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I'm going to try and build my own LED Lap Counter sensor assembly. Having never messed around with resistors and transistors (or even soldered ) before, I'm not real confident.
I started by buying the infrared LED's and infrared phototransistors from Radio Shack today. Same parts Greg Braun mentions using: 276-143 and 276-145. I'm already thinking the phototransistors are not going to work.
The plastic part is too large to fit between the rail and the slot on underside of track. So to use these, it appears they would need to reside in the table. Even if they would still be receptive to the light while 1/4" below the track surface, I think aligning these with holes drilled in the track would be a pain. It seems one would need to wait until the track is done and screwed down, and then drill through both track and table. Or, drill one (either track or table), and then use that as a guide to drill through the other, but again, once the track is all screwed down.
It's seems 100% better to have your phototransistors 'attached to' the underside of the track, so you can still fine tune your track positions. I read where Greg does not actually use these, and his site photos show a flat transistor that fits between rail and slot, so my experiment seems to confirm that he does not use these.
I think these transistors go back to RS....maybe the LED's too...and maybe, I leave this aspect of the track to those who know what they are doing, and just pay them for their skills.
.....but....I did buy a neat cordless soldering tool from RS!
I started by buying the infrared LED's and infrared phototransistors from Radio Shack today. Same parts Greg Braun mentions using: 276-143 and 276-145. I'm already thinking the phototransistors are not going to work.
The plastic part is too large to fit between the rail and the slot on underside of track. So to use these, it appears they would need to reside in the table. Even if they would still be receptive to the light while 1/4" below the track surface, I think aligning these with holes drilled in the track would be a pain. It seems one would need to wait until the track is done and screwed down, and then drill through both track and table. Or, drill one (either track or table), and then use that as a guide to drill through the other, but again, once the track is all screwed down.
It's seems 100% better to have your phototransistors 'attached to' the underside of the track, so you can still fine tune your track positions. I read where Greg does not actually use these, and his site photos show a flat transistor that fits between rail and slot, so my experiment seems to confirm that he does not use these.
I think these transistors go back to RS....maybe the LED's too...and maybe, I leave this aspect of the track to those who know what they are doing, and just pay them for their skills.
.....but....I did buy a neat cordless soldering tool from RS!
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