| Author | Message | ||
     Rory Swanson Unregistered guest |
Hello Everyone, First off, I'd like to say I'm a big fan of the site, I've completed 3 of your projects (penny radio, hydrogen bomb, and the compuer controlled transmitter, modified for USB usage, rather than the serial port) But I have a simple question about an external power supply for my laser transmitter. I've decided that I'd rather have stereo sound than mono sound, so I've hooked up 2 lasers running off the left and right channels of a mini stereo jack (using 2 seperate transformers etc). But, I was wondering if there was any way I could add in an external DC power supply, rather than using 4 batteries (My laser Pointers come with 2 batteries rather than 3). Can anyone suggest an adapter configuration to make this work? I can probably get any voltage/current ratings on the adapter. I'm not to familliar on the workings of current dispursement, but I know that these lasers will be operating in paralell, not series. I'm thinking of adding a 3v blue led into the box as well, for visual appeal (I mean, c'mon if I can amaze my friends with a laser transmitter, the box should at least... glow  ). Thanks for any input! | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 131 Registered: 12-2004 |
Measure the current in the circuit with the batteries. It will probably be something like 30 milliamps at 4.5 volts. As long as you keep the current at or below that number, you can use any voltage up to about 30 volts or so. Remember Ohm's Law. The you will need a resistor in the crcuit to limit the current to 30 ma. The resistance is the voltage divided by the current, in this case 0.03 amps. So, if you use 9 volts, you will need 9/.03, or 300 ohms in series with the power supply. If you use 12 volts, you will need 12/.03 or 400 ohms, etc. With two lasers in parallel, the current will be different. Remember to measure the current with the batteries in the circuit, and then match that current with the new power supply. | ||
| lysdexia Unregistered guest |
Nice job those teachers did on learning us how to make estimates by using significant digits. 5x5=30! | ||
| Chris Strawberry (Strawberry) Junior Member Username: Strawberry Post Number: 4 Registered: 6-2007 |
how did you mod for usb ? | ||
| Chris Strawberry (Strawberry) Junior Member Username: Strawberry Post Number: 6 Registered: 6-2007 |
How did you mod for usb? |
