electromagnetismsolenoid
I wanted to use solenoids in previous projects and have been let down by the fact that I can't find them here in Egypt. Plus they are a bit expensive. My question is: is there an alternative that it easy to control and cheap? If not, can you direct me to a way to easily make my own solenoids with limited materials (since I need 31 in a specific project)?
EDIT: I need to push or pull no more than 1". Please no links to buy solenoids.
It is insulated. Have you ever noticed that sometimes solenoids are made from copper wire that seems distinctly non copper coloured?
This is called enamelled copper wire, and it available in a whole range of colours.
The insulation is just a very thin coating of polyurethane, polyamide or polyester. It shouldn't be confused with vitreous enamel, which is glass. The good thing about it is that you can easily remove the insulation by rubbing hot solder on the wire.
Windings that are side by side that carry current in opposite directions cancel each others magnetic field - you need to wind the electromagnet so that current travels in the same direction in all turns of the coil. There is no sensible argument for doing differently.
The strength of the magnetic field is related to number of turns and ampere's flowing. For the same number of turns wound on a longer solenoid the field reduces with solenoid length.
These are your only options other than to use superconductors! Fewer turns can be compensated by greater current or reduced solenoid length (stacking turns).
Here's a calculator you can use to estimate field strength and it uses a field value called permeability and this means you can check on various materials and choose one that gives the highest strength BUT for household coil making a piece of iron is fine.
You can also enter the diameter of the coil.
Best Answer
Thread and nut actuator:
@KevinVermeer - gave a very good suggestion.
He said "you could use a threaded-rod linear actuator for slow but powerful actuation ..."
Any thread and nut system can be used including used nuts and bolts if desired.
Speed need not be overly slow and unlike a solenoid you can maintain constant force over as large a distance as your wish.
Any motor can rotate a threaded rod with a nut on it.
The nut travels a distance of RPM /60/TPI inches per second.
where TPI = turns per inch of thread.
eg with a 3000 RPM motor and 30 tpi thread the travel is
inches/second = 3000/60/30 ~= 1.666 inches/second.
Force is affected by motor power.
The thread is effectively a gearbox.
You can make a quick return system by using a half nut that is held against the thread by a weight and pulls against a spring. When desired the nut is lifted off the thread and spring returned. Care needed to avoid thread damage.
Electric motors of various sorts are available from many sources including new, in toys, in printers and in many domestic appliances. Non electric motors and even eg hand cranked systems can use this method.