Couple of general electical questions....

[rog8811]

I'm using rog8811's driver on his site. Will that still be ok?

That is the LM317 circuit so 9v battery will be good

Regards rog8811

 

[bhank]

Well, I'm happy to say that with everyones help I finished building my first laser last night. It's a bit more powerfull than I was actually expecting and I'd heard people say how the beam of the blu-ray is kinda strange but now I know exactly what they mean haha. Thanks guys for all of your help and i plan on making many more lasers now that I know what I'm doing a little more lol.

Again, Thanks guys

 

[bhank]

All right so I've got another question. In my last laser project, i used a phr blu-ray diode and the driver that rog8811 has up on his site, but instead of a 100ohm potentiometer i used a 25 ohm potentiometer. I used the 25 ohm partially because i couldnt find out at a radioshack near me and I was told it would work, and i also put in a push button switch to turn it on and off. SO, when I turn it on its still fairly bright at the lowest setting. So what i was wondering was this, is there anyway to use only a potentiometer or something similar to both turn the power on and gradually ramp up the power? Also instead of starting it off at lets say half power, is there a way to start off the gradual ramping up from 0. I may not be clear haha but if anyone has a question please ask and anyone who can help, please do haha. thanks

 

[chipdouglas]

a regular 9v alkaline will not be the best choice. they don't have the mah high enought to run the diode long enough. I use lithium ion rechargeables. if you were to go back and read old post (though i'll save you time by telling you) a lot of peeps ran into problems about not lasing or not being able to set the driver. it always came back to the 9v alkalines.

 

[pseudolobster]

Build a "dummy load", it's basically just 6 regular diodes in series to simulate the voltage drop of the laser diode, then a 1ohm resistor in series, across which you can measure the voltage to figure out the amperage the diode is getting.

So basically, wire 6 diodes end to end, then add a 1ohm resistor in there, hook these up to your driver, and you can adjust the pot without fear of destroying your laser... measure the amperage using the voltage setting on your multimeter, measure across the resistor. According to Ohm's law, at 1ohm, 1mV = 1mA.

Set your PHR driver to between 95mA and 120mA for a reasonable lifespan. You can't simply look at the brightness and determine if it's a safe level for your laser to be operating at.

 

[bhank]

I understand that i cant just look at it to determine what kind of power its pushing. the pot im using though is set on the case i set the laser in so that i can control power during operation. is that ok? and what i mean is, is there a way to make it so that the highest resistance on the pot will just turn the laser off completely? then still get up to about 125mA?

 

[chipdouglas]

you can do that. I don't know how. but i can explain it. on your driver if you use the correct resistor combo to, lets say there is no pot, use the resistors to set the max current you want. then you throw in a pot then you can adjust it all day long and not worry about going over the max current of the LD because the resistors are there.

 

[bhank]

Right and that is what i have been doing. but what i want to do is use just the pot to turn the laser on, then, starting from no power, ramp it up to full power. now like i said i have been doing just what you said Chip, but just turning on the laser with the pushbutton switch im using will put it to a higher power than 0 obviously, even if the pot is at its lowest setting. i guess what im wondering is if there is something that is a power switch AND a pot in one... i want to control the power from absolutely 0 or OFF all the way up to full power, wheather that is 125mA or anything else. I just want to control the power from off gradually up to full power.

 

[rog8811]

You would probably find that a 100ohm pot would do that as at max resistance it would only allow 12.5ma through.... A 1k pot would turn it right off but all the adjustment would be in the last few degrees of turn so not easily controlable.
What ever you use you will still need a switch as the circuit will draw current how ever high the resistance.

Regards rog8811

 

[bhank]

Oh ok. That is exactly what I was thinking lol. Thank you Rog

 

[Tw15t3r]

There are some potentiometers that have a built in switch, so after you reach the highest resistance that it can offer, a slight turn further would click, and break the circuit (i.e. switch off). Volume controls on pocket radios usually work this way. You turn to lowest volume, and a further nudge clicks it off.

I'm not sure what it's called though, but such things do exist.

 

[rog8811]

There are some potentiometers that have a built in switch

They do exist but tend to be quite large so it depends on what build is being undertaken.

Regards rog8811