TC AMP board for 3 probes


 
D

Dale Ward

TVWBB Fan
Has anyone found a TC amp board or designed an add on board to add three more tc probes to the HM?


Tired of the food probes failing on me.


Dale
 
I have a board that has 1 TC and 2 jacks. it was designed with the Rotordamper in mind but I could easily design one with just a TC jack and amp.

I am currently working on a Radical Heatermeter design that will be a tad different then the 4.2.4.

It will also work with the Raspberry Pi B+.

It will use a HDMI cable instead of a cat5 cable, the reason being, I was looking for a cable that had a small jack but more wires then a Cat5 cable, It has shielded power wires to help with noise, using that you could have different daughter boards with either 4 TC jacks or you could change and use 4 probe jacks. The Heatermeter wont have any jacks on the main board, making it smaller to fit a B+, but it would need a new case and a case for daughter boards.

But this would give people some options without having to build a whole new Heatermeter
 
Dale Ward said:
I was hoping to do it cheaper.
Click to expand...
That's surprising that board is so expensive, the new MAX31855 chips are fairly cheap compared to their predecessors. They also won't work with HeaterMeter without some hardware jiggerypokery and source code changes. They're SPI bus, not analog.

The best bet would be to just copy paste the existing schematic onto its own board x3 and just wire up the 3.3V, GND, and each output to a header you can mate to the Probe heater on the HeaterMeter. Still you're looking at $7-8 per plug plus shipping and the PCB cost, and you'd need somewhere to mount the board.
 
Bryan Mayland said:
That's surprising that board is so expensive, the new MAX31855 chips are fairly cheap compared to their predecessors. They also won't work with HeaterMeter without some hardware jiggerypokery and source code changes. They're SPI bus, not analog.

The best bet would be to just copy paste the existing schematic onto its own board x3 and just wire up the 3.3V, GND, and each output to a header you can mate to the Probe heater on the HeaterMeter. Still you're looking at $7-8 per plug plus shipping and the PCB cost, and you'd need somewhere to mount the board.
Click to expand...

Anyone have time to try and make a x3 board tried playing with eagle but my old laptop can hardly run it without freezing up. I don't use conventional HeaterMeter case so mounting is no problem, I would use panel mount TC jacks.
 
2mwuzyx.jpg


Here is a proto board that has what you would need, its the best routing board, but it should work. osh park, its 3.20 for 3
 
Are you planning to testing in the near future? Please PM me and I will try and get it assembled and will start some testing.
 
@John

I think this board is missing the 3.3V for the AD chips. It is not on the J2 header (only GND and the four sensors) and I do not see an additional hole for it.
furthermore it is a good measure to add a 100µF on the supply voltage (the 3.3V to GND) - at least one, better one close to every chip.

Best
Daniel
 
Good call Daniel. I see only 6 components per chip and there should be 7. 3 resistors, 4 capacitors. In addition if you want to score bonus points you could also make the ground connections to the ground pin through a single ferrite bead to reduce noise.

It looks like it has 3v3 though, because there are only 3 channels on this board plus power and ground so 5 pins.
 
I added the .1 to the 3.3v and I added a ferrite bead to the Ground. im not sure why I was missing the .1u on the 3.3v line as I have it on all of the circuits I have submitted to OSH so far.

Im still learning :)
 
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Each IC should have it's own 0.1uF decoupling capacitor as close to the VCC pin and ground as possible in theory. I'm not sure it matters in this case though, but having one on the board will definitely help stabilize the power especially in this case because this board will be far from the actual 3.3V supply.
 
ahhh, yes, my fault. Of course there are enough pins for VCC, GND, and the sensors...
I just had the original pinout for J2 on the main board in mind, as I also just made up a breakout board for TCs. Also untested, as I do not have my HM here yet (see my other thread).

Breakout.png


I designed it as a board to directly stack on top of the HM, it takes the 3.3V from the pull-up for the pit probe. Single-sided, so I can quickly etch it on my own, I'll leave the bottom copper as ground plane.

But I just ordered my HM two days ago - I will have to wait a bit for it to be shipped to Germany.

Best,
Daniel
 
Cool! Yah I like the idea to just stack them on top of the probe expansion header. I'm not sure if the image is just showing up funky, but it looks like the filter cap on the TC- side of FOOD2 and FOOD3 is grounded on both sides?
 
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