Heatermeter Aux. Thermocouple And two probe board V6.1(Final Version)


 
Never mind - it was my eyes, I was looking at the order lead time, not the quantity on hand (11,000+).

However now it seems the thermocouple socket is not in stock at Newark, the alternative they list has a minimum quantity of 100. Any suggestions on where to look?

RNMixon said:
If my eyes are working right the part in your link shows an 18 week back order - was that a typo?
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Thank you much - Richard
 
The capacitors are a super common part, any 0805 0.1uF MLCC capacitor will do, with at least 25V rating and I'd recommend X5R dielectric. Not sure if this search link will work, but I just went to mouser, passives, capacitors, MLCC, then selected 0805 case code (in), 0.1uF, and X5R, and it dropped down to just 12 in stock products (link). Forgot to select the voltage, but just add that and you'll be good to go.

EDIT: Oops didn't realize there were more posts on the next page. I fail at forums. The thermocouple socket is a real specialty part, I've only been able to get them from Newark for $2 each, or eBay for like $5 each.
EDIT2: Geez I need to just sell them on eBay since someone there has sold 7 at $15 each?!
 
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Steve_M said:
Sparkfun has them for $4 but no idea what shipping is like.
https://www.sparkfun.com/products/13612
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I actually noticed that mouser and digikey have them as well, except with the sparkfun part number PRT-13612 so you can get them with any other order, but at $4.38 each.

Why are connectors always so expensive? I can get TWO microcontrollers for that, or one and a half ESP8266 modules. I also balked at paying $7.50 for a knockoff replacement for a tiny switch that broke in a device I have, so I spent 20 minutes finding a matching part on mouser, only to find they are $8.50 each in quantity 1. What is inside these things?! :confused:
 
Bryan Mayland said:
I actually noticed that mouser and digikey have them as well, except with the sparkfun part number PRT-13612 so you can get them with any other order, but at $4.38 each.

Why are connectors always so expensive? I can get TWO microcontrollers for that, or one and a half ESP8266 modules. I also balked at paying $7.50 for a knockoff replacement for a tiny switch that broke in a device I have, so I spent 20 minutes finding a matching part on mouser, only to find they are $8.50 each in quantity 1. What is inside these things?! :confused:
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Thanks everyone for chiming in - I think I'm set now. Looks like the PCB is the slowest thing to ship - it's being made today but will not be back in until June 28th. Getting it built for brisket on the 4th will be tight.
 
Noob easy question... is the sole purpose of this board to allow the HM main unit to be a remote distance away (up to 50') from the actual smoker? So only the Cat5 cable + damper need to be on the grill/smoker?
 
Yes, the basic idea is the tc amp is inside the RD3 so the TC can plug directly into the TC amp (as is required) and the output of the amp can push down the CAT5 cable without issue (without using special TC extender cables). The board can also be used to add a TC to a HM that does not have one.
 
RalphTrimble said:
Yes, the basic idea is the tc amp is inside the RD3 so the TC can plug directly into the TC amp (as is required) and the output of the amp can push down the CAT5 cable without issue (without using special TC extender cables). The board can also be used to add a TC to a HM that does not have one.
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Thanks Ralph! Looks like a good way to keep the HM out of the elements or out of a curious kid's hands.
 
Kinda thinking out loud here, so let me know if you have any thoughts.

I'm looking at expanding the probe offset system to accept a larger range of values possibly, for better supporting TC amplifiers with offsets and allowing lower temperatures to be read (down to -200C or something). I want to make sure that this board is still well supported by the new configuration. I see that it uses an opamp to provide a low impedance reference voltage to the amplifier, but the reference voltage is set with a potentiometer, is that correct? I'm going to assume this is because HeaterMeter didn't support an off-the-shelf bandgap reference (1.25V / 250C offset) is that correct?

I'm trying to decide if I am just going to add another probe type "Analog Thermocouple with 1.25V reference" which is relatively easy to do, or expand the probe configuration field to 16 bit to allow offsets of up to +/-32,000 degrees, up from +/-127.

The down side of using a 1.25V reference is that the precision of the measurements drops by a factor of 3 for most of the temperature range. The precision currently is around 0.2C up to about 220C, then a not-so-great 0.64C. When using the higher reference voltage, you'll get the 0.64C precision for everything above about -50C. The oversampling and decimation code increases this precision somewhat, theoretically up to 0.05C and 0.16C.
 
Yes, I used an op-amp controlled by a trimmer resistor to provide the offset reference voltage to the TC amp on the Aux Thermocouple board.
 
Hello Everyone, I have a scenario that I can't find addressed previously in this thread (but I may have missed it).

I don't use TCs, just a couple of Thermoworks thermistors for pit and meat. All I'm looking to do is plug the probes in at the RD3 instead of my HM 4.3.

If I use the aux board, do I need any components other than the RJ45 jack and the probe jacks (and probably the header pins for the fan/servo)?

I have a HM4.3 board, do I just need to jumper between probe 0 and 1 and RJ45 pins 1 and 2 on the HM board? Do I need to do anything with a ground or is that already handled?

Does the standard RD3 box also accept the aux board or is it a different print from the one that takes the hand wired RJ45 plate jack?

Am I missing anything?

Thanks for any advice.
 
For standard probes you dont really need the Aux board, you can just add three panel mount probe jacks to the RD3 wiring box (the one with three holes in it), wire them to the CAT5 jack and then add jumpers on the HM board for them and your done. On v6.3 of the aux board we designed it so you can omit the TC parts and install a regular probe jack instead of the TC jack, the pit probe jack 'might" fit into the rectangular opening for the TC probe (haven't tried), or I do have a special box that will fit the Aux board with three standard probes, I have also shared that box with John.
 
Should the probes have a separate ground wire each from the RD3 side (using up all four extra RJ45 pins), can they share one, or can they share the solenoid/fan ground?

At the HM side, do I need to jumper a probe ground or grounds in addition to the probe signal side?

Thanks for the help!
 
You want to use all 4 spare wires, three probe leads and a ground. At the HM you can tap the gnd right over to the power jack ground.
 
HMWiring2.png


Does that look correct?

Do I want to leave the chassis ground tabs on the panel mount jacks open or ground them to the servo/fan ground in the RD3 box?
 
Run ONE ground, lets say you use Pin8, which I would jumper to the GND on the power plug right near by on the HM board. Connect that one ground to the ground lug (sleeve) on all 3 probe jacks on the RD3. Then run the tip from each probe jack to 1,2,7 on the CAT5 jack and jumper 1,2,7 to 0,1,2 on the HM probe header for standard pit probe plus food probe 1 & 2.
 
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