January 22, 2011
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Yesterday evening I was testing out the IR LEDs for the track timer when I remembered that not all digital cameras have a stiff IR filter on them. So I pulled out my cellphone and what do you know, it works. It appears that my HTC Tilt 2 is able to see 940nm (Infrared) light. This will make finding bad or under-performing leds much easier!
Today I wanted to breadboard out and test the remaining lanes but I am swapping out the IR emitters cause the original IR LED pairs I bought from sparkfun work great up till about 4 inches and on Wednesday I found out that the lane sensors will be at least 4.3 inches apart. So I bought some high power IR LEDs from Mouser. They put out 10 times the amount of light so I should be able to get the distance needed and then some.
Also decided on how to connect the main timer module to the rest of the track, Ethernet cables and keystone jacks. i had been considering using a serial cable but then i remembered that I have 9 data lines and not just 8 (8 lanes plus that start gate switch). In addition, at some point in the future I want to add a servo to the start gate and that would add a 10th data line. Therefore Ethernet seems like the best choice. There will be two Ethernet cables (8 wire each) to the finish line and then from the finish line up to the start gate there will be one.
Along with the order for the new IR LEDs i ordered a bunch of other parts and a project box. so today I wired up the Ethernet Keystone jacks and tested them on a 25ft Ethernet cable. I was getting about 0.9 – 1.2 ohms which seems in spec with 2 connectors and 15 feet of wire.
Tomorrow I will be focusing on the software side. I hive some Ideas on how to page out the text to the Nokia LCD and need to try it out. Also need to finish the Interrupt handles for lanes 2-8 (mostly a copy of lane 1 when I am sure it is complete) and start working on the serial interface. Thankfully I have been in communication with Jon Ficks who also built a track timer a few years back and posted it online. When I contacted him about the design to see if it could be modified for 8 lanes we ended up chatting for over an hour. Jon also posted the C code used with his PIC based timer. I will use it as the model for my serial interface.