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Turning LEDs on one by one

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Hi,

I am looking for some help in designing a simple flashing led circuit but i can only use JFETs and no i/c chips such as 555 timers etc.

I have already built a 2 flashing LED circuit using just caps, resistors and JFETs but now would like to build a circuit which turns on 4 LEDs, one after each other and then resets and starts again.

My electronics skills are not brilliant but can modify and build on a circuit once i have the basics.

Any helps would be greatly recieved.

Thanks

James
 
Why no ICs? Is this homework?
 
Nope not homework, that was many years ago. :)

The reason for no ICs is because as much as possible needs to be printed. The printed transistors work similar to JFETs and we can printed the resistors. Capacitors are more of a problem so these will be surface mount ones along with the LEDs for the time being.

I spent some of last night coming up with something that sort of works using NPN transistors but could do with some more help getting the circuit to reset them at the end. See my attached circuit image. The resistor and capacitor value can all be changed and i don`t mind playing around with those values. It is more the actual circuit design which i am struggling with.

Thanks for your help
 

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  • Sequencial flashing LED.jpg
    Sequencial flashing LED.jpg
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Hi,

How much delay between LEDs are you looking for? Like, one LED comes on then the next one comes on after 1 second or 2 seconds, or 3 seconds, etc. How much time between them?
Also, what supply voltage are you working with?
 
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Hi MrAl,

Thanks you for reply. I was looking at a supply voltage of either 4.5V or 6V and a delay of around 0.5-1 second between each LED. Like i said in my post once i have a basic circuit i can play around with the component values to give me the timings that i require. I just need something to get me started.

Thanks very much for your help.

James
 
Hi 4pyros,

Thanks very much. I have used a circuit simulator that i have and both work a treat. Many thanks for you help. I think this will be enough to get me started on.

Cheers

James
 
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