sculpture project question with a magnetic switch?

markmcleod50

this may not be the appropriate forum but it seems like you guys are pretty smart so i'll give it a go
i am using a slot car, the old toys with two strips of metal on a track and wire brushes on the bottom of a car, you pull the tigger and off it goes. basically, when a light sensor is triggered the car will play music as it travels around the track, as the light sensor detects a smaller amount of light, the music will stop and the headlights will turn on. neither the music nor the lights will be on at the same time, either one or the other will always be on. sice the track allready has two contacts, a third contact to control the speaker/music or the lights would be no problem. however the question is...what can i use to switch between the two? I was thinking something hidden below the track like an electromagnet and incorporating a magnetic spdt in the small car. i am not exactly sure how a magnetic spdt works. I am trying to acheive the fewest possible connections...batteries are no good because it will be running all the time and must be maintenance free. any ideas?

WNed

If you already have power coming in for the electric motor, you can use that to power the light as well. That way your third rail can carry the music signal (I won't put any guarentees on the quality). If you're sensing light levels, you can use the photo sensor to activate/deactivate a solid state relay to switch between music and lights. It should be no trouble to power it all from your original power strips.

Ned

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markmcleod50

i'm lost....if the little car must have power all the time, which means both strips are powered all the time, how would i go about wiring the light and the speaker to the brushes on the bottom of the car....only the light or the speaker can be on, not both at the same time. i was thinking instead of using another rail to carry the music signal to use a small microchip like the ones in a toy that replays a message over and over, that way i just have to supply power and not an actual audio signal. the microchip with the sound file and the speaker would be inside the car. any more ideas? know of any inexpensive chips to record sound too? thanks for the help. mark

Gadgetman

You could modulate the music signal onto the DC on the rails, so that you wouldn't need a third rail. (Don't ask me how to do this part, please

If the music signal is strong enough, just connect a ceramic capacitor in series to the lines to filter out the DC part and connect it to a small speaker.
As it's supposed to either have lights or play music all the time, use the absense of a music signal to switch on the lights.
(Run the music part through a rectifier. if it outputs a signal, the lights stays off)

The power to the motor and lights must go through a small filter to strip it of the AC music signal. (A small inductance in series and possibly a cap across)

Tony Ventura

Since light level is the determining factor as far as when the headlights are on or when the music is playing, I would think that the proper sensor for the job would be photo as opposed to magnetic.· For instance, two photo transistors could be used, one thats wired normally off operation (headlights)·and one wired for normally on operation (music).·These would in turn activate a standard transistor whose outputs would drive the lights or music.· The exact nature of the circuit really depends on the requirements of the device that your activating, for instance the input necessary to turn on the music chip and the current requirements of the headlights.· Your may discover that photo scr's would be more convenient.

To get you started as far as the music generator, check out this page:
http://www.electronics123.com/amazon/catalogue/c3-3-1a.htm

Hope this helps.

Tony

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