Chaining 4026 ICs

[krjhitch]

I have 2 4026 ICs set up on a single breadboard trying to count on a dual 7-segment display (which is common anode, and 4026 is built for a common cathode, I realize that), and it works (though reversed) when I have my 555 IC (roughly 1Hz) driving my first 4026 IC, but when I put in my second 4026 IC and only connect +V and ground on the second 4026, the first one can no longer count past 2, it just blinks and displays 2 again.

Anyone have any idea what I'm missing? I think it's basic.

 

[ericgibbs]

I have 2 4026 ICs set up on a single breadboard trying to count on a dual 7-segment display (which is common anode, and 4026 is built for a common cathode, I realize that), and it works (though reversed) when I have my 555 IC (roughly 1Hz) driving my first 4026 IC, but when I put in my second 4026 IC and only connect +V and ground on the second 4026, the first one can no longer count past 2, it just blinks and displays 2 again.

Anyone have any idea what I'm missing? I think it's basic.

hi,
How are you powering the circuit.?
Do you have a simple circuit diagram you could post.

 

[krjhitch]

It's powered by a 9V battery with +V on the top rail and ground on the bottom rail

I don't have a schematic that I'm following because I'm just tooling around. I can draft one up though. What's the preferred software for that?

 

[ericgibbs]

It's powered by a 9V battery with +V on the top rail and ground on the bottom rail

I don't have a schematic that I'm following because I'm just tooling around. I can draft one up though. What's the preferred software for that?

hi,
A free download of Expresspcb is OK, it has schematic and pcb drawing

ExpressPCB - Free PCB layout software - Low cost circuit boards - Top quality PCB manufacturing

 

[krjhitch]

**broken link removed**

 

[ericgibbs]

hi,
The 4026 RESET pins #15 need to be connected to 0V or to some logic to Enable a RESET

CYOUT on the 1st 4026 is the CLOCK for the 2nd 4026.

The +9V line needs decoupling with a 100nF and 22uF capacitor.

 

[krjhitch]

Yeah, CYOUT to CLOCK on the 2nd 4026 was my plan, I was just testing in the middle of setting the second IC up and noticed the first would no longer get past 2 in the counting.

I'll connect RST to ground and see if that fixes it. Thanks!

 

[krjhitch]

I connected pin 15 to ground and it's still doing the same thing as before, it works when I disconnect the second 4026, otherwise it counts to one, then two, then keeps staying at 2.

 

[krjhitch]

Well the issue went away when I was finished putting the second IC fully in place. I guess I shouldn't be worried about strange behavior when it's not completely set up.

Thanks for the help

 

[ericgibbs]

Well the issue went away when I was finished putting the second IC fully in place. I guess I shouldn't be worried about strange behavior when it's not completely set up.

Thanks for the help

hi,
CMOS type IC's will give unpredictable results if ANY of the input pins are 'floating',
ie: not connected.