Need some advice HM Power


 

MikeMcW

New member
Well my first build went great on to the second build not so much. I'm having a power issue on the main board the Power MOSFET Q3 only has 12v on the leg nearest the cutout on the board. The IC1 has the proper voltages accost all legs. I'm not sure where to go from here replace the MOSFET or should i be looking at something before here. I would post some pics but haven't figured out how I don't have a hosting service. Any help would be greatly appreciated.

Thanks
Mike
 
If you change the blower from voltage to pulse mode in the config screen, does the blower start working?
 
Yeah I'd check pulse mode first a well, as that eliminates half the circuit and HeaterMeter will just run the power blindly.

I'd check the 2.2k resistor right by the MOSFET. Make sure that leg you've got 12V on connects like this and that you've also got 12V there.
JQkf9uz.png


If that's good then check the other side of that resistor, it should also be 12V if the blower output is 0%. Then check from the end of that resistor to the MOSFET leg closest to that resistor, again should be 12V at 0% power.
 
Thanks for the reply I checked the 2.2k resister and have 12v , no power on the center leg of the MOSFET and no power at the diode D2

A little more background the display only has one line lighting up and no digits the Rpi can be seen on the web interface and it's not seeing the HM.

Thanks
Mike
 
Here is the blower circuit layout on the older HMv4.2 board, the component layout is different but the circuit is the same. It might help you in your diagnosis: a bit.

HM_Blower_Notes.jpg


And an shot of the HMv4.3 board with fewer notes:

HM_Blower_Notes_V4.3.jpg


That said, your more recent post about the overall failure of your HM display and rPi connection makes me think perhaps your blower circuit may be fine but your HM is not functioning. When you build the HM the ATMega chip is blank, upon first boot when connected to the rPi with the linkmeter software installed linkmeter will see the blank ATMega and flash it with the HM firmware. If your HM board is not talking to the rPi, or if the rPi is not booting linkmeter properly for whatever reason the ATMega will not flash. If this is the case you will generally get one line of black blocks on the HM display. Is this where you are at?
 
If this is the case you will generally get one line of black blocks on the HM display. Is this where you are at?

Yes it's exactly where i'm at
 
OK, so your HM is not talking to your rPi for some reason, or your rPi is not booting the linkmeter software.

Did you download and flash the linkmeter software to the sd card that is in your rPi?
 
Yes I downloaded the software and flashed the sd card.

I just tried to re flash the HM and now nothing on the display and it acts like a dead short somewhere the power supply and ic's heated up quickly.
 
Yeah if you're into the webui and it is saying that there's no HeaterMeter attached then I would start with that being your primary issue, because the blower won't run if there's nothing telling it to do so.

If you think there's a short somewhere, I'd start with measuring the resistance between 12V-GND, 5V-GND, 3.3V-GND and looking for anything with low resistance to give you a start of where to look. You can also check your MCP1700 3.3V regulator to make sure you didn't install a BS170 in its place, because that would exhibit similar effects. Verify you've got 3.3V at the microcontroller's VCC, RST, and AVC pins. Also check the continuity to the Pi on pins:
SCK
MIS -> MI
MOS -> MO
G25 -> RST

Finally verify that each of these pins does not have continuity to any adjacent pins. Not sure if you've seen this but this image might help trace out the issue, although it shows some voltages that are only accurate after the Pi sees the HeaterMeter. All tests can be done without the LCD/Button board to verify the issue is in the base. HeaterMeter can run without the board attached.
 
Thanks for the help I found some problems for some reason I swapped a BS170 for the MPC1700 at IC4 and a MPC1700 at Q4 on the LED board. I lifted both and replaced both and gave it a try and still no joy not sure what else I fried when I did this but I think i'm going to put this on the shelf for a while. Thanks again for all the help

Mike McW
 
I am always surprised when people give up so easily. If you did not have the MCP1700 in the right spot you did not have the 3.3v required to run the ATMega. Lots of people have made that mistake and most of the time once it is corrected you are on the fast track to getting things running. I would hang in there, do some measurements on your HM board to verify you have 3.3v in the places it should be, if all good then boot with the rPi, be patient, it takes some time for the ATMega to flash.... the HM will reboot and you should see "NO PIT PROBE" and you are there.... If it doesn't flash after a few minutes image your SD card again and try one more time...
 
I'm not giving up I just don't have enough time work with it at this time. My plan is to put together another HM and use it to help me diagnose the bad unit. I'm going to be out of town until Dec so i'll get back to it then. Thanks again for the help.
 

 

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