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Modify LED fade in/out circuit? Answered

I am building this circuit
https://www.instructables.com/file/F4J70N0FRAAPMYY/
Here is the breadboard of it. This works, so if the schematic is different, use this instead.
https://www.instructables.com/file/FEYVJ1FFRJKN3PR/

I want to modify it so that is uses a 5v power source. What resistor should I change and how many ohms shuld the new one be?

I also want to add a potentiometer so I can change the fade in/out speed. What resitor should I put it in place of?

Thanks for the help.

3 Replies

user
frollard (author)2009-07-12

Great question!

I'm surprised that your circuit works - its missing some components for a 555 timer to work...

Perhaps the missing components make it run slowly enough to make the eyes actually fade...

So... the 500 ohm resistor is to get enough current for 4 leds. To run at 5 volts instead of 9 you need a smaller resistor there.

http://home.cogeco.ca/~rpaisley4/LM555.html has everything you could need to know about the chip...

the spec sheet shows the 555 should run on anything from 4.5 to 16 volts.
Try applying 5 volts with a smaller current limiting resistor.

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user
lokivoid (author)frollard2009-08-15

"I'm surprised that your circuit works - its missing some components for a 555 timer to work..." I dont see anything missing, If your refuring to a resistor the transistor is acting as one in the terms of timing control for the astable circuit.

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user
frollard (author)lokivoid2009-08-15

Indeed...the wiring just totally threw me off.

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