HM 4.2.4 Build.. working... except....


 
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GeoffH

New member
So I built my HM last weekend. All went well, was very careful to use my cell phone to zoom in on all the components to identify them properly before soldering. Unit boots up and was able to connect to it and configure it for wifi with no problems. I have done two test cooks with it and the HM board has worked flawlessly. The problem I am having is with the Pi crashing. Or at least I think it is crashing as I am loosing it on the network. The HM never stops working and does it 's job. but here is the catch.. If I unplug the fan, the Pi will never crash. Chugs along just fine and never has a hitch. If I plug in the fan, the pi drops off the network. It works for some amount of time.. say 20-30 mins.. maybe longer.. until the pi crashes.. then after it has crashed if I power cycle it, it will crash again every 5 min unless I unplug the fan.

My thought at first was that my 1 amp wall wart was not giving enough juice to power when the fan is running so I picked up a 2 amp 12v wall wart. Fired it up and after about 5 min, both HM and Pi crashed from overheating I believe. They were hot to the touch, HM powered off. I unplugged it and plugged in the 1 amp wart and it fired up with no more issues.


From these symptoms, does anyone have any ideas on where to look for the issue?

Geoff
 
So I did some more testing. I hooked the pi up to a HDMI screen and found that it looks like it looses power. Screen goes black. I tried with a different Pi I have and got the same results.
 
I'd check the fan voltage at full on to see if it is sagging due to some sort of excessive load. Pieces should not be getting hot at all. The Pi cpu will be slightly warm but if anything else is getting hot that's a sure sign that something is pulling too much current. What parts are getting hot? Maybe I can point you in the right direction of where things might be going wrong.
 
It's using the stock fan that came with the kit. Raspberry Pi model B. I don't think heat is the main issue anymore as when I tested it with a monitor this AM and it crashed, both boards were cold. But when I used the 2 amp wall wart and it crashed, both boards felt hot. Something is pulling too much power I think when the fan is plugged in and more amps does not seem to be the fix. I'll give the board a good alcohol scrub tonight. I checked the power output to the Pi and it is getting a solid 5 volts. I'll check that again with the fan running and see if it browns out at some point.
 
As Bryan said, the boards really shouldn't be hot, though in a case or in the sun they can warm up. Are you sure the rPi not crashing while the blower is disconnected isnt just coincidence? It sounds kinda like the rPi is losing connection to the ATMega, so I would reflow the solder on the rPi header and remove the ATMega chip from the socket and reflow solder on the socket. Maybe you had an iffy solder joint that is making/breaking after being jostled around a bit...
 
My wifi crashed on the one cook I've done so far, and it did it several times.

I never noticed it do it while it was plugged in inside and not doing a cook, but I suppose it's possible it did then. My point -- I believe i may be experiencing the same issue as you. The web interface becomes pretty much unusable, the front page loads at best the background image and dashes for all numbers (no graphs at all), and often doesnt even respond to web requests at all. All the while, physical controls and LCD readouts were 100% fine and it controlled temp fine.

This is with a 2amp power supply and powering a 6.5CFM Auber fan, so it's hard to believe it's a power load issue. That being said, it's not crashing tons and tons of times, but when it goes unresponsive, it lasts for anywhere from 1 to 5 minutes. Just seems weird for it to be solder joint issues, though I'll take a look at my boards in the coming days and see. i don't recall it getting hot.
 
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It doesn't seem weird to me that an intermittent communication issue between the rPi and the HM would be caused by bad solder joints...

Also could be a SD card related issue. Is the card flakey? lock tab fully in the unlocked position? Is the card fully inserted?
 
I'll reflow the solder joints tonight. Unlikely to be SD card related as I can edit config files via SSH. Also it never crashes unless the fan is running. I think the fan needs to be at 100% for it to crash. I suspect a bad solder joint in the power regulator circuit. I think under load it is browning out the power to the Pi. The bad joint has a higher resistance and thus heats up with the two amp. It would explain both I think. Will see how it does.
 
There's not much in the blower driver to check (there's more in the blower feedback section), and most components are pretty large and easy to solder. It's much easier to get bad solder on the ATMega socket or the rPi header, but certainly check the solder on your blower circuit.
The only time I have had my rPi appear to disconnect/fail to respond is when I had bad solder on either the ATMega or the rPi, or having a SD Card not seated or not fully unlocked. So I am just speaking from my experience on that.... The HM certainly can brown out from the blower drawing too much power, and I have seen that (while running SUPER LARGE blowers, not the tiny stock one), but every time that has happened to me the HM has browned out as well which you can see by the LCD dimming and resetting (often times over and over again)
 
Its a little early to tell for sure, but I think the reflow of solder fixed it. Found two pins that did not have look to have enough solder on them. They were silver with solder but did not have the solder rising up the pin. It is running on the 2 amp power supply that previously over heated it. It's been running for about 30 minutes so far. Will report back if it turns south but I think it is resolved. Got it in a case today as well.
 
Still chugging along.. I'm calling it fixed and a new Heatermeter is born and healthy! Thanks guys! Will have to build one for my father now.
 
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