I'm building a laser driver for a dvd laser burner. I needs 200-250 mA and 1.8-2.2V.
Is it the right setup? Is the trimpot setup correct? The multimetre shows6.43V and the trimpot doesn't seem to change anything.
I'm building a laser driver for a dvd laser burner. I needs 200-250 mA and 1.8-2.2V.
Is it the right setup? Is the trimpot setup correct? The multimetre shows6.43V and the trimpot doesn't seem to change anything.
Afew questions first flease.
1. It's a 9V battery.
2. I think this is what I have, 100ohm TrimPot
http://jaycar.co.nz/productView.asp?ID=RT4640&w=100ohm+potentiometer&form=KEYWORD
Ok, it looks to me from your diagram, that you may have the pot, contented to the wrong pin on the lm317, it needs to be connected to the adj pin on the lm317, to the middle pin on the pot.
Than a ground ran over to the left pin on the pot.
Than a resistor ran from the output on the lm317, through a diode, to the right pin on the pot.
That should get you started, than look to my diagram if you are getting some movement on the output voltage, you may need to place caps to stable the output voltage.
Ok, it looks to me from your diagram, that you may have the pot, contented to the wrong pin on the lm317, it needs to be connected to the adj pin on the lm317, to the middle pin on the pot.
Than a ground ran over to the left pin on the pot.
Than a resistor ran from the output on the lm317, through a diode, to the right pin on the pot.
That should get you started, than look to my diagram if you are getting some movement on the output voltage, you may need to place caps to stable the output voltage.
That's a big help so the right pin connected to the resistor is the side with the "knob/screw"?
Also thx Johnd
If you look, pin 3 has a "CW" over it.
So that leads me to think the to out side pins are fixed at 100ohm's, and the center "#2" pin is the one that sweeps on the pot.
And CW=Clockwise, means all the way clockwise, will give you pin 3 to pin 2 connection. (Very low resistance.)
Thats the way my pots are anyways.
Right side will be pin 1
Center will be pin 2
Left will be pin 3.