Tosti Reflow Oven

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Revision as of 16:17, 21 April 2014 by Themba (Talk | contribs) (Progress)

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To make an smd reflow oven from an old sandwich oven.


April 17, 2014

Another run(see repo) confirmed that the overshoot is now fixed. We still have to think about the cooldown stage. In this run I opened the oven a little just after reaching the top. And then more and more towards the end. This makes the temparature decline more or less linear. I think that we need to test if the decline exceeds 5'C/s if we just open the thing after reflowing. If that is acceptable we can just buzz the buzzer at that point.

April 8, 2014

I assambled the thing and did the first full run. I visualized the heat-profile of this run in a fancy graph(see image in git repo).

What can be seen from this profile is that the oven is clearly capable of reaching the right temparature (which I was afraid would be a problem).

Secondly, the temperature change is not very steep. 1.5 degrees per second at the very max. When reading into the details of the reflow process it becomes clear that the strange shape of the ideal temperature curve is the result of different maximum dT/dt in the different phases of the process. Since we won't reach the maximum temperature change in many areas of the profile, our program will more or less boil down to: heat to 235 as quick as you can; then cool down as quick as you can. The only exception is the "soaking" stage where there is a maximum incline of 1 degree per second(violated in the first run:)).

Thirdly, there is a massive temperature overshoot. I had calculated for an overshoot of 5'C degrees and stopped the heating at 230'C. The temperature still reached almost 260'C which is 25'C above the desired maximum. I have changed the code for the second run to stop heating at 205'C which should result in a maximum temperature of 235'C.

Some images of the assambled parts:

All components working together for the very first time Close up of the display SSR in action Another shot of the SSR protective cover The thermocouple entering the oven

Note that not everything is connected at this stage: the buzzer is still missing and I connected only one of the buttons (I have to admin that I lost the other button:-().

March 12, 2014

Work has started on all fronts:

  • software: a beginning has been made
  • low voltage hardware: arduino and max6675 now have pin headers
  • high voltage hardware: a protective clip for the relay terminals was printed, it fits perfectly! The toster oven didassambly turned out harder than expected. Maybe we need another toaster oven:s This one has internal grill lines that will touch the pcb.

March 9, 2014

All parts received now! here are some more pictures:

Arduino pro mini microcontroller MAX6675 themocouple controller K-type thermocouple tip of the thermocouple

March 2, 2014

First part received!

Solid state relay


Project repo: at the moment it contains a 3d design for a protective cover for the relay.

Interesting reads:

Software inspiration:


what details status on ebay? price
sandwich oven jeroenh has it
thermocouple k type received @themba $1.22
thermocouple ic max6675 received @themba $4.95
sop8 adapter for max6675 received @themba $1.58
controller arduino pro mini received @themba $2.80
relay solid state 25A 350V~ received @themba $3.67
breadboard sjoerd has it
16x2 lcd display sjoerd has it
buzzer sjoerd has it

Total price: $14.22(=E10.51)


  • we will need an enclosure for the 230V part, it has huge screw terminals that will be at high voltage when in operation.
  • when(if) the thing works we may also want a case for the other parts to keep it organised.
  • we will also need a flat piece of metal to rest the subject on during soldering.