Shift Light for Racing

[TallAmericano]

I am interested in building an inexpensive shift light for a superkart racing application and need any help on designing I can get. Here is what I am thinking (so far):

1. (2) AA or (2) AAA batteries for power source (depending on load needed to meet other requirements. The point is, that AA or AAA batteries should be the power source.
2. Light needs to be clearly visible in heavy direct sunlight
3. Light will come on to maximum of 1500 times over course of one race day and power needs to be adequate for one full race day
4. Wire will be connected to spark plug lead to pickup when a voltage goes through powering the spark.
5. The spark "pulse" needs to be compared against:
a. clock
b. programmed trigger point for light to be greater than or equal to user input value
6. user input trigger point for light will be anywhere between 9,000 sparks per minute up to 12,000 sparks per minute (150 per second to 200 per second)
7. Light will go off after count drops below trigger
8. Size of light(s) needs to be 1" to 1.5" in diameter
9. Cost should be less than $25 total

ANY help is appreciated!!!

 

[RadioRon]

To start with, I think an LED lamp of some sort will be the most power efficient so I would try to find one that is a cluster of LEDs about an inch across. Suppliers like Digikey would be my first place to start on that. One nice thing about LEDs is that they respond so quickly that if you get hard up for power, you can pulse them on and off quickly enough so that the eye doesn't notice the pulsing, but enough to save some power, since its off part of the time.

As for the electronics, the first thing to come to mind is the LM2917 which can be used as an electronic tachometer. This would be an analog solution, so the precision of the shift point may be ok or may be not good enough. It is also going to be a bit of a pain in the neck that it wants a higher voltage than 3V to operate and draws more current than I think you can afford. So, a digital solution might be better. For a digital tach, which would be more precise, any AVR or PIC with a counter-timer function could be set up to work well. An AVR, like for example the ATTINY2313 series, can operate at 2.7 volts and draws very little current.

The user input to the AVR or PIC can be some sort of decade switches ($$) or some up/down buttons and a simple display which would be cheaper.

To pick up the spark, most tachometers tap into a low voltage input to the coil, not the high voltage spark lead. But if you must tap the spark lead, do it with a capacitive or inductive pick-up, not a direct connection. Avoid a direct connection to the spark lead as the high voltage is difficult to control and use safely.

 

[TallAmericano]

Shift Light

Thanks! I looked at the spec, but I do not know enough to know how the induction wire (non-grounded) that is coiled around the spark plug wire will feed into the RISC processor...

In any case, this helps me get on track!!!