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01/04/2019 10:55 AM
2 years today...Miss you Ginny!

01/04/2019 4:24 AM
A little shout for the G'ster. 2 yrs. roar

12/27/2018 5:14 AM
Hi Brandon, please disregard the "please update". I think we're all up to speed now. The need for cache clearing get's me every time! limb

12/26/2018 11:36 AM
Update? pouring Merry Christmas back atcha

12/26/2018 3:07 AM
Merry Christmas Brandon. Please update soon! christmas tree

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TC4+ Arduino coffee roaster shield (TC4-compatible)
I was thinking that there was an issue with the MOSFET, so I ordered some a few days ago, they should be here today and ill Swap it out, I didn't check middle leg to ground but i will when i get home, and yes the fan was running with those readings
Hi Matthias, Good News!!!
I replaced the MOSFET today when I got home and now the fan speed can be controlled by Artisan, Thanks for your Patience!!
Also Thanks to greencardigan AKA Brad for his input as well.

Oh, I am very happy to hear you got it sorted! Just out of curiosity, can you think of anything that happened when you set up the board that might have damaged the MOSFET? This is actually the second time that has happened in just over a dozen boards; the other time we assumed it happened during assembly, but this time I assembled the board and tested the MOSFET before I mailed it to you. If the MOSFETS are so sensitive to ESD I will have to look into that.

I'll in any case refund you a part of the order for your trouble and to cover the cost of the new transistor; However it got damaged, this is obviously not the robustness I am aiming for.
The only thing I do know was having the polarity of the flyback diode wrong, The fan wouldn't come on initially, I swapped the leads at the terminal strip and the the motor came on without any control.
I then took an re soldered the leads and diode so the red and black leads were correct along with the diode (which when I double checked I saw the polarity was reversed) . At that point I think whatever happened was already done and the fan would only run full speed.
Please there is no reason for a refund, I apologize that whatever i did caused a problem

Ahhh, yes, that would create a short, which could have damaged the MOSFET. Still a little surprised, as the IRF540N is rated for 33A continuous current, so I'd expect the power supply to go long before the MOSFET. ;) And no need to apologise, that's actually very good feedback - clearly there should be a prominent warning about this in the manual. ;))

Anyway, happy to hear it's sorted. :) Let us know how the roasting goes. :)
Wiz Kalita
How much power can the DC fan driver supply? My fan takes 20V and 2A, so I already burned through some L298N boards due to the 3-4V voltage drop.
Good question.

Short answer: 20V and 2A will be fine, in fact it's what the board is made for. ;) I have been running mine with 24V 2A. In theory you should be good to about 28V 2A without a heatsink, or 28V 4A with a small heatsink on the IRF540N.

Long answer: It depends. Voltage is limited mostly by the voltage regulator for the Arduino, the R-78E5.0 that the board comes with by default takes up to 28V. There's regulators that take a higher voltage too, or one could always use a separate AC-DC PSU for the Arduino, som ore than 28V are possible too. (That's for reasonably small voltages. I haven't really paid attention to separation distances on the board etc.; so don't go running 100V through the board.)

For current, it's all about temperature and cooling. The IRF540N is rated for up to 33A continuous current, but without any cooling I think 2A is a safe level, with a small heatsink on the IRF540N 4A should be fine. Beyond that you could probably manage with some active cooling or heavier heatsinks; but you'd soon be limited by the copper trace on the PCB rather than the IRF540N. You'd have to do some testing if you want to go above 4-5A. (If required I could actually have a small number of PCBs with heavier copper traces made, but I'd be surprised if anyone needed more than 5A.)

Also this all depends a little bit on usage - one 15 minute roast at a time is less stress on the system than continuous usage, obviously.
How are TC supposed to be connected to this board, naked wires and screws ?

Asking because I want a solution allowing me to preserve the genuine TC connector, either the fork clips, either yellow mini plug.
I can source such green connectors locally, as yours, but force me to cut the TC connectors, not like.
renatoa wrote:

How are TC supposed to be connected to this board, naked wires and screws ?

Asking because I want a solution allowing me to preserve the genuine TC connector, either the fork clips, either yellow mini plug.
I can source such green connectors locally, as yours, but force me to cut the TC connectors, not like.

The default connector is a 2.54mm spaced screw terminal. That works best with bare wires, but you could probably fit fork terminals in there too, if you preferred. I.e. you could screw one prong of the fork into the terminal, and have the other one stick out. Just have to be careful that the free prongs don't touch one another.

If your thermocouple comes with a yellow two-pin plug, you might not have to cut the wire - some of those plugs are screw-on plugs, so you could just unscrew them, and could screw them back onto the thermocouple wire if you needed to. Only thing you can't do is plug a yellow TC plug directly into the board. I was considering that at some point, but those are simply too large, having matching connectors on the board would increase the PCB size by a third if not half.

You could also solder any other 2.54mm spaced connector onto the board. I'm using mini Molex connectors myself, just need to crimp the appropriate connector onto the thermocouple wire.
I have now made a website! Check it out:

There is PayPal buttons for ordering now - hopefully that should make the process easier. No more emailing or PMing me. :) I'm also open to any other ways of making the ordering as straightforward as possible. I might put the boards on Tindie, but any other suggestions are welcome as well.

I have also been in touch with Jim (from the original TC4), and might take over his remaining stock of TC4 boards and parts, along with maybe ZCD and TC4C boards. So if everything works out, those should be coming soon. :)
Update: The board finally has a proper name - the TC4+. And boards are now available on Tindie as well as via the website:
Hi, congrats for the board and for the effort you put to set all this up.

Did you do some measurement to evaluate the accuracy of temperature measurement given by TC with voltage regulator and MOSFET ON? I am asking you this because these 2 components should generate quite a bit of heat that could make CJC measurement less accurate.

Where is the CJC IC placed? I'd expect on the back of the board, just below the TCs connector.
If there is a ground plane generous enough, then there shouldn't be a big temperature gradient across the whole board ...
Anyway, I seen setups where the whole electronics is in an enclosure just near RC, reading on LCD even +40 C for AT at the end of roast, so there could be worse Grin
Edited by renatoa on 01/23/2019 4:48 AM
In order to be as accurate as possible, you really need to have the cold junction temperature measurement done as close to the junction as possible.

This is especially important for boards with high temperature gradients or heating up unevenly. That's why I'd like to know something more about it.
Check board image at tindie:

The two smd chips that can be seen are the temp sensor in the left, the smaller with 8 pins, near the Arduino pins 5-6-7, and ADC the other smd chip, with 14 pins.
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