IN-8-2 Modular Rev 3 build - feedback and questions

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1 year 3 months ago #9729 by Ty_Eeberfest
It would be interesting to know a couple things:

- While it's making the high pitched noise, how much current is being drawn from the external power supply?

- Is Vcc really +5v or is it off spec?

If the 100uH inductor was shorted internally something like you describe might happen but I'm not real sure how the inductor would just suddenly develop a short. Capacitor C1 is also work checking.

I measured HVD at 32.5KHz on my Modular.

Look into it later when the dust is clearing off the crater.

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1 year 3 months ago #9732 by Ian
Hmm, is this a new controller? Did you set the fuses to use the 16MHz external clock? If not, it will be using the internal RC clock, and that won't provide the "pump" to get the high voltage up high enough.

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1 year 3 months ago #9734 by Phil_Mod3
Thanks for the input Ty & Ian

-Controller: The current controller ran the clock for a few weeks. Additionally, I still have the original µC that I got from your kit, which I did not modify. The problem is almost the same, old or new controller. I think fuses are OK.

-Vcc is 5 V stable, as long as the external power supply does not switch off. When I remove the µC (no HV generation) and switch on, a stable 5V results (also the external supply doesnt switch off in this mode).

-Any ideas about how to measure the current from the external power supply in the least "invasive" way? I don't have an additional barrel plug, don't want to cut any cords.

More things:
-My multimeter thinks the HV drive runs with ~9kHz (but I am unsure if this is a result of a long duty cycle which is provided as HV target is not reached, doesn't get above 160V)
-What I did before the problem started: I soldered the ISCP header to the board. However, the clock ran fine until about 48h later.
-Currently I think that there is a problem with the crystal oscillator and the hot inductor/mosfet and to high power draw are only results of a long duty cycle?!

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1 year 3 months ago #9737 by Ty_Eeberfest
I guess you don't have a scope? Not sure how crazy the duty cycle needs to be to confuse a mutlimeter's freq counter. It's certainly a consideration though, especially since the multimeter may actually be expecting sine wave AC.

I wonder what HVS signal (Controller Pin 23) is doing while the HV is squealing. Incorrect feedback voltage is yet another thing that might make the HV generator run wild. I read approx. 2.2VDC at Pin 23 on mine - approx. because it wanders around +/- 0.1V as the display digits change.

I don't think it's real important to measure the input current. You've pretty well proven that excessive current is being drawn and that the HV generator is what is drawing it. I got a big bag full of barrel connectors, males and females, with screw terminals (eBay form China) and just use those to make up a current testing "fixture" when needed.

Look into it later when the dust is clearing off the crater.
The following user(s) said Thank You: Phil_Mod3

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1 year 3 months ago #9738 by Phil_Mod3
Unfortunately no scope, correct. My multimeter (fluke) should be able to measure square-wave signals, if set correct (which I hopefully did).
HVS gives me ~1.9V when switched on. This should be OK, given that the HV is ~158V.
I tend towards the oscillator crystal or one of the capacitors driving it. What do you think?

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1 year 3 months ago #9739 by Ty_Eeberfest
Well... I see where you are going with the crystal. If the crystal oscillator is running at too low a frequency the HVD PWM frequency will be low, causing the HV to be too low, causing the controller to increase the PWM on time to the point the inductor is passing massive current. Makes sense.

I'm really not sure what to say. Without some scope readings I'm kind of stuck. Let's see what Ian has to say before doing anything.

Look into it later when the dust is clearing off the crater.

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