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Help with Daedal's Driver

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desslok

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Nov 28, 2007
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Hello,

First off I did a search and didn't find the answer to my question. I have built Daedal's driver circuit with all parts from Radio Shack, except for the trim pot that i found at an electronics store. It is a 100 ohm 25-turn pot. I connected everything up and mounted it into a Garrity flashlight I modded to fit 2x CR123 batteries. When I hook everything up and power on the switch, I get about 5.88 V at the leads, with nothing connected. Should it read that much Voltage? I was under the assumption that there would be voltage loss of ~2.5 volts in the circuit, thus reading 3-3.5 Volts. I understand the testing mA witha load and 1 ohm resistor, but I was worried about the Voltage being too high. Actually I'm worried that I blew one of the components while soldering. Any help will be appreciated. I want to get this right as a LD from Senkat is in the mail, and want to get everything prepped for it's arrival.

Thanks,
Steve
 





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disma

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Sep 23, 2007
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If you did it right, you could just take a 1 ohm resistor, and use that as the load, measure voltage accross the resistor, you should see your circuit work then. you should be able to adjust the pot for the right current, and it shouldnt change with the load, try adding more one ohm resistors in the circuit, and it should still regulate the current.

Max
 
A

Archane

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Sep 12, 2007
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until you put a load on it you won't get an accurate voltage reading. you have to measure voltage passively, that is in series with a load baring device. so hook up an LED or something to it and measure again, do NOT hook up the diode yet.

lets us know what you see after that.
 
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desslok

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Thanks for the quick responses. I have learned a lot form reading on these forums, but mainly I have learned how little I know about electronic components. Some of these concepts are hard to understand. I will try those tests when I get home today after work. I'll post the results.

Thanks again.
 
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disma

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by the way, did u get the name from starblazers? just curious.

Max
 
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desslok

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disma said:
by the way, did u get the name from starblazers? just curious.

Max
Click to expand...

Hehe, yeah. My favorite show growing up. I have played online games with this name for years and nobody has ever figured out where it is from. People seem to only know the new stuff.
 
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disma

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mine too, I used to watch it after school, couldnt wait to get home to watch it! how could anyone forget the desslok chant that the people did on his planet! lol...  hmm.. I wonder if that has something to do with our interest in lasers? thats what I want to build is a wave motion gun!

Max
 
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disma

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so, have you tested your driver yet?  :-?

also, these 2 different threads with the same name had me confused for a minute there! :eek:

Max
 
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desslok

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OK, after messing with it last night, I found I had a bad potentiometer ( cause of death most likely soldering iron too hot). Once i replcaed it, it started working. First run I put a LED and a 1 ohm resistor, and got a reading of 118 mV across the resistor. I then adjusted the pot to 25 ohm as I seem to remember that number from a thread. When I powered it up, the LED started burning up, I could see the chip burning inside the plastic. So I couldn't get a reading. I put 2 more LEDs on , one at a time, and they smoked right away. Is there a LED I can get that can take this testing? I have just the cheap multi-pack from Radio Shack. ( I felt like an idiot, when I was first getting readings of .4 mV, after a few minutes realized my meter leads were on mA setting)
 
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disma

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I think you should double check your circuit, make sure you have the lm317 wired right. with 25 ohms, you should get about 50 ma minimum...

Max
 
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desslok

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disma said:
I think you should double check your circuit, make sure you have the lm317 wired right.  with 25 ohms, you should get about 50 ma minimum...

Max
Click to expand...

I either have it wired up correctly, or completely flipped around. Would it work flipped? I was getting ~118 mV at one point so it seems like it is somewhat working.
 
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disma

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I dont know what it would do flipped, other than not work correctly.
if you look at the 317 where u can read the writing on it, the pins are from left to right: adj, out, in. the IN pin goes to the + on the battery, OUT and ADJ are connected togather with the resistor, and then the ADJ side of the resistor goes to the + on the load. Then the ground on the load goes to the ground on the battery. (-)    
The cap goes accross the load. + to +, - to -.


Max
 
rog8811

rog8811

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Use 4 rectifier diodes and a 1ohm resistor in series as your load then measure your mv across the resistor. Then your volts across the diodes....my guess is your circuit is OK, I started by trying to use a yellow LED as load....when it started to glow orange I knew it couldn't handle the power :)

Regards rog8811
 
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desslok

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OK, i'll try the resistor and diode method. I have now smoked too many LEDs. I did manage to get a quick reading of 394 mA on 5 LEDs, but once one blew, they chain reacted. Thanks again for the help. I have already learned a lot!
 
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