I thought it would be a nice project to build a vacuum desoldering station (similar to 948 types). I got the gun and a vacuum pump and I'm now onto implementing the control circuit, especially the temperature control.
The maximum temperature I got at the tip was around 450C, which is too much, I'd like to keep it somewhere in the range of 300-350C.
I measured the voltage coming from the thermocouple (assuming K-type) at different tip temperatures and noticed a few things:
- there's differences between readings (always starting with a cold tip and observing the voltages at different temperatures); probably due to the thermocouple not being compensated
- there's quite a lot of thermal mass, even after cutting the supply the temperature rises by another 20-30 degrees
- consequently, there's a difference between the voltage reading and the temperature reading (for example, the voltage starts to go down even though the temperature is still high)
So I'd like to start from here and do a correct reading of the temperature. I already ordered a MAX6675 compensator IC and I'll see what I get from that.
![](https://i.imgur.com/THfUJT5.jpg)