Hey,
That image was just a screenshot of the PCB layout from Eagle, not a schematic. It's basically just an easy board for soldering a bunch of SMD diodes in place, instead of soldering together a ton of through-hole versions during testing.
The OP suggested 15 Ohms for an entire channel, not per diode. So 15 ohms x 4 would be 60 ohms, if it worked like that. I'm fairly certain it doesn't. I don't think you can combine channels in parallel and then cumulatively apply the resistor trick.
In most of my testing, I've just used simple 1N4001 diodes. But for my board, I wanted to use as few componants as possible, so I just found the diodes with the crappiest (highest) voltage drop on Digikey that I could. I never ended up actually ordering them for my board, because before the fabricated PCBs arrive, I recognized that the problem was no longer electronics, it was collimation of the LED light. The need to push forward on the electronics front really isn't there until the LED collimation challenge is resolved.
"what im failing to see is if your saying the entire laser array only uses 28.5 volts @ 1 amp (1 amp for all 24 lasers) or if your saying each string uses 28.5 @1amp"
- Each string uses ~28.5 @ 1 amp
"(which should give me a theoretically total of 114v @ 4 amps) if each string is ran in series and each string is producing 28.5 volt,then it should be entirely possible for me to connect 1 string to another,(series circuit to series circuit) get more voltage and current,use whatever i need to power what i want ,and then feed the surplus to diodes and or resistors to bring the entire load down."
- Definitely not. Whatever is regulating the string internally within the projector, is almost certainly fed in parallel from the projector's PSU. If it was possible to series the strings together and quadruple the voltage, then we would have invented an awesome new voltage boost driverYou *might* be able to parallel the strings, but I'd bet my life on the fact that you can't series them.
"Ok what im interpreting is this,out of the available 28.5 volts in one string your using 13v and feeding the rest to diodes to (not entire clear on your hookup method) .now if its confirmed that the total output of 1 string is 28.5v (4.75vx6=28.5v)..then i should be able to use up to and including 28.5 volts from 1 string (six potions) to power whatever led i choose.from a 1 volt to a 24 volt led (i have a xj-a 140 @ 2300 lumens so im going to assume its got more current.) @1 amp current"
- Yep, that's pretty dead on. I'm dropping the rest of the (28.5-13) with diodes, simply by placing the diodes in series. The only glitch is where you said "from 1 string (six potions)". I'm not sure if you meant that there are 6 strings, but I'll clarify:
--- The projector has 4 string (or as I call them, channels). Each channel runs 6 LDs in series, at aprox 28V total drop per string, and the string runs at somewhere around 500mA to 1A (apparently) depending on the projector model.
Polarity is simple:
- The squared most eadge of the flex cable is the edge that carries the (-). Then it alternates back and forth all the way to the other side.
Regarding collimation:
- If we take wisdom from the LD arena, it's always easier to get a tight beam from a smaller emitter size. By that logic, something like an XML or SST-90 emitter would be ideal if there was a blue version. I don't know if there is, but you run into a bigger problem when you start looking at those types of emitters. They tend to use higher current, lower voltage. So a 28V string that delivers 1A is going to be of fairly little convenience for an emitter that wants 3.5V and 3A.
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Originally Posted by kobra000
