Pneumatics sensors?

[Gibbs]

My team has no experience using pheumatics, and we are looking for a sensor, not a gauge, that will tell us our P.S.I. Recommendations please.

[Qbot2640]

My team has no experience using pheumatics, and we are looking for a sensor, not a gauge, that will tell us our P.S.I. Recommendations please.

There was a recent (summer) thread on this topic which I believe ended with the conclusion that there is no legal way to sense your pressure. The more important question is "why do you want to know your pressure?" The regulator will set your working pressure to 60 - and the stored pressure / compressor will cycle on to maintain that at 60, as long as you have sufficient storage.

[cmwilson13]

There was a recent (summer) thread on this topic which I believe ended with the conclusion that there is no legal way to sense your pressure. The more important question is "why do you want to know your pressure?" The regulator will set your working pressure to 60 - and the stored pressure / compressor will cycle on to maintain that at 60, as long as you have sufficient storage.

you should note rules change year to year for example


R77 The only pneumatic system items permitted on 2014 FRC ROBOTS include the items listed below.

F. Pressure transducers, pressure gauges, flow control valves, and connecting fittings,

[Dale]

We use this sensor (http://www.digikey.com/product-detail/en/P51-200-G-A-I36-5V-000-000/734-1023-ND/1665784)from SSI Technology. It returns an analog signal that relates to pressure. It's somewhat non-linear so some software will be involved.

[AllenGregoryIV]

We have used this before for some off-season testing but never in competition, so I'm not sure how well it will work but it's much cheaper than other models I have seen.

http://www.ebay.com/itm/Pressure-transducer-or-sender-150-psi-stainless-steel-for-oil-fuel-air-water-/251362960044?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a866662ac&vxp=mtr

[Qbot2640]

you should note rules change year to year for example


R77 The only pneumatic system items permitted on 2014 FRC ROBOTS include the items listed below.

F. Pressure transducers, pressure gauges, flow control valves, and connecting fittings,

Point taken - thanks.

Still...Why? Unless you were trying to somehow regulate air pressure, perhaps by bleeding off air to drop pressure so you could get a "lower power" cylinder output or something, what is the benefit of having real-time pressure on your dashboard? I'd want the pressure to always be at maximum...and would design my storage system so it never drops below that during a match.

[LeadU2Fun]

Point taken - thanks.

Still...Why? Unless you were trying to somehow regulate air pressure, perhaps by bleeding off air to drop pressure so you could get a "lower power" cylinder output or something, what is the benefit of having real-time pressure on your dashboard? I'd want the pressure to always be at maximum...and would design my storage system so it never drops below that during a match.

Many variables such as bore, stroke, number of pistons actuated simultaneously, number of storage tanks, etc. can drastically change how long it takes to get back up to working pressure. We added extra storage tanks to test some ideas and it takes a lot longer to get up to working pressure. In order to be consistent you would not want to shoot if your compressor was on and you hadn't fully charged up yet. With a pressure transducer your software could look at the condition and wait, or your driver could look at the custom dashboard and make a decision.

[Mark McLeod]

Still...Why?
The last time we had a pneumatic catapult we had adjustable third stage pressure to vary the shots. The operator would adjust the pressure watching feedback on the Dashboard to shoot farther or make closer shots.

Other years it told us how many times we could fire some mechanism's cylinders in succession, or when some real air hog needed time to build up reserve pressure.

[Caleb Sykes]

I have always wanted to try to keep a running approximation of pressure just using observations. Something like:
if (compressor just stopped running)
approximate psi = 120
else if ((compressor just started running) and (approximate psi > 110))
approximate psi = 105
else if (compressor is running)
approximate psi = approximate psi + (1 psi/second)
else
approximate psi = approximate psi - (0.02 psi/second)

if (piston1 is actuated)
approximate psi = approximate psi - 10
if (piston2 is actuated)
approximate psi = approximate psi - 30

Given, the accuracy of the approximate psi value would probably decrease over time. Although it would reset to 120 whenever the compressor stops running. It could be very useful for checking to see if working pressure is >= 60, simply by checking to see if the approximate psi is > 70 or something like that.

Has anyone done something similar to this? I am curious to know if it was successful.

[Mark McLeod]

We did that for our 2003 robot.
The drive system was dependent upon having adequate pressure at all times, so the pneumatic arms were limited if the system thought too much air had been used.
Make sure you have a big obvious indicator to the drivers as to why mechanisms may stop working mid-match.

It worked quite well except for once when we drove under the bar with the arms too high and ripped off the fittings releasing all of our air with one whoosh...