Laser experimentation

Following the laser driver assembly (aka DDL circuit), and load testing circuit examples at http://www.rog8811.com/laserdriver.htm

Soldered the load driver board like this:
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Learned I really don't do solder bridges well, and I really should use a different solder tip for doing soldering vs. desoldering.

I used two 1 ohm 5w resistors, wired in parallel, rather than the single 1 ohm resistor called for in the diagram.  The wattage these can handle is way higher than needed, but they were handy because I'd gotten a bunch in bulk last time I was at Halted.  But why two?  Because I measured them and they came out to be 1.7 ohms.  I put two in parallel and that brings things down to about 1.2 ohms.  This will factor into the amperage computations later on.  The way the web page describes the measurement, they figure voltage equals amperage, but that only works if the resistor is really 1 ohm.

The amperage I got was 1.7 ohms.  So by putting two in parallel, the formula is
(1 / R1) + (1 / R2) = (1  /Rtotal)

(1 / 1.7) + (1 / 1.7) = (2 / 1.7) = (1 / 1.176) = (1 / Rtotal)
thus Rtotal = 1.176 ohms.  The ohmmeter, when run across the resistors in parallel, bears that out.  I might be off by a little, since the ohmmeter isn't that precise, but it's way better than assuming 1 ohm when it's really 1.7.  Funny thing is, the bag was labeled "precision" resistors.  Maybe I just got the wrong thing in the bag.

Next: wiring the laser driver.

I got the main parts from Jameco:
LM317 part 23579 $0.35.  I don't understand why there are others of the same nature for $1.50.
100 ohm 25 turn pot = 853530 $1.75.  This is the most expensive piece of the puzzle.
RESISTOR,CARBON FILM,10 OHM,1/2 WATT,5%,(100 BAG) 659817, order 10 ($0.099 each, so say 20 cents)
16057329

I have the a 10 ohm 100V capacitor, and a spare 1N4001 diode still.  For the switch, I found something that's like an old keyboard switch in the bins at the Tech Shop, so I'll check that and should be able to use it.  Its pins are a little funny, so a little drilling might be needed.

Once I wire that up, the only thing left will be getting a 9V battery.  I also have to check the resistor -- whether I need 5 ohms or 10 ohms, depending on the kind of laser diode I'd be driving, and will have to plan space on the board accordingly.

7/3/13
Last night I built the driver circuit and the load tester circuit.
When I measured voltage across the 1 ohm resistor in the load circuit, all I got was a range from 6 mV to about 42 mV, this when driving the load across 4 diodes and the resistor.

I put the ammeter in series with the load instead, and got a reading of up to 80 mA.

Now either way, something seems amiss.  I should be able to get 125mA to 250mA, depending on the resistor (either 10 ohms or 5 ohms) that I put onto the laser driver board.  And, I should be getting matching voltage as driven amperage, but I'm getting different results.

Frustrated.  Going to mess with other things.