# Electromagnet control of cycle and strength

#### Frankster

Joined Dec 31, 2019
4
I have a 12v 55 kg electromagnet. Two wires. I want to run it off a 110 V converter with an on off switch. Further, I want to rheostat the strength with a simple dial or a up/ down button. Lastly, I want to be able to run it on a variable timer I set, i.e. cycles once every five to fifteen seconds and for it to stay on five to fifteen seconds as I need again with a knob or up/down button. List the part numbers, inexpensive but reliable

#### LesJones

Joined Jan 8, 2017
2,687
How much current does the electromagnet need ? (Or what is it's resistance so we can calculate the required current ?)
Probably using a microcontroller would be the cheapest solution as it could generate the PWM signal to adjust the magnet's strength and also perform the timing. You could connect three potentiometers (One for the strength, one for frequency and one for the duration.) to three ADC inputs. It could be done by other methods but would require many more components.

Les.

#### Frankster

Joined Dec 31, 2019
4
How much current does the electromagnet need ? (Or what is it's resistance so we can calculate the required current ?)
Probably using a microcontroller would be the cheapest solution as it could generate the PWM signal to adjust the magnet's strength and also perform the timing. You could connect three potentiometers (One for the strength, one for frequency and one for the duration.) to three ADC inputs. It could be done by other methods but
How much current does the electromagnet need ? (Or what is it's resistance so we can calculate the required current ?)
Probably using a microcontroller would be the cheapest solution as it could generate the PWM signal to adjust the magnet's strength and also perform the timing. You could connect three potentiometers (One for the strength, one for frequency and one for the duration.) to three ADC inputs. It could be done by other methods but would require many more components.

Les.
.57amps advertised to hold 55 pounds.

#### Frankster

Joined Dec 31, 2019
4
.57 amps. Advertised to hold 55 pounds

Joined Jul 18, 2013
21,235
If this is a lift magnet or magnetic table, usually you require a reverse DC de-magnetize action, to counteract the residual.
Max.

#### Frankster

Joined Dec 31, 2019
4
The metal will not come within five inches of the magnet. Would I need demagging? No direct contact. I see potentiometers on ebay. I don't know what to buy.

Joined Jul 18, 2013
21,235
If there is no material contact with the magnet then there should be no need for de-mag.
Max.

#### LesJones

Joined Jan 8, 2017
2,687
You will not get a pull of 55Kg or 55lb (Which is it as you use these different values in different posts.) at a distance of 5 inches. The specification of 55 ?? will probably be with the metal in contact with the electromagnet. With the frequency and duration controls how do yo want it to behave if the frequency is set to once every 5 seconds and you set the duration to 5 seconds or greater. would it be better to have one control for the on time and the other for the off time. You could also have one for frequency and one for the ratio of on time to off time. Telling us what you are trying to achieve would probably help with suggested solutions. Also giving us some idea of your knowledge of electronics and if you choose the microcontroller solution which microcontrollers you are familiar with and what programming languages you prefer.

Les.

#### crutschow

Joined Mar 14, 2008
25,267
It could also be done with three 555 timers, one for the period, which controls the second for the on-time, which controls the third for the PWM, which drives a MOSFET to control the magnet current.
If you like that approach I can gin up a schematic.

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#### Orson_Cart

Joined Jan 1, 2020
18
you really want a controllable buck converter to do this efficiently, 15kHz to limit heating in the electromag wires ...