Issues with a 3V solenoid. Need some advice :D

[alexeilb]

Hello everyone I am new to this forum, I needed some help with a solenoid I made and could not think of a better place. I needed a very small solenoid measuring no more than 6mm so its very small. Nothing on the market is that small so I made my own with an insulated copper wire and a steel rivet as the rod. Then I took a spring from a pen which will push the rod back out of the solenoid.
So that is the basics of the solenoid.

This is my rig, the completed one had shrink electrical tape on it, and it was connected to a battery. Well it worked, but not with a 3V flat battery, it was too weak. It worked perfectly with a 9V, the steel rivet would retract into the solenoid, and when  the battery was disconnected the steel rivet went back to its original place with the help of a small spring. The project I want to use this for is a locking mechanism, and its for a very small application. Can you guys please help me, is there a way to make a lock this small with just a 3V battery? The solenoid does not have to do much, just retract that rivet back in order to unlock the hinge.  

[Soeren]

Hi,

Just add more windings (use a smaller wire dimension).

And with such home spun coils... Make sure it isn't a disaster if it stops working.

[alexeilb]

Hi,

Just add more windings (use a smaller wire dimension).

And with such home spun coils... Make sure it isn't a disaster if it stops working.

So with more windings and smaller wire, 3V battery should work? Because with the current setup the 3V did not even nudge the rod. I'll have to try and see, hopefully the battery wont discharge too fast.

[Soeren]

Hi,

Just add more windings (use a smaller wire dimension).

And with such home spun coils... Make sure it isn't a disaster if it stops working.

So with more windings and smaller wire, 3V battery should work?

No, I just said it to yank your chain...Gee, I love it when my answers gets returned as "new" questions - a bit like saying "now are you really-really sure you meant that?"-

Because with the current setup the 3V did not even nudge the rod. I'll have to try and see, hopefully the battery wont discharge too fast.

No wonder. The wire you used is of a much too large gauge, so it's like a near short for your 9V battery and it's the internal resistance of the battery that has limited the current through the coil and kept the battery from melting down.

You need a wire of say 0.1mm in diameter and lots of windings - wind it on a thin walled plastic tube that the pop rivet fits in with just enough clearance to let it move freely. the former may be compressed a bit when winding it, so experiment to find the best former size, as well as the number of windings - count on using a couple of hundred turns at the very least.

However you make it, it will be sucking some juice, so don't use a lithium button cell for driving it.

[Admin]

You need 'motor wire'. It has a coating of plastic over it so you can very tightly pack your windings. It's specifically designed for stuff like this.

Get a straw and wrap the wiring around it very tightly, and your rod can slide within it. You may need to look around for a straw of just the right size.

Also, 3V is a bit low for something that big. Torque increases exponentially with voltage.

[Soeren]

Hi,

Usually the lacquer isolated copper wire is called "Magnet Wire" on your side of the pond and "Lacquer Isolated Copper Wire" this side (and "lakisoleret kobbertråd" in Danish) - so to save time, I usually go with "Magnet Wire".

It is also known as "CuL" (Cu for Copper and L for Lacquer) and I think that is an international term, although no shop clerk would know what you were on about if you asked for it - probably best to keep that for schematics and such 
I'm pretty sure the photo shows exactly that kind of wire.

[Admin]

Forgot to mention . . . you can get motor/magnet wire from inside any el-cheapo motor you can find. Just open it up and unwrap it. Be careful to not scratch the wiring (ie protect the thin coating).