, being nice and faded.

Thanks again!
 

crutschow

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Glad you got it working.

You learned one of the first rules of circuits.
There must always be a ground (common) path between all circuits (unless they are isolated such as with an opto coupler).
 

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