New Heater Meter 4.3 Build Servo Issues


 
S

ScottH IL

New member
Hi guys - I have a HeaterMeter v4.3.5 (and RPi 3b+) that I built last week. Everything works great except for the servo on the adapt-a-damper. I have followed the following threads trying to diagnose the issue with no luck.

https://tvwbb.com/threads/heatermeter-adapt-a-damper-all-ok-but-servo-is-not-working.75023/
tvwbb.com

Servo troubleshoot

Hey guys, I just made a Heatermeter 4.3! Everything is working except the servo.. :confused: I was hoping some of you could give me a hand troubleshooting my issue. Raspberry Pi 3 B Power Supply (Same brand as suggested) 2A Servo MG90D Blower 15cfm (works properly) I know the MG90D is working...
tvwbb.com tvwbb.com

I have similar issues as the above threads but no strange readings on the Q5 mofset or anywhere in the 5V circuit. I am able to run the HM without the servo installed and everything works fine. When I wire up the servo and power up the HM the RPi loses power when I increase the blower percentage above zero. The HM display dims slightly and displays negative temperatures even when there aren't any probes connected. Could the issue be that the RPi 3B+ is drawing too much causing it to brownout when I connect the servo? I am using the Triad Magnetics WSU120-1000 for my power supply. What else do you guys suggest I try?

Thanks
 
Yike`s. That's not good. Did you buy the Adapt-A-Damper already assembled and ready to go or did you buy parts and assemble. Also, if you bought parts and assembled it, is the servo a sg/mg 90. The "D" series really should not be used. Check the keystone in the damper to make sure it`s got good connections and nothing has come loose. Check polarity of capacitor on keystone if it has one to make sure the polarity is correct. Also I do know the 1a power supply should work, but if you have access to a 2 amp supply or a 12 battery source capable of providing a couple of amps, give that a try.
 
I assembled all of the parts myself so I'm guessing its my lack of soldering skills causing the problems. The servo is a TowerPro SG92R that came with the Adapt-A-Damper. I have verified that the keystone jack is wired properly. I do not have a capacitor on the jack. I also tried a 12V 2a power supply that I had laying around, no change. The HM behaves the same with and without the RPi installed. I've looked over each board with a magnifying glass to check for solder bridges and reflowed a few pins. So far nothing has helped.
 
I can definitely run a 12V blower, servo, and a Pi3B+ without it browning out or ever displaying a negative temperature so something sounds fishy for sure.

I see you said it works fine without the servo attached, but have you checked the blower output by itself to see if the blower turning on is what is killing it? If that works, is the servo binding up? The dial should move freely without any resistance because the servo can definitely pull more than 1A if it gets stuck so also try it without the dial on the Adapt-a-Damper (with just the servo gear sticking up, or even remove the servo entirely from the damper housing).
 
The only time I have had the servo installed in the damper assembly was the first time I fired it up all of the rest of my testing has been done with the servo loose on the table. So the servo should be able to be moved easily by hand? I think mine is stuck for sure then. I couldnt even move the dial when I disassembled the damper to start debugging.
 
There is a decent amount of resistance if you try to backdrive the servo (which you generally should not because the plastic gears aren't up for it) but with the leverage of the dial it should be doable. I'll send you a new servo in today's mail either way though to get things rolling.
 
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