Solenoids - what have you used them for?

I like the engineer moving his hand, that's a cool idea!

Lee,

If you can, try and get what is commonly called a Keeper Solenoid. This is a solenoid that pulls and repels. It has three leads verses the normal two. It basically pulls the plunger down and a permanent magnet holds the plunger in that condition. To move the plunger back out the other coil is energized to repel the plunger and over-ride the magnet.

This allows it to be a momentary energize to open or to close a door for say without the solenoid staying energized for the entire time the door is open.

It is more costly but they are great, I scrounge a lot of mine off of older devices so they are no cost for moi.

Lee, I like the way you think.  I have some far out ideas myself but first I have to finish my bench work. 

Jack

I was thinking about burying one in a turntable and having receiver holes in the pit wall, centered below the tracks.  Then when the turntable came around and the solenoid was released it would be a guaranteed alignment. Possible overkill, but that's the solenoid idea that I had.

Another really useful mechanical actuator is a model airplane servo.  They come in all sizes and will adapt to a variety of uses.  I ended up using one of these to automate my Tie-Jector TMCC upgrade.  It was the only way I could think of to move the mechanical arm to start and stop the tie ejection mechanism.

You could have the alignment holes in the turntable and the solenoid in the pit wall and not have to have additional connections to the moving table.

Good point.  Lots more wiring but potentially simpler by eliminating the accompanying slip rings that I had envisioned.

You could fit a rotating disc with the alignment holes underneath the turntable (Either below the whole mechanism, or above the mechanism but below the well.) with one hole for each track, and a single fixed solenoid to engage with the holes. This would keep the wiring simple.  

Used selenoids on the temperature control loops for million pound a day polypropylene reactors.

No more wiring, you're just wiring the solenoid at a fixed location.  You still have to have the same amount of alignment holes, they're just in the turntable instead of the fixed base.

John - How do you activate the servo?

Pete

Pete, I actually used the smoke output of the ERR MiniCommander 2 to trigger it.  I had to build a little pulse width modulation circuit to position the servo to the two positions for on/off that was driven by the smoke output.  It worked out great, and was a perfect fit.

I knew that the servos are driven by pulse width modulation, but I lack the knowledge to make such a circuit.  Does the MiniCommander 2 provide the DC voltage to the servo?

I can see a potential market for an all-in-one device to operate a servo.  Would open up a whole world of possibilities.

Pete

The ERR MC2 does not have PWM output.  I just used a 555 as a bi-stable oscillator to give me two output frequencies, one for each position I needed.

My long term plan for using these servos would be to use a microprocessor to offer greater positioning flexibility.

Solenoids technically operate the same as a relay coil. Apply voltage and the electromagnetic field causes the plunger to change position.  Motion will be fast and abrupt. Using it for a lock pin on a turntable is a great example (and very prototypical too). Unlocking spring loaded doors to the missile silo would be another good use.

For controllable motion, the servo motors are the way to go (as already mentioned).

As for launching your missile, I’d suggest starting with an Estes 001695-E16-0. That should make a sufficient mess of whatever gets on the business end of the rocket.

You don't fool around!  I was flying some "fireworks" with the Estes E motors, they really took our stuff for a high ride, they were too powerful for the job!  For inside, I'd stick with the C motors.

Here's a nice project....

If you want to Sim a Heavy Lift vehicle, I can launch a 29mm dia. H motor for you.

Can you say "Bowling Ball Launch" ?  60.225 lbs of thrust for almost 1 second.

I do not recommend being anywhere near your house... 

As a matter of fact, It's against the rules.

I don't launch bowling balls in my house either!

This sounds so Lee Willis. (no, that's not a bad thing)

A thing to remember about solenoids is that some are not rated for continuous power and will overheat if left on too long. Keep this in mind when circuiting them in a project. Another issue is that they will generate voltage spikes in the circuit and solid state electronics should be protected if they share it.

Dale H

I saw a video of an RPO car where the door opens and mail bags are ejected when the hook catches the pickup bag.  I'm not sure how the door mechanism and pickup accumulators were done (motors, servos, whatever) but I'm pretty sure the mail bag ejection was done with a solenoid.

Similar to the jump roping is the jack-hammer animation though the pulse rate is faster and you need a sound module to complete the effect.

In the book Realistic Animation, Lighting, and Sound, John Armstrong's article "Tale of a Turning Head" shows the engineer leaning out the window with a solenoid rotating his head to look backwards whenever the engine is in reverse.

While the "explosive" effects that everyone's talking about certainly need the size of solenoid you show, I've found that when dealing with figure animations or more "delicate" motions in 1/48 scale or smaller, tinier solenoid are required since there's always less space than you want.  Obviously you can wind your own solenoid but I've also used those like shown below which IIRC were about $1 a piece online. 

NQDY - good idea, and would certainly make things simpler, but that won't fit the overall design I have had in my head.  I'd love to tell you more but this is at least two years off and I want to keep some ideas in reserve.