New HM 4.3 Build - Wonky Pit Probe Port Issue

Ted F

New member
Hi, I just finished building a HM 4.3 with a Pi Zero W that boots up with LEDs working, it connects to the network, and seems to work with the blower except for something wonky with the pit probe.

I had intended to use my Maverick 732 probes with the HM (understanding they aren’t ideal), but they are flaky in all the probe ports. I plugged in a Weber BBQ probe and it is rock solid stable in ports 1-3.
The wonky part is that when I have a probe in the pit probe port, the HM display will show “no probe” then high numbers like 843 or 569 degrees, then read a stable temp for a while, then jump around again and go back to no probe then a stable temp (this happens with the 732, Weber, and Ponder probes). I changed the pit probe to port 1 (disabling the pit probe in LinkMeter as recommended in a recent post), and the HM seems to otherwise work perfectly. In an oven test the Weber probe is accurate from ambient to 300 degrees using a 31 offset and the fan goes on and off at the appropriate temps around the set point.

I was hoping to find out whether someone had seen my pit probe port issues, and had guidance on whether I should take the HM apart and try troubleshooting or use the HM with ports 1-3 and quit while I’m sort-of ahead. I’m electronically challenged, so I’d prefer not to have to dig back into the HM unless necessary.
 

RalphTrimble

TVWBB Diamond Member
The probe circuit is quite simple, see below:
There is one resistor in series with the probe jack and one capacitor in parallel, plus an additional resistor in parallel for standard probes. Check solder on all those components for Probe 0, and if you have excess flux around there wash it with alcohol and a soft brush (let dry completely!)
 

Ted F

New member
Thank you very much for the reply. I checked the solder on all of the components and used alcohol and a soft toothbrush, then let it dry thoroughly. Unfortunately I get the same result after enabling port 0. I disabled port 0 and will try a cook in the next couple weeks, then see if I should use it as is. Thanks again!
 

Ted F

New member
I haven't been able to find the values required to configure the Weber probe under "custom," and plan on acquiring a Thermoworks probe eventually. The strange thing is that with all of the ports configured the same, the Weber probe has no problems and gives identical readings in ports 1-3 and only gives a weird/flaky read-out in the pit probe port. Although I've gone over the soldering on the pit probe circuit, I'm figuring I messed something up on that circuit and will try using the HM with it disabled.
 

Ted F

New member
Thanks, but I did check that. I made sure that all ports were set the same then tried the probe in each port, and consistently port 0 does the random high numbers, "no probe," and a stable reading, then occasionally the cycle repeats. I tried putting the soldering iron on the circuit components/connections and it still does the same thing.
 

RalphTrimble

TVWBB Diamond Member
You dont have the TC amp (SMD) components on your HM board, right? If not there are literally only 3 components between the probe jack and the ATMega to check.... The pit probe connects to the corner pin in the ATMega...
 

Ted F

New member
No TC components, and the base board assembly went smoothly following the instructions, without any missing or spare parts. Tonight I re-soldered the components, wiped everything down with alcohol, and get the same wonky results for the pit probe and it is rock solid steady for probe ports 1-3. The one thing I noticed is that sometimes the erratic pit probe read-out occurs if I'm moving the probe cable, however slightly (it never happens for ports 1-3). I disabled the pit probe and will try using the HM with port 1 as the pit probe for now. Maybe if I get adventurous in the future I'll try swapping probe components for zero and 3 on the HM board to see if the problem moves as well.

I'm super-appreciative of the comments and suggestions for trying to resolve this.
 

Larry Naylor

New member
Don't know if this is the right place ( i'm new at this ) But i have a probe issue. Have a heatermeter 4.3 with a thermal couple and 3 thermoworks pro probes.2 weeks ago i did a cook using this as just a thermometer and all went well. Last night i did a 10 hour butt smoke using the rd3 with pblower and servo. The trouble i'm having is food probe 1 says it is 182 room temp, Changed probes and all read the same in probe 1, but works ok in 2 ,3. Did the cook using probe 2 and all worked very well. The only difference from the last cook was i connected the rd3 to it. Did some testing this morning without the rd3 and all the voltages in the probe circuits look good. The heater meter ic configured for thermistor probes from thermoworks and all port are set the same. If some one could point me in the right direction i would really appreciate it This is the third time iv'e tried to post this so hope it goes through.
 

RalphTrimble

TVWBB Diamond Member
When you add the RD3 are you still connecting the probes to the HM or are you using them remote through the RD3? Are you using the hand wired RD3 or do you have the RDTC board?
 

Larry Naylor

New member
The probes are connected to the heatermeter , and the rd3 is connected to the HM with a cable.. Forgot to mention that the probe 1 voltage is the same as probe 2 &3.
 

RalphTrimble

TVWBB Diamond Member
Since the probe circuits are not connected to the CAT5 cable in any way by default the issue must be related to voltage... I would try a different power supply, sometime the servo moving and the blower blowing can brown out the 1A power supply and make the HM do strange things.
 

Larry Naylor

New member
Ralph
Ok tried a different pwr supply same results.this is what i have input voltage 12.06 the pads on the board above the probe jacks 1=grd 2=3.280 3=3.231 4=3.276 5=3.2766=3.276 I have 3.276 at the jacks, with probe in it dropped to 2.952 on all 3.on the atmega238p i have 3.199 on pin 28 (pit) on pin 27 i have 3.245(probe 1)pin 26 an 25 (probe 2&3 i have 3.245) all three circuits for probes have the same voltage. I know the 3.3 is a little low and the 3.2 a little high bit that might be the meter. On the 5 volts i read 4.95 volts.These are readings with out the rd3 plugged in or the cable. Outside of prob 1 reading an room temp og 182 degrees ( i can see this in Florida on a summer day, don't know how they survive there) everything works perfect just probe 1 is having a problem. And i'm having trouble posting this
 

RalphTrimble

TVWBB Diamond Member
Well, I am at a loss because the probe jacks do not connect to the CAT5 jack, therefore plugging in a servo and blower should not effect the probe readings (unless it was somehow effecting system voltages)....
I would make sure you have a good CAT5 cable, make sure it is NOT a crossover cable, make sure things are wired cleanly on your RD3 cat5 jack (no shorts etc). Other than that IDK what to say....
 

Bryan Mayland

TVWBB Honor Circle
I'm a little confused, can you clarify:
You see the same results with no output plugged into the HeaterMeter?
When you just have 12V in and plug a probe in, all the probes read the same value?
The issue is when you plug in Food 1 / Probe 1 only, or does it do the same thing if only something is plugged into Probe 2 or Probe 3?

That second one sounds like they're all bridged together somehow. That you can check with the power off and see if any of the pins on the "PROBES" pin header shows continuity to any other pin. Also be sure that you didn't install the 10k resistor on the thermocouple probe, but I do not think that would cause these symptoms.
 

Larry Naylor

New member
Ok here's what i have, put hm together several weeks ago without rd3 and cabling. Used it for a cook as a thermometer only and probe 1 work fine. Then last week i put rd3 together and connected it with a cable. Servo and blower worked fine. Then did a pork butt and plugged probe 1 into the butt, noticed the temp was really high while on the kitchen counter,pulled probe out of butt and it showed a room temp of 185 degrees. Moved to probe 2 &3 jacks and temp was normal tried the other probes in one and got same 185 reading. Did the 10 hour smoke using probe 2 and the Blower and servo worked great. As it sits now without the rd3 and cable connected, i get the voltages mentioned above.The only change to the HM from the first time was to change the probe display colors and get the rd3 working.
I'll check the probe pins now for you Bryan
 

Larry Naylor

New member
JUst measured the pins on the jacks and are not bridged together. Every probe i plug into jack 1 reads 185 degrees. The voltage on the tip of the probes read 2.95 plugged in on all 3 jacks. Could the atmega chip be getting a little flaky? I even measured the voltage on the chip legs to make sure they were connect to the pc board through the socket. This has me stumped do to it being a simple circuit
 

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