how to index turntable on a budget

[Anonymous]

I am looking for info on how to index a turntable by using materals from Radio Shack etc. ? any info would be great

[Anonymous]

we are working on doing just that - elect. engineer friend made a plan using Radio Sh. stuff - Ea. track has a photo transistor @ rail level on outside of rail, against the rail so wheels will not hit it. Then a 1.5 DC, 330 ohm. 1.4 W, LED mounted in the same manner on corresponding rail on turntable. The beam is quick enough and focused enough that for practical purpose the rails will allign sufficiently for the locos to pass.

ken

[Anonymous]

Thanks Ken any chance of getting info on hooking this up? I'm not an elect wiz but i understand what your doing. ie;how to wire and power? If not I understand. by the way I'm in Naples FL. Thanks again

[Anonymous]

I m sorry but I don't.. my friend is an electro/mechanical engineer. He drew me a picture of his idea - but I don't know who to wire it - except that the phototransistor goes onthe track ends and the LED on the end of the track on the turntable. they are imbedded in tiny blocks (plastic).

ken

[Anonymous]

Hey, David. Why can't you do it with a rotary switch (with as many poles as TT positions) and a bunch of normally closed, SPST micro switches? Here's the plan: 1) Wire the wiper (common) of the rotary switch to one side of the power source. 2) Wire the poles of the rotary switch to the micro switches. 3) wire all the other poles of the micro switches to one side of the TT motor. 4) wire the other side of the motor back to the power source. The micro switches are positioned radially around the turntable and are opened by a tab on the table. Mount the switches so they may be adjusted for precise allignment. When the rotary switch is moved, a circuit is formed thru the rotary switch, thru one of the closed micro switches and the motor. The TT will turn until the tab opens the micro switch associated with the rotary switch position. For my money, I would also put a small solenoid in series with the motor that retracts a holding pin whenever the motor is activated, and a spring which returns it when the motor stops. The pin should be conical so as to further allign the turntable at the current position. The motor and the solenoid will present a large inductive load to the power supply and some reverse current when the motor is turned off, so make sure the power supply can handle it.

[gerryleone]

David -- I really don't mean to toot my own whistle here, but back in November 1980 MR ran a "Symposium on Electronics" column in which they printed 3 pages by yours truly on the multitude of uses for one easy-to-build, cheap electronic circuit. One of them was indexing a turntable. If you can get your hands on that issue, it may help. If you can't, I've got it posted on my website: http://home.earthlink.net/~gerryleone/trains.htm . Go to the "in print" section, then look for the "Train Situation Indicator Uses" article. Hope it can help.
-Gerry