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Led circuit

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tibbles
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Username: tibbles

Post Number: 4
Registered: 02-2008

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Posted on Friday, 22 February, 2008 - 02:17 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

sorry about reposting this but a bit of time has elapsed since my original post.
(needed circuit to sequentially light first a red led, then a green led. with just one control input)
The 4013. and stocked at local maplin,what a great piece of kit,anyway, built the d-type flip flop,made a lovely job of it,but guess what, switched on and nothing (much) happened!re-checked everything, all ok but still nothing,thought i must have blown the chip. maplin here i come, then i spotted switch debouncer, surely not? ive always thought these were for wimps,anyway nothing to lose- a couple of ressistors and caps later... PERFECT!
just when i got over the shock,i realised that i actually needed three states- 1. both leds off.at start. 2. red on.on first pulse. 3. then green on and red off.on second pulse.
so im thinking of cascading or paralell the 2 flip flops on the chip- red on first one, green on second one,which should give me a both off state,i think?
now i also need each led to be manually turned off when observed(blanked) (untill the next input pulse) , without disturbing the circuit count , so to achieve this i may need to add two more basic flip flops with a push button off control.
well i did say a simple circuit.
plan B. i could i suppose use a ripple counter resetting on a count of two or three,but id still have the blanking problem,
thanks to all
regards
dougal
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joe
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Username: joe

Post Number: 384
Registered: 05-2005

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Posted on Friday, 22 February, 2008 - 02:55 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Dougal,
What about the 4th pulse. Both off, Red on, or somthing different ?

In theory, you could use an AND (7408 or CMOS equiv) gate on the to trip the reset of the 4013
That would set both off.

The better, and more flexible way, may be to use a 4017 - 10 stage decade counter.
http://www.doctronics.co.uk/4017.htm

Give it a pulse and it moves to the next output.
(Debounce issues still apply!!!)

On the IC,
Leave output 0 empty
Red Led on output 1
Green Led on output 2
Output 3 connected to the Reset to restart the
squence.

You can connect outputs together with diodes if you want to create "interesting" patterns of LED's.

If you need more info, drop me a line.

Joe
Do one thing each day that scares you – work here !
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joe
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Username: joe

Post Number: 386
Registered: 05-2005

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Posted on Friday, 22 February, 2008 - 05:04 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Dougal,

Have just noticed if you scroll down to the end of that URL link, theres a traffic lights demo circuit that creates "OR" gates using diodes.

This circuit could be modified to do as you require I think.

You just use a switch and debounce circuit in place of the 4093 connected to pin 14 (clock)

Joe
Do one thing each day that scares you – work here !
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tibbles
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Username: tibbles

Post Number: 7
Registered: 02-2008

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Posted on Friday, 22 February, 2008 - 08:04 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

sorry i missed that,as you guessed ,third pulse green, then back to start again
thanks again
dougal

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