Driving 12vdc push/pull solenoid for proof of concept

Thread Starter

manual

Joined Jul 16, 2019
5
I'm working on a silly little project and need to physically move something a short distance, very quickly, without breaking the object. My background is nearly 20 years as a programmer. My boss got me into 3D printing a few years ago. Now, I'm trying to get into projects that require circuits. I've learned enough to add some LEDs to the wearable (XBox game: Halo) Master Chief helmet I printed out. My two boys love it. I bought some Arduino kits so as to have some things I can play around with, bread boarding and whatnot. While reading this, please keep in mind I'm very much a beginner. Also, feel free to correct anything I have wrong (verbiage, design, etc.).

Basically, I'm just trying to build a proof of concept. I'm a see and do learner so I purchased this solenoid to see how it worked for this project. I don't know how to test, or even what tools I might need, to test the actual force needed. Since the solenoid was cheap enough, I bought it based on it's dimensions. If what I need is larger than that, I probably can't make it happen. If this size works (or even better, it's too strong), then that's great news. My issue is powering it for my needs. I need it at full power for <= 1 second. It's going to hit something and then it's job is done. Worst case scenario, it may be fired again in 30 seconds but in reality, it'll probably be much longer (minutes, hours) than that. The power source can be anything (A23, 9v?), but size is the ultimate issue (smaller the better).

I've chosen a solenoid because that's where my research has taken me thus far. I've thought about springs (which may work) or air (impractical) but this seems to be the most ideal solution. Some of the other posts here (i.e. "Solenoid Charge-up driver schematics", "Powering a Solenoid") were not much help to me because of my limited experience. Much of the circuit schematics are greek to me. Similarly, YouTube has only been so helpful because they tend to cover electronic formulas. I'll get there eventually, but for now, I'm not grasping it.

I was able to get the solenoid to fire with an Adafruit project (showed exactly how to breadboard it) that showed how to drive a motor. However, it wasn't firing it at anywhere near full power. I tried learning enough about transistors but it seems I may need some help from a capacitor. Considering the steep learning curve, I thought asking for help would be the way to go.

Any help is greatly appreciated. Just keep in mind my current skill level if you respond. :)

Thank you for reading,
John
 

MaxHeadRoom

Joined Jul 18, 2013
21,412
What you could try Pushing the armature over physically to see if it holds in when fully seated, if it does, using double the voltage to move it to the engaged position and then immediately drop back to the rated voltage, this is a characteristic of a DC armature device, it is weak when extended.
Use a reverse (BEMF) diode across the coil.
Also a Logic level gate Mosfet could be used to turn it on.
Max.
 

Thread Starter

manual

Joined Jul 16, 2019
5
Thank you for your reply. I've done some searching on DC Armatures and I'm not sure that will work for me. My issue is that I need the solenoid to fire very quickly, with a fair amount of force. I'm trying to move something that weighs nearly 2 ounces about 24 inches. The worst case (needing the most energy) will be pushing straight up.

Best example I could find.. searched google for things that extend and found this image that is a fair example to what I'm trying to do:



I just need a method to extend that. In the case of a solenoid, I need it to fire and then power can be shut off to it. It does not need to be anything close to continuous use. I'm just trying to build a proof of concept. So my real question is, can I safely/correctly do this with this solenoid that I have? If so, how might I breadboard the circuit? If not, I'm open to any/all suggestions.

Thank you!
 

AlbertHall

Joined Jun 4, 2014
10,393
I'm trying to move something that weighs nearly 2 ounces about 24 inches.
Your selected solenoid says it is 20N with a stroke of 10mm. Now 24 inches is about 610mm or about 61 times the stroke of the solenoid.
20N is about 72 ounces which is about 36 times the force of the selected solenoid. So that solenoid is about half the power you need.

BUT note that the force of a solenoid begins very gentle and gets stronger as the plunger is pulled in so some experiment will be needed.
 

Thread Starter

manual

Joined Jul 16, 2019
5
Your selected solenoid says it is 20N with a stroke of 10mm. Now 24 inches is about 610mm or about 61 times the stroke of the solenoid.
20N is about 72 ounces which is about 36 times the force of the selected solenoid. So that solenoid is about half the power you need.

BUT note that the force of a solenoid begins very gentle and gets stronger as the plunger is pulled in so some experiment will be needed.
I am both baffled and amazed. So if I need double the power, that would likely make the solenoid far to large for this project. Even the size of this solenoid is pushing the tolerance for how much I could alter my 3D print. Looks like I'll need another solution. I'd still like to see what this thing can do at it's maximum output. I have my eye on a variable power supply. Can't justify spending the money right now but I'll try to pick one up to make projects like this easier.

In any case, thank you for your input sir. I'm not sure how long it would've taken me to think about doing the calculations like that.
 

Sensacell

Joined Jun 19, 2012
2,596
A solenoid is not the right part for this problem.

I think Alberthall was poking fun- 61X stroke and 36X force is 2000 X more power.

Solenoids are crude and inefficient, useful for only very short movements, and light forces.
You can get a little more force by over-driving them with a pulse of higher voltage, but it's not going to help with your situation.

Think about it- have you EVER seen a solenoid with 24 inches of travel?

Look into linear actuators.
 

Alec_t

Joined Sep 17, 2013
11,641
If this size works (or even better, it's too strong), then that's great news.
I don't think it's going to be powerful enough :(.
According to the link, that solenoid is rated at 20N pull/push and 10mm movement. 20N = ~72 oz, so theoretically could be used to give 72 cm.oz of torque, whereas you require about 2oz x 24 x 2.54 = 122 cm.oz. Moreover, the solenoid rating is almost certainly for the case where the armature is fully centralised; not with it fully extended, so 20N would not be available over the whole travel.
 

Thread Starter

manual

Joined Jul 16, 2019
5
Think about it- have you EVER seen a solenoid with 24 inches of travel?
No, but that's also not what I'm looking for. It's rather hard to articulate exactly... I'm looking to extend this very fast while the extension method/device would only take up a small amount of space. So if the solenoid could strike the bottom with enough force, it would extend each piece fully. After the strike happens, the solenoid's job is done. It will stay extended because the pieces are printed to where the bottom of one will catch at the top of the other. It has to be let down by hand. The solenoid would only be responsible for the initial strike. 10mm isn't much but I figured for a proof of concept, if it would come close... Well, that was the idea anyway. :)

Wish I had a good way to share photos or a video. It makes a lot more sense if you can see it.

Also, I did look into linear actuators. Unfortunately, that are really slow and take up far too much space. The right spring might work. It could be cocked like a Nerf gun and then released with a button. That's actually a very good example for what I need. Extending it quickly like a bullet but after the 'strike', the gun's job is done. The bullet will continue to fly under it's own power. If there were enough power for it to extend fully. It would stay in place.

As always, thank you everyone for your comments.
 

AlbertHall

Joined Jun 4, 2014
10,393
As it needs a manual reset, how about this:
Have a cord attached to the top which goes up over a pulley and then back down again with a weith on the end sufficient to complete the extension. Then there is a catch which stops the weight falling operated by a small solenoid (could be a lot smaller than the current suggestion).

The manual reset lifts the weight and catches it on the solenoid and lowers the arm (or whatever it is).
Operating the solenoid releases the weight which pulls up the arm.
 

MrChips

Joined Oct 2, 2009
21,855
I think you should back up and review your design specifications.

1) Length of travel
2) Force exerted
3) Time of total movement

Review your 24" travel specification. That is not going to happen at any significant force and speed.
What are you trying to do?
Sometimes a different solution is called for once one sees the full application.
 

Thread Starter

manual

Joined Jul 16, 2019
5
You can post photos (not videos) to this forum if the image file isn't too big, using the 'Upload a File' button.
DOH! Never read past the "Post Reply" button. I saw where you can add an image from the toolbar. Since there was no upload option there, I didn't think to look further. Thank you.

What are you trying to do?
A picture is worth a thousand words. I'm trying to extend the 'blade' quickly, like one might see in the movies. My boys and I already like playing with them but this would give it the ultimate coolness factor. Keep in mind that these are 3D printed and I can modify any aspect of the design. Making more room for components is fine, but only to a point to where it still resembles a lightsaber. I'm working out other kinks like the blade is a bit more brittle than I'd like. I have a few ideas on how to address that. I want to get a 1mm nozzle and print in vase mode and test the strength there. I printed one blade with thicker walls so it doesn't extend as far but it's proven to be quite sturdy. My five year old plays with it and hasn't broken it yet. I could just make the blade light up but that's easy.

2019-07-18 15.20.06.jpg 2019-07-18 15.20.19.jpg 2019-07-18 15.20.49.jpg 2019-07-18 15.21.23.jpg 2019-07-18 15.21.45.jpg

As always, thank you for any and all feedback.
 

Alec_t

Joined Sep 17, 2013
11,641
You might want a sponge ball on the end of the sabre, or you could take someone's eye out if the sabre deploys rapidly :eek:.
 

djsfantasi

Joined Apr 11, 2010
6,803
To extend something 24”, a solenoid won’t cut it. You’ll need a linear actuator or something like what used to be used to extend a whip antenna.
 

BR-549

Joined Sep 22, 2013
4,938
Use a BB CO2 canister in the handle. Blow it open. You might add a muffler for sound effects.

Or one might design a internal baffle system. You will need a trigger and valve.
 

JordanF

Joined Jan 30, 2018
1
Hi, my suggestion is to change the spring with a stronger, use the current to compress the spring and let the spring give you the energy you need. If they look like Greek to you, it's because I'm from Greece :).
Jordan.
 
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