# Infrared Beam Break Circuit

Discussion in 'General Electronics Chat' started by Peterboardman, Mar 1, 2011.

1. ### Peterboardman Thread Starter New Member

Mar 1, 2011
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Hi all, I was wondering if anyone could help me with a circuit design I'm finding quite complicated that I need for a little project of mine.

My aim is to build a motor to propell a levitating train around a magnetic track using the electromagnetic force generated via current carrying coils on the side of the track.

I want magnets on the side of the train to firstly be attracted and then repelled by the coils, which can be achieved through reversing the current when the magnets are at the mid point on the coils. This is explained on the diagram below.

I need a circuit so that the once the infrared beam is broken, the current in the coils is automatically switched for a certain period of time and then reverted back afterwards.

The currents I am using in the coils will be very large (in excess of 10A) so this may cause some concern. Also the switching of the current will need to be of around a few milliseconds so that the train does not come to a halt.

Any suggestions or ideas would be greatly appriciated, particularily circuit diagrams. Thanks for your time,

Pete

2. ### GetDeviceInfo Senior Member

Jun 7, 2009
1,571
230
Do you understand how an AC induction motor works? If you 'unwrap' a cylindric motor and lay it flat, you'll have a linear motor.

3. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Check the many posts on H Bridges for coil drive reversing, same for beam break??

4. ### Commander#1 New Member

Jan 22, 2011
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Hi Peter -
Here's an idea to kick around. You may not need to reverse the coil drive. Use two coils very close together (you may need a magnetic
partition between them). The first one attracts - it's cut off just as the P.M. on the car reaches it - and the second one repels - it's
turned on just as the P.M. passes it. You can keep the pulses short, but, any particular coil is always energized with the same polarity -
Plus or minus. Therefore, the drive electronics is simpler. And after the car gets up enough speed, you'll only need the repulsion
coils to continue accelerating or maintaining a set speed. What do you guys think???

Phil Potter.

5. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Still need train position. Use the length of beam break vane to control firing timing, fire on break with one polarity, fire on make with reverse polarity, so if best attraction is one cm before dead center,& repulsion one cm after, then vane would be 2 cm long.