It's a TC4429 - makes a difference.
Well I got the numbers switched and then kept copying it.
You'll probably be terribly insulted, that I'm trashing your creation, and that's wholly not my intention, but I take particular issue with your grounding in addition to other aspects of your wiring and construction technique.
I'm not insulted. I am still very much a beginner. I know the circuit isn't pretty but I do make sure all the solder connections are very strong. I am grateful for any criticism.
1. I can't see any wires connected to the drain terminal of the mosfet in your photo. Was the load actually connected during your testing? If so, how was it connected (in particular, where was it connected to the ground line), and how much current does the load take?
There was no load during my most recent test.
In a previous test, with the first TC4429 that I burned, it was connected to the 8 amp lighting. The ground lead on the board was connected to the vehicle ground. I do not know exactly where the ground wires go inside the vehicle, but I do get good continuity between my point of connection and the lighting ground.
2. What is the value of the decoupling capacitor connected between the supply and ground pins of the TC4429?
1 μF, 50v.
3. What is the nature of the 12V power supply, and what is its off-load voltage? I'm wondering whether it produces a temporary voltage reversal during startup or shutdown, or alternatively that it produces a lot more than 12V when the load is not energised. Assuming you didn't short the output of the TC4429, there must be something nasty happening on the supply pins to cause it to fail, and this would likely cause any other driver chip to fail too. The Arduino is protected to some extent by the diode you put in series with the Vin pin.
My testing power supply is a switching transformer. It outputs a constant 11.9v, with or without load (load being the Arduino in this case, it is not powerful enough to power the lights). I do not have any reverse voltage protection between the power in and the TC4429, and after sleeping on it, I am thinking that may be the problem. It was working for a while with the 32KHz PWM. When I came back the next day and powered it up it had failed. So maybe it is something to do with power cycling.
In the vehicle, where the first TC4429 failed, the power is just a 13.8v lead.
Any switch can cause reverse transients can it not? I just didn't think of that before.
4. Why are you using a switching frequency as high as 32KHz? The higher the switching frequency, the more careful you need to be with circuit layout, to keep the inductance of critical paths low.
To eliminate a disturbing hum which these lights make when pulsed. I had the dimmer working before with an IPS6021 high-side switch (I really like them), but they have a maximum frequency of 1.5KHz. At that frequency the lights sound like a horde of mosquitoes.
I have calmed down since yesterday's bitter disappointment.I will order a couple more TC4429s (maybe I should get a reel!) and put reverse protection diodes on the voltage inputs.
To avoid such transients, add a decoupling capacitor between the -ve side of the LED and the source of the mosfet.
Between pins 1 and 8 of the TC4429, correct?
Any other suggestions would be very much appreciated. I really do not want to take any more chances, I have learned my lesson.
Thanks very much.