Flashing LED/Screen after dropping it


 
J

JayC

TVWBB Fan
Man, this is a bummer. I got my WiFi card today at lunch and thought I'd set up the WiFi. I had the HM, power supply, and some probes in a small back and dropped the thing. I sort of caught the bag on my foot and didn't think too much about it other than "be careful with this thing" but didn't think the impact was enough to hurt the HM.

I plugged the WiFi card into the bottom USB jack and powered the thing up and it started flashing green/yellow/red/LCD in a strobe fashion and thought that maybe I should have put the WiFi card in after I booted. Sure enough, unplugged, took the WiFi card out, powered on again and had the same results and realized that drop may have been harder than I thought and I obviously hurt something.

I took the thing apart and removed the rPi and plugged in power. The result was similar only instead of the LCD just strobing with the background, it actually says no pit probe during that strobe. I unplugged the ATMega chip and plugged it back in thinking that it unseated but still the same thing. I searched the forum and found a guy that had a diode in wrong that caused flashing but that's about all I could find.

Any ideas? I can't believe I already messed the thing up.
 
Sounds like HeaterMeter is constantly rebooting. It is possible that something is shorting and the power supply is cutting out. Check the resistance between the 5V line and ground maybe at the Pi connector, and the VCC/GND pins on the FTDI connnector.
 
Steve_M said:
Sounds like maybe one or more of the BS170 MOSFET's near the display got damaged.
Click to expand...

Thanks, Steve. I have some on the way from Mouser. I'll rework those and report back.

I'm also attaching a video of what is happening without the rPi connected to the board:

[video]http://vidmg.photobucket.com/albums/v615/jay_ntwr/VIDEO0394_zps3exvs7kc.mp4[/video]
 
Bryan, I just plugged the power supply in and noticed that the green light on it is flashing on/off each time the HM flashes so maybe I do have a short. I'll check everything with the meter tonight. Thanks for the suggestion.
 
Oh it is definitely rebooting over and over. If it is flashing at the power supply also check the resistance between 12V and GND at the barrel jack.
 
Yah, looks like a reset cycle to me...

If you had it booted up at least once and working normally then it's not a backward diode.... Something is making the power drop enough to reset the HM... Since you dropped it I would say first look for stuff that could have bent and shorted out.... I would start with that jumper wire you had to add on the 3.3v power... did it move enough to touch something it shouldnt? Or a transistor that bent and now has two legs touching? Or a leg of a component on the solder side of the board that was left long enough to get bent over and touch something else? Look for something like that... and also try a different 12V wall wart if you have one, not sure if you dropped that too? Either way, they're cheap and you can always get a lemon so try another if you got one... My HM did the same thing once, it was when I put a servo and a big old whopping fan on and used the stock 1A power supply, got the same type of reset cycle. Put on a better 2A Power Supply and it was golden...
 
RalphTrimble said:
and also try a different 12V wall wart if you have one, not sure if you dropped that too? Either way, they're cheap and you can always get a lemon so try another if you got one... My HM did the same thing once, it was when I put a servo and a big old whopping fan on and used the stock 1A power supply, got the same type of reset cycle. Put on a better 2A Power Supply and it was golden...
Click to expand...

You guys are awesome. I feel like I owe each of your a six pack.

Looking at the board, I had no idea how anything could have been affecting this even with my funky 3.3v wire. I dropped the whole enchilada though, probes, HM, power supply, fan assembly, all together in one big zip lock bag. I took the thing outside and hooked it up to the 12v power in my windsurfing van for the house lights and wouldn't you know that it's operating just fine that way? I'm assuming that what got damaged wasn't the HM but the 12VDC power supply. I've got another on the way.
 
Glad you worked it out before you started surgery on the Heater Meter!!!
12VDC is really common and so is the power plug on the HM, I bet if you look around you have one somewhere... Old wireless phone, answering machine, router, cable/dsl modem etc... The stock PS is 12VDC 1A (I think it's still 1A?), I would buy at least 2A power supply, cost is usually about the same...
 
Yep, found a 12v one from an old router and plugged it in and all is fine. Put the pit probe in and it's reading about right as well. Wow. What a relief. I need to learn to hope for the best rather than expect the worst. I'll monkey with the WiFi tomorrow. I'm drowned in tequila sorrows tonight from this whole ordeal. I still have a new 6 amp one coming from Amazon Prime for $9.
 
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