Electrical Solenoid Actuators
 

Looking at 4.1.8 park J we are now allowed:

electrical solenoid actuators, no greater than 1 in. stroke and no greater than 10 watts continuous duty

Can someone explain the following.

no greater than 10 watts continuous duty

Can I use an actuator that is 25 watts at a 10% duty, but drops below 10 watts at 100% duty, or must the maximum power be no greater than 10 watts?

Also, now I know this is probably very difficult to answer as it varies upon actuator design, but what range of forces could I expect to obtain using actuators that meet these requirements?

Many thanks

Stephen

Re: Electrical Solenoid Actuators
 

go here and get yourself one of the sealed pull style, 1", 10 W units and give it a try, something like p/n - 69905K85

Re: Electrical Solenoid Actuators
 

Stephen,
The 10 watts relates to the way solenoids are rated. 10 watts at 12 volts is no more than 0.84 amps.

Re: Electrical Solenoid Actuators
 

A given solenoid size can dissipate a certain amount of heat. So depending on the input voltage you can operate it at varying duty cycles on a given solenoid.

Take a look at this solenoid's data sheet.

It is rated at 10w continuous duty in all it's configurations. The size of the wire used for the coil determines the voltage vs duty cycle.

Look at the first line using awg 23 wire which gives the coil a resistance of 1.52 ohms.

If you operate it at 3.9 volts it is rated at 10w with a 100% duty cycle.

Operate it at 12.3 volts and it will be rated at 100w and a 10 % duty cycle.

Order it with a 4.01 ohm, 25 awg coil and you can operate at 12.7v with a 25% duty cycle.

Be sure to note the heat sink requirements for the listed ratings.

Re: Electrical Solenoid Actuators
 

It is really hard for the inspectors to verify your promise to not run the solenoid at greater than x% duty cycle, and I therefore expect the intent is 10W @ 12V w/ 100% duty cycle. I would ask the GDC for clarification.

Re: Electrical Solenoid Actuators
 

thats what i was thibking as well...

...

I wonder if one could shift a 2 speed with one of these....

Re: Electrical Solenoid Actuators
 

I think the GDC is a little more sophisticated than that. I believe they purposely left out the @12v since it is unlikely that you would use a solenoid at 100% duty cycle in a FIRST robot. Solenoids have a wattage rating based on the heat they can dissipate that is independent of the voltage used to power them.

As far as using them to shift a 2sp gear box keep in mind that a solenoid is designed to either push or pull but not both. So using one you would only be able to shift once. Now if you had one where you could link the pintles, IE the pintle of a "pull" solenoid hooked to the back of a "push" solenoid, then you could use them to shift back and forth between gears.

Re: Electrical Solenoid Actuators
 

Team Update #1 amended <R48J> to read as follows:
You could easily use two solenoids and a "seesaw" arrangement to control gearbox shifting by pushing only. You could also use a single solenoid and just add a spring to pull it back when you remove power.

Re: Electrical Solenoid Actuators
 

There was an update about the actuators being @12V DC.

6873K4 from McMaster -Carr is a less than 10 watt continuous duty push/pull solenoid, however only 0.31" stroke, making difficult depending on the width of the gears.

Re: Electrical Solenoid Actuators
 

Why not use a spring to retract?