From and for an electronics newbie


 
Speaking of reflowing, I discovered another mistake last night. When I soldered the LCD, I thought I had it laying flat so that the pins were inserted all the way. But it looks like the board was angled a bit, so the left side of the LCD is maybe a millimeter or two higher than the right.

If I end up needing to correct that, am I looking at desoldering every pin and resetting them? I don't suppose I can put some downward pressure on the high end and start heating up pins one by one to ease it down.
 
KellyMc said:
Speaking of reflowing, I discovered another mistake last night. When I soldered the LCD, I thought I had it laying flat so that the pins were inserted all the way. But it looks like the board was angled a bit, so the left side of the LCD is maybe a millimeter or two higher than the right.

If I end up needing to correct that, am I looking at desoldering every pin and resetting them? I don't suppose I can put some downward pressure on the high end and start heating up pins one by one to ease it down.
Click to expand...

If you can get your iron hot enough, you might be able to quickly run the iron back and forth across the pins and get all of the solder soft enough for a brief moment to push the display down.
 
KellyMc said:
Speaking of reflowing, I discovered another mistake last night. When I soldered the LCD, I thought I had it laying flat so that the pins were inserted all the way. But it looks like the board was angled a bit, so the left side of the LCD is maybe a millimeter or two higher than the right.
Click to expand...

When I am soldering in a long component with a lot of legs I generally solder in one leg from each end first, this way you only need to reflow one solder joint to adjust the position of the component on each side. Once secured in its proper place with the two solder joints I then solder the rest.

I know that doesn't help you fix your problem, but it may help you next time around or help someone else...
 
Well then, that'll teach me to be so proud of myself... help.

After getting the HM and rPi up and running the other night, I started on blower testing. I had the fan wired into a Cat-5 jack (4 and 5) and that plugged into the HM, but was getting no response.

So, I thought I'd just touch the wires to the appropriate, and oh-so tiny Cat-5 connector joints on the board to test. I assume I must have inappropriately bridged two of them, because the LCD flickered and went blank (still lit) and now the system's no longer working.

Specifically, the LEDs blink and the 5V regulator sub-board gets very hot. However, if I take the rPi off, and plug in 12v, the Heatermeter appears to work fine, I get correct display on the LCD and the sub-board stays cool.

Did I send 12v to the rPi and fry it?

If I plug 5v into the rPi, its red PWR led flashes, but I never get anything on an attached HDMI display.

ugh.
 
Well, if the rPi wont boot from the USB power on its own (not connected to the HM), and you are not getting anything on the monitor through the HDMI, it sounds like you might have killed the rPi... unfortunately.

The way the power works in the HM (with v4.0, not sure if Bryan changed this on v4.1?) is, the 12VDC comes in from the wall wart, the DC-DC converter creates +5VDC from that which is fed to the rPi, the rPi in turn feeds back 3.3VDC to the HM board. There is an optional 3.3VDC regulator on the HM board that will create its own 3.3VDC when running the HM without a rPi...

The CAT5 jack does have +5VDC for the servo and +12VDC for the blower, if you short them together that could bump up your 5V line to 12V and possibly fry the rPi... as you had suspected... The power light working on your rPi is somewhat encouraging, though it could still be fried. I would try reseating the SD card, maybe even re-image it, make sure your monitor is working over your HDMI cable independently (it didn't come unplugged in the back of the monitor?) If there are no further signs of life then I guess it's time to chalk it up and order another rPi.... Sorry man....
 
If the light comes on but it doesn't boot powered over USB, I'd say check the SD card first. Also feel the voltage regulators on the Pi (RG1 and RG2) with no SD card while it is powered up. If they feel hot almost immediately after plugging in, then something is broke broke on the Pi.

Ralph: The v4.1 design has dual isolated 3V3 supplies to eliminate the question "Do I need to buy/populate that part?", so everyone should have a the 3V3 regulator and can run standalone.
 
Bryan Mayland said:
Ralph: The v4.1 design has dual isolated 3V3 supplies to eliminate the question "Do I need to buy/populate that part?", so everyone should have a the 3V3 regulator and can run standalone.
Click to expand...


"dual isolated 3V3 supplies", one being on the HM and the other on the rPi? Are you saying that both the HM and the rPi regulate their own 3.3V and the rPi no longer feeds back 3.3V to the HM on v4.1? Just want to make sure I understand clearly...
 
Thanks, Ralph and Bryan. I tried re-imaging and reseating the SD card with no luck.

Some Googling tells me that the red rPi led should never blink, it just indicates presence of 3.3v power, although I'll try a different power adapter when I get a chance. But I also learned about tripped polyfuses on the rPi, which apparently can take days to recrystallize. Maybe it's a slim chance, but I'll certainly wait a few days and try again before giving up on it entirely.

One other issue -- even before this, the HM's red LED never lit. I tried replacing it and reflowing the joints on the connected resistor, but no luck. Any likely culprits?
 
It is positioned in correctly?

dave

KellyMc said:
Thanks, Ralph and Bryan. I tried re-imaging and reseating the SD card with no luck.

Some Googling tells me that the red rPi led should never blink, it just indicates presence of 3.3v power, although I'll try a different power adapter when I get a chance. But I also learned about tripped polyfuses on the rPi, which apparently can take days to recrystallize. Maybe it's a slim chance, but I'll certainly wait a few days and try again before giving up on it entirely.

One other issue -- even before this, the HM's red LED never lit. I tried replacing it and reflowing the joints on the connected resistor, but no luck. Any likely culprits?
Click to expand...
 
If you suspect a blown polyfuse on the rPi perhaps locate them and measure them with a multimeter to see if they've opened up? I don't have a rPi board handy but I'm sure you can find the info on the location of the fuses in question online. I ran across a youtube video that might be helpful, though it is about an earlier rPi version that had polyfuses on the USB power (not the same fuse you would be looking for) the same ideas/methods could be applied to your fuse.
https://www.youtube.com/watch?v=aJp-QAZFJbs
 
Speaking of no red LED...

My new v4.1 build appears to be in good working order other than my red LED is not coming on. The LED and resistors have been tested and are working.

Update: I'm getting 4.3v at the atmega when the red LED (LED1) should be lit, but there is no voltage at the top of the LED1 resistor. If I carefully jumper the atmega pin to the top of the LED1 resistor, the red LED lights up.

Jumper:

VTcsXg0l.png
 
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Steve_M said:
Speaking of no red LED...

My new v4.1 build appears to be in good working order other than my red LED is not coming on. The LED and resistors have been tested and are working.

Update: I'm getting 4.3v at the atmega when the red LED (LED1) should be lit, but there is no voltage at the top of the LED1 resistor. If I carefully jumper the atmega pin to the top of the LED1 resistor, the red LED lights up.

Jumper:

VTcsXg0l.png
Click to expand...


I wonder if we are getting a lot of bad boards of late. My last two have not worked(more then likely my fault though). I think someone else had a problem with their board and needed to put a jumper on it. I have 3 4.1 boards on the way so hopefully I wont have any problems. Although, my problem might be related to using a 3mm soldering tip, lol. I'm getting a new Weller with a .031 tip today in the mail
 
Steve_M said:
Speaking of no red LED...

My new v4.1 build appears to be in good working order other than my red LED is not coming on. The LED and resistors have been tested and are working.

Update: I'm getting 4.3v at the atmega when the red LED (LED1) should be lit, but there is no voltage at the top of the LED1 resistor. If I carefully jumper the atmega pin to the top of the LED1 resistor, the red LED lights up.
Click to expand...

I would reflow solder on both the ATMega and that resistor...
 
Can you measure continuity on the trace?

Edit: Looking at the closeup pics of the HMv4.1 board I took before I assembled it I see the trace in question seems to be on the top side of the board, and takes a rather direct and unobstructed path between the ATMega and that resistor. It should be pretty easy to inspect it for flaws with a magnifying glass or closeup picture...
 
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I had 0 continuity between the end points of the trace. Not sure if it was a manufacturing defect or what, but the jumper fix was simple and cured the problem.
 
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