Custom Pneumatics - Control Board Selection?

[Erin Rapacki]

Hi,

If somebody could help me out, that'll be great! I work as a researcher at school and my professor has asked me to put on an "electrical hat" for a certain project... problem is, it's not my area of expertise and I see conflicting information.

I first looked at the FIRST pneumatic circuit for like comparisons; the problem is I see a discontinuity between the amount of Amps the compressor pulls (Thomas 405ADC?). It operates at 12 V-DC but pulls a current of 10.5 Amps. The IFI controller sais "The total combined current supplied from all 16 Analog and 18 Digital +5V Power header pins is 1 Amp. The 1 Amp max can come from a single +5V Power pin" or that it has a 7mA max... which is not near 10.5 Apms. Where is that current coming from then?

I'm looking to put on a 12 V-DC compressor that has 1.9-3.2 Amp current consumption. The board I'd like to use is PC-Gadget's Gradget Master 2, but its current draw is less than 0.24 Amps continuous and everything has to have 50Ohm resistance.


Um... help?
Should I look for more powerful controllers or less powerful compressors/vaccums?

Essentially, I'm making a system of a compressor, storage cyclinder, Pressure regulator, pressure switch, solenoid, the bladder for the compressed air movement (inflatable sack), another solenoid, the vent valve, and a vaccum to suck air out of the sack. The projext to to make a bag that inflates & deflates at pre-controlled intervals.


Thanks,

erin

[Mark McLeod]

The compressor doesn't pull it's power from the control board. It pulls it from the 12V battery source through a spike relay.
The controller only serves to switch the spike on/off based on the pressure switch and actually stays out of the main current flow.

Try thinking of it as two separate circuits you are building:
1) A 12v circuit connects a 12V DC source through a spike (and a circuit breaker or fuse) to the compressor and also through spikes (and breakers) to power the solenoid valves. The control board will also need to be supplied power just to run.
2) A separate control circuit overlays this with the control board sending control PWM cables to each of the spikes.

Take a dorm room overhead light as an analogy. The control circuit is the "finger" that flips on the spike "light switch" allowing the house power (your 12V) to flow to the overhead light (your compressor).

In your case run the compressor to reach your operating pressure using the pressure switch, and use different limiting switches to control the solenoid values inflating/deflating the bladder.

[Al Skierkiewicz]

Erin,
I looked at the Gadget Master II and it is designed to run small hobby motors at 12 volts output max. You can use a relay that is controlled by the Gadget Master to switch 12 volts to the compressor. Just wire the relay coil to the output of the controller and insert the normally open contacts of the relay in series with the 12 volt positive power supplying the compressor.
Are you coming to Atlanta, look me or Mark up and we can further explain. 12 volt relays with a coil resistance of 500 ohms or greater should be available at Radio Shack.

[Erin Rapacki]

Thanks for help guys.

No, I'm not going to Atlanta this year (first time in seven years!) Lots of Senior project stuff to finish up; final presentation on April 17 & then a Final Exam on the 18.