compressor and light question...

[archiver]

Posted by Anton Abaya at 2/13/2001 3:34 PM EST


Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT! .



if say the compressor was running all the time with varying amounts of pressure, what's the average as well as the maximum amperage draw that it's taking? i'm curious to know if it will interfere with our drive train.

the second question is the light. what's its average draw as well from the battery?

i'm afraid of tripping breakers now considering we have a bunch of things being powered at the same time.

-anton

[archiver]

Posted by Joe Johnson at 2/13/2001 4:43 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: compressor and light question...
Posted by Anton Abaya on 2/13/2001 3:34 PM EST:



It is not that hard to wire in the pressure switch. I recommend agianst running the pump all the time.

I have not tested the pump, but you will probably draw close to the 10 Amps that the device is rated for.

As to the light, I think last year's lamp used 2-3 amps but I could be wrong.

Joe J.

[archiver]

Posted by Lloyd Burns at 2/14/2001 9:20 AM EST


Other on team #188, Woburn Robotics, from Woburn Collegiate and Canada 3000, ScotiaBank, Royal Bank Financial.


In Reply to: Don't do this...
Posted by Joe Johnson on 2/13/2001 4:43 PM EST:



: I have not tested the pump, but you will probably draw close to the 10 Amps that the device is rated for.


: Joe J.

The previous (two years ago pump) was rated at 8 A, which was true while running (perhaps a little lower current was drawn on average), but on start-up, into a pressurized system, it would draw OVER 20 A (locked rotor current, basically). It blew fuses. The motor couldn't start with the load of the pump working into pressure.

Some wrote to First, and the rules were expanded to allow the use of a motor speed controller, which could handle the current better than the relay circuit in the controller.

[archiver]

Posted by Eric at 2/15/2001 10:30 AM EST


Coach on team FEDS from RHS sponsored by Visteon.


In Reply to: Re: Don't do this...
Posted by Lloyd Burns on 2/14/2001 9:20 AM EST:




: Some wrote to First, and the rules were expanded to allow the use of a motor speed controller, which could handle the current better than the relay circuit in the controller.


I want to clarify this. Which update was this in?
Are you allowed to wire the pump to a speed controller?
If so is it to be fused at 20A or 30A?

[archiver]

Posted by Ed Sparks at 2/13/2001 5:41 PM EST


Engineer on team #34, The Rockets, from Bob Jones High / New Century High and DaimlerChrysler.


In Reply to: compressor and light question...
Posted by Anton Abaya on 2/13/2001 3:34 PM EST:



Ok, if you do this you will discover a feature about your compressor you may not have noticed. It has a thermal cutoff and if you run it constantly at 120 psi head pressure, you WILL experience it.

Actually, this is a good thing because the alternative is to buy a replacement pump at $177 ea (I bought a spare).

I ran into this cutoff problem with my initial version of our compressor control software but using a couple of tricks I solved our problem as follows:

rc_sw1 is where my pressure switch is wired
relay7_fwd is where my compressor is wired

I defined compressor_delay as variable VAR byte
I initialized compressor_delay with a value of 0
I defined delay_setpoint as a constant CON 120
bbox_compressorswitch is a switch on the operator panel

My MAIN LOOP calls the following SUBROUTINE

COMPRESSOR_CONTROL:
if bbox_compressorswitch=OFF then compressor_stop:

if rc_sw1=OFF then delay_compressor_stop:
compressor_delay=0
goto compressor_start:

delay_compressor_stop:
if compressor_delay > delay_setpoint then compressor_stop:
compressor_delay=compressor_delay + 1 + delta_t
goto compressor_start:

compressor_start:
relay7_fwd=ON
return

compressor_stop:
relay7_fwd=OFF
return




The plan is to keep pumping air into the volume tanks past the pressure switch trip setting (about 110 psi) until you reach the point where the pressure relief valve starts to open (about 120 psi). I do this by counting the number of program cycles plus delta_t from the point where the pressure switch opens. In my case a value of 120 (about 3 seconds) for delay_setpoint works good. When the air is consumed and the pressure drops below the pressure switch trip setting, the whole thing starts over.

It works fine for us and keeps the compressor from short cycling (not good) when there is no demand for air .

Hope this helps!

[archiver]

Posted by Al Skierkiewicz at 2/14/2001 2:04 PM EST


Engineer on team #111, Wildstang, from Wheeling High & Rolling Meadows High and Motorola.


In Reply to: compressor and light question...
Posted by Anton Abaya on 2/13/2001 3:34 PM EST:



Anton,
We measured compressor draw with a Fluke Current probe. At low PSI current is low, but goes up to steady 9-10 amps above 60 PSI. Current is very high at start no matter what system pressure is, but is short duration.(less than one second) If I am not mistaken, FIRST requires the pressure switch to be linked to pump so that it does turn off electrically. The relief valve on the pump opens reliably at 120 psi.
Lamp draws in the neighborhood of 3 amps, a lttle less that last year.(smaller motor, smaller turning assy?)
Considering the specifications on the breaker, I don't expect to see any robot trip the main breaker for electrical reasons. If it trips it will be due to mechanical "hit" or excessive temperatures.
Running pump and multiple drive motors may draw down battery terminal voltage. We are always concerned about this since the robot controller will reboot under 8 volts. For this reason, our drivers monitor battery voltage at the opertor interface.
Al