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View Thread » DATALOGGERS - CONTROLLERS - RATE OF RISE METERS » Dataloggers/Controllers/Rate of Rise Meters
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CR3 Arduino coffee roaster shield (TC4-compatible)
Hi all,

A few months ago I started designing my own Arduino shield for my coffee roaster, as I wanted a few additions to the TC4 design, ideally all on the same board. The result is a fully TC4-compatible shield, that also has an on-board voltage regulator, DC fan driver, and header for a bluetooth module. I've been using this for a while now myself. I've recently had access to a decent electronics lab space, so I decided to make a small batch of these boards, since a few people on here seem to be looking for thermocouple boards. I've got about a half dozen of these that I could part with - let me know if you're interested.

My “coffee roaster board version 3” (“CR3”) is a TC4-compatible Arduino shield featuring MCP3424 ADC, MCP9800 on-board temperature sensor and 24LC512 EEPROM. In addition, the board features an on-board PWM driver for a DC fan, a voltage regulator to power the board & Arduino, and a header for a Bluetooth module. This allows control of a popcorn roaster with only a single controller (Arduino + this shield), one PSU and one SSR, and wirelessly. The board is fully compatible with all TC4-based Arduino sketches, and should work with any other type of roaster as well, of course.

Additions compared to TC4
• PWM control for DC fan. Board includes an IRF540N transistor that can drive a DC load, attached to the IO3 pin. When using a popcorn roaster with a DC fan, the fan can be attached directly to the CR3 board. (Up to about 4 amps.)
• On-board voltage regulator. Board comes with a 5V switching regulator to power the board & Arduino, accepting a wide range of input voltages. This is running of the same supply as the DC fan driver, so you only need one power supply for both. The PCB itself is designed as flexible as possible in regards to the voltage regulator, and has space for either a switching regulator or a linear regulator in a TO-220 package plus heatsink; as well as space for extra smoothing capacitors if needed. When using a voltage significantly higher than the Arduino’s 5V (e.g. 20V for a DC fan), a switching regulator is strongly recommended over a linear regulator.
• Bluetooth header. A header for a HC-05 or HC-06 Bluetooth module. Allows communication with the module wirelessly, via Bluetooth serial port. Selectable attachment either directly to the Arduino’s serial port, or to two DIO pins (for software serial or configuring the BT module). If using a HC-05 module, the module can optionally reset the Arduino when a new BT device connects – that way sketches can be uploaded wirelessly from the Arduino IDE.
• Two extra IIC headers for displays etc.

Other differences compared to TC4
I did not include a JeePort header, Analog In headers, or a reset button. (The functionality of all those is still present of course, just not in a single header.) Everything else that’s on the TC4 is also present on the CR3.

Cost, availability and shipping
For now, I am able to offer a handful of kits for EUR 48 / GBP 42 / USD 58 plus shipping. The kit includes the PCB with SMD components already soldered on plus all through-hole components (headers, jumpers, screw terminals, one R-78E5.0-1.0 switching regulator, capacitors, one IRF540N transistor.) You will have to do the through-hole soldering yourself. Alternatively, I could do fully assembled boards for EUR 93 / GBP 82 / USD 113.

Shipping should be USD 14 for US, EUR 11 for EU, GBP 5 for UK. For other destinations, contact me with your location for shipping costs and options. Payment can be made via PayPal Invoice (with full buyer protection) - message me your details and email address, and I can send one over.

Frequently Asked Questions

Why the name CR3?
I originally started with a small shield with only the voltage regulator and DC fan controller, which was stacked on top of a TC4 board. I named that one CR2, as the TC4 was the main board. So the next version was CR version 3. (If anyone already has a TC4 and is interested in the CR2 board with voltage regulator and DC fan controller, let me know. It’s all through-hole, so I could easily make the bare PCB available.)

Can I use any TC4 software with this?
Yes. I've tested it with aArtisan, but any other TC4-based Arduino sketch should work just as well.

I don't need any of the additional features, can I use this just as I would use a TC4?
Yes. The ADC, temperature sensor, and EEPROM are the same chips as on a TC4, and all the additions are entirely optional.

Does this work with an AC fan? Do you also make a zero-cross detector?
Sort of, and no. I have designed this with DC fans in mind, so the board does not include a ZCD or any other hardware specifically for AC fans. But you could still attach an external ZCD board and us a random-fire SSR to control an AC fan, IF you can find or make a ZCD. At this time I am not making or selling a ZCD myself.

Known issues
On the current PCB revision the labelling of the thermocouple channels is hidden by the screw terminal. The labelling will be moved further afar in a future revision. Note that from left to right the pins are Ch2- Ch2+ Ch1- Ch1+ Ch4- Ch4+ Ch3- Ch3+.
mg512 attached the following file: [1022.36kB / 43 Downloads]
mg512 attached the following image:

Edited by mg512 on 05-27-2018 04:00
Hello Mg512. Very intersting board. Could you provide more info about the intrnal code you use to drive it (is it the tc4 original library?). Is it also fully compatible with Artisan (especially regarding regulation of fan, which seemed to be modified) and Android TC4 Roasting app from Greencardigan ? As I am very interested’ could you let me know when you start shipping in Europe? Cheers.
Edited by RoastingBen on 05-01-2018 10:03
Hi Ben,

Thanks for your positive feedback - happy to hear that.

I am using the exact same code as with a TC4; in fact I was using a TC4 originally which I switched out for the CR3, without any changes on the software side. It's the same hardware plus some extras, so any sketch designed for the TC4 should work with this too. I've been using aArtisan; but any other TC4-based sketch should work just as well.

It's fully compatible with Artisan - I've been using it that way without any problems. Fan control too, it's just a transistor attached to the IO3 pin. The difference in this regard compared to a TC4 is that you already have the transistor on board. With a TC4 you would have the transistor too, just on a separate PCB or with wiring soldered directly to it. From a software perspective there's no difference, just hardware-wise I wanted everything on one board. (This is assuming a DC fan. AC fan is a different story.)
I've attached a (very) quick drawing to illustrate the difference - with the TC4 you would need some sort of power supply for the arduino, and an external mosfet transistor to drive the DC fan. With the CR3 the mosfet is on the board already, plus there's a voltage regulator so you can run the board of your DC fan power supply, eliminating the need for the 5V/USB power supply.

I haven't looked at the Android app in detail, but if all it needs is the Arduino's serial connection over bluetooth and aArtisan, then it absolutely should work. The header is specifically for the HC-05 / HC-06 line of bluetooth modules wich greencardigan also seems to use, and is attached to the serial TX/RX ports of the Arduino.

I'm in the US at the moment; I could ship a board from here if you needed it urgently, but it'd be a bit more pricey. Alternatively I'm back in Europe in about three weeks, and could post it from there. PM me your country and zip code, and I can look up some options either way.

mg512 attached the following image:

Edited by mg512 on 05-01-2018 12:32
Hello Matthias. I have sent you my details in MP.
hi there

I am really interested in buying one of your shields. I am in the uk.
can you give me details on how I can buy.

Ben, just replied to you.

Hi James, glad to hear my board might be useful to you. You could pay by PayPal if that works for you; shipping depends on how soon you need the board. I'll pm you for details.
Is it possible with your shield to control a heater on OT1, AC fan on OT2 and a DC motor for the drum at the same time? Nice work with the shield!

ROSTARN wrote:

Is it possible with your shield to control a heater on OT1, AC fan on OT2 and a DC motor for the drum at the same time? Nice work with the shield!


Hi Johan,

In principle that should be possible. A few things to bear in mind though:

1. The DC fan circuit on the board isn't meant to drive huge loads. What's the voltage and amperage of the drum motor?
2. You'd need a ZCD for the AC fan, which at the moment you might have to make yourself.

And thanks. :)

A small 12V DC motor pulling 2A, so nothing huge.
I have the original TC4 board already with ZCD so that not a problem.
The problem is that i cant get the DCFAN command to work on IO3, where i want my drum motor.
I tried different options in the software but no luck.
OT1, resistive heater and OT2, ac fan, works like a charm but it would be nice to control the drum motor as well =)

ROSTARN wrote:

A small 12V DC motor pulling 2A, so nothing huge.
I have the original TC4 board already with ZCD so that not a problem.
The problem is that i cant get the DCFAN command to work on IO3, where i want my drum motor.
I tried different options in the software but no luck.
OT1, resistive heater and OT2, ac fan, works like a charm but it would be nice to control the drum motor as well =)


Just to be sure, you don't have the ZCD connected to IO3, do you? Does IO3,100 work? How about IO2,100 (when you connect the fan to io2)? How are you connecting the fan to io3/2?

You should be fine with the TC4 - the only advantage of the CR3 if you already have a TC4 would be that everything is on one board.
...Is it possible ... at the same time?...

Without modification in the aArtisanQ_PID, it will not be possible to use 3 outputs at the same time.
Perhaps it will not be possible to modify it for lack of memory.
Maybe I'm wrong, important is what Brad thinks.
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