Isolating Case + from Case - best way? Also need pot to go from 0 to 12v

[Dr_Evil]

I am working on a project that is going to have a red, DPSS green, 450nm and a 405. I am going to be using 4 of these.

12X30mm aluminum mount for AixiZ 12X30mm units, AixiZ

They are going to be mounted on 1/8" aluminum. Two on top and two on bottom directly opposite of each other. I'm thinking of using double sided tape underneath the blocks and non-metallic hardware.

I also need a pot that has enough resistance to drop 12 down to 0v. I don't really care if it goes down to 0 as long as I can get down to 6v or less.

 

[LaserAdct]

I also need a pot that has enough resistance to drop 12 down to 0v. I don't really care if it goes down to 0 as long as I can get down to 6v or less.

Why not go for a lm317 voltage regulator with a pot to adjust the current instead? All you then need is a decent heatsink to eat the excess heat from the voltage that is not used. With the current pot you can then regulate the intensity of the laser. Using a pot to "eat" voltage is not a pretty or good solution.

 

[Dr_Evil]

The pot isn't for a laser. It is for a motor.

 

[LaserAdct]

The pot isn't for a laser. It is for a motor.

Ahh I see. I am a little embarrased now hehe :beer:

 

[AUS]

Any pot will have 12V at one end and 0V at the other no matter what value it is, if that's how you hook it up. It's a matter of application- if you use a 1 megaohm pot you won't get much current through the wiper, and if you use a 10 ohm pot you will be drawing I=E/R or 12/10= 1.2 amps just heating up the pot.

If you want to go 6V to 0V then put a resistor the same size as the pot between it and the +12V rail, ie a 10k pot use a 10k resistor. Look up voltage dividers and ohm's law.

If its driving a laser diode then you really need to keep a close watch on the voltage and the current so you don't blow it up as has been said above. A laser diode needs to be current limited. The current will vary wildly with the voltage as above.