New 4.2 Build, Blower Output Voltage issues


 
C

CEFuller

New member
Hi Guys,

Just completed my first Heatermeter build and everything seems to work great with the exception of the blower output voltage. 12V is getting in but it will only output 1.2 V regardless of the software settings I change on the fan.

My first thought is that the MOSFET is bad, so I did a NPN transistor test with a multimeter and it seems to be good (although that was in-circuit so could that be giving me false results?), so now I am thinking the issue might be more upstream.

Not the most circuit savy, so any ideas on where to start would be appreciated.

Thanks!

Chad
 
Are you testing voltage on the HM board or the CAT5 cable?
Make sure you are measuring from GND to SERVO pin, make the HM blow 100% and check from any gnd to the servo pin on the CAT5 header.
 
RalphTrimble said:
Are you testing voltage on the HM board or the CAT5 cable?
Make sure you are measuring from GND to SERVO pin, make the HM blow 100% and check from any gnd to the servo pin on the CAT5 header.
Click to expand...


Hey Ralph,

I measured from GND to BLOW pins on both the CAT5 and the HM board. I was only planning to use the fan at this time and was under the impression that only the center pins (GND and BLOW) were used to control blower output.

Let me know if I am mistaken.

Thanks.
 
So it seems you measured (properly) on the CAT5 jack from gnd to BLOW while the HM output is 100% and you are not getting voltage... If that is the case you do have an issue...
Next question, are you powering from the 12V to the HM board or through the rPi... Everything EXCEPT the blower will work when powered from the rPi, for the blower to work you need the 12V...
 
RalphTrimble said:
So it seems you measured (properly) on the CAT5 jack from gnd to BLOW while the HM output is 100% and you are not getting voltage... If that is the case you do have an issue...
Next question, are you powering from the 12V to the HM board or through the rPi... Everything EXCEPT the blower will work when powered from the rPi, for the blower to work you need the 12V...
Click to expand...

Powering with a 12V (stole it off my router) to the board yes and confirmed that the 12V is going into the MOSFET. I did read a similar thread where the power supply was the issue. I have the power supply I plan to use coming in tonight so I will see if that does anything.

I would think if the MOSFET was functioning correctly that I would at least see my blower output change (even though its only 1.2V), but its constant no matter if the output is set to 0%, 50%, or 100%, but it also could just be that its not getting the signal right?
 
there is a bs170 MOSFET in front of the big MOSFET that drives the blower, could be an issue there... There is also a feedback circuit for voltage mode that has quite a few components. You could try changing to PULSE mode, which doesn't need the feedback circuit.
Check the orientation of D2 & C12 (the diodes and capacitors around the MOSFET)
Post a pic of your board and maybe someone will spot an issue somewhere....
 
RalphTrimble said:
there is a bs170 MOSFET in front of the big MOSFET that drives the blower, could be an issue there... There is also a feedback circuit for voltage mode that has quite a few components. You could try changing to PULSE mode, which doesn't need the feedback circuit.
Check the orientation of D2 & C12 (the diodes and capacitors around the MOSFET)
Post a pic of your board and maybe someone will spot an issue somewhere....
Click to expand...

Tried Pulse mode last night...no dice.

Ill check those tonight and post a pic. Thanks!
 
Pull your ATmega328 out of the socket and make sure that pin 5 did not get bent under the chip when it was seated. Sometimes when seating a chip in a socket the pin will curl under instead of going in the socket.
 
After zooming in as far as I can on your picture, the far right lead of the FQU11P06TU MOSFET which is the gate pin that turns the device on does not look like it is soldered well (at least on the top side of the board). I would heat that up and add a little solder there. The signal that goes to that pin comes from the BS170 and you can see the trace is on the top of the board. If this does not fix it then try this:

I am assuming that you have a voltmeter based on previous comments. With the board oriented like it is in the photo, select voltage on your meter and put your positive probe on the FQU11P06TU MOSFET right lead near the 2.2K resistor (make sure its on the MOSFET lead and not the PCB trace). Put your negative probe on ground. What voltage do you have there? Then check the voltage on the ATmega pin 5. What should happen is 3.3V out of the ATmega should switch on the BS170 which will put a ground on the gate of the FQU11P06TU MOSFET and switch it on supplying +12V power to the blower.
 
Last edited:
You can also try shorting the gate pin on the power mosfet to ground, which will force it on. You should see the full 12V at the blower pin then (with nothing plugged into it). If you do not then it seems like a short somewhere in the blower line between the mosfet and the output? If you do then there's likely an issue in the triggering circuit.
 
David Crawford said:
After zooming in as far as I can on your picture, the far right lead of the FQU11P06TU MOSFET which is the gate pin that turns the device on does not look like it is soldered well (at least on the top side of the board). I would heat that up and add a little solder there. The signal that goes to that pin comes from the BS170 and you can see the trace is on the top of the board. If this does not fix it then try this:

I am assuming that you have a voltmeter based on previous comments. With the board oriented like it is in the photo, select voltage on your meter and put your positive probe on the FQU11P06TU MOSFET right lead near the 2.2K resistor (make sure its on the MOSFET lead and not the PCB trace). Put your negative probe on ground. What voltage do you have there? Then check the voltage on the ATmega pin 5. What should happen is 3.3V out of the ATmega should switch on the BS170 which will put a ground on the gate of the FQU11P06TU MOSFET and switch it on supplying +12V power to the blower.
Click to expand...

Resoldered the joint same issue. The voltage on the gate pin is 12V. Voltage on the attmega 5 pin is 3.3V at 100% fan speed And goes down to 0 at 0% fan speed.

Turned out it was the solder joint on the right pin of the BS170. Works like a charm now!!

Thanks for the help troubleshooting!
 
Bryan Mayland said:
You can also try shorting the gate pin on the power mosfet to ground, which will force it on. You should see the full 12V at the blower pin then (with nothing plugged into it). If you do not then it seems like a short somewhere in the blower line between the mosfet and the output? If you do then there's likely an issue in the triggering circuit.
Click to expand...

Thanks Bryan! Shorted the gate pin and saw the 12V coming out. Figured out everything was working coming into the BS170 so resoldered and it works great now.

Your instructions are awesome and had a great time putting everything together. Just need to improve my soldering skills it seems. Thanks for all your work on this project!
 
That's great! I am glad you got it all figured out. I know I've built some kits, powered them up and NOTHING and you just stare at it wondering "Well what now?". Several hours later, you've learned what all the parts do and it springs to life. Nice work sticking with it.
 
You must log in or register to reply here.

 

Back
Top