Gazoo
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What are you supplying the circuit with. If it is getting enough voltage the current should be ~400ma's regardless of the diode.
1.25/3 = 417ma's.
1.25/3 = 417ma's.
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Gazoo said:[quote author=spinout059 link=1198336575/0#11 date=1198372065]w00t i got it to work!!! I dont know why I couldnt before.... Will a driver make it burn better? BTW put black sharpie on my arm, now that was cool
Video coming soon!
xanatos said:Yeah... I'm lazy. I always just start with high R and tune for current to the diode - I don't really even look at voltage... but I just did. Measuring 854 mA across my 3 ohm resistor, yielding 284mA to the diode. Measured the battery voltage under load - 5.73 and slowly dwindling.
Like I said - lazy. But the diodes burn wonderfully, only cook when I spike them accidentally in-circuit, and should last a long time as long as I never overdrive them. My philosophy is to KNOW the math, but only rely on measurements!
Dave
PS., I just poked a hole in a black CD case back from about 10 feet in 12 seconds with my saggy batteries!
xanatos said:without me risking cooking the diode.
xanatos said:That's the beauty of ohm's law - measure the voltage drop across the 3 ohm resistor, divide by 3 and you have the LD current - regardless of what the supply voltage is doing (to a point).
My "final" revision to the first project will include a current monitor that will watch the voltage drop across the fixed resistor, and a battery voltage monitor (both bar graphs). All in a tiny little package.
Gazoo said:Yeah and isn't it funny that even though we know the math, we always measure to be sure.. ;D Well anyway, I think any kind of battery monitoring device is a very good idea especially when using li-ions. I will be looking forward to pics of your build. Sounds like it will look and be awesome with those bar graphs.
xanatos said:The prototype is using the cheapo Radio Shack "bricks" - stacked rectangular LEDs in a bar. Problem is that they're FAT. I'm using all surface mount components, and the entire circuit for the driver for the LD, the scanning circuitry, and the voltage monitoring COMBINED is about the same size as one of the 20 pin DIP LED Bargraph displays. I'm searching around for a MUCH more compact way of doing this - will probably have to go with discreet surface mount diffuse-lens LEDS - I found them on DigiKey, Jameco & Mouser.
I don't think I have posted any pics of the displays yet - you may be recalling some of the circuitry running in the background of my video of my first SenKat diode lighting matches. I had a scanning circuit running on the protoboard (indicating which input ports on an array I'm using were being sensed sequentially, but I digress).
I'll be posting pics soon - along with a library of surface mount component templates for use in making your own surface mount PC boards.
Best,
Dave