# Multi-Stage Linear Solenoid

Okay, first of all let me apologise if I've got the wrong forum, and do excuse any lapses in terminology also, as this isn't my normal field of expertise ๐

Anyway, I have a small robotics hobby project that I'm working on, and need linear motion. Now, I'm doing this on a small scale so far, so I just picked up a cheap DC linear solenoid for experimenting with.
This works fine, however, the motion is only binary (extended or retracted), and I'm thinking I might need a bit more freedom than this, specifically so I could do fully-extended, fully-retracted, and one or more mid-points between the two.

I'm hoping to do this electrically/electronically, but I'm not sure if what I'm looking for already exists (or if it does, where to look). After doing a bit of research, it seems that what I'm looking for is similar in principle to a Coilgun, except that instead of firing a projectile from the end I'd be shifting an armature to one of several coils and holding it there.

I think this would give me the kind of freedom I'd need, with the multiple magnets I should be able to get a fair range of linear movement since I could bounce between any two coils, in theory at least, which would be ideal, as I should then be able to handle the rest through programming a suitable sequence, which is where I'm more in my comfort zone, as I'm hoping to avoid anything too mechanically complex.

So, I'm curious to know if what I'm describing is something that is easily obtainable (if so, what exactly am I looking for, and how well does the device scale in terms of strength at larger sizes?). Or if not, I'd welcome any advice or guides on how I'd go about making my own; I've made a really simple linear solenoid back in my school days, would it need to be much more complex on the mechanical side (ignoring the actual timing which I think I can do)?

i.e - is this simply a case of a suitable rod, then three or more coils along it, all hooked up to a power-supply via a control chip, or am asking for trouble? ๐

I'll also welcome alternatives if there's a better way of doing this, however I'm not 100% sure what range of motion I require, which is why I'm shying away from the mechanical methods I know of that would use a motor, since adjusting these dynamically would be a lot more tricky, I think.

Thanks!

## Replies

• Haravikk
I'll take from the silence that this may not be a very standard arrangement at all ๐

In that case, I'm interested if anyone familiar with building electromagnets can give me an idea of the best materials to use for the magnet and rod. In particular I'm hoping to just build for overkill by making very powerful electromagnets that can have their strength easily scaled with voltage, such that I can be sure I won't have too little, and then simply scale the voltage back to the minimum I need in practise. I can then try building two or three magnets and seeing how well I can get these to operate as a test. I may do a small-scale prototype to avoid spending too much.

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