Power problem?


 
Bryan Mayland said:
Oh man that sounds serious. I can tell you that when I designed the PCB and had the input and output traces reversed so I put 12V everywhere 5V was supposed to go. It burned out the 3.3V regulator in the Pi, which I replaced, but something else on the board is also burned out because when I plug it in the regulator gets really hot and it never turns on. The shift register was also blown as well but I think that was it. Your shift register seems fine though because the LEDs and LCD works.
Click to expand...

Bryan,
My last power up, the lcd was not working.
How do I know if the shift register is blown?
 
You can tell by it not working! You can tell with an oscilloscope or logic analyzer by watching the inputs and outputs. If you don't have that then when the HeaterMeter boots it should light all 3 LEDs for 0.5s. If only the bottom one comes on, the shift register isn't working. Also if it is at all warm to the touch it is probably dead.
 
John Case said:
Bryan,
My last power up, the lcd was not working.
How do I know if the shift register is blown?
Click to expand...

At this point I am assuming you are powering up the HM with the USB cable to the rPi? Do you have the display connected with the header going from board to board or do you have a ribbon soldered in? If you have a ribbon on the display make sure you didn't break a wire loose while fiddling with the voltage regulator.

You can always check if the rPi is working by unplugging it from the HM board and booting it up off USB power with a monitor connected to HDMI header....

I'm about the same age and have been messing with electronics about as long as you, when soldering up the HM I was surprised how hard it was for me to see if the solder work was good (had to use a magnifying glass too). At first I thought it was my eyes, but my vision has been and still is pretty good. Eventually I came to the conclusion that the purple board makes it hard to see where the traces stop and the solder starts. Some of the solder joints and traces are pretty close together on the HM board as well. I had set out on the job with my butane portasol iron but later realized a regular soldering iron would have been more suited for this job.

Using the digital camera to shoot a high res closeup is indeed a great way to check up on your solder work, you can zoom in on the picture and see the solder joints and traces really well compared to the naked eye or even using a magnifying glass....

Now that you know the +5V regulator is blown, do we have any idea what caused that to happen???

If you are ordering another +5V regulator might as well throw in another shift register too, they're cheap enough... I would buy a spare oscillator as well since I was able to break mine loose after too much fiddling with the board. (in and out of the case too much, I guess it got pushed back and forth one too many times). The parts are so cheap, might as well avoid the frustration of needing one little part and buy some spare parts while you are at, at least that's the way I think....
 
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RalphTrimble said:
At this point I am assuming you are powering up the HM with the USB cable to the rPi? Do you have the display connected with the header going from board to board or do you have a ribbon soldered in? If you have a ribbon on the display make sure you didn't break a wire loose while fiddling with the voltage regulator.

You can always check if the rPi is working by unplugging it from the HM board and booting it up off USB power with a monitor connected to HDMI header....

I'm about the same age and have been messing with electronics about as long as you, when soldering up the HM I was surprised how hard it was for me to see if the solder work was good (had to use a magnifying glass too). At first I thought it was my eyes, but my vision has been and still is pretty good. Eventually I came to the conclusion that the purple board makes it hard to see where the traces stop and the solder starts. Some of the solder joints and traces are pretty close together on the HM board as well. I had set out on the job with my butane portasol iron but later realized a regular soldering iron would have been more suited for this job.

Using the digital camera to shoot a high res closeup is indeed a great way to check up on your solder work, you can zoom in on the picture and see the solder joints and traces really well compared to the naked eye or even using a magnifying glass....

Now that you know the +5V regulator is blown, do we have any idea what caused that to happen???

If you are ordering another +5V regulator might as well throw in another shift register too, they're cheap enough... I would buy a spare oscillator as well since I was able to break mine loose after too much fiddling with the board. (in and out of the case too much, I guess it got pushed back and forth one too many times). The parts are so cheap, might as well avoid the frustration of needing one little part and buy some spare parts while you are at, at least that's the way I think....
Click to expand...

Ralph, Bryan
Right now when I power up the HM4 connected to the Rpi powered via usb it comes up ok, except the LCD does not function. There is no 5v regulator as I removed it.
I get accurate probe readings over the web interface.

The 3 LED's on the HM board blink for a fraction of a second on power up.
But at this point the LCD is not functioning. And of course I have no blower as there is no 12v connection.

I'm not sure what the problem with the LCD is?
Shift register?
Blown LCD?
Other?
 
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Is the LCD connected directly or via ribbon? If by ribbon make sure a lead hasn't broken while you were fiddling with it over this power problem. It has happened to me, and I noticed Bryan commented recently about the same thing happening to him. Either way, inspect the solder connection first before assuming bigger problems...
 
RalphTrimble said:
Is the LCD connected directly or via ribbon? If by ribbon make sure a lead hasn't broken while you were fiddling with it over this power problem. It has happened to me, and I noticed Bryan commented recently about the same thing happening to him. Either way, inspect the solder connection first before assuming bigger problems...
Click to expand...

The LCD is connected directly. (not ribbon cable)

I'm able to configure alarms to toggle all 3 LED's on & off.
 
My original intention was to build 2, 1 for the smoker, the other for 22.5 OTG

I ordered 2 circuit boards, but only parts for 1. After my problem with the first board. I ordered the parts to build a 2nd, which is now running.
I have to figure out the problem with the first board. I installed a new 5v regulator. The LCD is still not functioning, but through the web it appears to be working.

Any suggestions as what is wrong with the first board?
Bryan, you had mentioned the shift registers, How do I test that?

Using the power supply labeled as 12vDC, 1000mA, with no load it outputs 15.8v, I'm getting 13.8v with the fan running & 14.8v with the fan off.

Thanks,
John
 
The shift register is hard to test without an oscilloscope, but if you say you can toggle all of the LEDs on and off at will then that's a pretty good sign the shiftreg is in good shape. Unfortunately that points to a bad LCD.

You can check the voltages going to the LCD as well:
1 - GND
2 - 5V
3 - ~1V depends on the contrast setting
4 - Signal - 5V/0V probably see 0V more often than 5V
5 - GND
6 - Signal - 5V/0V almost always 0V but jumps around once every second
7,8,9,10 - Floating
11,12,13,14 - Signal 5V/0V will jump around then stay at some value for a second
15 - 5V
16 - Who knows, doesn't matter as long as the backlight is on
 
Bryan Mayland said:
The shift register is hard to test without an oscilloscope, but if you say you can toggle all of the LEDs on and off at will then that's a pretty good sign the shiftreg is in good shape. Unfortunately that points to a bad LCD.

You can check the voltages going to the LCD as well:
1 - GND
2 - 5V
3 - ~1V depends on the contrast setting
4 - Signal - 5V/0V probably see 0V more often than 5V
5 - GND
6 - Signal - 5V/0V almost always 0V but jumps around once every second
7,8,9,10 - Floating
11,12,13,14 - Signal 5V/0V will jump around then stay at some value for a second
15 - 5V
16 - Who knows, doesn't matter as long as the backlight is on
Click to expand...

Thank you Bryan!
 
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