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SMD reflow oven (c-flow)


  1. connect the 230V into a socket
  2. remove usb dongle and usb cable from inside of the oven
  3. put your board with solderpaste applied and components placed into the oven
  4. click the tumbler on the controller box to ON position
  5. because of arduino compatibility, it takes microcontroller 8 seconds to boot (old atmega8 compatible arduino bootloader waits for programming instructions all this time). It will blink the RUN led after the boot is complete.
  6. remove all the junk from the top of the oven - it gets hot, you don't want anything to start smoking
  7. press the red button
  8. watch the board, wait till the solder reflows, press the red button and open the door slowly
  9. replace usb dongle and usb cable back into the oven as it cools down
  10. unplug the 230V connection

If you don't want to watch the board while it reflows, the microcontroller is programmed to raise temperature up to 205°C, keep it there for 15 seconds and turn off. This should be suitable for the most boards, but it can differ depending on board/component size and solderpaste used.

A computer can be connected to a serial port accessible on the side of the control unit, the pinout is marked. Communication can be carried out by a simple serial terminal program. Rudimentary command line interface is available:

  • stop – stops the process
  • run – starts the process and outputs the measured temperature
  • setTemp – sets the max temperature for the current temperature profile step.


Hacking on code and hardware is encouraged and welcome, just leave the oven in operational mode after the hacking session and inform the others.

All the sources are available at

The same usb dongle connection can be used to program the unit. Arduino code is available at Programming is transparent - just open arduino environment and press the program button. Ping me if you want to contribute some code, I will add you as a developer on the github repo.

The current choice of PT100 temperature sensor is not optimal as it's connections will corrode with time and it can be broken easily. The choice was driven mainly by price. Luckily the design is modular and temperature sensor module can be replaced by a new design. If someone wants to put in a thermocouple, you are wolcome to do so.

The SPI interface is broken out on the controller board, so a 74HC595-based LCD interface can be connected to it. I've bought a couple of ribbom cable connectors for small LCDs we have available, I'll bring them and leave in the same drawer as LCDs. Unfortunately there is not much space left in the box for the LCD.

Long bootloader times are anoying, anyone is welcome to work on the old arduino bootloader code to shorten that. ISP header is available on the controller board for standard AVR firmware uploading.

We didn't implement a proper PID control as the oven is underpowered and does not suffer from overshoot problems. If the oven is replaced with a more powerful module anytime, PID control might be appropriate.

Feel free to hack the current firmware by adding new commands to command line interface.

Ethernal respect for the implementation of the project goes to: uk, riot, mic.

c-lab/c-flow.txt · Last modified: 2015/01/23 17:41 by xen