Solenoid from a car door, any car door: are they legal in 2016?

[Al Skierkiewicz]

Gus,
Please remember that measuring a CIM it is possible that you are measuring two windings in parallel due to brush size and commutator spacing. This is not true for all FRC motors but certainly some of them have this design.

[Richard Wallace]

Originally Posted by GeeTwo

Agreed, and further, because the peak power output is usually around half speed, where the back-EMF is half the input voltage, the continuous power draw is even less. My point was that if the resistance was 14.4 ohms or higher, the device could not dissipate/convert a total of more than 10W. The actual resistance of a 10W motor could be much lower.

For example, the static resistance of a CIM is around 0.09 ohm, which tells you that its maximum power is no more than 144/0.09 = 1600W. The rating is about 337W.

You're right about the impact of back-EMF on output power of electromechanical energy conversion devices. However, the rule governing solenoid actuator ratings is expressed as a limit on continuous duty electrical input power.

The CIM example is interesting to FRC competitors; however, our CIM motors do not have a continuous rating. Their normal load (4 lbf-in, 27A at 12V) is the basis for an intermittent test cycle with 16.7% duty. See the data sheet (excerpt attached).

[Mr V]

I fear that things may be getting confused with discussions of relating the current a motor will draw vs its resistance and the need to determine the wattage of a solenoid.

If the item in question is indeed a motor and is used in car doors then it is legal with no restrictions. The power draw of the motor is only relevant when choosing the wiring and thus breaker sizing, to prevent nuisance trips.

Solenoids on the other hand are limited in their power rating. Calculating the wattage from the resistance is valid. A solenoid acts as an inductor. It will generate back EMF as a function of the rate of change of current flow. If an inductor is fed DC current an equilibrium will be reached where there is no change in the current flow and the current flowing through the coil will be dictated purely by the resistance of the wire that makes up the coil. Yes the fact that part of the core is mobile will induce some back EMF as it moves but that too will stop as the core comes to a stop at the end of travel.

So because of the way an inductor works the peak current of a solenoid is determined by resistance and the current ramps up to that peak, never exceeds it.

Now to determine what exactly the OP has. The YMM or Yr Make Model along with the exact location and function it was used in said vehicle would go a long way to determining what exactly we are talking about, or a picture of the device.

A few key points about solenoids. They often have a single wire and ground through their mounting. If they do have 2 wires one of them is usually black and/or is connected to the body someplace near the device. It will only actuate in one direction. There is usually some sort of spring that will return it to a resting position. Push it in and it will spring back.

A motor will always have two wires. When you manually move the rod/lever you can hear and feel the gear train and making the motor move. The rod or lever will stay where you leave it. It can provide force in two directions.

Solenoids do have their uses in automobiles but since they only provide force in one direction their use is limited to releasing trunks, hatches, fuel doors and things of that nature. Also note for things like a trunk or fuel door leases solenoid you'll typically find the circuit protected by a 20a fuse. No it probably doesn't draw anywhere near 20a but I'm betting it is more than 1a worth. In other words if it is a solenoid then it probably isn't legal.

[aldaeron]

Digikey will list the power consumption for you. From what I learned there are are a few types: continuous, pulse and intermittent (defined on data sheet below)

Here is a sample showing one series of solenoids, with the different power consumption values for each type. I got some of the continuous duty variety since they are listed at <10 W continuous. Have not had time to test yet.

I wish I had more time to ask a Q&A before ordering because I really only need a pulse type solenoid for what we're doing, but a pulse lists its wattage as well over 10 W as shown here My curiosity is if the continuous version of the solenoid uses 4W and the pulse version of the same series uses 40W for short periods of time, does it meet R29? My guess was no.

-matto-

[dkavanagh]

Thanks for bringing these actuators to my attention. Just what we needed for a specific application on the robot where a solenoid just wasn't strong enough. I ordered a pair off Amazon for $9.95 and found a CAD file at grabcad.com, and converted for solidworks. This is why I read Chief Delphi!
https://grabcad.com/library/8kg-actu...al-door-lock-1

[Mr V]

Originally Posted by aldaeron

I wish I had more time to ask a Q&A before ordering because I really only need a pulse type solenoid for what we're doing, but a pulse lists its wattage as well over 10 W as shown here My curiosity is if the continuous version of the solenoid uses 4W and the pulse version of the same series uses 40W for short periods of time, does it meet R29? My guess was no.

-matto-

The difference between an intermittent and continuous duty solenoid that otherwise looks identical will be the resistance of the coil. The intermittent version will have higher resistance than the continuous duty version. The high resistance version will not generate much heat but the continuous duty version will and thus heat up, potentially to the point of failure if left energized significantly longer than the rated on time or duty cycle.

[Al Skierkiewicz]

D,
The drawing you link looks suspiciously like a motor, not a solenoid. There is restriction on automotive motors in that they must be "Select Automotive Motors (Window, Door, Windshield Wiper, Seat, Throttle)". You will have to document that these are in fact automotive motors that fit one of the criteria above.

[dkavanagh]

Yes, it's definitely a motor. The way I read R29 was that this may qualify as a "door" motor. It resides in the door. I don't know of any car that opens a door using a motor, so I can only imagine a door motor may actuate something in the door (like locks). How can I get clarification on that?

[aldaeron]

Originally Posted by dkavanagh

Yes, it's definitely a motor. The way I read R29 was that this may qualify as a "door" motor. It resides in the door. I don't know of any car that opens a door using a motor, so I can only imagine a door motor may actuate something in the door (like locks). How can I get clarification on that?

Read the second post in this thread. The answer is there.

[Al Skierkiewicz]

D,
Van doors have had motorized open and close for sliding doors and hatch for many years. My 2004 Odyssey has them. When in doubt ask the Q&A for clarification.

[paul.dornfeld]

Originally Posted by EricH

I would also attempt to find the model number and a spec sheet. Model number would likely be found on the device itself (if it survived the whole "being removed from the vehicle" routine) or in an owner's manual or repair guide (if you could find one that listed the parts). Once you have a model number, a bit of Google and you should have a spec sheet. I have yet to see an inspector debate a spec sheet that matched up to the component, unless the spec sheet showed the component was actually illegal.

Great idea. Thank you.