4510 counts up (skips 8) counts down (skips 3) !?

[Crax0r7]

Having a little problem here and trying to see if anyone can help. I've got a 555 timer (astable) generating a pulse connected to the CLOCK in on a CD4510BE. I'm using 4 LEDs as a display and when it counts UP it skips 8 (0, 1, 2, 3, 4, 5, 6, 7, 9, 0...) and when it counts DOWN it skips 3 (9, 8, 7, 6, 5, 4, 2, 1, 0, 9...)

I'm fairly clueless when it comes to debugging circuits and I'm pretty new to digital electronics in general so any assistance is appreciated.

I'm roughly working off of the diagram on this website (under section 3. Basic Operation):
**broken link removed**

Here is an image of the circuit on a breadboard:
**broken link removed**

 

[ericgibbs]

hi,
I see that you are using a 555 timer and not a 4093 for the clock generator.

The 47uF +Vs rail decoupling capacitor shown on the original circuit is not on your BB layout, it important to have decoupling on most circuits.
Add the 47uF and I would also use a 100nF across the BB supply rails.

 

[Crax0r7]

Is there an issue in this particular case with the switch to use a 555 for the clock generator? It seemed that it would be an acceptable alternative to the 4093 from the link.

I did see the 47uF in the diagram but the description made it sound kinda optional and I didn't have anything over 1uF sitting around (except the one used with the 555 which is 10uF). I'll pick one up later today and add it, thanks!

I'm not sure I understand the last thing you suggested; where would I be inserting these 100nF across the BB supply rails?

 

[ericgibbs]

Is there an issue in this particular case with the switch to use a 555 for the clock generator? It seemed that it would be an acceptable alternative to the 4093 from the link.

I did see the 47uF in the diagram but the description made it sound kinda optional and I didn't have anything over 1uF sitting around (except the one used with the 555 which is 10uF). I'll pick one up later today and add it, thanks!

I'm not sure I understand the last thing you suggested; where would I be inserting these 100nF across the BB supply rails?

hi,
No problems with using a 555 for the clock.
EDIT: I guess you wired it as standard astable.?

The decoupling caps should be across the +Vs and 0V of your Bread Board, the 100nF would be in parallel with the 47uF.

Did you see my note about the adaptor being a DC output not AC.??

 

[Crax0r7]

Yes standard astable

I did not see any note about the adapter being DC ouput not AC. I'm using a 9v battery for the source if that's what you're asking.

 

[crutschow]

Are all the unused inputs connected to common or the plus voltage? If any input is left floating it can cause flaky results.

 

[Crax0r7]

1 - Preset - Gnd
2 - Q4 - 4th LED's transistor (2n2222A)
3 - P4 - Gnd (3, 4, 5 wired together and a 10k resistor to the 0v rail)
4 - P1 - Gnd (see 3)
5 - Carry IN - Gnd (see 3)
6 - Q1 - 1st LED's transistor
7 - Carry OUT - floating
8 - Vss - Gnd
9 - RESET - Gnd through 10k (connected to the push button switch at the right for +V)
10 - UP/DOWN - +V or Gnd depending on the count direction
11 - Q2 - 2nd LED's transistor
12 - P2 - +V
13 - P3 - +V
14 - Q3 - 3rd LED's transistor
15 - CLOCK - 555 timer through 1M resistor
16 - Vdd - +V

 

[ericgibbs]

Yes standard astable

I did not see any note about the adapter being DC ouput not AC. I'm using a 9v battery for the source if that's what you're asking.

hi Crax,
Sorry about the mix up on the psu adaptor..
Is the project now working as expected.?

 

[mbarazeen]

check for any lose / rusted wires..

 

[Crax0r7]

Unfortunately no, I added a 47uF and 100nF parellel with the supply (I think this is right see image)

It's driving me up a wall, I've probably been on this *seemingly simple* issue for 6+ hours now. This is actually the second iteration (the first didn't use transistors it just supplied +V across the LEDs straight from the 4510). I've switched ICs out, changed resistance and capacitance values around a little but consistently it skips 8 on the way up and 3 on the way down. Luckily I'm difficult to discourage

Update below:

**broken link removed**

 

[Crax0r7]

What really sucks is this is like step 1 of n of a much larger project

 

[crutschow]

Have you double-checked all the connections?

Can you post a schematic?

 

[Brevor]

Check for a short in the wiring from pin 14 of the 4510, this is the C output. This output switches from high to low when the count changes from 7 to 8 and also from 4 to 3. It may be getting into the clock line somehow.

 

[KJ6EAD]

I think the excessively large 1MΩ resistor from the 555 clock is leaving the 4510 clock input too floaty (sensitive) and the C output is triggering it capacitively through all those long, silky, flowing wires. I'd try 10kΩ.

Why do you have a pull down resistance on pins 3, 4 and 5? If you're not planning on driving these pins high at some point, why not just ground them completely (0Ω pull down).

 

[ericgibbs]

hi,
Looking at your BB layout, whats the resistor is series with pin3 output of the 555 to pin15 [clk] of the 4510 for.????

 

[Crax0r7]

crutschow:
Rebuilt the circuit this morning to check the connections.
Will try to draw a schematic and post soon, got family stuff to do today so it'll probably be tomorrow.

brevor:
Not sure how to check for a short on pin 14 but i switched out ICs and moved it's position on the breadboard.

KJ6EAD:
Are you making fun of my wires? lol yea i bought one of those "beadboard wire packs" I'm probably going to purchase something different soon.
I've switched out the 1MΩ for a 10k and removed the pull down resistor on 3, 4, & 5 based on your suggestion

ericgibbs:
When i first built the circuit all the LEDs would blink randomly with no resistance in series from pin3. I can't explain it

 

[KJ6EAD]

Are you making fun of my wires?

A little. I've just always used solid 22 AWG wires that I cut and stripped myself. I've made some flexible jumpers but seldom use them. When you wire the board with excessively long wires you introduce stray capacitance (crosstalk) between connections that can pass level transitions undesirably. Flexible jumpers make the circuit harder to read and troubleshoot because of all the extra bends and curves.

As Eric said, you don't need even the 10kΩ on the clock input. When you had the clock hard wired before, you had a strong clock signal that may have driven the weakly pulled down inputs on pins 3, 4, and 5 high.

https://www.electro-tech-online.com/threads/weak-strong-pull-up.93491/

 

[Crax0r7]

Success! Pulling the resistor on the CLOCK line fixed it. I feel like saying "that's so crazy" but really it's my ignorance of how all this works that messed me up.

I'm very excited to keep going and learning more and more so expect to see me around. Possibly even answering someone else's question when I have the knowledge!

Also I know I said earlier that this is step 1 of n for a larger project so I'll probably post updates somewhere when it gets further along.

Thanks everyone for the help/suggestions/resources.

 

[mbarazeen]

congrats..