Cooling fans...
That needs some discussion for these boards.
I use beecroft ball bearing fans 5". They are good value for money, and i like the ball bearings too. The following pics depict the fan I use, and how to put a 2k2 resistor onto the circuit board so we can get a pulse to replicate what the board expects for the tacho readings.
Without the tacho readings, the board will assume fan failure and shut down.
It won't do this straight away, it is when it looks for the fan, or the temp sensor tells it it is hot, then it looks for it.... if it cant find it, we stop.
So pic one ... the beecroft
Now we remove the stick on disk on the rear, and we find the circuit board under neath... a careful solder with the 2k2 resistor and shrink wrap, and we now have a 3 pin fan with plus, minus and tacho.
This will allow those who just want to use the boards as they are supposed to be used........
But...
For the rebels.....
Next how to control it..
That image you posted of the temp switch is fine, but I prefer to use a gradual driver, not a bang bang..... I need to live/work in the same space too sometimes... and a fan on.... fan off does not do it for me... so we build this for a few cents.
This has two pots, one for the ramp rate, and one for step off temperature setting... the temp one is marked temp, the ramp rate is the other... devilishly cunning really...
So we can bang bang it if we use no neg feedback/ramp, and as we add feedback we start to make a ramp up to the top speed.... so as the temp approaches the set point, the fan will start turning, and disturbing the still air, if thats enough then good... if not then the temp will rise, but so too will the fan speed, until it gets to full speed if it cant stop the temp going past the set point with lower speeds... its simple as..not very often are they running full speed.
I use two fans, and they have no tacho needed... so no conversion on them. They push pull the main heatsinks.
I use a tiny fan with the tacho wire to fool the board... it never needs to come on anyway.
It is wise to still use the temp sense they supply as is where is... so if your fan techniques fail for some reason, it will turn off from over temp and save the day.
We can get the 12v for the fans from the front two pin socket. It will run two fans comfortably.
Here are half a dozen being built for this and other projects.
Just the pins and odds and ends to add.
The noise... This is the sort of thing we want.... a dual filter.
It has capacitor, torroid, capacitor, torroid, and capacitor.
These are too small, but the ones from the aero sharp 3kw units are fine doubled up for 40 amps.
Plenty on ebay in various guises..... look for EMI filter. You may need a few to get the current rating. I see a few from china 20A fir 10 AUD... four fo these series parallel would be fine. They are single stage, so one after another will be ok, and doubled up in parallel to get the40amp rating we need.
Perhaps try these...
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....................oztules
PS somehow the pics are all queer at the end ... I can't get the pic to display properly