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With a 100ohm multiturn pot it is amazing just how little you have to turn it to raise the ma and get a noticably brighter output, then it reaches a plateaux (the knee mentioned by people who have done a graph) where if you turn on more ma's there is no increase in output.I am getting about 38 ma but it seems much weaker. can this small change really affect the output that much? is it safe to up the current to around 45 ma or so?
chido said:Welcome to the forum.
The LED doesn't turn off because it doesn't need a lot of current to work.
What I mean is that even with the pot set to its maximum resistance (25 ohms) it still lets through 50mA which is more than enough to light up your LED. If you lower the resistance on your pot and let more current through you'll probably blow the LED.
chido said:The LM317 keeps 3v to itself, and in average a diode takes around 3v, (voltage depends on the current you're driving the diode at) so you need at least 6v to be able to power the laser. Of course you're not going to just throw in a couple of batteries that give you a total of 6v, because as soon as those batteries get weak the diode won't get enough voltage, and if the voltage drops the current will too, so in turn your laser will keep getting weaker and weaker until the batteries die.
To have the batteries last longer you're going to need to input at least 7v, you can use 5 or 6 AA batteries, 6 NIMH rechargeable batteries, 2 CR123 rechargeable lithium batteries, etc. And in case you ask, you can't use a 9v battery because its mAh rating is too low so it won't last too long.
You can use a higher resistance pot but remember that the higher the resistance the courser the adjustment will be... try to stay in the ohms range rather than K-ohms. Also with a 25ohm pot you can get away with a single turn type, if you go higher a multiturn is essential.can i use a higher pot ohm
muslimballa911 said:thank you for your information, but how much energy does it take to power up a 16x diode or a 20x diode.