hi all,


In my colori meter product, as discussed in "cooling fan" thread over heating by the lamp was creating problem. i replaces the bulb with a ENT doctors torch bulb, it has very bright focused light.

now the problem is this bulb is not linear all over the spectrum. it has very low intensity light for some blue an violet filters. i can increase the amplifiers stage gain but this will make cause a overflow in my ADC for bright filters. programable gain amplifier is another way but i choose a simpler one. I decided to have the two level light intensity for the bulb, controled by the single i/o bit of 89c51. presently LM317 is used to provide 3V for bulb. with 120/220 ohm voltage divider at its adj. pin. i will place a transister across 220 ohm resistor so that i can turn the transister on and off, back and forth to get 1.25 and 3 volts respectivly.

My question is will this work? specialy will the output of the regulator will remain as stable as it was before when i will turn the transistor on.


if not how to make the output stable because i can not allow intensity to change while the pathological tests are being run.

thanks


abhishek