Base parts of a compressor
A compressor can be piston or turbine based. Thus device dictates the pressure and the amount of air that can be produced in a certain amount of time.
We also need a motor, a motor starts the device for air compression. A motor can be electric, diesel or petrol.
The transfer of these two can be done with a belt or with a drive shaft.
You would need a regulator that regulates the motor depending on the pressure in the reservoir. This regulator can also work on exit pressure. Manometers that show the pressure in the reservoir as well a manometer that shows the exit pressure.
You would need a hose that connects all the elements above, so that the compressed air can flow. You will also need electric cables.
Compressor out of a fridge motor
This is actually a small compressor that can give compressed air without the elements listed above. A compressor like this without any elements is pretty week, you can pump a bicycle tire in about 10 mintues.
Adding a reservoir to this compressor increases it’s air capacity. This compressor can compress air up to 6 bars, with a 40 liter reservoir. While working it pumps out around 3.5 bars of air, which is a minimum for painting for about 10 minutes.
By adding a regulator you can control the exit pressure as well as the motor. If you want to add a regulator first you’ll need to take off the stock one.
Checking for air leaks
Because we are talking about compressed air it’s really easy for it to leak. Sometimes you can hear it it leaking but sometimes you can sense it with your hand. Smaller leaks are more difficult to hear or sense, you can use something like dish soap. There will be bubbles where air is leaking.