For a guess, lead inductance caused a switch-off spike greater than the rated 65V at the R pins and the power supply didn't react fast enough to catch that. If that spike caused breakdown within the IC then excess current flowed where it shouldn't and cooked the IC.
I reckon when the DMM was disconnected then the voltage present could have been anything upto mains voltage depending on what the rest of the circuit is connected to.
The lead inductance is a possibility, not a probability.
Another possibility is that sudden reduction of the load from 3.2A confused the stabilisation circuitry in the power supply, so that there was overshoot beyond 65V. Do you know what the transient response of the supply is like?
because of ground loops and the cotek having no reference to AGND. you dont know how high the voltage could be floating on the +48v in respect to AGND and your MCU power suppplyvne147 said:Why would the voltage have been as high a mains voltage? As far as what the rest of the circuit was connected to, there's a microcontroller, some I/O peripherals, and few other bits and pieces that were bypassed via relays at the time, but the 2Ω resistor was the only load connected to the Cotek supply.
Thanks.
because of ground loops and the cotek having no reference to AGND. you dont know how high the voltage could be floating on the +48v in respect to AGND and your MCU power suppply
A TVS on your equipment would go some way to protecting it.
Connection looks fine. The 4951 has a rated clamping voltage of 70.1 (i.e above the magic 65V), but a breakdown voltage of 51.05. I'm not sure how to interpret those figures to say if that would be suitable in your application. Someone with experience of TVS use will hopefully chime in. What is the maximum supply voltage your circuit should see?
Good suggestion. If you do that, set up the same voltage and current as before, remove the IC to stop it being fried, then disconnect your meter lead, you could monitor/record the supply transient response with a 'scope.The way forward would seem to be to measure what your power supply does when you connect and disconnect the resistor.
Then the roof of the building would cave in or you would be struck by lightning. I had the former happen to me.Good suggestion. If you do that, set up the same voltage and current as before, remove the IC to stop it being fried, then disconnect your meter lead, you could monitor/record the supply transient response with a 'scope.
Depends if you believe in Chaos Theory or not. If a butterfly flapping its wings in Africa can cause a hurricane in the Bahamas, then surely the lights failing in response to changing the wheel would not be surprising?You change an auto wheel and then the lights fail and there is no relationship.
Depends if you believe in Chaos Theory or not. If a butterfly flapping its wings in Africa can cause a hurricane in the Bahamas, then surely the lights failing in response to changing the wheel would not be surprising?.
(1) The chip was faulty
(2) Something got shorted while you were disconnecting
(3) Your circuit is in fact not what you think it is.
The way forward would seem to be to measure what your power supply does when you connect and disconnect the resistor.
Good suggestion. If you do that, set up the same voltage and current as before, remove the IC to stop it being fried, then disconnect your meter lead, you could monitor/record the supply transient response with a 'scope.
perhaps post an image of your circuit for us to have a look at!
Then the roof of the building would cave in or you would be struck by lightning.
Faults are God's way of showing who is in charge. It always amazes me how often you get two totally unrelated faults at the same time. You change an auto wheel and then the lights fail and there is no relationship.
Depends if you believe in Chaos Theory or not. If a butterfly flapping its wings in Africa can cause a hurricane in the Bahamas, then surely the lights failing in response to changing the wheel would not be surprising?.
Stranger things have happened at sea... and in the lab.Possibly. Although I only had 2 to start with, more are on the way. For the first one to be faulty, that seems quite unlucky from a statistical standpoint. It certainly would be consistent with other experiences in my life though.
Try connecting a one Ohm resistor in series with the PSU output and then connect a large electrolytic capacitor from the free end of the resistor to 0V. Then use the capacitor as your PSU.Unfortunately, I don't have suitable equipment at my disposal to perform these tests
That would be fine by meHowever, if you and/or Alec are willing to invest a little time looking as it, I'll gladly PM it to you.
If it made it to Facebook, some people might confuse it for news and elect it president.
A whole roof section blew off in a gale. I was picking shards of glass and tile out of equipment and documents for months after that.I'm sorry you had a roof fall on of your head.
Electronics is not natural. It is the gods trying to tell you something.I require precious few reminders to show me I'm not in charge of anything, let alone what an electron decides it wants to do.
Yes, visualizing things is useful. I always liken electrons to water.In my head, I contemplate nearly all principles of electric theory by imagining hand drawn diagrams featuring a cartoon electron named Sparky. Translation: I know I know nothing.
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