Solenoid Questions

[Particle]

I would like to use more than four solenoids this year. Since this year's KOP only offers one solenoid (the Fesco 24V solenoid with 2 coils) and there are only 8 solenoid ouputs on the NI 9472 module, I'm left to ask if one of the two options below are rules-legal. Both seem to be, but I don't want to make any assumptions.

1) Can we use solenoids other than those in the KOP? R78 would seem to suggest we can use any solenoid from any source (KOP or not) so long as the parts are rated for 125 PSI working pressure.

2) Can we install more modules into the cRIO controller? If I could install a second NI 9472 module to gain another 8 24V solenoid outputs, that would let me use the Fesco solenoid found in the 2013 KOP. I've not found anything in the rulebook regarding what modules we can and can't use as well as in what quantity. R47 seems to hint that multiple solenoid modules are a possible configuration, but again it's just not explicitly stated anywhere.

Thanks

[MrForbes]

We used to run solenoid valves with Spike relays, from a relay output on the digital sidecar. Do you see any rules prohibiting this approach?

[MrForbes]

Also, as for which solenoid valves are legal, refer to R78. Finding air flow specifications for some of the valves is a challenge.

R78 The only pneumatic system items permitted on 2013 FRC 
ROBOTS include the items listed below.

...

C.    Solenoid valves with a maximum 1/8 in. NPT port diameter, and 
a maximum Cv of 0.32,
D.    Solenoid valves that are rated for a maximum working pressure 
that is less than 125 psi rating mandated above are permitted, however 
if employed,  an additional pressure relief valve must be added to the
 low pressure side of the main regulator. The additional relief valve must 
be set to a lower pressure than the maximum pressure rating for the 
solenoid valve

[Particle]

I don't know if R78 specifically means that parts outside of the KOP can be used.

---

As for using Spikes, that won't work if we're using the solenoid included in the 2013 KOP. It has 24V coils and Spikes can only switch 12V.

[Mark McLeod]

We are limited to a single solenoid breakout running on 24v.
That's to avoid undue voltage draw on the limited 24v power supply.

4.1.8.10 R43
The cRIO power input must be connected to the 24VDC supply terminals on the PD Board shown in Figure 4-8.
With the exception of one Solenoid Breakout Board, no other electrical load can be connected to these terminals.

You can have a second solenoid module/breakout running at 12v.
You just have to purchase 12v solenoids for the extras that you need. AndyMark offers some.

Spikes are also still legal for 12v solenoids.

Another option is to use some single solenoids if the application allows for it.
That effectively doubles the number of solenoids that the 24v solenoid breakout can handle.

[Bill_B]

If you decide to go the 12v route, message me before buying 12v solenoids. We have some that are now orphaned by a team decision to go all 24v the next time we use solenoids.

[Particle]

Yikes. AndyMark does have some other solenoids not on their FRC page, but there isn't enough information to tell if they are rules complaint.

This one for instance:
http://www.andymark.com/product-p/am-2304.htm

That would work, but it isn't clear if it would be compliant. The page gives a different set of specifications from Festo's datasheet for that same valve. AndyMark's page shows a flow rate of 220 L/min with a Cv of 0.22. If that same ratio applies, the flow rate listed on the Festo data sheet for that same valve of 1380 L/min would be a Cv of 1.38 which wouldn't.

I'm also not clear about what NPT means. The rules state that 1/8" is the largest permitted, but that would seem strange given that the KOP includes 1/4" parts.

[Mark McLeod]

NPT = National Pipe Taper specifies the size threading on screw fittings such as those that screw into the cylinders of solenoid valves. Ports are rated based on the inner diameter of the fitting inserted into this taper, not the thread size.

1/4" generally refers to the pneumatic tubing size that we use, e.g., push-to-connect fittings on the solenoid must be 1/4" on one end, but 1/8" on the inside of the threaded end.
There are push-to-connect fittings that we use with larger threaded ends to connect to storage tanks and regulators.

[Particle]

I'm afraid I really don't understand yet. I've been checking various places and get different answers from different people.

R78c says 1/8" port diameter but even the KOP valve is itself 7mm (0.27") with fittings that convert that to 1/4". Does anyone know somewhere we can get a definitive answer on solenoid selection?

[Tristan Lall]

Originally Posted by Particle

I'm afraid I really don't understand yet. I've been checking various places and get different answers from different people.

R78c says 1/8" port diameter but even the KOP valve is itself 7mm (0.27") with fittings that convert that to 1/4". Does anyone know somewhere we can get a definitive answer on solenoid selection?

This is a longstanding issue with the rules. Historically, when they've given a port size, they were actually referring to the nominal NPT pipe thread size of the port. (Nominal, because the NPT size is correlated with the approximate inner diameter of the pipe or fitting.)

The specification should really be in terms of the limiting orifice size (at some well-defined point).

[FrankJ]

2013 KOP vavles (first choice) are by definition legal.

We have used these in the past. It uses one coil per valve so you can put 8 a breakout. You will have to do the load calc to be sure you can power 8

"46A series MAC valves The part number we use is 46A-AA1-JDA0-1JM which gets you a 4 port single solenoid spring return valve. 1/8 ports .3 Cv. Part number changes with options, that one is just what out local distributor We have not had a failure with them"

[Particle]

Frank, do you mean you've used the ones I linked to earlier?

http://www.andymark.com/product-p/am-2304.htm

If I understand things correctly, the problem is that everyone is rating the same basic concept but different parts of it and in different units. The valve I've linked to for example has M7 ports which are internally threaded with a major diameter of about 0.4" which accept 1/4" fittings by which it is really meant that it will accept a 1/4" OD tube and that tube has a ~0.16" ID which is compliant with the rules. If I understand it correctly, NPT refers to the OD of the tubing that can be accepted. The port will be larger and the ID will be smaller. Or something. Honestly, this all seems needlessly confusing to someone who doesn't already have an industrial understanding of the topic. How are high school students supposed to pick a valve correctly? It has been days and I still don't feel confident enough to pick a valve that I'm reasonably sure will be within the rules.