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Undiagnosable circuit problem

Gazoo

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One of the biggest mistakes people make is to connect the LD after applying power to the circuit. They may not always realize this as it can be on account of bad connections, especially when working with breadboards.

If you notice, the voltage is quite high with no load on the output. If you apply power to the circuit and then connect the diode, the spike as the result of the higher voltage will kill it, and because the capacitor is charged up to the higher voltage.

I would say you are good to go, solder the diode up...and fire that puppy up. Enjoy ;)
 



dilmah

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WOOO thanks a lot guys

especially daedal, chimo and gazoo, seriously guys i could have never worked this out without you guys

i love this forum everyone is so helpful haha

special thanks to daedal for helping me so much with the flu, get well soon!

thanks again guys

cya

dil

p.s shoud i still turn the pot up and slowly reduce it? or should i connect the LD as it is, on 0 resistance?
 

Gazoo

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With a 5 ohm resistor the LD would draw 250ma's. You said the combined resistance of your 2 10 ohms in parallel was 5.8ohms so this should equate to about 210ma's. I think you are safe no matter what you have the pot turned to.
 

dilmah

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phew ok good so the pot is regulating current? i saw a post in daedals thread that said it was regulating voltage...which got me confused..

thanks again

dil
 

Daedal

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chimo said:
The 1n4004 should be fine - it's in reverse bias so it should read the load voltage.
D'oh!

Another XXQuil side effect... I blame the flu... ;D

Either way, glad you got it working Dil :D

--DDL
 

Gazoo

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dilmah said:
phew ok good so the pot is regulating current? i saw a post in daedals thread that said it was regulating voltage...which got me confused..

thanks again

dil
That might have been me before I got it through my thick skull what the LM317 was doing, and how it is being used. :p

It can be used as a voltage regulator, but for the LD's we are using the LM317 to regulate current.

The LM317 is regulating the current. Neither the pot or the resistors are regulating the current in this circuit. But the amount of the regulated current output from the LM317... is dependent on the resistance used between the output and adjust.
 




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