FET not behaving as expected

[HappyOldtimer]

Hi all,

I'm starting to be really frustrated with the situation here, as I cannot explain it so far. Still grateful for the help here though! Let me explain:

@AnalysIR:
Yes, I measured everything from the control pin to the power supply GND. All ground connections were coupled with the power supply GND.
I've also tried the 10K resistor between Gate and Source of the FET, and it doesn't change anything.
I've checked the resistance of the ground connections to the power supply GND: every connection is 0.1 Ohm

So I decided to take a couple of steps back and try to simplify the equation:
I've disconnected everything in terms of switches, motors and the pump, and only left the solenoid connected to the TinyG with a 3v relay instead of the FET to see what is going on. Result:
- the light on the relay shows that there is a voltage that is not stable (its changing in brightness)
- the SpinDir light comes on on the TinyG, but after a restart it is off
- The TinyG is giving multiple popups in the software with a message about "timeouts at commands"
- the TinyG resets itself when I switch the pump on with the 3v relay

I've tracked down one possibly bad connection to the solenoid on the ground wire. Repaired that, and tried again. Result:
- still 0.6 volts on the control pin for the solenoid when starting up, so with solenoid turned off
- SpinDir light keeps flashing even if nothing is connected
- SpinDir light goes off after several resets, power downs and reconnects with software
- When turning on the solenoid from software the TinyG goes into error state, and the relay briefly switches on and off again
- the TinyG keeps giving this error randomly: timeout on command {sr:n}
- the tinyG goes into error state or says that a limit switch has been hit when I only try to measure the voltage with a multimeter and do nothing else or when I turn on the solenoid in software

I'm a bit at a loss here... Its like I try and find out whats going on only to have everything change on me into other errors, as it indeed seems less and less likely that the FETs are bad
What am I doing wrong here?? At this point, the entire control board seems unstable with only the solenoid, power supply and usb cable connected to it...

[AnalysIR]

I'm a bit at a loss here...

....me too



sorry...only other suggestion is to take lots of good photos and send them to Juha

[HappyOldtimer]

@AnalysIR: at least that should mean that I'm not completely crazy... thats a plus
And I get your thought of taking photo's, I'll contact Juha I think and see if we can work through photo's and/or maybe a video call or something.

I would just love to hear what I've done wrong, you know? And get the LP working.

[infinitemach]

It might be useful to have a description and/or pictures of your electrical assembly - type of connectors, wire gauges, power supply setup, USB connection, etc. The fact you're getting intermittent errors and strange behavior from somewhat random sources is really suspicious.

Also, on my build I intentionally separated the GND from the TinyG and the PSU. They are not connected. I only use the PSU Ground (earth mains) to connect the wire shielding.

[JuKu]

The intermittent errors on TinyG are expected if trying to drive a relay. TinyG can’t give enough current from an output pin for a relay. When it tries, the 3v power supply dips and causes a reset.

[pumpguy]

I had a similar problem when building my LitePlacer, when the vacuum was switch on in software it would run normally, when switched off it still ran, and as if it was getting lower voltage. I replaced the FET and everything worked normally. I never figured out how the FET became damaged.

infinitemach thanks, I had the same problem and your answer helped me set it up.

[HappyOldtimer]

Hi All,

It has been quite a while, but other projects/work interfered, and I've done extensive testing.
My setup seems to be rather stable, up to the point where I'm fiddling with panelizing my boards.

Just a short recap:
- I've had a replacement TinyG and replacement FETs from Juha that I'm using now
- I've tried putting the TinyG behind a UPS: no result
- In the end I've put a netfilter between the power from the wall and the TinyG, and that solved most of my issues.

The one thing that remains is that when I switch the vacuum pump on, the TinyG would sometimes reset. And now, after more testing, it just resets straight away every time I turn on the vacuum pump in software.
I'm kinda stumped, as it was only the occasional reset and after that it seemed to work before. So I'm unsure as to what has changed. I think I'll just go for a workaround and just run the pump straight off of the power, outside of the software. I've spent so many hours troubleshooting, and I'm kinda done with it. I want to use the PnP, not fiddle with it.

So there you have it: the result and one remaining issue

Thanks all for the help!!
Paul

[infinitemach]

>>The one thing that remains is that when I switch the vacuum pump on, the TinyG would sometimes reset. And now, after more testing, it just resets straight away every time I turn on the vacuum pump in software.

Can you share pictures of your wiring? Did you use shielded wiring? All I can think is that there is some serious induction going on when the pump is turned on.