View new posts | View your posts Changing the LED sequence in PKE meter

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Hey All,

Sorry to open up a new thread for this... Any one be able to tell me if the chaser kit I have can be made to only cycle "one way"? It currently goes left to right then back again. I pretty much only want it to go left to right.... then start again from the start. Once again, I'm heaps sorry to open a new thread.



Cheers all

Yes.

The 4017 decade counter is a chip which has 10 outputs, each of which go high in turn when a pulse is sent to the clock pin. After 10 pulses, it loops back to the first output, unless the reset pin is triggered somewhere in the middle in which case it will go back to the first pin early. For example, if you wire output 3 (output 0 is the first one) both to an led and to the reset pin, (10K resistor from output 3 t reset) then after four clocks it will go back to output 0 again.

Your circuit goes back and forth because each LED in the middle is wired to two outputs. So the 4017 counts 0..9, but both 4 and 6 light the 5th pair of leds on your circuit board.

In order to do what you want to do take a look at section 1 here:
http://www.doctronics.co.uk/4017.htm

Then solder a 10K resistor across the top of the IC, from pin 15 to pin 1. That's the second pin across the top of the IC (reset) to the first pin along the bottom of the IC. (Output 5)

This will cause the 5th LED lighting to trigger the reset pin, and cause the chip go back to Output 0.

Yeah, basically don't add half the diodes and short the "end" of the sequence to the reset.

So basically remove 4 of the diodes and then ad the 10k on the top... Seems easy enough. See how i go tonite. Cheers again guys. Not so great with electronics.

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Wait.

I screwed up.

Pin 13 is being pulled to ground to keep the reset from triggering. That's fine, but it's not being pulled to ground via a 10K resistor, so pulling it up via a 10K resistor or even without any resistor, wouldn't work. At best, without a resistor, you'd get 2.5v at the pin which probably isn't enough to trigger it.

What you should actually do is run a wire from pin 15 to pin 1. Then cut the trace on the board which connects pin 13 to ground, and solder a 10K resistor across the gap.

And yes, you can remove some of the diodes. Just make sure you remove the right ones. Pins 5 6 9 and 11 are the ones which are unnecessary.

Again the schematic on this page will be useful. Don't accidentally confuse the output numbers with the pin numbers:
http://www.doctronics.co.uk/4017.htm

Damnit, I keep screwing up and I can't edit my post.

I meant to say cut the lead from pin 15 to ground. Not 13.

Also I am checking now to see if is okay to wire pin 15 directly to pin 1. I am concerned about how much current would flow. A 4017 is a little different from a microcontroller.

Alrite ghostguy. Ill have to sit down at home and get my head around it... Im getting a tad lost now maybe. Prob need to sit at the computer and read it.... And draw it up on my picture.

Ive already fried a board so trying to avoid that again....

Maybe if you didnt mind... Amd have time... Could you draw it on the diagram i posted please? no biggy if you cant ill try to nut it out

Cheers again for all the help... I love this forum

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Hm... it must be okay to connect that pin 15 directly to pin 1. I'm just worried cause I don't understand how the chips really work inside. But what I've been taught is you pull a pin down via a 10K and connect it to +5v to pull it high or vice versa. That must be okay here.

I can't draw it on the diagram because the digram doesn't show the trace going to ground from pin 15.

Just run a wire from the second pin on top of the 4017 to the first one on the bottom. Then cut the trace on the circuit board that leads from the second pin on top to somewhere else, and solder a 10K resistor across the cut.

I can't promise it'll work, but it's my best guess.

If you see the last LED in the case go much dimmer than the rest, turn the circuit off immediately and let me know. That would indicate all the current is going through the 4017 instead of the LED, and that would be bad.

Cheers GhostGuy. Ended up putting the 10K between pin 15 and 1. Now its chasing spot on!!! Thanks so much. My sound now is a bit full on.... beeps with every LED, but is sorta fitting.

Thanks again every one. :)

It worked with the 10K between pin 15 and 1 with no other changes? Odd. Well, I'm glad you got it functioning.

Yeh.... I kind of stumbled on it... Seems to work fine tho..... Now ive got to source a screen to cover up the screen LEDs. Cheers again mate.

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If you just want clear plastic, Tap Plastics can cut colored acrylic sheet to size.

Ive noticed that the screen that shouldve come with it has a grid cut into it.

Ill keep hunting but ill keep it in mind. Also im from Australia too... So maybe a shipping issue....

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