Pneumatic Pressure Switch

[duff]

Hi. Ive been looking through all the old posts about using compressors for flippers. It all seems quite straight forward, apart from this pressure switch business. I understand it all, its just I cant find a suitable one. Ive tried technobots and cant find one there. Can anyone reccomend one and where to get it from, or does anyone have one for sale?

Cheers

[stu]

Pneumatic Pressure Switch

I beleive people got them from http://www.RSWWW.comwww.RSWWW.com
Have a look there mate.

Mr Stu

[woody]

Pneumatic Pressure Switch

http://www.airlines-pneumatics.co.uk/webcat/Detprod.asp?ProductCode=S07014420http://www.airlines-pneumatics.co.uk...Code=S07014420

[duff]

Pneumatic Pressure Switch

Cheers Woody.

Stu, any ideas what one? Ive taken a look at a few but they either dont look suitable, or theyre way too expensive.

But if that one woody says is ok, Ill get that.

[stu]

Pneumatic Pressure Switch

No idea which one, i know people were spending around £25 from RS for one. Get the one Woody suggested. Id take Woodys advice any time

Mr Stu

[woody]

Pneumatic Pressure Switch

Theres more than one on the page so ......Id suggest this as your choice.

1 - 16 bar 106888 £14.37

[duff]

Pneumatic Pressure Switch

It says max voltage is 250V AC. Does the fact that the robot is going to be run from a 12v battery make any difference?

Im not too sure how these things work, so I just want to know if itll do the job.

Cheers

[stu]

Pneumatic Pressure Switch

It will work fine Rhys.

Mr Stu

[woody]

Pneumatic Pressure Switch

Note the low amperage rating.
This isnt enough to reliably switch the inductive load of the compressor motor.
So it will be a good idea to add a higher amperage relay to the circuit.

Sorry to complicate things Rhys

(Message edited by woody on March 12, 2006)

[duff]

Pneumatic Pressure Switch

Excellent. Thanks a lot.

Thats fine, not complicating things, Ive read that a relay will be needed. Just wasnt sure about what switch I needed.

(Message edited by Duff on March 12, 2006)

[big_nipper]

Pneumatic Pressure Switch

We used RS Stock no. 398-7045 (£15) for Blue with a mosfet switch instead of a relay, but found out the hard way that they bounce. They are only made of a spring and set of contacts that the spring closes (or opens) when it gets to the set pressure. When near the set pressure any shocks cause the contacts to bounce. Hence when they reach pressure they will turn on and off several times very quickly. This was enough to burn out the motors on the cheap compressors alone. Also trying to start the motors while pressurised at 10 bar also overloaded the motors.

The solution for us was actaully quite simple. Use a time delay, so if it fires it turns off for 5 seconds or so before allowing it to turn on again. This can be done by adding one resistor and capacitor so its not that hard.

In the end we found a large compressor as the cheap ones were not reliable enough for us and we wanted more flow rate as always. They are a good starting point for someone who wants to use pnumatics, thats how we started, and as long as you dont push them too hard they will last a while but they are cheap for a reason.