Hi,

Saw a guy with a makeshift unit on wednesday.

Build a bank of about 10 infra-red leds (maplins) on the side of a box with a large alarm/bike battery in, put in correct resistors or regulator to lower the current for them and a switch. Should do the trick.

Andy

Cool. I'm up for trying this, but don't know what parts to buy.

Can someone link me to the correct resistor(s) to go with 5 of these?

Will a 9v square battery do the trick? or will I need 4 AA's - I don't know how it works with amps and volts etc.

If someone can give me a detailed shopping list, I'll buy it all on www.maplin.co.uk and have a go at it.

Thanks everyone. Really appreciate it.

Thinking about rigging it up in something like a Coke can or something, so that when Chass is on pit wall, he's not holding a beacon ;) Sneaky eh :D

Well first up, you need a 'receiver' not a transmitter, the beacon itself transmits the signal - the laptimer recieves it to trigger the timer.

Are you familiar with soldering, PCB (printed circuit board) design? Ok, there might be some PCB designs already on the web that will suffice but are you going to be comfortable soldering it all together? Given that too much heat will kill a component, and too little won't make a good enough electrical connection.

Hrmm? :D

It wouldn't actually be that hard I don't think - if you know how to do all those pieces. I was an electronics technician in a former life so if you're super keen I could probably help. Just not sure if I'd have the time really.

You're right, the cost of the components would be quite cheap - it's never really the parts you pay for when buying this stuff ... you're usually paying for the knowledge that some super geeky dude has when he dreams up this stuff.

twpd has experience of PCB design, a lot more than me, so he may e of some assistance. Antonye is also pretty handy in this area - fill your boots mate.

Increasing the number of IR emitters won't help, as they would all emit (roughly) the same distance of beam.

Depending on the scatter of the IR emitter, you could increase the number but I doubt it would be worth it. The dome in the top acts as a kind of lens to disperse the beam anyway - remember that it is a laser (but at a IR wavelength of ~940nm) and lasers have a narrow scatter; that is to say that the beam itself does not radiate from all over the emitter like a lightbulb does. It may well have a viewing angle, and you could possibly work out the size over coverage at certain distances, as if it was a spotlight, but I'd be tempted to just build the damn thing and test it!

All LEDs emit light from the top (domed) part, with the connections (legs) at the bottom.

Just stick it all in one of these boxes. Drill a hole in the side and push the IR led out and glue in place.
http://www.maplin.co.uk/Module.aspx?...sures&doy=23m6

You need to work out the voltage required by the IR emitter to power it, and add the resistor to drop any input voltage to that amount.

Too much power and it goes pop. Too little and it doesn't work.

Read this:
http://www.ngineering.com/LED_Calculators.htm

And this is the circuit you need ... I'm sure you'll be able to figure it out ;)

http://www.montage.co.nz/led/images/LED_CircuitPlan.gif

Ps: a = anode, k = cathode; check the spec sheet of the IR device to see which is which!

The problem with IR is that you can't see if it works - obviously, normal LEDs are much easier!!

You silly boy - I have a reciever. It's called a LAP TIMER!!

What I want to make is the bit that sits on pit wall - coz not all circuit beacons are turned on for trackdays and I don't have £40 to buy a Rollcentre one (which is made from £5 worth of bits).

Go to the back!! ;)

Thanks Ant - You're a star mate.

I did do this kind of stuff at school in technology (or whatever it was called) so I'm not a total muppet, but it was a looooooooooooooooooong time ago.

Cheers :)

My most humble apologies oh guru, please allow me to prostrate myself before thee and beg thy forgiveness!

Alternatively you could just pish off!

:D

:lol: Naturally ;)