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Hijacker needs help (LED traffic lights)

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Firstly, don't hijack other people's threads.

Secondly, what do you mean by "the q outputs arent high enough"?
 

trickytrev

Apr 26, 2012
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the Q outputs for the 4017 cant handle all of the leds because the Q outputs are only 5mA and i would say i need about 10mA to each LED
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Have you tried it?

At 12V you should easily be able to get 10mA.

Remember that the same current flows through each LED so you only need 10mA.

You could use the output to turn on a transistor if it was insufficient.

BTW: I've put the link back since whatever edit you did caused nothing to display
 

trickytrev

Apr 26, 2012
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and yeah i have tried it at 12 but doesnt work i have tried transistor to boost the current but still doesnt work
 

timothy48342

Nov 28, 2011
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So whys he gettin nothin?

tricktrev, are any of your LEDs connected in reverse?

What is the voltage drop across each? They don't add up to near 12V in any one LED chain do they?

You might try checking the voltage across the 100 ohm resistors. Find out just how much current flow you are getting. If its just microamps, then it's not a source issue.

-tim
 

duke37

Jan 9, 2011
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I made one to drive a single light which included a red and amber phase. The 4017 drove three fets which could switch 5A at 12V.
It is on this site somewhere, I could try to find it if you are interested.
 

timothy48342

Nov 28, 2011
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Hey duke37, that made me think of something.

FIrst thought, fets don't take much current, so of course the 4017 could drive them.

Second thought, he already tried to drive the LEDs with a transistor and that "didn't work." We don't know much about how he had it hooked up, so there is a million questions there.

Third thought:
trickytrev. Try hooking the 12V supply directly to one of your LED chians and see if it lights the LEDs. If a direct connection won't do it then the 4017 won't do it either.

(and still find out the current by checking the voltage across each of the 100 ohms. With it connected as in your schematic and with it directly connected to the supply.)
-t
 
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trickytrev

Apr 26, 2012
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no all my LEDs are connected properly timothy48342 and yeah i am interested at your design duke37 as it might help me on my thanks :) and timothy48342 i connected a 12v supply directly to the chain it worked so its definately the 4017 thats the problem
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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OK, and the 4017 is running from 12V?

When connected to the 4017 are the LEDs dimly lit, or not lit at all?

Do you have anything else connected to the outputs of the 4017?
 

duke37

Jan 9, 2011
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I do not see how the red leds can show without other leds showing also. There are other traffic light circuits out there with the leds diode connected to the 4017.

I attach a diagram of my circuit which was used to train children in the operation of traffic lights and so it needed to provide a lot of light. This circuit can drive 12V 36W bulbs without any heat sinks.


Driving a few leds (or even a lot) would be trivial.

You would need another array of diodes and fets if you wish to do N/S and E/W.
 

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trickytrev

Apr 26, 2012
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the LEDs are on and i have diodes connected as well steve and thanks duke where do the 3 nang gates connect to though
 

duke37

Jan 9, 2011
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The three spare gates need their inputs connected to something to stop them going bananas, I chose ground. The outputs are left open.
The 555 will do the same job as the NAND gate but the NAND gate is a bit simpler.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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The three NAND gates go nowhere. Duke37 has used a quad schmitt trigger NAND gate to get a single schmitt trigger inverter.

The other three MUST have their inputs connected somewhere, and he has chosen ground.

Yes, you can get a 5 pin chip that has only a single inverter in it, but they're very small and you may not want to deal with surface mount chips.
 

trickytrev

Apr 26, 2012
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thanks :) just got it working by using the darlington pair transistors and made it more complex but now works thanks everyone for the advice :)
 
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