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Discussion Starter · #1 ·
need help. I can make a unit like a ds bridge with emitters and sensors. however I need to create a switch to control some counters.
the bridge uses 8v does anyone have any wiring diagrams incorporating a relay switch? Or can anyone help design the circuit? i have read about a 555 chip do I need that in the circuit?

I'll post my diagram of the sensors and emitters when I can get to a scanner.
 

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I am unclear what you need relays for.

Could you explain with a little more detail

From my perspective I am thinking - if you have opto-electronics using photo transistors and LEDs, you have your "switch" to count the laps, all you have to do is hook it into a PC in a way compatible with one of the several free or paid software only timing packages available (ie, not using an exterior hardware board like trackmate.)
 

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Discussion Starter · #3 ·
QUOTE (slotcrazy @ 15 Jul 2011, 05:09) <{POST_SNAPBACK}>I am unclear what you need relays for.

Could you explain with a little more detail

From my perspective I am thinking - if you have opto-electronics using photo transistors and LEDs, you have your "switch" to count the laps, all you have to do is hook it into a PC in a way compatible with one of the several free or paid software only timing packages available (ie, not using an exterior hardware board like trackmate.)

Thanks for your reply.

we want to trigger an 8 segment counter such as the old scalextric building with a display inside it needs and on/off signal to count the laps.
no pc is being used here. or the scx lap counter uses a reed switch and the old ones an mechanical switch inside the rails.
 

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*** Leo A Capaldi ***
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Hello,

I have fitted photo-transistors to both of the units you mention and they work great. Both units have a sensor wire for each channel and a common wire. I fitted the sensors (with in-line resistors of about 560 ohms) across the sensor wire and the common. The polarity is important but "trial and error" won't harm anything. A light source can be the same as you have mentioned, indeed could use the existing one.

As Slotcrazy says - at the end of the day a transistor works just like a relay.

Linky to Ebay item

Kind regards, Leo
 

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I've been playing around using LDR ,741 chip and a variable resistor to sense a car travelling over the start/finish straight. I de-bounced the output with a 555 timer which then using a dil reed switch counted laps using 4510 and 4511 chips. It is then possible to work out what will happen on certain laps using logic gates eg stop timer when the timer counts down and reaches zero.

Well, my prototype worked well, you could set the counter to say 7, as the car passed the LDR this triggered the lap counter to change to 6 and also start the stopwatch (one purchased from sports store and buttons re-wired). It would then continue to count down the laps until zero was reached when stop watch would stop.

However, the PCB I made did not work and the stripboard I then used became progessively more and more complex.
Work commitments have hindered my progess of late but I'm keen to make something work in the future.

It's fairly easy to find a circuits on-line that sense light/dark it's just a matter of linking everything together!
 
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