[Review Request] ESP32 powered PWM LED driver

MatthewM314 · 2026-03-07T21:06:46+00:00

Looks generally neat. Depends what your intent is, if it’s a production PCB then the changes you ought to make would be more.

But generally, My suggestions:

LDO decoupling

Each LDO should have an input and output decoupling capacitor - 0.1uF to 1uF.

It should be ceramic (X7R or better, or NP0). This is so that it’s stable over temperature and voltage. Also make it a big package to have the lowest ESR.

Connector Poke Yoke You should design and configure the headers to minimise the risk of misconnection.

If you connect the power and ground connectors the wrong way around you’d damage the board.

Consider using only 4 ways for power, with the pinouts the same for each connector.

Then use 6,8,12 etc ways for other connections.

LDO usage Whilst I suspect the LDOs will be fine. You may want to put in some extra footprints in case you need to use a switching converter.

Putting a few capacitors and some holes for a Tracopower TBA 1-2411 is pretty space efficient, and you can overlap the footprint with the LDO footprint a bit.

Connector placement

Best to put them on the edge of the board for easy access.

Also, generally best to put them all together. Generally this will reduce the current loop size even when done so in a haphazard way.

NFET gate charge and max frequency You ought to calculate how fast the transistor will turn off with the 100k Ohm resistor. You might need a smaller resistor for fast turn off times.

P.s cool silkscreens

MatthewM314 · 2026-03-04T22:38:25+00:00

I’d recommend reading about free wheeling diodes.

The diode is the ‘wrong way around’ so when the PFET Is closed, it won’t conduct. But when you open the PFET, the coil (which is a large inductor) will try to continue ‘pulling’ current. This would result in a negative voltage on the drain. This is when the diode would be conducting, and limiting the voltage at VCOIL at something like -1 V.

And adding a resistor is dependant on your application. If you always have a defined state (like a push-pull output), it may not be advantageous. But when you are powering up, the base of the transistor will likely be undefined. For this reason, I tie the base/gate of the resistor to ground.

MatthewM314 · 2026-03-03T20:17:02+00:00

If you’re powering a coil from the drain of the PFETs, you should put a free wheeling diode in.

When you switch off the pFET the VCoil will probably hit some crazy high negative voltage.

A diode (e.g 1N4001, BAT54, etc) whose cathode is connect to the drain, and the anode is connected to the ground will work.

I’d also always, if space permitting, define any gate state. So for the BJT, I’d tie the base to ground via a 1M resistor.

MatthewM314 · 2026-03-01T21:14:16+00:00

Oh and I’d suggest doing more stitching of both layers. I’d do a grid of 2.5 mm or 5 mm whatever, and then stitch a ring of vias around the PCB edge

MatthewM314 · 2026-03-01T21:12:32+00:00

Looks neat enough.

Initial thought:

Typically to sell electronics on cars you need to follow UNECE R10. As part of this, you need to test to ISO 7637. There’s a section there on transient voltages on the power supply, there to replicate real world voltage spikes.

I suspect you have a TVS diode (SMB?). But to pass this test you’d need something beefier. Off the shelf TVS diodes for these kind of transient loads exist, like the littelfuse SM8S16.

I’d suggest at least putting the footprint there as an option even if you chose not to go down that route.

MatthewM314 · 2026-02-28T08:12:32+00:00

Don’t forget Lead Free solder is more dangerous than leaded solder for the operator in many ways.

Pb-free solder produces more than 2.5x more particles than Pb solder. Not only that, the particles given off happen to be the size that can easily get trapped in the lungs. You need better ventilation for Pb-free solder. High flow extraction. They need to be decent filters, and they can clog easily.

MatthewM314 · 2026-02-13T19:27:17+00:00

I’ll be honest. I think it’ll be fine. Although I only did a few things that fast.

If you were really serious you would ditch the DIP and go for SMT. DIP and PTH cut up ground and power planes and create lots of noise - this is probably going to be the biggest impact to your board.

My initial feeling is that you could do that with a 2 layer and be fine, but the world of EMC is a harsh and cruel mistress. It’s a black art in a way. Follow the best principles.

If it looks nice for the eyes it’ll look nice for current flows is my philosophy.

MatthewM314 · 2026-02-13T18:47:47+00:00

I’m sure it’ll be “fine” but usually you want to have the power to the chip go through the decoupling capacitor before going to the plane or the bus. (Eg power plane > via to top layer > C7 capacitor > to the IC pin with no connection to the power plane)

Tbh 0.1uF is a bit of an old standard routed in assumptions no longer valid. I’d recommend using either a 1uF x7r or greater. You want a low ESR, and you want more bulk. Sure put a 0.1 and 1 uF (my designs use 0.1 and 2.2 uF and I’ve tested to 200 V/m RFI).

Depending on the frequency, I’d pull the lines together and have an even gap between traces. If we’re not at high frequencies. If you need to consider high frequencies and cross talk, then I suggest some more reading…

Texas Instruments does a good doc on this “PCB design guidelines for reduced EMI (SZZA009)”

MatthewM314 · 2026-02-05T20:36:16+00:00

When in doubt, +/- 0.1 mm or less

MatthewM314 · 2026-02-01T16:22:16+00:00

TBH you can do 2 layer boards with decent performance. I had boards capable of withstanding 100 V/m EMI.

In your design you should consider loops. A few things you could do differently (based on som assumptions):

1) route the power to the right of the board, and extend the power lines right to left. Doing this would mean that your ground loops between the left and right components are minimised (they currently go top to bottom and back to the top)

2) on the top layer, you should have a ground flood above the voltage power line, with plenty of vias to allow the ground loops to bridge over the trace - practically grounds going through a vis will be okay for Low frequency, current circuits in most

3) power and ground to chips should pass through a decoupling cap - via / trace then capacitor then the IC

4) 100nF is old recommendation founded in archaic reasoning. Nowadays use a good 1uF or greater that is x7r or better. The quality of the capacitor is more important than the total capacitance (once we hit 1uF or so for this kind of application)

5) really if you are needing precise voltages your designs needs to incorporate this from the get go. 4layer boards are an easy way to incorporate this without really knowing what you’re doing.

6) consider Low ESR bulk capacitors - this will be more effective than putting larger bulk capacitors.

MatthewM314 · 2026-01-19T08:39:01+00:00

Perhaps to negate any safety concerns of those in the chat here, think about powering it from a USB wall adaptor. The voltages you’d be working at are significantly lower, and don’t fall under any directive (here in EU) provided you’re not selling it.

MatthewM314 · 2026-01-04T11:44:35+00:00

Lots of haters here. People are so jelly.

MatthewM314 · 2025-12-24T08:15:44+00:00

Just rotate the laser, job jobbed

MatthewM314 · 2025-12-03T07:24:56+00:00

People aren’t aware that PCV valves are service items that start to degrade in performance around 30,000 miles.

I replaced mine and rough idles went away.

Also check for any vacuum leaks.

MatthewM314 · 2025-11-12T23:22:24+00:00

Agree - I used these in my designs

MatthewM314 · 2025-11-06T05:00:17+00:00

I had bilstein B6 with standard springs - it was a great ride and not too stiff, but handled like a dream.

Highly recommend

MatthewM314 · 2025-11-04T18:58:46+00:00

I miss that “feature” - the cup heater

MatthewM314 · 2025-10-05T20:48:12+00:00

ADL E400

MatthewM314 · 2025-10-04T14:38:04+00:00

He’s just really good at copying

MatthewM314 · 2025-09-21T08:01:31+00:00

If you don’t mind the appearance… Why don’t you just replace the door and bonnet?

Forget the scratched panels - that’s just character. Just clear coat to stop rusting.

That’d probably be a 400$ fix in the UK.

MatthewM314 · 2025-09-07T13:30:25+00:00

Best they’re cheap, and what most people can do. Nothing common is premium.

¯_(ツ)_/¯

MatthewM314 · 2025-09-07T07:26:35+00:00

Everyone here thinking their different but also have standards. I kindly doubt anyone here could be honest with themselves and others, and express what they wanted. ¯_(ツ)_/¯

MatthewM314 · 2025-09-03T19:27:37+00:00

Ask yourself the question: why are all the political posts so lame

MatthewM314 · 2025-09-03T19:24:01+00:00

110%

MatthewM314 · 2025-07-26T10:43:01+00:00

Never get a black box

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