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stablised high intensity white light source for fibre optics

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Im a currently trying to build the above titled project. So far i have designed the filtering section and power supply. However i am having difficulty with the feedback section of my circuit. I need to place a fibre optic at the end of the bulb and have this connected to a photodiode. By doing this i will be able to control the light intensity, i.e keep it stable by using a voltage controlled resistor of some sort.
My main objective will be to provide more voltage to the 12v bulb if it's intensity starts to drop. I will be running 2A of current through the circuit and this is why i choose to use a voltage regulator as my power supply.
I would really appreciate it if someone could share their views on this matter and help me design the best possible circuit.
Layout: Mains input ->Filtering->Voltage regulator->Bulb->Fibre optic->
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New Member
Are you trying to compensate for long term light loss due the ageing of the bulb or for short term light fluctuations due to input power fluctuations?
For short term a very stable power source would be simpler than adding feedback. If not possible to stabilise the source you could add, after the photo diode output, a comparator and a reference voltage. The output of the comparator controls the input voltage regulator. Make sure the reference does not fluctuate, it should have an independant supply source from the lamp.
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