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I have created a circuit for controlling my 12V RGB LED strip using 3.3V microcontroler (ESP8266). I have used IRLZ44N N-MOSFETs to regulate the colors. The circuit worked great, when the microcontroller was powered by external power supply, but when I added a voltage regulator (LF33CD to drop 12V to 3V) and disconnected the 3.3V source, the MOSFETs started to act strange. The LEDs stays on, and also, the ESP8266 won't connect to WiFi.

//EDIT: I have updated the schematics, I have made the schematic wrong

Schematic with the external PS (this one works) Schematic with the external PS (this one works) Schematic with 3.3V regulator Schematic with 3.3V regulator

I am new to electronics, I was mostly making software before, so please excuse me if I made some stupid mistake.

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    \$\begingroup\$ Your schematic is wrong, you have the LEDs connected to the gates of the FETs, the sources connected to the GPIOs, and the drains grounded. All wrong. You also have no current limiting for the LEDs. If the first circuit worked it's not hooked up per your schematic. You will need resistors in series with your LEDs to limit the current. \$\endgroup\$
    – John D
    Feb 1, 2017 at 20:23
  • \$\begingroup\$ @JohnD You were right, the schematics were wrong. \$\endgroup\$
    – jsonode
    Feb 1, 2017 at 20:51
  • \$\begingroup\$ take great care that the high LED current return path goes directly to power source gnd and does not share the 3v3V return path to avoid ground noise. Use separate short low inductance grounds to sources as well for all loads, not series chain as shown. \$\endgroup\$
    – Tony Stewart EE75
    Feb 1, 2017 at 21:01
  • \$\begingroup\$ The schematics look OK now, except you still need resistors in series with each LED to limit the current, unless your LED strip has built in resistors or current sources. \$\endgroup\$
    – John D
    Feb 1, 2017 at 22:00

2 Answers 2

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I may be wrong, but IMHO 78XX needs capacitors to work correctly and as it is switching, it would generate noise until filtered out after. And the ESP also wants capacitors on power/gnd to have no noise and enought reserve in power for short peaks (especially when connecting/transmitting). Maybe your 3V3 source is stabilized enought for ESP to work somehow, but the 78XX so near produce so much noise, that ESP does not work (at all/reliably)

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First, the gate of the N-MOSFETs needs to be connected to your GPIO. I am assuming the MOSFETs are simply used as switches for +12V power supply. You have the source connected to the GPIO pin which does not make any sense to me.

Then you can either connect the LEDs as a high side configuration or low side configuration. Personally, I would connect the MOSFET drain to the 12V rail and the MOSFET source to the LEDs. You will also need a resistor to limit the current going through your LEDs. Look for your diode forward voltage for each LEDs and make calculations.

Make all those changes and if it does not work, let us know. But your MOSFETs are definitely not connected properly.

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  • \$\begingroup\$ I have updated the schematics. I have made the schematic wrong, now it should be right. \$\endgroup\$
    – jsonode
    Feb 1, 2017 at 20:49
  • \$\begingroup\$ Add resistors to your LEDs. What current do you need across your LEDs? \$\endgroup\$
    – 12Lappie
    Feb 1, 2017 at 21:45

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