Multiplex Festo Valves
 

It appears that only four FESTO valves (8 solinoids) can be driven by the 24V breakout board AND only one breakout board can be used in the robot. Does anyone know if it's legal to to multiplex the 24V breakout board lines via additional relays driven via the digitial side car relay drivers? In other words, one 24V line from the breakout board would be used control both of the solinoids on the Festo Valve.

Any thoughts would be greatly appreciated.

C3PO

Re: Multiplex Festo Valves
 

C3PO,
I seem to remember that the 24 volt supply on the PD cannot supply enough current for more than 8 solenoid coils.

Re: Multiplex Festo Valves
 

This rule only says that a maximum of one solenoid breakout can be powered with 24 volts, I can find no rule that would stop you from using a second, 12 volt breakout. See if you can make your pneumatics system work with 12 volt solenoids instead.

Re: Multiplex Festo Valves
 

You can actually use 2 solenoid breakouts, this was addressed in an update. Up to one of these can be 24V.

Al is (as usual) correct. You can not drive >8 24V valves with the 2010 control system. It is both illegal and there is not enough headroom in the 24V supply to do so.

Re: Multiplex Festo Valves
 

Thank you all for your wonderful help. We don't plan to use more than 2 FESTO solonoids at any time. So, I think the 24V supply would provide plenty of power. I'll look at the updates for information on additional 24V breakout boards.

Again, many, many thanks.


C3PO

Re: Multiplex Festo Valves
 

The experts say it won't, perhaps you should reconsider?

Re: Multiplex Festo Valves
 

Hi Don

Gulp,……the 24V breakout won’t provide enough power to drive two (2) solenoids simultaneously? In other words, only one half of a Festo valve (one solenoid coil) can be driven at any time? If this is true, we are doomed.

C3PO

Re: Multiplex Festo Valves
 

I'm pretty certain it will run 2 at a time. I'm fairly certain it could run 8 at one time.

But what you're asking is if there is a way to get it to run more than 8 at one time. That's not legal, and there isn't enough oomph in the 24V supply to do it. (See EricVanWyk's post.)

Now you're looking into using a second 24V breakout. That is also illegal. <R45-A> makes it clear that only one solenoid breakout and the cRIO can go into the 24V terminals on the PDB.

Your best bet is to find a bunch of 12V solenoids and run those on a 12V breakout, or through a Spike run by the relay board.

Re: Multiplex Festo Valves
 

C3PO -

There is some miscommunication occurring here. My understanding of your situation follows. If it is incorrect, ignore the rest of the post:

You have more than 8 solenoids that are 24V, but you only need to activate up to 2 at any one time.

This is do-able from an engineering point of view. The 24V supply can most certainly power 2 valves at once, and it doesn't matter how many valves you aren't using. Great. However, the rules prevent this. Since the penalty of trying to power >8 valves at once is that your robot reboots and you likely lose the match, the rules are written conservatively. I strongly agree with (and proposed) this conservatism.

In post #5, you spoke with respect to tech, but Don responded to you with respect to rules. You interpreted Don's response as if he was also talking tech, which resulted in the confusion.


Long story short, use up to 8 24V solenoids. All other solenoids will have to be 12V. If you wish, request a change for 2011.

Re: Multiplex Festo Valves
 

My apologies for the confusion. In a nut shell:

1. I wish to control a MAXIMUM of two(2) Festo solenoids at ONE time.
2. I wish to multiplex each of the 8 24V solenoid breakout lines with a SPDT relay driven by the digital side car so that the 24V breakout line can connect to either Festo of the two valve solenoid coils but only ONE at at time.
3. This would allow the control of 16 Festo solenoids (8 complete valves) as long as power only two solenoids are energized at any one time.

My question is ....................Is the multiplexing legal?


C3PO

Re: Multiplex Festo Valves
 

Nope.

Re: Multiplex Festo Valves
 

Thank you all very much for helping me with this. I really appreciate your input and patience.

May the force be with you all,

C3PO

Re: Multiplex Festo Valves
 

I think this prevents using 24 volts with the spike relays, the only legal relays.
Also,
I believe that this prevents relays from being used to switch solenoids controlled by the breakout.

Re: Multiplex Festo Valves
 

Alan et al,

This is the more pertinent answer:

<R45> All electric power utilized by the ROBOT shall be distributed from the load terminals of the Power Distribution Board. Circuits may not bypass the Power Distribution Board to connect directly to the 120-amp loop.
A. The cRIO-FRC power input must be connected to the 24 Vdc supply terminals on the Power Distribution Board. With the exception of one Solenoid Breakout Board, no other electrical load can be connected to these terminals.

Re: Multiplex Festo Valves
 

Al,
I think more relevant is (emphasis mine, also below)
Which, when combined with prohibit using a relay to alter the control path to a solenoid valve. Thus Eric VanWyck's succinct response.

Of course, it IS legal to use 24V to power solenoids as you quoted.