Infrared LED's

[moe]

Hello Iam looking for a schematic to wire some infrared led's for my B/W yard camera to use at night. Power is 12 volts dc at 750ma. I am under the impression the more I wire in the better the illumination. Thank you

[russlk]

If you connect 4 LEDs in series with 100 ohms, you can put 18 of these in parallel (72 LEDs). The resistors can be 1/4 watt.

[Chris Smith]

If your good in the workshop with all sorts of goodies and tinkerings, use IR lasers instead. <p>Compared to a ordinary IR led, a 5mw laser is like comparing a grape to a beach ball. <p>If you can work with small tubes and slides you can use a common tiny single lens to make a Focousing lens to spread the light to the desired area and width which will be ten times brighter and shine ten times the distance with only 80 mA @3volts or so.<p>Using Multiple lasers and lens are like driving lights from an off road jeep. <p>You can find IR lasers surplus in broken CD ROMS and all sort of places these day and the only thing special is the feed back circuit which stops the laser from over driving. <p>When Coupled to a proper collimating lens, a star light or IR scope with telescope, the laser can be easily spotted at ten miles or more and still only be 5 MW in size.

[moe]

Chris & Russ Thanks for your help as I have about 100 of the led's I will start out like Russ said. Chris I will start looking for the IR lasers sounds like that will be the way to go in the long run. Any idea of cost for the IR lasers?
Thanks again guys.
Moe

[Chris Smith]

I get them surplus with or with out the driver board for around 5 bucks. Also old cd players gone dead and such. All together in all my bad cd players and old equipment, I probably have 50 or more? If you need a driver Circuit, I have a real simple one. Its uses about five pieces and cost about a buck to build. Common like 123 ap transistors, resistors and a pot. It takes up less than one square inch and Can be made to fit in a thimble if you want? I have fit lasers and power supplies into pens and such. Check out a stereo store that repairs CD and such and ask for any dead CD players.

[gadgeteer]

CHRIS --- will that drive circuit work on a Nichia purple laser diode? I've had one for a couple years but never had the courage to power it; at the time I got it, it was selling in sample quantities for $1000. I do NOT have the blue laser diode, it was $3000...<p>The bad side is that it has cathodes common; I know how to reverse-biase a PIN and convert the leakage into a voltage to drive a common-emitter laser drive, but how do you drive a setup when the internal PIN cathode is common to the laser cathode???<p>Moe, each infra-red diode drops ~1.6 volts; thus you can run maybe 6 in series (for a total of 9.6 volts), leaving 2.4 volts left over; if you're running each LED at 20ma, 2.4/.02 gives you 120 ohms. So a 12 volt supply can run one series connection of 6 LEDs, with a 120 ohm resistor to limit current. Use the real value of IRLED voltage and real current as I did to come up with a different resistor, if needed...<p>Most LEDs have 30-35ma absolute maximum current; 20ma is a safe region; but new IRLEDs can handle 50-100ma...<p>You can make as many of your 6-LED branches as your supply can support (don't forget the camera current)...<p>It's nice to have a couple volts buffer (2.4 in this case), to compensate for power supply variations; LEDs are non-linear, so the smaller the buffer-space, the more intolerant the system is to power supply moves...<p>POWER through that resistor will be 120, multiplied by (.02)² --- or .048 watts (I²R)...<p>Clear as mud???

[mmitchell]

Chris, Can you send me the driver circuit for the ir laser.

[toejam]

Chris what about a super short high current pulse to the lasar diode? Can it be made faster than an xenon strobe? How many watt seconds do you think ?

[Chris Smith]

Chris what about a super short high current pulse to the laser diode? Can it be made faster than an xenon strobe? How many watt seconds do you think ? <p>Toejam, <p>only pulsed lasers, not CW lasers want ultra fast pulses, up to 80 or more amps, at nano second pulse lengths. Different power supply?

mmitchell <p>Chris, Can you send me the driver circuit for the ir laser. <p>Yes I'll dig it up, I think I have it scanned already?<p>gadgeteer <p>CHRIS --- will that drive circuit work on a Nichia purple laser diode?<p>I don’t know the laser you mention, but I assume you mean UV laser, and the Blue Japanese ones?<p> Before you ever touch a laser like that, You need to know if its Pulsed, or CW. <p>CW, yes this circuit can be modified and played with very carefully to power any size CW laser within reason. <p>Pulsed lasers, are totally different and need heavy power pulses short, nanno seconds long, and amperages starting at 10 amps and going up. That might equate to 100 or more volts? <p>Max CW power to a Pulsed laser is the same as a led, not much [20 ma], and it wont lase. What do you know about YOUR power requirements? <p>
The bad side is that it has cathodes common;<p>Common pins refers to the feed back monitoring circuit. It has a pin diode that the laser lights up, leaks, and feeds back to keep the power from exceeding its input. <p>
I know how to reverse-biase a PIN and convert the leakage into a voltage to drive a common-emitter laser drive, but how do you drive a setup when the internal PIN cathode is common to the laser cathode??? <p>Off hand, I would have to check on my other circuits, but If I remember right, feeding the power in reverse, feeds the pin diode the proper way. IE, positive feed is reversed, and the control is positive? Id need a diagram as to what you have before attempting to say anything for sure. I have had a few lasers that way, but that was a while back, and I don’t remember it being any hassle? I think you just treat it [the laser] like pnp VS NPN? <p>Moe, each infra-red diode drops ~1.6 volts; thus you can run maybe 6 in series (for a total of 9.6 volts), leaving 2.4 volts left over; if you're running each LED at 20ma, 2.4/.02 gives you 120 ohms. So a 12 volt supply can run one series connection of 6 LEDs, with a 120 ohm resistor to limit current. Use the real value of IRLED voltage and real current as I did to come up with a different resistor, if needed... <p>I found it best to add one resistor to each LED, for ease of control and balancing each diode to a specific draw and maximum out put. Each diode doesn’t have exact characteristics to another, and taking the time with each one insures best performance, and reliability. <p>I use a pot to find each value, then substitute it with a fixed resistor. I never had much success piggy backing or paralleling or series. Especially with IR diodes.<p>But do what ever is best for you? <p>I start with 12 volts, and tap off that for everything, using VRs and/or Resistors as necessary. Reliability is paramount with me.<p>This Just in......<p>I have to power up my other three hard drives and do a search for the BMP of the driver circuit. <p>10 million files or so, wont take long to sort through? Laser "somthing" will help, down to about 10,000 files? <p>Might take a little while, and I also have it in the vinal sheet covered original, some where.<p>[ April 26, 2003: Message edited by: Chris Smith ]</p>

[Chris Smith]

gadgeteer <p>
I just read the press release on the violet laser, the nitride laser, and others. The technical papers are available and the wattage value of yours would be necessary before starting to design a driver circuit. If 50mw or so is the power requirements, you need to up the transistor size[?] keeping in mind the same gain and specs etc. Also many little tricks to protect the diode should be applied even before firing up any circuit or driver, as one little mistake, and its all over.

[gadgeteer]

Thanx, Chris. Yes I know about mistakes; I was playing with a sample of a 635 three-mW diode from Toshiba (they didn't know that I'm one of many who would NEVER USE TOSHIBA PARTS). Carefully adjusted the drive current, and -FLASH!- it was history. Hitachi then sampled two 5mW 635 diodes...<p>As I said, I have not yet had courage to even TRY to power the thing...<p>I once put a laser beam around the folks' yard to catch fruit-thieves, with a Digi-Key 780nm. By driving the laser anode with a common-emitter PNP (as I remember it, I tied the laser cathode to ground), I then tied the PIN cathode through a resistor to V+ (since its anode was already at ground common to the laser cathode) --- and the voltage developed on the PIN's resistor was a function of the laser output. A simple amplifier (with predictable delays for soft turn-on) worked fine. What I don't know, is how to use a PIN, when PIN's CATHODE is tied internally to the laser cathode? If I tie the LASER CATHODE to ground, then the only way to reverse biase the PIN, is to have a SPLIT SUPPLY (PIN drive below ground). Can I use the FORWARD PIN CURRENT??? Or maybe I can use the PIN in VOLTAIC mode --- as if it's a SOLAR CELL (it will develop voltage and current on its own, rather than use leakage current from the supply)! It's so CONFUSING...<p>What I have is actually a VIOLET laser, 407nm; ultra-violet would be in the 385nm range. Down side is that my part seems to be obsolete; mine is only 5mW, looks like all you can get now is 30mW. At the time I got it, they actually suggested not using the internal PIN, and using CURRENT SOURCE and a TEMPERATURE OVEN (well, "oven" isn't quite the word, 'cause over-room-temp drastically reduces the life; but they wanted the temperature stabilized). If I can get ahold of a 30mW part, I can dispense with the controller circuit, and simply fix the current; over the expected temperatures, the extra head-room will make operation easy (and safe from over-power).<p>MEANWHILE, anyone ever use a PIN in VOLTAIC mode???

[Chris Smith]

If they suggest not using the photo circuit, its real easy. You power it thought a very accurate ten turn pot, or more, and ammeter until you get near the five MW draw, and back it off ten percent or so as long as it doesn’t drop below the lasing action. 85 percent is a good number. Then place a voltage regulator and fixed resistor back in place permanently, re check everything 12 times using the pot, and Your off. <p>What you have to understand about the pin diode is that its not part of the laser circuit at all, and not actually needed. <p>But what its for is a regulator of consistant brightness and over current sensor. As long as it produces a voltage or current, it can be read for any type of circuit gain in variance as a relationship to how bright the laser out put is. It’s a light meter. If you do a voltage reading and Op amp, or a amperage reading and a simple transistor follower, its all the same as long as that feed back controls the amperage into the diode it self. It’s only a control to the main feed, a feed back circuit to maintain the main controller. The hard part would be how to guess the gain feed back, and have that amount control the other circuit feed, and go up or down in the right manner, from scratch.<p> But all lasers can be fed at room temperature by a fixed resistor, at below the peak, and above the minimum lasing. Accuracy at start up is very important, as a 3/4 turn pot WILL NOT work. <p>Ten turns or more. And the more accuracy of control at the beginning start up level of lasing the better. IE, it starts lasing, and you still need five turns just to bring it up to 5mw. I’ve popped a dozen lasers not having the sensitivity of adjustment in the pot, where now its lasing, and two thou on the pot, on poof! <p>You need at least five or more turns at the threshold current. Soft start is another problem, but easy to fix. A pot at the input regulator circuit of one turn or more fixes that. On off slow one turn. Also large cap [10uf] at the out put of the Voltage regulator takes up spikes at Start and Stop.