Automation Direct solenoid question

[Nebster]

My team has been looking into these solenoids for stocking up on this year, as they are the cheapest we could find and we're on a budget.

However, the solenoid cables have 3 conductors instead of the normal two. Does anyone know why this is, and if they will still work with the PCM? The spec sheet for the cables is here. Thanks.

[Peter Johnson]

Originally Posted by Nebster

However, the solenoid cables have 3 conductors instead of the normal two. Does anyone know why this is, and if they will still work with the PCM? The spec sheet for the cables is here. Thanks.

According to the spec sheet, the wiring diagram for that part number is Figure 10. The figure shows the two black wires are the solenoid, the green/yellow wire is shield. To use these with the PCM, you just wire up the two black wires to the PCM (red and black for a single channel, polarity doesn't matter), and ignore the green/yellow wire. You'll need to set the PCM to 24V.

[rfolea]

Also look for your $30 coupon from AutomationDirect. It will definitely be part of the kop and may even be available in December via TIMS.

Also note that 2 day shipping is always FREE from AutomationDirect if you spend more than $49 beyond the coupon.

[rfolea]

... and if you want one to play with PM me ... I may have one laying around you can have.

[Joe Ross]

Per R66-D (2015 rules), these must be used with a secondary regulator to set the pressure less then the rated working pressure of 115psi.

[otherguy]

FYI, it looks like the valves cone with two connectors already. You shouldn't need to buy the cables you linked unless you don't want to have to wire up the solenoids yourself, or you want indicators for when the solenoid is energized.

I haven't purchased these before, but it looks to me like a similar style connector to what is on some old festo solenoids we have in our shop. A screw at the back of the housing attaches the connector to the valve, remove that and you should be able yo pull off the back shell of the connector. Inside there are a number of screw terminals which you could connect a small gauge wire to (needs to fit in the PCM connectors). Should be pretty straight forward.
The PDF you linked includes the wiring schematic for all the connectors. I think the stock connector uses Figure 9.

[cbale2000]

Originally Posted by Joe Ross

Per R66-D (2015 rules)...

Does anyone have a link to the 2015 manual (or this specific set of rules)? I've been looking all over for it but FIRSTs new website has broken every old link and made stuff like this impossible to find.

EDIT: Nevermind, finally found it after like 30 minutes of digging.

Originally Posted by Joe Ross

Per R66-D (2015 rules), these must be used with a secondary regulator to set the pressure less then the rated working pressure of 115psi.

If the main regulator is restricted to 60PSI, isn't a secondary regulator a bit redundant (or is that the idea)? I could see if the maximum pressure was less than 60PSI it would make sense, but otherwise it just seems silly IMO. Either way, I chalk this up to yet another ridiculous pneumatic rule (much like the huge debate about using an off-board compressor to pre-charge a bot with an on-board compressor a few months back).

[Al Skierkiewicz]

R66 d reads as follows...
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.

This is one of those rules written on industry specifications that are changing. The "working pressure" spec now used by manufacturers are the optimum settings for valve operation not the maximum safe pressure for the device. The max pressure for these valves is 125 psi. Please check the 2016 rules when they are published.

[FrankJ]

Originally Posted by Al Skierkiewicz

R66 d reads as follows...
This is one of those rules written on industry specifications that are changing. The "working pressure" spec now used by manufacturers are the optimum settings for valve operation not the maximum safe pressure for the device. The max pressure for these valves is 125 psi. Please check the 2016 rules when they are published.

Thanks to Al & the GDC for updating this. Although putting in the extra relief valve isn't that big a deal, there is a cost to it and more places for air to leak. Minimal safety benefit.

We always use single solenoid valve unless there is a design reason to use a double solenoid valve. The din connector that comes with the valve has the LED indicator as well. I like the cable assembly because the connector is potted. The wire pair are both black & numbered 1 & 2. They poke nicely into the PCM. Valve directions show terminal 1 as positive. I have not tested to see if that really matters, It matters on some DC solenoids and not on others.

[Al Skierkiewicz]

Frank,
I meant to say, check for any changes to this rule for 2016. I did not mean the rule was changing. Sorry for the confusion.

[FrankJ]

Originally Posted by Al Skierkiewicz

Frank,
I meant to say, check for any changes to this rule for 2016. I did not mean the rule was changing. Sorry for the confusion.

I should have realized you cannot comment on actual rule changes before kick off. One can only hope the rule is revised.

[GeeTwo]

Originally Posted by FrankJ

We always use single solenoid valve unless there is a design reason to use a double solenoid valve.

We used double solenoids exclusively our first three years because it's all we had. We figured out late in the 2014 build cycle that single solenoids would have been much better. Our understanding is:

• Single solenoids are less expensive, use fewer electrical ports, and are appropriate for a mechanism that has a "default" state which it is in most of the time, and is only actuated occasionally, e.g. a launcher. We should also have used singles to emulate a 3-position valve, where we kept air pressure on both sides of our pistons most of the time, and exhausted air on one side or the other to move our arm.
• Doubles are better when the cylinder spends similar amounts of time in each state.

[Nate Laverdure]

Originally Posted by GeeTwo

We used double solenoids exclusively our first three years because it's all we had. We figured out late in the 2014 build cycle that single solenoids would have been much better. Our understanding is...[/list]

The main thing that should drive the decision to use single- vs double-acting solenoids is the desired failure behavior. When the controls enter a disabled condition (between auto and teleop, at the end of a match, when the e-stop button is pressed, etc) double-acting solenoids will remain in the state that they were last actuated into. Single-acting solenoids will automatically (regardless of the amount of air pressure) return to their default state; a competent robot designer would evaluate whether this will have any safety or gameplay implications.

[GeeTwo]

Originally Posted by Nate Laverdure

The main thing that should drive the decision to use single- vs double-acting solenoids is the desired failure behavior.

Agreed. I was pretty much assuming that a failure mode of returning to a "default" state was reasonable; I see now that this will not always be the case. Behavior on brown-out must be taken into account as a special case of this as well. Another related consideration is that with a double solenoid, you do not know know a priori which state the solenoid is in at startup; with a single solenoid, you can be fairly confident that it has returned to the default state if the power was off for more than a few milliseconds.