All TC probe HM?!?


 
J

JohnW

TVWBB Member
Wondering what the cons/issues would be for a HM having all (4) TC probes???

I have a HM 4.2.4 and loving it, and will be building a 4.3 HM soon. Many thanks to Bryan and all those that have contributed to such an amazing device.

I have found that my TC probes provide more accurate temp readings (when tested against a very accurate external probe unit I have) through the range of temps (cold to hot) than do the TR probes (which are closer to accurate only at the higher temps). Now it is very likely I have been a complete bone head in configuring the HM probe offset settings or I may be having a build issue with my HM, so someone please speak up and tell me so.

For example, here is what I am seeing (TC/TR probes temp readings are from the HM); *testing done with a pot of water on my stove*
@70* (as read by my accurate probe) the TC reads 62* and the TR reads 18*
@170*, TC = 169*, TR = 155*
@212.9*, TC = 212.8*, TR = 212.4

Yes, I know...who cares about temps down around 70*, but even at 160* the TR probes are off by quit a bit. These lower temps (140*-160*) are important to me as I want to try my hand at some cold smoking. And with HM being the coolest thing around, I want to make use of it for these smokes as well.

My other desire for TC probes is that the cables are much longer and thusly work better for my smoker setup. If someone knows where to get TR probes with cables that are closer to 72" long vs the 47" ones I have, I'd appreciate a link to the site.

Many thanks in advance for your replies.
 
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I want an all TC HM too. Problem with all TC is that you'd have to have all the surface mounted stuff for each probe and that's kinda pricey, kinda takes up a lot of space, and makes it a little more difficult for your average person who only knows basic soldering. Perhaps bryan has it in mind for when HM 5.0 comes out in a couple years
 
What make and model of thermistor probe are you using for your tests? The thermoworks probes should give you pretty solid readings.

I doubt there's any real demand for an all TC HM, but the good news is that all of the diagrams and code are online, so anyone is able to go ahead and make it a reality!
 
Steve_M said:
What make and model of thermistor probe are you using for your tests? The thermoworks probes should give you pretty solid readings.
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All my probes and handheld units are Thermoworks.


Steve_M said:
I doubt there's any real demand for an all TC HM, but the good news is that all of the diagrams and code are online, so anyone is able to go ahead and make it a reality!
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Yeah, I too am sure there is little to no demand, but I'm in the process of building my 2.0 smoker, a really nice one so 1) need longer cables to accommodate the tall height, 2) will be smoking much more meat at a single time and would like to get good readings throughout the smoker.


I've seen where RalphTrimble had made his RotoDamper with the ability to have the probes connect at the damper unit location. So maybe expanding on that design to have a daughter board with 4 (or more?) connections. Lots of studying ahead for me ;)
 
SteveCK said:
I want an all TC HM too. Problem with all TC is that you'd have to have all the surface mounted stuff for each probe and that's kinda pricey, kinda takes up a lot of space, and makes it a little more difficult for your average person who only knows basic soldering. Perhaps bryan has it in mind for when HM 5.0 comes out in a couple years
Click to expand...

Very true, it would add to the cost $$$$$! I need to check with Ralph Trimble and John Bostwick to see what their cost was for their design.

One other suggestion HW v5, make # of probes a variable settingso we could have more than just 4. Of course I am sure there would have to be a limit, I mean how many graph lines and colors can you have on one screen?!?! LOL
 
I think it's already possible with some Rewiring of my adapter board and some Rewiring of the cat5 jack. And then you would need a small rj45 jack pcb with one input and 3 outputs. You won't be able to get 4 TCS but you would have 3. The HM would basically be the same without any probe Jacks unless you installed a total of 3 switches.

Putting 4 Tc's on a heatermeter would require a larger pcb for the TC Jacks or you could double them up, and have two on top and two below the pcb, but they would need to be staggered.

The cost would be fairly high for minimum gain.
 
JohnW said:
So speaking of cost, at Pi Supply one can get a TC Amp breakout board for $20, for all the parts already soldered and ready to go. So that's not too too bad for four of them.
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The problem with those is that they are digital thermocouple amps and HeaterMeter wants an analog output. The 4.2 board was actually designed in a way that some folks requested: that the board was wide enough that 4 thermocouple connectors could fit without the Pi getting in the way so you wouldn't have to rearrange the whole board to route them. I don't think anyone ever made one though.

But yes a separate board could be made that mounts to the probe extension header that has 3 more thermocouple jacks and amplifiers on it but it would require them to stick out further so they wouldn't hit the button board / LCD. Or as John suggested a separate external board that is run from the RJ45 jack.

I do have a schematic sketch and parts list I've drawn up for a circuit that does 4 thermocouples with a single digital amplifier with the idea that any of the inputs could be either thermocouple or thermistor but I haven't had a chance to test it out or maybe even finish it. It is also only all surface mount because the amount of board space to do all the necessary analog switching would itself be half the size of HeaterMeter if it were through-hole (if it were available in through-hole).
 
I was almost certain someone had made an aux board that had 3 or 4 TC amps on it to support an all TC HM??? It's not really that big a deal, just need four copies of the TC amp circuit on it, then connect it to the probe input header on the HM. Personally I don't see the need, TC's seem to be more aimed at the chamber sensing job and less at the food probe job, standard probes are more common for the food probes and do a fine job... Unless you are doing some sort of high heat cook that needs food probes, which is less likely, because high heat cooks can generally be timed, in minutes, to get the desired doneness.
 
Bryan Mayland said:
The problem with those is that they are digital thermocouple amps and HeaterMeter wants an analog output.
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I linked to that one as just an example, there are several others available, like this analog one and this I2C one that can address up to 8 sensors.


Bryan Mayland said:
The 4.2 board was actually designed in a way that some folks requested: that the board was wide enough that 4 thermocouple connectors could fit without the Pi getting in the way so you wouldn't have to rearrange the whole board to route them...I do have a schematic sketch and parts list I've drawn up for a circuit that does 4 thermocouples with a single digital amplifier with the idea that any of the inputs could be either thermocouple or thermistor but I haven't had a chance to test it out or maybe even finish it.
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That is awesome! and would love to see some further development in this direction possibly as suggested for v5 of HM. You've got support from me.
 
RalphTrimble said:
I was almost certain someone had made an aux board that had 3 or 4 TC amps on it to support an all TC HM??? It's not really that big a deal, just need four copies of the TC amp circuit on it, then connect it to the probe input header on the HM.
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Would like to find out more on this and who that was. Apologies on my earlier reply when you mentioned this, I thought you were referring to yourself (and Bostwick) in the development of your RD3 (yes I read through your entire RD thread...in one night).

RalphTrimble said:
Personally I don't see the need, TC's seem to be more aimed at the chamber sensing job and less at the food probe job, standard probes are more common for the food probes and do a fine job.
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Not sure I agree, on Thermoworks website they have at least 32 TC probes dedicated to food.

And as mentioned, I also need probes with longer cables, my damper/fan is near the bottom of my smoker which will also be where I'm locating the HM, I need a probe that can get to the top which is about 50" up. Of course I could move the HM further up to be in-between the top of the smoker and the damper and all the cables would reach, but the indicated layout is my preferred config and thusly I'm trying to find a solution for that.
 
RalphTrimble said:
... standard probes are more common for the food probes and do a fine job...
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just wanted to mention, it's my OCD that keeps me from accepting this :D

All of this is my issue/fault, I'm a long time geek and I'm too anal with most everything. I spend hours agonizing over my smokes ;) good grief!
 
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It may have been me at one point. I designed a pcb with 4 thermocouples. I may still have the design on my old home computer. But, I will be moving into our first house the next two weeks and everything is getting packed up for the move.
 
JohnW said:
Would like to find out more on this and who that was. Apologies on my earlier reply when you mentioned this, I thought you were referring to yourself (and Bostwick) in the development of your RD3 (yes I read through your entire RD thread...in one night).




Not sure I agree, on Thermoworks website they have at least 32 TC probes dedicated to food.

And as mentioned, I also need probes with longer cables, my damper/fan is near the bottom of my smoker which will also be where I'm locating the HM, I need a probe that can get to the top which is about 50" up. Of course I could move the HM further up to be in-between the top of the smoker and the damper and all the cables would reach, but the indicated layout is my preferred config and thusly I'm trying to find a solution for that.
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I also designed an heatermeter adapter board that worked with a Din cable and it was able to relocate the probes and thermocouple into a smoker like you described. All that was hooked up to the heatermeter was the din cable and power. Everything else was routed in the smoker to the top and in a compartment I had a adapter board that had solder pads so the owner could mount the probes and thermocouple Jacks. Made 5 of them. That project took over a year to develope
 
John Bostwick said:
I also designed an heatermeter adapter board that worked with a Din cable and it was able to relocate the probes and thermocouple into a smoker like you described. All that was hooked up to the heatermeter was the din cable and power. Everything else was routed in the smoker to the top and in a compartment I had a adapter board that had solder pads so the owner could mount the probes and thermocouple Jacks. Made 5 of them. That project took over a year to develope
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I'll be looking forward to chatting with you about that, but not till after you are settled in your new home.
 
YAh, right, since you mention the din cable I remember it was you (JohnB).
JohnW, it sounds like what you need is an aux board with several tc amps on it that you can sit conveniently where your probe leads reach, then use some sort of cable to connect it to your HM. You can run as many TC's as you want to build TC amps for (up to 4).
As for cables, just counting, 3.3v, gnd, probe1 probe2, probe3, probe4, so six wires, so you could use a CAT5 jack/cable. Bear in mind, this would be a different CAT5 cable from the one that powers the blower and servo. On your HM you would need to remove the 10K pullup resistor for each probe and wire the TC amps to the aux probe input header plus 3.3v and gnd, and select TC in the software config for each probe.
 
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