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That's like asking "How long is a piece of string?" . We're not psychic. What are the relay specifications (closing force, spring constant, pole-to-armature spacing, core permeability, required field strength, coil resistance, coil volume, power consumption, operating speed ....)?
i just open a ready made relay, so no idea of specification.
but is there any formula to know number of turn to be there in electromagnet relay.
How to measure the diameter of small wires coil?diameter of wire (by measurement)
Just wind 30 turns on a rod and then get other wire and wind 30 turns and see if the length is the same.
No dial-micrometer needed. Just intelligence.
That may be true, but is also inconvenient if you have a fixed voltage supply for other components in a circuit. If, for example, most components required 5V, then a standard 5V-rated relay drawing 40mA would be more convenient than an arbitrarily wound one whose coil needed 400mA at 0.5V to operate.As long as you fill the bobbin, the relay will activate.
So, simples then. One turn of very thick wire will do it. Shame my pic can't deliver the 150A required.It relies on AMP-TURNS and the space inside a relay can be filled with thick wire or thin wire to produce the same result and thus the wire-size can be anything.
As long as you fill the bobbin, the relay will activate.
There is one underlying fact that no-one has brought up and no text book has covered.
I wrote it up recently while covering the impedance of a speaker.
8 ohm speakers are expensive and 50 ohm speakers are cheap because no-one thinks you can substitute the two.
So you can pick up 50 ohm speakers for almost nothing.
When you test them in an amplifier, the output is almost the same.
The reason is a speaker works on the principle of AMP-TURNS.
The magnetic flux produced by the coil interacts with the permanent magnet to move the cone.
The multiplication of the number of turns on an 8 ohm coil and the current delivered by a circuit to drive it, it almost the same as the number of turns on a 50 ohm coil and the current.
The same applies to a relay.
It relies on AMP-TURNS and the space inside a relay can be filled with thick wire or thin wire to produce the same result and thus the wire-size can be anything.
As long as you fill the bobbin, the relay will activate.