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Weird 4017 behaviour

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Special Mike

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I need to build a circuit for the Motorola radio console that will decode 4-beep tone signal (received page signal) and trigger a small flashing led.

I used a 567 decoder which converted it into a nice pulse output. Then I used 4017 to count pulses to 3 and reset on 4. However the LED on the output instead of flashing once on every 3rd count just starts behaving erratically as you can see from pics below... I tried using 4520 binary counter but still no dice...

pics:

**broken link removed**
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any help whould be appreciated... I will quickly put together a diagram if needed when i get time, but its pretty straightforward circuit
 
A schematic of your circuit(s) would be helpful.
 
^^ will do as soon as i get back to work tomorrow. btw, the yellow line on oscilloscope is the 567 output and blue is 4017 output

and before someone says that motorola xtl5000 radios have h/l output that can be used for strobes.... unfortunately astro consoles don't have h/l output :(
 
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You are using a resistor in-series with the led, right?

Are there always exactly four pulses from the 567?

It seems to me that your logic is flawed. Shouldn't the 4017 reset unconditionally some fixed delay after there have been no 567 pulses for a time longer than the pulse burst? That way, the counter is guaranteed to be sitting in state Q0 when the next burst of pulses arrives, and you can flash the LED during state Q3.
 
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On your bread board i can not see how you can have V+ to the 4017 or any other chip.

Me thinks you are missing a power rail.

Pete.
 
Read my previous post again. I edited it while you annotating the picture.

Here is what I think would fix it:
 

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The schematic would be great. In the interim, you might look at your reset (pin 15) on the 4017. From the breadboard view, I see no provisions for a reset of the counter upon power up to set all outputs to zero state. Without that feature, the counter may well set up randomly resulting in the apparent "wierd behavior" you are experiencing.
 
I still dont see where the V+ is jumpered back to the power rail, have you checked pin 16 of 4017 with a meter to see it actually has 12v.

I looked over you wiring several times and cant find a V+ link.

The red supply wire appears to go to nothing.

Pete.
 
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Are there always exactly four pulses from the 567?

It seems to me that your logic is flawed. Shouldn't the 4017 reset unconditionally some fixed delay after there have been no 567 pulses for a time longer than the pulse burst? That way, the counter is guaranteed to be sitting in state Q0 when the next burst of pulses arrives, and you can flash the LED during state Q3.

Yes, there are always four pulses. I tried removing reset line and just linking to ground.
 
Read my previous post again. I edited it while you annotating the picture.

Here is what I think would fix it:

Thanks, I'll look into that tomorrow

I still dont see where the V+ is jumpered back to the power rail, have you checked pin 16 of 4017 with a meter to see it actually has 12v.

I looked over you wiring several times and cant find a V+ link.

The red supply wire appears to go to nothing.

Pete.

**broken link removed**
 
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