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DIY Small Size Air Compressor on the CheapAuthor
Giorgos Lazaridis
August 17, 2012

PAGE 4 of 6 - Testing the performance of the air tank and the compressor

So, let's make a first test of the compressor. I really had absolutely no idea if the small air compressor would be enough to fill the container with air at 9 bars within a small time, because (as per specs) the pump can only work continuously 10 minutes MAX...

This is the test setup. The pump is powered from a PC PSU, an ammeter will measure the current needed for the pump. A timer will keep track of the time The current started from 3.5 amperes and climbed fast at 5.8 amperes when the pressure reached 6 bars The time to reach 6 bars was only 2.5 minutes! That was better than i expected, but then a problem occurred This connector failed to properly seal the tube, so at 6 bars the hose leaked...
I replaced the sealing collar with a pneumatic quick self sealing connector The second test began with a higher current, about 4.5 amperes This time, the pressure reached 7 bars at 2.5 minutes It took 2 minutes and 40 seconds to reach 8 bars! Excellent performance!

The current at 8 bars climbed up to 6.6 amperes...

Better than expected!
Indeed, much better than expected. I takes less than 3 minutes to get a pressure of 8 bars, so the small compressor operates way bellow its limits. The 6.6 amperes current is a very reasonable current to handle with a simple PSU, probably switching.

Then, i made another final test to see how good the construction is sealed. Without removing the compressor, i measured how much pressure escapes form the tank:


It took some 25 minutes for the pressure to drop from 8 to 6 bars. This is a rather poor performance. I am thinking of using a one-way valve between the tank and the small compressor, because i think that 99% of the loses comes from the poorly sealed compressor...

Generally, i am very pleased with the results.

What about the air capacity? (October 17 2012)
In the first page of this project i did some calculations to see if the volume of the air in the tank is enough - but now things changed. The pressure range is now from 5 to 7 bars. To avoid doing the same calculations again, i made a dirty spreadsheet to do the calculations for me. Here it is:

Download file
Spreadsheet Calculator for the Pneumatic system

Tweaking the calculator? (October 21 2012)
The idea is that i will use a 3-way (or 5-way converted to 3-way) pneumatic valve to actuate the piston. The purpose for the 3-way is that i want the compressed air in the cylinder to be exhausted upon release, so that there is no remaining pressure. But this means that in my calculations, i have to include also the hose air volume, since the air in the hose will also be exhausted. So i made another spreadsheet with the hose volume included:

Download file
Spreadsheet Calculator for the Pneumatic system - Version 2, including the hose air volume

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  • At 7 July 2014, 9:47:00 user daniel wrote:   [reply @ daniel]
    • I have published post about homemade airbrush compressor http://www.myairbrushcompressors.com/how-to-build-a-cheap-airbrush-compressor-using-refrigerator-parts/

  • At 29 January 2013, 6:51:41 user Giorgos Lazaridis wrote:   [reply @ Giorgos Lazaridis]
    • @Nikos i've got the system but i have not installed it yet.

  • At 28 January 2013, 13:39:37 user Nikos wrote:   [reply @ Nikos]
    • Has automatic system to turn on while you use it to refill or you turn on manually?

  • At 28 September 2012, 5:16:50 user Air Compressor wrote:   [reply @ Air Compressor]
    • I appreciate your interest to make equipment. Many companies give illustrated explanations about air compressors.

  • At 18 September 2012, 10:59:44 user Giorgos Lazaridis wrote:   [reply @ Giorgos Lazaridis]
    • @George Actually, i'm building my pneumatic solder paste dispenser. My next addition will be the smd pick-and-place, for which i already have the pump (USD4) and a manual dispenser (USD 2) which i will hack. Both the solder paste dispenser and the pick and place will be housed under the same box, will have the same foot pedal for operation, and will have a switch to choose which one i currently use.

  • At 18 September 2012, 6:12:25 user George wrote:   [reply @ George]
    • Het Kam, whilst you are building your smd 'picker', here's a cheap one you could use, looks like it's using a modified fish aquarium pump for the vacuum


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