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-   -   Relay to control 2 outputs (http://www.chiefdelphi.com/forums/showthread.php?t=95572)

Micah Chetrit 10-06-2011 13:52

Relay to control 2 outputs
 
Hey everyone.
I have an off season project to make LED rods and put them on the robot and get them to light up in patterns (I am also a programmer). Being that there are going to be 4 rods, I thought I could save space and money by using only two Spike relays, attaching two Positive wires to it and using a common ground that isn't run through a relay.
If I recall right, this has been used for solenoids (? might be wrong). In my mind it should work, is there any reason it shouldn't?
Secondly, is it legal to control two outputs with one controller? (haven't read rules for a long time, I forgot many of them)

Thanks in advance,
Micah

apalrd 10-06-2011 14:31

Re: Relay to control 2 outputs
 
This is an off-season project, legality is not an issue.

There is no reason why it wouldn't work. In LV at least, the Spike has four output states (Off, Forward, Reverse, and On). Fwd will set one on and the other off, Reverse will set the second one on and the first one off, and On will turn them both on.

Micah Chetrit 10-06-2011 16:39

Re: Relay to control 2 outputs
 
the reason legality is an issue is that I am making two sets, one for the current bot, and one for next years bot (using the same code)

Travis Hoffman 10-06-2011 17:05

Re: Relay to control 2 outputs
 
Quote:

Originally Posted by Micah Chetrit (Post 1065356)
the reason legality is an issue is that I am making two sets, one for the current bot, and one for next years bot (using the same code)

See R42. Controlling 2 solenoid or low-current light outputs with one Spike has been legal for many years. As long as you properly send the negative wires back to a black PD board negative terminal (presumed ok to splice the negative leads to fit into a single terminal), you should be fine.

However, what would not be legal is preparing these LED arrays and wire harnesses for use on a 2012 FRC robot - you must wait to perform all such work after kickoff of the 2012 season, during approved robot work times.

Micah Chetrit 10-06-2011 17:13

Re: Relay to control 2 outputs
 
Oh, I didn't know about that.
what specifically is forbidden? Can I wire the leds and put them in a tube (therefore just creating a part), but not wire it to a relay? or is making custom parts before season not legal?

Travis Hoffman 10-06-2011 17:18

Re: Relay to control 2 outputs
 
Quote:

Originally Posted by Micah Chetrit (Post 1065360)
Oh, I didn't know about that.
what specifically is forbidden? Can I wire the leds and put them in a tube (therefore just creating a part), but not wire it to a relay? or is making custom parts before season not legal?

The latter case is true. Until the rules change, you cannot fabricate custom parts or construct custom assemblies for your official FRC robot prior to the start of the season. This is one of the core tenets of the FRC program - every team must engineer their robot within the same time window.

Micah Chetrit 10-06-2011 17:20

Re: Relay to control 2 outputs
 
Thank you for pointing that out. I guess I only have to make one set this summer then.

Al Skierkiewicz 10-06-2011 19:10

Re: Relay to control 2 outputs
 
Micah,
It is also possible that this wiring method would be illegal during next year's game and rules. I would hope that the GDC allows teams to use this method but you never know for sure. As stated the Spike is capable of switching either or both outputs between high and low states. The manual for the Spike explains this.

Hugh Meyer 11-06-2011 17:27

Re: Relay to control 2 outputs
 
Micah,

If you connect them to a Jaguar or Victor you could dim them. With different colors that could give you some interesting effects. You would need to put the LEDs in series to be able to tolerate the 12 volts...maybe 6 LEDs and a current limiting resistor. Just an idea...

-Hugh

slijin 11-06-2011 23:31

Re: Relay to control 2 outputs
 
Just as a note, what Travis said is perfectly true; any design done preseason is not legal for use during competition. However, if the design is modified (i.e. improved or optimized during competition) for the robot, then it is indeed legal.

Warlord 12-06-2011 00:19

Re: Relay to control 2 outputs
 
Although it is worth noting that given that this seems to be more decorative than functional - designing a whole drive train in the offseason is one thing, designing some pretty lights is something else entirely. I wouldn't worry too much about breaking the intent of the "6 weeks" thing.

Steve Warner 12-06-2011 11:39

Re: Relay to control 2 outputs
 
I don't have the latest version of the C++ WpiLib source code available to look at right now, but I don't think it allows both relay outputs to be turned on at the same time. Could someone explain why the Relay class was written this way and if it can be changed for the next library release.

Ether 12-06-2011 12:48

Re: Relay to control 2 outputs
 
Quote:

Originally Posted by Steve Warner (Post 1065469)
I don't have the latest version of the C++ WpiLib source code available to look at right now

Whenever you have access to the web, V20110203rev2259 is available online for browsing.

The only stated differences from V20110203rev2262 are:
1. A NetConsole error in the cRIO that under some circumstances corrupt memory in the cRIO.
2. Fixed an error with the ADXL345 I2C accelerometer.
3. Fixed an error with allocation tracking in the Counter class.




Steve Warner 12-06-2011 16:02

Re: Relay to control 2 outputs
 
Thanks Ether. So in Relay::Set there is no way for the kOn case to set both outputs true. I think this is something that could be easily fixed.

slijin 12-06-2011 20:37

Re: Relay to control 2 outputs
 
To my memory, I believe controlling the 4 states of a Spike involves splicing together two outputs into the Spike input, though I could be wrong.


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