The following is as collection of frequently asked questions about the TC4+.

How do I…? / Can the TC4+ do …?

Can the TC4+ control {some device}?

  • … a popcorn machine with a single AC heating element, and a DC fan motor? Yes! This is exactly what it has been designed with in mind.
  • … a popcorn machine with an AC fan? Yes, although it requires a little bit more effort. The easiest way to control an AC fan is using an AC PWM Dimmer module: Tindie Amazon US Note that other similar modules may not work in the same way.
  • … some other coffee roaster, or an entirely different kind of device? Probably, but we likely won’t be able to comment on a specific device. The TC4+ is meant to provide:
    • One fast-pwm control channel, which can provide gradual control of a single fast-acting device like a fan motor. This has a DC driver circuit for up to 24V 2A DC devices attached on-board, and also provides a 5V logic level PWM signal on the IO3 header to attach other driver circuits (like the above AC PWM dimmer module).
    • Two slow-pwm control channels. These can provide gradual control of a slow-acting device like a heating coil, or on-off control of any other device (e.g. a fan or drum motor that only needs to be on or off, but which doesn’t need to be set to some intermediate power level).

    If your device fits these, the TC4+ could control it. For instance, a small drum roaster with a DC fan, AC heater, and an AC drum motor, would work, as long as the AC drum motor only needs on-off control, not different speed levels. If you need to control more devices than that, then in principle the TC4+ could still work. You could use any unused Arduino pin to connect additonal DC driver circuits, SSR driver circuits, or AC PWM dimmer modules. Similarly, if you need to drive a more powerful DC device, you could build your own DC driver on a separate PCB. However, this would all require some electronics knowledge, and would be a more elaborate DIY project.

Troubleshooting Questions

In almost all cases, if something doesn’t work as expected, the first thing to try is to remove all components except the one not working, and see if it is still not working. Sometimes one defective component can affect seemingly unrelated components in unexpected ways. The following are some more specific things to try depending on what the issue is. If you need to contact us, please check these steps first, and include in your message what you have already tried, and what the results were (feel free to copy-past from below and fill in what happened).

I can’t connect to the TC4+ at all.

This means, for instance, that neither temperature readings nor fan or heater control work, or that you just get error messages in Artisan.

  • Check that you have flashed the correct Arduino sketch (unless you ordered a pre-configured Arduino from us).
  • Check that you’ve selected the right serial port and settings in Artisan, especially if you get messages along the lines of “error opening serial port”.
    • If you don’t get a serial port for the Arduino showing up, you might need to install a serial driver depending on the USB-to-serial chip your Arduino board is using. Check with wherever you bought it from. This shouldn’t happen with pre-configured Arduinos you get from here, nor with original Arduinos from the Arduino store, nor with any boards using a 16u2 USB-serial chip.
  • Check that the BT_SEL jumpers are set correctly. To connect via Bluetooth, they should be horizontal and on the left (see figure in the manual or quick start guide). To connect via USB, they should be horizontal on the right or removed altogether.
  • If connecting via Bluetooth, check that you have the correct PIN and your computer paired with the BT module correctly. If you ordered a pre-configured BT module, the PIN will be listed in the shipping confirmation. If you can’t find it, send us an email.
  • If you have trouble connecting via Bluetooth, try connecting via USB first (pay attention to the BT_SEL jumpers as per above).
  • If it’s still not working via USB, you could try connecting via the Arduino app instead of Artisan. To do this:
    • Download and install the Arduino IDE, if you don’t have it already, from
    • Connect your Arduino & TC4+ via USB. Open the Arduino IDE, and under Tools > Port select the correct serial port.
    • Open Tools > Serial Monitor, and select the correct baud rate (usually 115200) and “CR and LR” for newlines.
    • Enter “READ” with quotes, and hit Enter. You should see several semicolon-separated numbers that give temperature readouts.
  • In very rare instances, a defective device can bring down the entire Arduino. To rule this out:
    • If you have a display, disconnect it, and try again. If it is working now, it was likely a faulty chip in the display that caused the issue.
    • Disconnect all thermocouples and try again. Remove all other connections from the TC4+, and try again.
    • You could remove the TC4+ from the Arduino, and connect only the Arduino via USB, and follow the steps above to connect to it via the Arduino app. If the READ command is getting a response without the TC4+, but not with the TC4+, it’s possible a defective chip or short circuit on the TC4+ is to blame. In this case, contact us.

My display is not showing anything.

Most often, the solution is very simple: There is a small dial at the back of the display that controls contrast. If this gets turned all the way up or down, the display will look completely blank or completely black, even when it is all working. Try turning the dial up or down a little, and see if that fixes things. If your display backlight is off, check that there is a jumper on the two pins sticking out on the left (in most models) of the PCB on the back of the display. This is needed to turn on the backlight but occasionally falls off during transit. If that’s the case, short the two pins with another jumper or a short wire.

I can’t control a DC fan.

If your DC fan that is connected to the DC OUT terminal doesn’t react to commands sent from Artisan (but everything else works), it’s likely one of three things: 1. a configuration issue somewhere in Artisan or the Arduino sketch, 2. a damaged MOSFET on the TC4+, or 3. an issue in the fan motor or the circuit connecting it to the TC4+ itself. A couple of things you could try to narrow things down more definitely:

  1. To test that the correct control signal gets sent to the TC4+: If you have a v5 board or later, see if the IO3 LED reacts to changes. If you have a v4 board or earlier, use a multimeter to measure the voltage between the IO3 and GND pins on the IO3 header. When the fan slider in Artisan is off, that should be 0V, when it’s on at 100%, it should read 5V. If either of those measurements is different, or if the IO3 LED doesn’t react when you try to change the fan level, it could point toward an issue somewhere in the Arduino or Artisan. Double check that you’ve set up sliders / buttons in Artisan correctly (they should send an IO3,xxx command, where xxx is the fan level), and unless you got a pre-configured Arduino, check that you’ve configured your Arduino sketch correctly (it should be CONFIG_PWM mode).

  2. To test only the MOSFET and DC driver circuit on the TC4+, you could do the following: Disconnect everything from the TC4+, including the Arduino. With only the bare TC4+ board, on the IO3 header short the IO3 pin to GND (use one of the jumpers from the BT_SEL header, or a short jumper wire). Then connect only the DC power suppple to DC IN, and the fan to DC OUT. The fan should stay off now. If you short IO3 to 5V, then the fan should be on 100%. If either of that doesn’t work like that, it’s likely a hardware issue. See below for what to do.

  3. To rule out an issue with the fan motor or circuit itself, connect the fan wires that you would connect to the DC OUT terminal on the TC4+ directly to your DC PSU instead. Then fan should now run at 100%; if it doesn’t check that the fan motor, the DC PSU, flyback diode and all the wiring is OK.

If you have narrowed the issue down to a damaged MOSFET, the quickest fix would be to replace the MOSFET. The required IRF540N is widely available (check local electronics suppliers, eBay, Amazon) for pennies or at most a dollar or two. It requires a soldering iron and a few minutes of time to desolder the damaged one, and solder a new one in its place. If you aren’t equipped or able to do this, send us an email and we will figure something out.

The temperature readouts aren’t working.

If Artisan is showing -1 for all temperature readings, the issue is most likely that Artisan isn’t connecting to your TC4+ properly. Follow the steps above under “I can’t connect to the TC4+ at all.” Otherwise, read on:

  • Try only one thermocouple at a time, and try a different thermocouple if you have one. Sometimes a single defective thermocouple can mess with readings for all other thermocouples as well. Try with all other devices (DC PSU, fan motor, display, heater SSR) disconnected, to rule out interference from any of them.
  • It is possible that the thermocouple ADC chip got damaged, for instance through a temporary short circuit somewhere. When this happens, you would usually see all thermocouple channels in Artisan showing the same temperature (+- 0.1), and roughly at ambient temperature. If you cool down or heat up the TC4+ (do this by walking into a different room with your laptop + TC4+, for instance. Avoid touching the chips on the TC4+, and avoid hairdryers) the temperature readouts on all TC channels will roughly track that temperature change, even when thermocouples are connected and at a very different constant temperature. Changing the temperature of the thermocouple probes (e.g. by putting them in ice water or hot water) will not lead to any change in temperature readout.
    • If this describes your issue, it is likely that the thermocouple ADC chip on your board got damaged. This is unfortunately not easy to replace yourself, unless you are equipped for SMD (de-)soldering. Send us an email, and we will assist.

I can’t control the heater.

Most likely, the issue is with your heater, e.g. a burnt out thermal fuse, or a software configuration issue (e.g. if you are using aArtisanQ_PID as your Arduino sketch, make sure it is set to the correct configuration mode, usually CONFIG_PWM). To rule out a software issue, check that the OT1 LED reacts to changes in heater level. If the LED reacts, and you have also ruled out an issue with the heater itself or the SSR, you could try to use OT2 instead of OT1 to rule out a hardware issue in the OT1 circuit, although I haven’t encountered a single instance of this failing so far.

TC4+ board side view