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pot help please

bcroft

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Dec 28, 2007
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I have put alot of time into this laser project and im now stuck and looking for help. i finally got everything to work on my breadboard with a LED, but my new pot i bought will NOT turn the LED off at all. i can dim it, but not turn it off. when i used a mystery pot i aquired off a toy helicopter it worked fine, but i dont know the specs of it. if someone could look at my setup and tell me if it will be ok for a red or even a blue ray i will GREATLY appreciate it! as i am a 'newbee'.
here is what i have
25 ohm rheostat pot
47k ohm resistors
LM317T
47uF capacitor
1N4001 silicone diode

i tried to follow DDL's tutorial and he recomends a 100 ohm pot i had a 10K pot but i dont think it works anymore and I wonder if my new 25 Ohm pot will work, common sense tells me there is no way 25 ohm will work when 100 ohm is recomended, but i hope you all know something i don't. Thank you for taking a look at my post, any help is much appreciated!!!!
 





chimo

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Jun 20, 2007
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You are not supposed to use the pot to turn it off. It just adjusts the output within a range. Use a switch between the battery and the LM317.
 
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Nov 21, 2007
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that rheostat will work perfectly! in fact, it is recommended in DDL's post to use it if you look closely. i use one for my circuit, and it hasn't failed me. but chimo's right, a pot isn't for turning the unit on and off, its for adjusting output and current. use a small momentary switch between the LM317and the battery. or, if you want continuous on/off without holding the button, use a rocker or toggle switch. i usually stay away from toggle because they tend to turn on by accident too easily. hope this helps ya. ;D
 

bcroft

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Dec 28, 2007
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Thank you very much thats what i needed to hear. i probly miss typed or something but i am not planning on using my pot as an on off switch i know its just to set the output. i cant thank you enough, i read and read and read DDL's posts guess i overlooked that part
 
Joined
Jul 24, 2007
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You list in your components.....
47k ohm resistors

That is a very high resistance, a 25ohm in series with 47k will have a very small effect, I am surprised that the LED lights at all :-/.
To run a laser you will need ohm, not Kohm resistors, (3 to 10ohm for red and around 20ohm for blue).

When you get the correct resistor fitted use the suggested method of testing in post 2 of this thread before adding your LD.
http://www.laserpointerforums.com/forums/YaBB.pl?num=1197651171

Good luck

Regards rog8811
 




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