Challenger Posted December 29, 2009 Share Posted December 29, 2009 Making a really simple circuit but have a really simple question... Heres the plan, I have 5 IR LEDs that Id like to hook up in series with a 9V battery source. The specs on the LEDS are: forward voltage= 1.2V and forward current=100mA. I used an online calculator with this information and it showed to use a 33 ohm resistor to make it all work fine. Does this sound right? Anyone able to verify I was reading the results of the calculator correct? Heres the website. Used the following values in order of imput, 9V, 1.2V, 100mA, 5 LEDs. http://led.linear1.org/led.wiz Thanks for the help! I have my fundamentals of electrical engineering for mechanical engineers next fall so I guess Ill get to learn this stuff at some point. Quote Link to comment Share on other sites More sharing options...
garvice Posted December 29, 2009 Share Posted December 29, 2009 LEDs are current controlled devices, you want to make sure they are getting the right current (in your case 100mA). When you put rated current (100mA) through your diode you will have a voltage drop (in your case 1.2V). So you want to add up all your voltage drops (5 off 1.2V = 6V). This leaves 3V that you need to drop across a load. Now you have your voltage law of V = IZ (Voltage = Current * Impedance). So to drop 3V with 100mA running through it you would run a 30 Ohm resistor. Having a 33 Ohm resistor will draw a little less current (not a bad thing as you don't want to fry your LEDs). So a car has a 12V system, a bike a 6V system, so why would you need to build anything on 9V? HA. Quote Link to comment Share on other sites More sharing options...
Challenger Posted December 29, 2009 Author Share Posted December 29, 2009 Its not for a car or motorcycle, itll hopefully be running on a 9v battery. I dont want to have a car battery running the LEDs. Quote Link to comment Share on other sites More sharing options...
garvice Posted December 29, 2009 Share Posted December 29, 2009 Come on you have to elaborate then. What are you building? Quote Link to comment Share on other sites More sharing options...
MAG58 Posted December 29, 2009 Share Posted December 29, 2009 I'm going to guess... 9volt battery with an array of IR LED's, he's creating a transmission array to be picked up by a sensor on some bit of robotics to sense some function. If that's the case than you could start with a 33ohm, and in the event you find you'd like a little more signal strength than you could go to a 30ohm and be safe. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted December 31, 2009 Share Posted December 31, 2009 He's going to make a remote "sensor bar" for his nintendo Wii is what i'm guessing. iirc those things have 5 ir leds in them too Quote Link to comment Share on other sites More sharing options...
Challenger Posted December 31, 2009 Author Share Posted December 31, 2009 I dont have time for video games. Quote Link to comment Share on other sites More sharing options...
garvice Posted December 31, 2009 Share Posted December 31, 2009 Plus it is hard to play the Wii while driving. Come on mate, spill the beans, what are you building? Quote Link to comment Share on other sites More sharing options...
Trevor Posted December 31, 2009 Share Posted December 31, 2009 A remote to control stoplight timing, so the lights are always green in your direction of travel? Quote Link to comment Share on other sites More sharing options...
Challenger Posted January 4, 2010 Author Share Posted January 4, 2010 Alright heres the project. A most of you know we cant see infrared light but most video cameras can. So I bought a VHS camcorder for the view finder and the camera. The plan is to some how hook up the video camera to the viewfinder and a power source and then set up a circuit of infrared LEDs and then mount it all on some sort of helmet. Also I took back the small LEDs back and am looking for something more powerful but still relatively cheap. Anyways, any comments would be helpful. Ill have to take the parts to a camera repair shop to see if he can tell me which wires are video, power, ground, etc. Heres the gear.... Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted January 5, 2010 Share Posted January 5, 2010 nice, DIY night vision goggles! Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted January 5, 2010 Share Posted January 5, 2010 http://geektechnique.org/index.php?id=254 Quote Link to comment Share on other sites More sharing options...
Challenger Posted January 6, 2010 Author Share Posted January 6, 2010 Thanks for the link. So after reading this Im curious if Id have to find actual IR LEDs or if I could just get a very bright headlamp and use filters to have it only transmit IR... Quote Link to comment Share on other sites More sharing options...
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