USB power

Hi all,

I'm quite new in the laser burning business and I've done some reading and research on your forums but I have not found the answer yet to one of my questions:

Is is possible to use USB as a power supply for my laser?

I'm using the RKCSTR driver from the StoneTek shop (aaargh, can't post links yet...) and the Sony SLD1239JL-54 diode. I know USB gives me 5 Volts of power. I guess it should work all right, but I wanted to check on you guys if you know if it works.

I cannot test it yet because I need to get some elements to build my own dummy load. But the shop in my town will not be open until next tuesday.

dont you want it to be portable? :-? you would have to get a usb cord and cut it apart...i dont know how many wires are in there but if there are 2 that are red/black then it should probably work...

I've done this with a DX red module, works fine, I think there were 4 wires in the cable and I took the red and black for positive and negative respectively.
The 5V from the USB should be just enough for a rkctsr red laser build.

yes the usb would work with a rkcstr driver, i no i built few of them called "pc labby"
http://www.laserpointerforums.com/forums/YaBB.pl?num=1218727477/5

Thanks for your replies .

I've found out that I need pin 1 and pin 4 of the USB. Those are the power pins. 1 being the pos. and pin 4 being the common.

I do not need it to be portable, because I will use the laser in a construction that I'm building. The construction will be computer controlled, so that is why I have the opportunity to use USB power.

Do any of you know if the 5V would be enough to get a powerfull burning diode. Let's say enough to cut/burn black paper? If not, what power will I be wanting to have? And how much mA? Would 250 mA do the trick?

Do any of you know if the 5V would be enough to get a powerfull burning diode. Let's say enough to cut/burn black paper? If not, what power will I be wanting to have? And how much mA? Would 250 mA do the trick?

Click to expand...

You probably want at least a couple of hundred mA to get burning power.

The USB spec guarantees 100mA. If you want more, you can request up to a guaranteed 500mA by making the request through the USB port so unless your device can communicate to the USB controller to request the extra current, you will only be guaranteed 100mA.

The good news is that although the USB spec states these things, most motherboard implementations don't actually adhere to this at all and in many cases you can draw more than 1A from a single port.

So I got it working on the USB port, but my port does not give the power I want it to have. So I got my hands on an adjustable power source (dunno if that is the correct name, but you can adjust the current and the amount of volts on it). So the situation is like this: I've build an test load (4x1N4007 in serie with an 1 Ohm resistor). So I adjust the voltage on the power source to 7.2 before I connect it, and my multi meter measures about 5,12V when I connect my driver+test load to the power source. My question is:

Should the voltage be 7,2V without the driver and test load connected or 7,2V WITH the driver+test load connected.

With 5,12V with driver connected, I get about 180 mA which is sufficient to burn through my black paper. I want to check on you guys first before I do anything wrong and burn up my driver or something.

Now you could take it one step further and implement a microcontroller that can communicate to USB directly and add modulation and even data transfer through your laser. You may need to get a slightly different driver board to do this though. Just imagine a USB controlled laser. You could adjust on, off, and to an extent intensity through PWM.