Building my own solenoids AskElectronics

I am currently in the process of making my own solenoids (I need 20 of them, so buying them isn't an option). I am currently using a 3d printed tube (PLA material, not that it matters given that it's plastic) and 28 gauge wire. I have wrapped the length of the tube (about an inch) three times over. I am using a nail as a plunger. To oppose the field created by the coil, I put a magnet on the head of the nail (slightly stronger than a refrigerator magnet). This increases the force of the solenoid. The nail is about 2.5 inches long. I need a short stroke length, about a fifth of an inch and I'd like to maximize the pull force per unit of current.

The solenoid will be horizontal, pulling the nail sideways, but I've been holding it vertically when testing it (making the nail hover in the tube is giving me a decent idea of how much force I am producing). It takes about 3 amps to get the nail to lift off of the solenoid by about half an inch currently. I'd like to improve on the efficiency of my design to the point where I can limit the current to half an amp or less. Here are my ideas for how to do that, please let me know which ones are the best ideas/investments and why.

• Higher gauge wire (36 or so?). More wraps per unit area means more field per unit of current, but mean more resistance and less current handling ability.


• Using stronger magnets (these were the ones I had in mind) [http://ift.tt/1yWDiwt] Stronger opposing field means stronger force, at the expense of a slightly heavier magnet. The added weight is probably negligible.


• Instead of using the 3d printed tube, use a steel tube slightly larger than the nail as suggested here: [http://ift.tt/1omthBr] I'm not certain of why this would be an improvement except that steel has better magnetic permeability than air/plastic. This is the tube I am considering [http://ift.tt/1yWDhsc]


• Fold sheet metal around the wraps (mentioned in previous link) or put a larger steel tube around the solenoid. I believe this has to do with making the path of the magnetic field shorter, but am uncertain of how useful this is as well.

Trying to keep the total expense around 60 bucks if possible.

Thanks in advance for any help.

Submitted January 12, 2015 at 05:58AM by chippylongstocking http://ift.tt/14LNWbY AskElectronics