HeaterMeter v4.1 Trouble - Fan Not Working


 
J

Jarom Bodell

New member
First build trouble. It appears that everything is working properly with the exception of the fan output. The servo works great as well as all the probes. I initially thought there was a problem with pit probe connection because when I plugged a probe in the HM freaks out (see video). If I turn off the fan (set the max. output to 0%) I can plug the probe in without trouble and the servo runs. But as soon as the fan is engaged by software the display and LED's flash until the pit probe is unplugged, also the rPi reboots. The fan has never spun up (also no voltage change on the fan leads). And the HM freaks out with or without the fan connected.

I've followed all the traces for the fan and all my solder connections look ok. Any help would be appreciated.

 
If you don't plug the fan in at all does it still do it? It sounds like when we flip the fan on, the power is cutting out.
 
Yes, with the fan unplugged (even with the rPi disconnected) it still does it. My power supply is the 1A version suggested off of Amazon.
 
Check your diode located between the MOSFET and 5V regulator to make sure it isn't installed upside down (which would cause a short to ground). It should be mounted with the white band furthest from the edge of the board. Also check your solder joints at the RJ45 jack to make sure there's not a teeeny bit of solder connecting BLOW and GND or 5V which would also be a short.
 
I believe the diode is installed correctly but I will double check. Also the RJ45 looks clean, but I will verify. Thanks! If anyone has any other suggestions I will try it.

One thing I noticed in trying to measure a voltage on the blower output. There was like -0.8v between ground and blower and it never changed. I would think there should be 0v then climb to 12v when the fan engages. But as I said it just sits at -0.8v. What is the expected readings?
 
With no fan plugged in: If you take a fresh device that's been powered off for a while it should be 0V. Once it turns the fan on for an instant once, it will charge the capacitor which will very slowly discharge over time. It drops from 12V to a volt or two in a matter of seconds but the charge lasts on the order of minutes. It should never be negative though, assuming you've got your multimeter probes right.

There's not many components that could be wrong here because it only seems to have a problem when powering the blower section. That's the MOSFET, the diode, the 22uF capacitor, and the jack.
 
If you are unable to nail down the problem take a CLOSE-UP picture of the entire board front and back and post it here. With that we can zoom in and inspect your component placement and solder work and see if we can spot your problem....
 
I had a problem similar to this. Turns out after I built another HM and the fan still didn't work it was the power adapter itself. I took it apart and a capacitor on the PCB was loose. You may have a faulty power adapter. Before I fixed it it provided enough power for everything to work except the fan.
 
Everything looks clean of solder bridges and I'm working on pictures. With everything unplugged and turned off measuring with my multimeter there is a dead short between pin 4 (Ground) and pin 5 (Blower). That can't be right, correct?
 
Front and back. The LCD display header is a mess but works (I initially soldered it on the wrong side).


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So the fan is working now. On a hunch I removed the jumper I added as described in this post. I soldered it to the what I hope is the other ground on the power connector (J9) and things worked. So Bryan any insight?
 
Silly question, but did you do this part?

Step 1: Remove the barrel jack and cut the 4 connections to the ground plane with a razor.
 
I did do step one. I tested and it was disconnected from ground. I'm a little concerned that solder may have wicked up and shorted it to ground again, but I don't think so.
 
hahah no, your problem is you're shorting the MOSFET to ground. Your jumper wire needs to go to the middle pin of the NEXT component over, not the one you've got it hooked to.
 
Ugg. That was the exact thing I was hoping to avoid. Wasting everyones time here because I can't follow instructions like my teachers always said. :) Thanks Bryan your advice was right on from the beginning. I guess I should be happy that I didn't manage to fry something with my mistake.

This now will take on the feel of an oscar acceptance speech, but I would like to thank you Bryan again for the design and all the work. You've taken on quite the role here not only with design and updating but the neverending troubleshooting and feature requests. Thank you Ralph and Tom for the "Darth Damper" and case. As well as Tristan for sharing a OSH order.
 
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