(More) Power Problems - Inrush Current too high

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infinitLoop
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(More) Power Problems - Inrush Current too high

Post by infinitLoop » Sun Mar 24, 2019 6:39 pm

I was trying to re-do the power on my 3a+ build, and now I'm stuck with this problem where it won't power up when powered through the power supply, but everything will power up if plugged into the pi directly, and will keep running on the power supply when you unplug the pi power.

I had been using Helder's Retro PSU successfully with it, and was switching to a different one while re-doing and adjusting the build, but ran into this boot-up problem. I thought that the new PSU couldn't handle the current, so I switched back to using the Helder one, and still can't get it to power up from the power supply. Once I prime it, or whatever, with 5v from the pi power, it works though. I had 2 Helder PSUs and tried both, with the same issue.

I'm using the Tinkerboy v3 for everything except the screen, which is a BW model with a 5v mod. The screen and pi power through that board. I also have some button leds and a fan that are powered at the 5v from the power supply, in a strip that the aio board also connected to, so everything is basically sharing the 5v, and multimeter tests all look good. The leds have a switch to turn them off, and i have tried disconnecting the fan, but even having both those out of the picture, the pi still will not start from the PSU. When I disconnect the board/pi/screen and just use the PSU to power the leds and fan, they work, and those also work fine when i do the "5v prime" from the pi.

i'll try and describe it simply:

battery -> PSU -> fan
-------------------> switch -> LEDs
-------------------> Tinkeryboy v3 -> Pi 3a+
----------------------------------------> Screen
----------------------------------------> Ext USB port

switch for on/off goes to "en" on the PSU for the Helder setup, and I also have the ADC connected, but I tried without it as well just to check (no difference)

any ideas or anything I could look into to fix it? I thought a resistor/capacitor combo to delay the boot of the pi might help, but it didn't seem to (although it's likely I just didn't do it the right way if that is something that might work).

i can try and post pictures, but a lot of stuff is too obscured to be much help. i could show the power supply wiring at least, but there's not really a lot to that (even the basic, battery in, 5v out just to the board didn't work). like i said, though, it works fine when starting at the pi, so I think it's current/draw related, not the wiring, but I definitely could be wrong. I'm just not sure what I can do to fix it.

thanks

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 12:31 pm

So, from what I'm experiencing, it seems like my issue is the initial / inrush current, and I've been trying to wrap my head around that in research. My initial resistor, capacitor attempt didn't help. It seems like a common approach is introducing a mosfet gate, but I can't quite figure out that solution or what values I would need to utilize where and how.

I'm wondering if anyone has used an Inrush Current Limiter? I'm thinking of maybe trying one of these at 2 or 2.5ohm (I used https://www.ametherm.com/inrush-current/calculators to get about that value with the retropsu's rated output ). It looks like that just connects in-line with the power + but they are kinda pricey.

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Re: (More) Power Problems - Inrush Current too high

Post by gambino37 » Mon Mar 25, 2019 3:00 pm

I am also having power problems with the V3. I have a 3b+ build going and I am constantly getting a lightning bolt. Helder PSU -----> V3 ------> DPI adapter (with the 5V wire from the DPI adapter to the 5V pad on the bottom of the pi. With a multimeter the voltage from the 5V and GND out of the V3 fluctuates from 5 volts all the way down to 3V all the time. Its intermittent but still frequent enough to be a very noticeable problem. I really think the problem lies with the V3.

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 3:14 pm

gambino37 wrote:
Mon Mar 25, 2019 3:00 pm
I am also having power problems with the V3. I have a 3b+ build going and I am constantly getting a lightning bolt. Helder PSU -----> V3 ------> DPI adapter (with the 5V wire from the DPI adapter to the 5V pad on the bottom of the pi. With a multimeter the voltage from the 5V and GND out of the V3 fluctuates from 5 volts all the way down to 3V all the time. Its intermittent but still frequent enough to be a very noticeable problem. I really think the problem lies with the V3.
interesting theory... i was thinking the screen might be what was pushing it over.

ugh. if it is the board, that really sucks. that would mean scrapping this whole build and throwing out the case and all this work, after trying to pull out whatever i can salvage. i'm using the two analog stick capacity on there, and i don't know of another board i could swap it out for and still keep that (or even just a better one to swap it out for without that). gpio wiring isn't an easy option so it would need to be another usb solution, and there isn't exactly much (any) room to try and wire a bunch of stuff together.

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Re: (More) Power Problems - Inrush Current too high

Post by gambino37 » Mon Mar 25, 2019 3:20 pm

I was thinking about just wiring the pi to one of the PSU outputs and the V3 and fan on the other one. Direct power to both "units" and that way they dont rely on each other and one wont be affected by the other's power fluctuations. I already talked to Helder and he said that PSU should handle a 3B+, screen, DPI adapter, fan, and board no problem so I dont think its the PSU.

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Re: (More) Power Problems - Inrush Current too high

Post by gambino37 » Mon Mar 25, 2019 3:22 pm

The V3 has always worked on my setup, even with its fluctuations. As far as I know anyway. Haven't gotten to test much as it re-sets whenever it wants to.

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 3:56 pm

gambino37 wrote:
Mon Mar 25, 2019 3:20 pm
I was thinking about just wiring the pi to one of the PSU outputs and the V3 and fan on the other one. Direct power to both "units" and that way they dont rely on each other and one wont be affected by the other's power fluctuations. I already talked to Helder and he said that PSU should handle a 3B+, screen, DPI adapter, fan, and board no problem so I dont think its the PSU.
I was thinking of wiring from the PSU to the pi, and then from the pi to the 5v for the board and everything else, but that will be a pain to do with how it's all in there right now. I would be afraid if the board is the big draw, then connecting it to the common 5v / directly to the PSU would still have the issue. Maybe regulating it through the pi would work better.

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 6:11 pm

gambino37 wrote:
Mon Mar 25, 2019 3:20 pm
I was thinking about just wiring the pi to one of the PSU outputs and the V3 and fan on the other one.
i just tried this, basically (rerouting just the pi power to the psu, and also powering everything else from the psu) and it didn't work for me, which i assumed since its still sharing the output without anything gating or regulating them.

unplugging the tinkerboy board (and the screen thats powered from it) from the psu makes everything else thats still plugged in, including the pi, power on successfully after that.

so now i have to try re-routing everything but the pi to the 5v somewhere on there, but i have it pretty much covered in tape... i think the usb port's 5v might be the most accessible, since i had trimmed that of for space... i wonder if that has regulated current, since it's usb 2.0 (i think? and i think that's limited to a certain current?)

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 6:39 pm

infinitLoop wrote:
Mon Mar 25, 2019 6:11 pm
so now i have to try re-routing everything but the pi to the 5v somewhere on there, but i have it pretty much covered in tape... i think the usb port's 5v might be the most accessible, since i had trimmed that of for space... i wonder if that has regulated current, since it's usb 2.0 (i think? and i think that's limited to a certain current?)
.. well, not looking good... i routed the board/screen to the pi's 5v - so the fan and pi were powered at the psu (also tried disconnecting the fan so just the pi got power from the psu) - and still the same issue ... it doesn't boot if i try to start from the psu, but does boot if i plug into the pi power directly, and keeps running on psu/battery when i unplug the pi from direct power.

not sure what to do now... i guess it's back to trying to regulate the initial current draw somehow

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Re: (More) Power Problems - Inrush Current too high

Post by infinitLoop » Mon Mar 25, 2019 8:20 pm

ugh... this is so frustrating... i guess i'm at the point where i'm going to pull out the tinkerboy board and find some other board to use somewhere, somehow, to replace the functionality... that sucks. i wish i had some other option, but i don't know what to do...

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