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# Regulated pwr supply using one pwr source to supply 3 lasers w/ diff amounts of V and adjstable mA (info in Details)? Answered

I am working on a multicolored laser unit combining 3 different colored lasers (violet, red, and green) and i would like it so that they can all be supplied with power from one source (such as a AC-DC wall transformer). But each one runs at a different amount of mA's and Volts. I cannot figure out how to get the exact voltages and mA's that i need to run each laser from one power source. here is what the circuit needs to do: --- Use one power source to simultaneously supply 3 lasers with constant voltage and adjustable (using a POT) current. --- Be able to continue to supply constant voltage and current to the other lasers if one is turned off (i dont want the mA or volts to suddenly rise and blow one laser if i turn the other off). --- Use 3 seperate POTs be able to individually adjust the mA delivered to each laser (all of them will run at max mA and if i want to turn down the green i would up the resistance of one of the POT's to reduce the mA flow to the green laser) the 3 lasers that i will be running each have different power specs. below is the max power that i will want to run each laser at. the voltage delivered to each laser this circuit must always remain CONSTANT. the mA's delivered to each laser must be able to be LOWERED from the below specs using a potentiometer or variable resistor. 6V 120mA 4.5V 420mA 3V 340mA If anyone could figure out a circuit or design that delivered these 3 voltages and the same or similar ampages to the lasers from lets say a 12v 1amp power source (it could be more or less as long as i can buy it online), i would be eternally gratefull. i could allways change the resistor and POT values to make the mA's match what i need exactly. I have been looking for somebody to help me out with this and i can find absolutely nobody who knows how to do this. thanks for the time. -Jakob

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Use a 9V 1A PSU and 4 LM317T mounted on a heatsink. Convert the 9V to 6V using 1, then use the other 3 LM317 to create current regulators with your desired current limits. They should be powered from the 6V. You shouldnt need to regulate both the voltage and current, just the current. The drop to 6V is to minimise power dissipation for the lower voltages.

Everything you need is here http://www.national.com/ds/LM/LM117.pdf

You can buy parts from www.farnell.com