DIY 948-type desoldering station

[bogdan2014]

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.

[ralphrmartin]

I'm about to do a project which needs similar suction to a desoldering gun. Can I ask which vacuum pump you used?

[tooki]

FWIW, Pace (which makes excellent desoldering tools) uses a 12V DC, roughly 20inHg/70mbar vacuum pump, which they then overdrive at 24V for around 1/2 second before dropping down to 12V. That gives an initial burst of higher vacuum to clear the hole.

If you decide to emulate that behavior, then you want to get a pump with a brushed DC motor, not one with a brushless DC motor, since the overvoltage would likely just fry the controller. (Just don’t try to sell anything using that approach, since they patented it.)

Here’s a video I took of it in slow-mo, by the way: