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X-toaster Board Layout

 

RESET Reset for the Xmega, not mounted.
PDI Programmer/debugger interface for the Xmega, if you have one of the latest PDI capable Atmel programmer like the AVRISPmkII and the ATMEL-ICE you can use it to upgrade X-toaster with future firmware revisions.
INT SENSOR Populated with a DS18B20+, used to read the temperature around the board.
If you are going to fit X-toaster in an hot environment (like inside the oven itself) it can be used to keep track of the temperature and shut the system down if temperature goes above some limit that you can program via GUI.
EXT SENSOR  Unpopulated. You can fit another DS18B20+ to read temperature from another area. Like the internal sensor it possible to set a maximum temperature after which the system has to be shut down. If you mount the controller in a separate box but if you fit the SSR inside the oven, you can use it to make sure that the SSR is not overheating.
G: ground, V: 3.3V, D: data
HEATERS CTRL  This is used to drive the SSR which controls the oven’s heaters.
Its output is a slow PWM with a peak voltage equals to VIN less voltage drops on D3 and Q4 which results in around 4.70V. Some Chinese SSR are not able to fully turn on and work properly even if they have 3V~32V INPUT written on their labels. If you find that this is the case you may want to short D3 terminals to have a driving voltage almost equals to VIN. If you get our kit with the SSR that we supplied you should not have any problem and no actions is usually required.
FAN CTRL  Used to control the oven’s fan if your oven has one.
It is based on the same circuit of HEATERS CTRL so the same considerations about SSR connections are valid. Since this is not switched on and off so often like the heaters you can also use a mechanical relay to drive the fan.
THERMOCOUPLE  You can connect any K-type thermocouple but because we are using a MAX31855 it has to be isolated from GND.
VCC IN  Used to power the board. You should use a power supply with a clean and stable voltage of 5VDC capable of supplying at least 500mA.