Simple Electromagnet driver?

Thread Starter

sloanthrasher

Joined Mar 24, 2012
4
Hi,

I'm working on a project that uses electromagnets to turn a ring. There are three rings, and each uses 3 electromagnets, so I want to keep the circuit simple, and the parts count low. The rings each have 20 high power magnets around the edge. That is the "target" of the electromagnets.

The idea is to use a higher current on the electromagnet initially, then a lower current to hold the position.

I've created a schematic to illustrate the idea I had, but would appreciate and comments or suggestions.

Is the basic circuit idea the way to do this?
What size/value of capacitor should I use?
R1 is intended to liit the charge rate of the capacitor, What value should I use?
R2 is intended to limit the current through the coil. I was thinking of 220ohms?

Thanks!
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
Many magnet operations require a reverse demag shot pulse due to residual magnetism, not sure if you need this in this application but something to consider.
Max.
 

Thread Starter

sloanthrasher

Joined Mar 24, 2012
4
MaxHeadRoom, Not sure if I need that. This is a variation on a digital motor. Three coils that are energized in sequence to move the rings. Much slower than on say a quad copter. One ring turns at 1rpm, the next at 1/60 rpm, and the last turns once every 12 hours. Yep, seconds, minutes, and hours. It's a clock.
 

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If you're using a MCU, why don't you consider PWM? Of course, you need to consider some technical specs you didn't mentioned, as the expected current drawn by the electromagnet. Furthermore, according to your schematic, you must add a freewheeling diode across the inductive load.
 

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