Electric solenoid experience

[aldaeron]

R29 allows:

Electrical solenoid actuators, no greater than 1 in. stroke and rated electrical input power no greater than 10 watts (W) continuous duty at 12 volts (VDC)

I am curious if anyone has used electrical solenoids and if there is one you would recommend? I see some on McMaster that explicitly list continuous wattage (part weight not listed) and some on Amazon that list weight but not explicit continuous wattage.

Will FIRST accept (continuous duty power) = (nominal voltage) * (max rated current) as an acceptable way to calculate this?

I could only find 1 recent thread on electrical solenoids (plenty for pneumatics), but no feedback on how well it worked. In particular I am curious if these would work for disengaging dog gears (not in a gearbox, and for short periods of time).

Thanks!

-matto-

[electroken]

Would power door lock actuators do the job for you?

They're small, inexpensive, and AFAIK, legal under the motor rules (I know they were legal last year). They can push or pull with a surprising amount of force for a $5 mechanism.

http://www.amazon.com/High-Power-Doo...lock+actuators

[aldaeron]

How did you calculate the continuous duty power? I see no data sheet or specs in the amazon link.

[Dad1279]

I ordered one a few days ago, will report current draw. Couldn't find a spec sheet.

[electroken]

Originally Posted by aldaeron

How did you calculate the continuous duty power? I see no data sheet or specs in the amazon link.

I didn't, and as they aren't solenoids I don't need to. They are brushed DC motors with a whole lot of gear reduction and a rack and pinion output. These devices are intended to be run for a second or two at a time and will die a miserable death if held in stall, much like a RS-550 motor.

I have a few of them and will measure their current draw under some varying conditions this morning.

[electroken]

This is for a sample size of two pieces that were in my office. The actuators were clamped down and powered by a bench supply capable of 30A continuous with the output voltage set to 12.0V. Pull force was measured with a gauge that is calibrated once per year, so I trust it.

The two actuators performed identically within my limits of measurement. They stall at a pull force of 18 pounds with a current draw of 4.9 amps. Push force was not measured but should be the same.

I attempted to measure their response time by looking at the current waveform delivered to the motor. Lightly loaded with a compression spring over the output shaft retained by a pin through the clevis, the full-stroke response time is about 80 mS. The stroke length is 0.73".

While not the most scientific of tests, it gives some idea of the capabilities of these devices.

[FrankJ]

Originally Posted by electroken

I didn't, and as they aren't solenoids I don't need to. They are brushed DC motors with a whole lot of gear reduction and a rack and pinion output. These devices are intended to be run for a second or two at a time and will die a miserable death if held in stall, much like a RS-550 motor.

I have a few of them and will measure their current draw under some varying conditions this morning.

You do realize if they are motors and are not on the approved motor list, they are not legal for FRC use? Just because your inspector missed it doesn't make it legal.

[aldaeron]

Originally Posted by FrankJ

You do realize if they are motors and are not on the approved motor list, they are not legal for FRC use? Just because your inspector missed it doesn't make it legal.

This was my thought too - did you replace the internal motor with an RS 550? Else this is not legal last year or this year.

[electroken]

Nothing has been missed. R29 allows for "Automotive Motors (Window, Door, Windshield Wiper, Throttle)". Under part number it shows "Various".

I've inspected myself for a few years now, and run these devices by several LRIs at events after seeing them on a few machines. The summary of their responses was: If it comes out of a car door, it's OK.

[philso]

Originally Posted by electroken

Nothing has been missed. R29 allows for "Automotive Motors (Window, Door, Windshield Wiper, Throttle)". Under part number it shows "Various".

I've inspected myself for a few years now, and run these devices by several LRIs at events after seeing them on a few machines. The summary of their responses was: If it comes out of a car door, it's OK.

You may want to use OEM parts rather than the generic ones. The generic ones I have purchased for fixing my vehicles have been pretty low quality. You are putting in a lot of time and effort to build the rest of your robot and it would be a shame to see it break down.


At first, the thread title made me think it was about someone wiring their robot while under the influence of mind-altering substances and listening to Jimi Hendrix.

[aldaeron]

Im not sure they are legal this year. See this Q and A. The list in parentheses are the only types allowed. While door motor is allowed, I always took to that to mean the old Van Door opening motors from past KOP (from a mini van door). If these are legal door motors that is fantastic

[FrankJ]

Originally Posted by electroken

Nothing has been missed. R29 allows for "Automotive Motors (Window, Door, Windshield Wiper, Throttle)". Under part number it shows "Various".

I've inspected myself for a few years now, and run these devices by several LRIs at events after seeing them on a few machines. The summary of their responses was: If it comes out of a car door, it's OK.

My mistake. You are correct. Given vagueness of the rule & the literal interpretations the GDC seems to like. I would go with if it comes out of the of a door it's OK.

[Dad1279]

https://frc-qa.firstinspires.org/Que...-dp-b0088ye6yq

[aldaeron]

Yay! Legal!

I wanted to be absolutely sure. We had an issue in 2014 with how timeouts worked that required us to show the FTA a Q&A and had it not been so explicit on what was allowed, the FTA would have made an incorrect ruling (he was a real jerk about it too and was bullying our kids).

-matto-

[MisterG]

Back to the question by the OP.

These lock actuators look nice but what about an application where the force needed to be applied for longer (say raising a small mechanism and holding it for 30 seconds)?

The solenoid seems like it would be more appropriate for this type of long duty application. Can anyone share legal experience with using electric solenoids on their robot?

Also can someone comment on the rated Volts * rated Amps method to calculate continuous Watts when there is no power specification listed; this seems like it would be accepted at inspection.