First HeaterMeter 4.2 Build


 
R

RS Robinson

New member
Hey Guys,
Just finished my first HM build using 4.2.4 and it actually went rather well. I have built the thermocouple unit and it seems to work ok. I am reading about 15 degrees higher than my oven. But, My main issue is probe 3 (food probe) is reading about 650F in my 350F oven. The pit probe and the Thermocouple are both reading between 350 and 365F respectively. Any ideas why probe 3 is reading so high? I am using the Maverick ET-732



Also is the fan supposed to run at different speeds? Mine is either always full blast or off.

Any help is appreciated and Thanks in advance.

RS
 
Did you use flux on the board when you soldered? If so try cleaning the board on the probe jack end with some isopropyl alcohol and a soft bristle brush (old toothbrush?), let it dry thoroughly, then see if the readings are any better.... Also double check and/or reflow the solder on the set(s) of resistors and capacitors that are standing up in the probe jack area of the board, and the first four pins on the ATMega in the corner by the TC amp... Those are the only components between the probes and the ATMega.
and yes, the fan should run at variable speed relative to the HM output percentage, unless you have something screwy in the config like the Min and Max values being the same.
 
Ralph made some good points. I would also make sure you're not plugging that ET732 all the way in. The ET732s have a slightly longer plug length than other probes, and will result in erroneous readings if not seated in the correct position.
 
Ralph and WBegg,

Thanks guys. I finally got around to reflowing the solder on the board and cleaned it as directed. I also spaced the plug on the ET732 with some really small orings. Now my reading are all almost identical. I am still a little confused on setting the min max levels and perecentages. Could some one show or explain how they have theirs is set up. My fan is always off or on full blast.

Thanks
 
If the fan doesnt ramp from off to max after those settings are correct, then make sure R14 (2.2K) is soldered on both sides of the board. It is the resistor that sits between the two transistors that control the blower. (located on the side of the large MOSFET that drives the blower)
I had one HM build where the fan refused to cooperate, tested continuity on everything, which was good on the solder side of the board. After much fiddling I realized the trace on the top of the board did not have continuity with that resistor so the bias on the MOSFET that drives the blower was never right. After I soldered up the top of side of the board on that resistor the blower behaved perfectly.
 
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