Reed Switch Location

[Wicker Bill]

Decided to try reed switches for lap counter activation on MaxTrak HO track.
Should they be mounted at the start/finish line or a car length before the line? I’m not sure how the system would handle the car sitting on top of the switch at the beginning of a race.

[glen]

I have the starting line a foot behind the finish line. Or you could start a few inches after the line. How you do this will depending on software capabilities.

[Al's slotracing]

I've some experience with reed switches for lap counting in larger scales. I couldn't get them to work properly unless they were only just below the track surface. Putting them on the bottom of a routed track wasn't satisfactory, but cutting a recess into the underside of a routed track was OK.

MaxTrak's web site offers the option of a recesses for reed switches so it seems a recess is needed.

[jmacartney]

Make sure that the switches are next to the rail, and the reeds are upright and parallel to the rail. Think about the lines of flux from the magnets. I used reeds successfully for many years before I converted to IR (Just because everyone else did). You can use hot melt glue to keep them in position.

Jim

[RichD]

If you buy a MaxTrax with the reed switch option there will be pockets in the track surface next to the rails for the switches. What you are actually trying to do is to get the reeds to touch, so how the reeds are oriented is important. The switches will work better if they are parallel to the rails. If they are perpendicular to the rails powerful magnets like neos will bend both reeds in the same direction and they may not touch.
If you run T-Jets those have minimal magnetic downforce, so you would need to use switches that are sensitive enough or those cars will not count.
You do not want to start out with the cars right on top of the reed switches. You can position the switches behind or ahead of the starting line. I expect that most people have them behind, if they are before the line the cars will register a lap as soon as the cars start moving. If you are using computer software you can program it to skip the first count. That would be fine if you were not using lane rotations. If you were running races with lane rotations it might skip the first count at the start of each heat, but in fact it might only do that when a car first rotates in. It would be a good idea to check on that.