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Count

Dead Strip Question

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Hi everyone, I need your knowledge.

 

I am thinking about installing dead strips on The Pretzel. I am currently using a very ugly light bridge with LDRs mounted in the slot, but am getting HEAPS of missed laps when the cars are at racing speed, particularly on one lane (it's OK when they are slow). Now, don't tell me I need to put a resistor-ma-jig in the circuit to slow the pulse, it was a definite stretch of the grey matter to get it working at all, and anyway, I don't want a light bridge! (OR MY PULSE SLOWED!)

 

Dead strips seem to be a fairly simple and efficient way of triggering laps (am I right?). I'm not worried about the 'dead' effect as the straight I'll put it on is about 6 metres long, but I'm wondering:

 

1. Will a dead strip work in both directions, or is the polarity wrong as soon as you turn your car around? (The Pretzel is great (and quite different) in both directions - don't want to frig with that!)

 

2. If my 'missed laps' at the moment are simply because I've got an old (slow) PC, will it be just as bad with a dead strip?

 

I've tried searching for these answers, but to no avail...

 

Thanks a lot

 

Count


mt1135840120-1.jpg

Ask not what MDF can do to you, rather ask what you can do to MDF!

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An old (slow) PC won't help, depends on how old and what timing software you are running. There are circuits to stretch the trigger pulse but that depends on how keen you are to build circuits. Using the light sensors can be be much simpler than a dead strip as a dead strip definitely needs a circuit to be built. As far as the light sensors go there is a simple light detector zd1951 ( I think) that simply can be plugged straight into the parallel port, I had 2 of those on my scalex track and they worked very nicely with a light bridge. I started with LDR's and had lots of problems, there are much better "photo transistors" that simply turn on when light is on them and off when there is "darkness". I'll see what else I can dig up for you.


Paul

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Throw away the LDRs and replace them as mentioned above. The Darlington Pair Photo transistor is either on or off like an optical switch and reacts MUCH quicker than an LDR which has to have its resistance fall the rise again for the software to count a lap. Add to that LDRs can be a little bit off or a little bit more off.

 

Dead strips must be isolated from the PC power else nasty things will happen plus depending on set up they can be direction sensitive

go with the Dick Smith ZD1951

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Count I am having the same problems with the photo interrupters, only one lane giving problems and it goes off when it feels like it. (although it dose not do it with no mag cars) I have just about pulled my hair out trying to sort it out. Cheers Bill.

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How often does your PC "look" at the port? When the slotcar is at full speed every 25mm of travel takes about 3 milliseconds. So if your pC updates every 10ms you would need the strip to be at least 75mm long to avoid missed laps.

 

Id direct you to my cct in another thread but it involves building and soldering. Depends how much electronics know-how you have as to whether or not you would like to attempt it. It definetly works, been built and tested.

 

cheers

rick1776


cheers

rick1776

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If you use one of these:

 

http://www.altronics.com.au/index.asp?area=item&id=Z1670

 

you can install it like this:

 

http://neophytte.mine.nu/forum/forum.pl?fi...c_id=1199609487

 

Two of our members here in the West have done this, and neither have complained about it.

 

HTH!!

 

Richard

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thanks everyone very much for your replies...

 

It seems the consensus is the in-track infra-red sensor (ZD1901 from Jaycar) instead of dead strips? I know you have mentioned the ZD1951 from Dickie's, but aren't these the same thing?

 

I used to use these in tape recorders as tape-end sensors. Had a disaster one day when a clear piece of leader tape went through one in fast forward and the machine thought it would be a good idea to hit the brakes! Tape EVERYWHERE!! Never thought I'd be using them to measure slot-car laps!

 

I already bought some of these from Jaycar, but the thought of doing surgery to the track and discovering they were no better didn't thrill me! (Especially as they have a 3mm gap and my slot is 4mm). But I'm prepared to give them a shot if they are a simple install (i.e no circuits to construct).

 

I know that these need to be powered. Can I simply use the power (about 5volts) coming out of my printer port on the PC?

 

thanks again,

 

Count


mt1135840120-1.jpg

Ask not what MDF can do to you, rather ask what you can do to MDF!

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thanks everyone very much for your replies...

 

It seems the consensus is the in-track infra-red sensor (ZD1901 from Jaycar) instead of dead strips? I know you have mentioned the ZD1951 from Dickie's, but aren't these the same thing?

 

I used to use these in tape recorders as tape-end sensors. Had a disaster one day when a clear piece of leader tape went through one in fast forward and the machine thought it would be a good idea to hit the brakes! Tape EVERYWHERE!! Never thought I'd be using them to measure slot-car laps!

 

I already bought some of these from Jaycar, but the thought of doing surgery to the track and discovering they were no better didn't thrill me! (Especially as they have a 3mm gap and my slot is 4mm). But I'm prepared to give them a shot if they are a simple install (i.e no circuits to construct).

 

I know that these need to be powered. Can I simply use the power (about 5volts) coming out of my printer port on the PC?

 

thanks again,

 

Count

The Dick Smith ones are darlington LEDs and react to day light as well as IR light and from reading do react quicker - makes it easier for light source

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