Sending specific IR codes to a laser tag target

[Haku]

I was in my local Home Bargains today and saw a shelf full of WowWee Light Strike Targets, aka laser tag targets, for 29p each (yes 29p each!), so I bought one.

Closer inspection with a screwdriver revealed some useful salvageable parts: a wide angle RGB LED, SMD stereo headphone socket, couple of capacitors, some SMD resistors+transistors, a switch, a small speaker and a 38khz IR receiver. I'm thinking of going back and getting a couple of armfulls of them tomorrow

When switched on it cycles through the four team colours, red, yellow, green, blue, then goes dark and waits for a specific IR sequence which a little Googling revealed this page where someone figured out the codes and timings for the system.

However I'm not sure where to start with trying to get a Picaxe to send the codes (I have a lightgun I rewired ages ago with a Picaxe to send IR I can use on such a target), especially as it requires some precision timing on sending the '0's and '1's, and I'm not so great with understanding 'foreign' code.

Can anyone point me in the right direction?

 

[hippy]

Given the IR timings ( Header Mark: 6750us, Inter-bit Mark: 900us, Zero Space: 900us, One Space: 3700us ) That should be possible with a PICAXE running at a high enough speed; I'd choose a 20X2 at 64MHz but it might be possible at 32MHz or even lower.

Sending 32 bits should also be easy enough, and using w0 and w1 you have bit0 to bit31 so you can easily set the bits to the command send. Then all you have to do is pump those bits out at a fast enough rate with the right timing.

As to actually doing that; here's one place to start -

http://www.picaxeforum.co.uk/showthread.php?14747-Sky-Remote-Control

There are likely other IR sending solutions on the forum. This code is slower than Sony IR and I am sure there are do it yourself bit banging examples which simulate sending the Sony code.

To get the timing right really requires a logic analyser or scope or someone who has those and can produce the code for you with the desired timing.

 

[Haku]

Thanks for the pointer of where to start looking, I've spent the half the morning learning about how IR are made/transmitted with the help of the link you provided and the code from the pages I found.

I haven't managed to trigger the target yet, and you're right about the logic analyser / scope, I think it's time I looked into that because right now it feels like I'm stabbing in the dark not knowing how un-precise the pulses are.

Oh and the other half of this morning was spent cycling into town to get 10 more of those laser tag targets Even if I can't figure out how to trigger them the parts can be useful and didn't cost a fortune, or I could rewire some with Picaxes instead.