As well as enjoying FPS's and driving games, I also enjoy scalextric. Currently I am building a permanent track in my garage. As part of this I would like to build a lap counter. I have ordered from maplins some photo transistors (SFH309) and their corresponding IR emitting diodes (SFH409). The photo transistors will be wired up to the LPT port on my laptop. The plan being lane 1:data on pin 10 lane 2: data on pin 11 both have ground going to pin 25 The next step and this is where I need help is in wiring up the IR emitters. These need 12volts, Now if I was using a PC I could get this from one of the PSU connectors. Instead I would like to use an AC adaptor. I know I need to use a resistor (probably 470ohm) on the cathode side. I am now stuck on how I get the 12v from an adaptor (to be purchased) to the emitters. Also can someone confirm which way round the current should go to the emitters. From what I have seen its +12vdc to the anode, and then -12vdc connected to the resistor. All help appreciated
If you get yourself one of these, you can wire up a 12V AC->DC convertor very easily (the kind you buy from argos etc with a million connectors). Then all you have to do is wire it up like a simple 12V circuit, just like the PSU style one.
If you go for a regulated AC-DC adaptor it's no problem. Maplin's 1200mA adaptor is good value IMO (though mine was better value at the £10 promo price ). Get a socket fitting as Krikkit says - Maplin do panel mount, pcb mount, and line, such as JK12N - to match one of the power plugs supplied and you can convert to a couple of supply wires for your setup. btw, it's not +12V and -12V, it's +12V and 0V.
I'd also be keen to see a log for this, only I'd use it at the real race tracks Would there be any issues with using these componants for a real race track (where the track is more like 10-15 feet wide rather than 10-15cm wide?) or would I need to swap in much more powerful IR bits?
Yes I can start a log, when I start building (hopefully this weekend). In terms of using real size cars, I would imagine the components Im using are a little weak. You would need to provide a high IR emitter for the sensors to work. I imagine you would need something a little more powerful like using a laser.
Thinking about it, a common TV remote has around that range, so you don't need anything too powerful. Though for accurate timing the very narrow beam of something like a laser pointer may be needed.
i am still going to blab on about this... Velleman USB experimtation kit K8055 Perfect for this.... (USB has the +5v you can use to)
I had a little experiment in my moments of boredom. It's easy enough to get a beam break system working and it would seem that after adding a small gain to the phototransistor it is possible to detect objects just from reflection of objects. The picture below shows my thumb triggering the photo transistor from a distance of about an inch so that you could see my thumb in the photo, but it actually works upto about 2.5" inches. White objects work up to about 4 inches and reflective objects work over 1m away.
SteveG - Thats great work. I was hoping to make a start myself this weekend on it, but I've misplaced my soldering iron. I also need to find it to fix some of my classic scalex track too.
I'm tired to explain everything right now, but why don't you take a look at the guide I did? http://www.gideontech.com/content/articles/212/1
