Instructables

How do i make a coil?

The might sound a bit childish but i want to know about a coil. I am currently making a voltmeter(analog).I need to make a coil for it. I have a magnetic wire(around1.5 meters).Every time I make a coil out of it and supply it with power the battery shorts. I get no responce from the coil(like it does not attracts or repels a magnet or nail).So how do make a correct coil for my voltmeter and how do i know weather it responces.

If you're making a voltmeter, the resistance of the coil needs to be very, very high. This is usually achieved by winding an insane number of ultra-fine wire turns to the coil. Coil winding like that isn't done by hand, and you need to build a little coil winding machine.

We have a machine that I used to wind 0.002", 50micron wires on coils for a seismometer, we had nearly 300 grammes/ 3/4lb of wire on the coils, and no breaks. About 2 hours to wind !

The resulting coils were so sensitve to magnetic fields, they would detect me moving a small magnet 309 feet/10 metres away
rickharris1 year ago
You will need many turns and much more than 1.5 mtr of copper wire to make a successful electro magnet.

The resistance of the copper is very low and so it will pull a large current from a battery (The battery - even a small AA battery - may be able to supply Amps for a while if the resistance is low enough)

This results in your wire getting hot and possibly melting.

Your going to need to apply Ohms law where the relationship between Amps (current), Volts and resistance is given as:

Volts = Amps x Resistance
Amps = Voltage / Resistance

or

Resistance= Voltage / Amps.

IF you know 2 of these parameters then you can calculate the other.

Also pay attention to the need for insulation.
framistan1 year ago
Your question sounds rather ODD, I guess because you are unsure of the proper procedure to accomplish what you are trying to do. Lets start with a VOLTMETER. If you have an analog meter movement that says it is a 1 milliamp movement (or it might say "1mA/FS" that means the needle will read at top of the scale (fullscale), when 1milliampere flows through it. You should realize, you are utilizing a AMP meter to measure VOLTAGE. Lets say, you are wanting this 1ma/fs meter to measure 12 volts FULLSCALE. We know the VOLTS is 12... The AMPS is 0.001A and the SERIES RESISTOR you will need will be calculated simply by OHMS LAW .... R=E/I... Resistance equals VOLTS divided by AMPS. So, 12 volts divided by 0.001 amps equals 12,000 ohms. Thats a 12K ohm resistor you will need connected in SERIES with the meter and your meter will read at the maximum mark when 12 volts is applied to it.

On the OTHER HAND, maybe you are trying to make an AMPERE METER... which I doubt you are trying to do, but IF YOU WERE, then you would wind a coil of THIN wire to act as a current shunt around the meter movement. Then most of the amperes would go through this small coil which is connected in PARALLEL with the meter movement. Only a slight current would go through the meter because the coil is connected in parallel. This is more difficult to calculate, and I doubt that is what you are trying to do anyway. Then this meter is NOT CONNECTED DIRECTLY TO THE BATTERY!!! it is connected in SERIES with some load... like a small lightbulb or motor. This is because AMP METERS are not supposed to be connected directly across the battery supply. That just places a short across the supply! because remember the coil you wound is like very LOW OHMS unless you would thousands of turns of very thin wire (unlikely).

So, I hope that clears up some of your misunderstandings, and maybe puts you on the path of what you are trying to accomplish.
Kiteman1 year ago
You need to use insulated wire. Usually, in a coil, that means enamelled wire.

If your coil is acting like a short, it is probably not enamelled, or has been used so much that patches of enamel have been worn off.