Keep letting the smoke out

I keep letting the smoke out on this. I am trying to control a 12v RGBW Led strip and I keep blowing my board.
Everything is on a common ground. I did not find any shorts.

I am wondering the emitter should actually go to 12v instead of ground or if it is because my regulator is putting out just a bit over 5v (5.04).

Anny suggestion would be helpful..

The attached picture is a simplified version with only I TIP120 but the other 3 are wired up in the say way
GND -> GND Regulator
5V -> Output Regulator
D8 - Base TIP120
D7 - Base TIP120
D8 - Base TIP120

D6 - Base TIP120

Base -> Wemos Pin
Collector -> LED
Emitter -> Ground
output -> 5v wemos
GND - Common Ground + 12vPower Supply Ground
Input -12v Power Supply

Reaf the first topics like "How to use this Form", "How to attache......".
Post a proper wiring diagram containing pin designations for the components.

What's burning-up? The TIP120? You may need a heatsink (and/or use a MOSFET driver which won't heat-up as much).

What's the current rating on the LED strip?

I am wondering the emitter should actually go to 12v instead of ground

Ground is correct.

Schematic, please. Not pictures.

No caps on regulator? Only 220Ω base resistor, how much current is drawn from 3.3V Wemos pin?

What type is that regulator?

I have burned a Wemos this way. I was using ams1117-3.3, which I believed could take 12V input, but blew immediately when connected. When it blew, it allowed 12V to pass thru to the output! This of course immediately damaged the Wemos, by which I mean the ESP chip itself, the on-board regulator was not being used. I suspect the ams1117 was a poor quality copy, not a genuine device.

I would recommend using a DC-DC "buck" converter instead of a regulator. You can adjust these to 3.3V and power the ESP chip directly, although my story might make that sound like a bad idea.

Apologies for the picture instead of a schematic.

I have now attached the schematic. I am trying to run a RGB LED strip, I have not actually attached the LEDs yet. I only (had) the example blink sketch loaded. It burns out the wemos as 0o0soon as I connect it

Welcome to the forum.
Have you looked at the datasheet for the LM7805? It requires some capacitors around it to perform correctly.
What are you using as your 12V power supply?

Can you please post a picture of your project so we can see your component layout?

So if you just connect your Wemos to the 5V, does smoke come out, are the TIP120s in circuit?
Have you built your circuit on protoboard or strip/vero board?

Thanks.. Tom... :slight_smile:

I think the first thing to check, before you connect the wemos, is that you are getting 5V from the regulator. If you don't have a multimeter, get a multimeter! As mentioned above, you need 2 caps connected to the L7805 for stable operation.

Is it definitely L7805, not 78L05?

As Paul said, don't use the 7805- it is 1980 technology and things have only gotten better. If you MUST use a linear regulator, you MUST use the appropriate bypass capacitors on it, otherwise it won't regulate low current outputs.

If you don't have a DMM, you can probably get one from Amazon tomorrow.

Remove the regulator from the circuit and power the Wemos through a Micro USB power source. If it works as expected, then your problem is the 7805.

BTW- do not power the Wemos from an external 5V supply AND the Micro USB at the same time. If you plan to make a PCB, then put a jumper header in the 5V line to the Wemos.


I would also add a 10uF electrolytic or tantalum capacitor on the output. This would reduce any ripple that might be present on the input side.


thanks for all the input, it sounding to me that the issue is probably the regulator. I am going to swap it out for a buck converter and see what happens.

Added a picture as well. Would like to know if there is anything else that could be wrong. I only have 2 more wemos boards to try.

I understand (now) that i may be using the regulator not in spec but it seems to be putting out 5.04v. Could not using capacitors mention potentially cause the issue?

Just a comment... -12 is completely different from 0V
I don’t think it’s what you meant, but technology communications can be very unforgiving.

Thanks for the pic, can we have a pic of the other side please?

I think you had better go over your solder joints, what solder are you using?

Have you got a header socket under that Wemos, or have you soldered the PCB to the protoPCB?

Thanks.. Tom... :slight_smile:


Yes there is a header socket under the wemos so that I can remove it when I need to change the code.

Added picture of the under side -

*noted the ground instead of -12v.

Thanks for the pic.
Can I suggest;

  • You start with a new board.
  • Gently clean the board with an abrasive cleaner like JIFF or at least scrub it with dishwashing liquid.
  • Rinse and dry it.
  • Use Isopropyl or in a pinch, Methylated Spirits to make sure it is clean.
  • Use a lead based solder preferably with rosin core.
  • Use an iron with more heat.
  • Clean the board after you have finished soldering to check for adjacent conductor shorts.

What iron are you using?

Tom... :slight_smile:

I would actually try to clean that board first with alcohol. Solder flux is electrically conductive and this doesn't really spark confidence.

My approach is a bit different.

buy a power supply. they make low cost ones that area easy to use.

or, better yet, run the Wemos from a phone charger. there is nothing wrong in testing things as you go along, get them to work, then modify, work around, replace or eliminate them.
use a phone charger, get the system to work, then move towards working off a single power supply.

post a link to the LED. so many other issues that the LED is not even discussed. but hate to have part of this figured only to blow out another part.

I will rebuild and post back in a day or so.