Wiring
The only thing you need to do to control the oven is connect the two relay output wires appropriately. All the Reflowduino does is control the live (L) wire from the AC outlet on/off while the other neutral (N) prong is always connected. In the US the live prong is the straight, narrower prong whereas the neutral one widens at the end. When the controlled "leg" is connected, power flows to the oven (or hot plate). The following diagram shows the general wiring scheme:
Please note that this control scheme is exactly the same for hot plates. Also, for the Reflowduino Basic you will have to connect an external relay to the relay control pads on the Reflowduino.
IMPORTANT DISCLAIMER: Again, if you don't know what you're doing, please do not attempt this! All actions are are you own risk. It is not recommended to use this setup for extended usage and this was used for demonstration purposes only! If you attempt this project please solder the wires and use proper insulation and take proper safety precautions like certified safety glasses and gloves. Never adjust wiring with the power cord plugged in!
For hot plates with a single temperature control knob you can either choose to break open the device and bypass the temperature knob or you can simply turn it to max it out at HIGH. The reason this works is because the temperature control operates on thermal expansion of metal contacts inside. By turning the the knob to the highest setting you're simply allowing the the device to always conduct, which is just what we want since the Reflowduino will be taking care of the control anyway. If you want you can permanently glue the knob to HIGH if you think you'll forget to check it. This method leaves us with only the power cord to worry about! Below is a test setup I used for the hot plate:
Here's a closeup of part of the wiring:
If you are using something like this enclosed relay with the Reflowduino Basic, you simply only have to plug in the hot plate's power cord into one of the provided receptacles; solder wires from the Reflowduino's "RLY+" and "RLY-" pads and secure them in the relay module's screw terminals; and finally, plug in the relay module itself and turn the switch on! (NOTE: I haven't personally tried that relay module myself) I'm currently working on a junction box for the Reflowduino Pro that will simplify the wiring and consolidate everything as a single box!
In order to keep the thermocouple pressed against the hot plate, I used a large wrench socket which I placed on top of the metal thermocouple tip. This turned out to work quite well. However, a more permanent solution would be to drill a hole and fasten the thermocouple with a metal shim attached to the hot plate using a screw.
This video shows the app collecting and graphing the data via Bluetooth.
Toaster ovens are a little harder to work with (but not much harder) than hot plates with since they have multiple knobs and these knobs don't only control temperature. Also, depending on how fancy you want to get, you might want to drill a hole for the thermocouple to be routed inside the oven. This means we have to take a look at the guts of it!
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