74LS92 Divide by 12 Counter Not Counting, Outputs Random—Wiring or Pin Setup Issue?

I can't get 74ls92 to count. I tried studying the datasheets. I tried settingPins 2 and 3 to low.  The output is random. Nothing I tried works. Has anybody used the 74ls92 divide by 12Counter.

DavidOK.... basics:- Vcc (5V) is on Pin 5, and GND  (0V) is on pin 10 - a bit unusual for 7400 ICs- at least one of the MR1/2 inputs (Pins 6/7) should be low, I suggest you tie both to ground.- tie Q0 Pin 12 to/CP1 Pin 1- feed clean clock pulses in to /CP0 Pin 14.- Tie all NC pins to Ground (though I will admit I did not find specific advice on this in my datasheet)By Clean Clock Pulses,  I mean use something like a 555 in astable mode, fairly slow at first so you can see the counts - 1 or 2 Hz.  DON'T use a push button switch - the switch bounce will cause  multiple counts per push and give you exactly the random outputs you describe.If you still have problems check that your power supply is good - clean and at 5V +/- 0.1V.  Put a 10uF or bigger electrolytic  and a 0.1uF poly or similar cap across the power rails as close to the IC as you can.What are you using on the Qx outputs?  I'd suggest a red LED with a 220 ohm resistor in series, to ground for testing purposes.If the above gets success, good!  if not come back here and we can look at something else.  I have not got time now to get one going on my breadboard but I can do so.

Hi DavidIn addition to the ideas by DA above, what is it you are trying to do?I haven't used one of these but easy enough to get a datasheet and from the one I have I see that if configured as DA suggests it is a BCD counter. Is that what you wish or are you trying to get a "change of state" on a pin every twelve "counts"?Regards

The clock pulses are not from a 555 timer. I connect jumper wire connectedAt one end to the clock pin and thenConnect it to the Positive terminal.  The pulses come from that. Could that be causing random output?

David Lopez wrote: The clock pulses are not from a 555 timer. I connect jumper wire connected
At one end to the clock pin and thenConnect it to the Positive terminal.  The pulses come from that. Could that be causing random output?A jumper wire will bounce like any other switch contact.  When you touch the wire you'll get multiple clock pulses.  I had exactly this problem with a 7490 counter when I was a teenager.

The 74LS92 is a divide-by-twelve counter, cascading divide-by-two and divide-by-six stages, a part that is both unusual and classic, descending from the 7492 in the original 1960's Texas Instruments TTL series. The datasheet usually covers 74LS90, 74LS92, and 74LS93 in one datasheet. The 74LS90 is a divide-by-ten BCD counter, cascading divide-by-two and divide-by-five stages. The 74LS93 is a divide-by-sixteen binary counter, cascading divide-by-two and divide-by-eight stages. I agree with David Ashton's suggestions. I last used a 74LS92 in a design in 1992, where the specific divide-by-six waveforms were exactly what I needed to cancel the third harmonic in a squarewave.If you have a single-pole double-throw SPDT switch or pushbutton, you can use two NAND gates in a 74LS00 to debounce the switch and give clean pulses. You can also use two normally-open NO pushbuttons, pushing the buttons alternately:Connect one input of each NAND gate to the output of the other NAND gate, creating an RS flipflop. You now have two free NAND-gate inputs. Connect one free input to the normally-closed NC contact of the switch and through a 1000-ohm resistor to +5V. Connect the other free input to the normally-open NO contact of the switch and through a 1000-ohm resistor to +5V. Ground the common contact of the switch.When you actuate the switch, the first bounce flips or flops the flipflop, giving a single clean bounce-free edge on the outputs of the two NAND gates. With two pushbuttons, pushing one flips and pushing the other flops.
Use the other two NAND gates in the 74LS00 to debounce another switch, or else ground their inputs.

Thanks

Could a capacitor provide switch denounce?

David - I am in Australia so had to go to bed so thanks to the others who helped out while I was abed.  Your poking a wire onto the + terminal would absolutely cause multiple pulses as the others above have confirmed.  For more on switch bounce, I did an article on this not long ago here:https://www.eeweb.com/profile/david-ashton/articles/switch-bouncing-around
You will see there what kinds of multiple pulses you get from the average switch, and believe me  a bit of wire will do very much the same.  Max has written other stuff on debouncing, but most of it using microcontroller techniques.You could try a capacitor for switch debounce.  From the pin to ground put a 100K resistor and a 0.1 uF capacitor in parallel,  then take a 22 or 33 K resistor from the pin and poke that on your + terminal.  That will have a time constant of around 20mS which should help.  But it think it will just be better, not infallible.But why not get to know the 555?  You can get a 555 to act as a 1-shot (ie debounce a push button or even a piece of wire) or to deliver a pulse train of anything from 1 pulse per minute or so up to several hundred KHz.  Construct it on one end of your breadboard and leave it there for any future experiments.One breadboard I built had a power supply built in.  I used the 50Hz mains pulses into  7490 dividers (much like your 7492 but divide by ten) to deliver pulses of 50/10/5/1/0.5 Hz to a row of sockets.  SO easy to get a pulse train when you want.  If you're in a 60Hz area, you can use the divide by 6 / 2 parts of the 7492 to get that down to 10 Hz and 5 hz, then use a 7490 for 1/0.5 Hz.  It's very nice to see guys like you playing with 74 series ICs.  Most people now go straight to microcontrollers.  But an understanding of logic can only benefit you in the long run.

A capacitor will provide debounce delay, but will not provide the 15-nanosecond rising and falling edges the 74LS92 clock inputs want to see. The 74LS 92 may see slow edges as multiple clocks. The 74LS92 clocks on the falling edge of the clock pulse.
The two-NAND-gate flipflop is effectively a one-shot with infinite pulse width, and provides the fast edges the 74LS92 wants to see. The 74LS279 contains four of these flipflops.

Excellent point Peter and one I should have picked up on.... :-(Your two-NAND flipflop is great except that you need a double pole switch (well you could alternate your wire between Vcc and GND).  The 555 was made for things like this...

Not one wire alternating between Vcc and GND. Rather, one grounded wire alternating between R and S inputs to the flipflop.
I would expect the 555 to trigger once when the button is pushed, and again when the button is released, as the contacts bounce on both pressing and releasing the button. To prevent this, the 555 timeout needs to be longer than the longest time the button is held pushed. Alternatively, the 555 pulse could clock a falling-edge D flipflop at the end of the pulse. This flipflop would sample and hold the button state soon after the contacts stop bouncing.
The 555 output idles low and pulses high during the timeout. The 74LS92 clocks on the falling edge, so would clock at the end of the 555's output pulse.
Consider the 74LS123 dual retriggerable multivibrator instead of the 555. The 74LS123 has both Q and Qbar (inverse of Q) outputs. The 74LS123 is retriggerable, so contact bounces extend the output pulse.

74LS132 (quad NAND gate) and 74LS14 (hex inverter) Schmitt-trigger gates have input hysteresis (positive feedback), so they can reliably convert slowly-changing inputs (such as from a discharging capacitor) to fast output edges.

So tell us David, have you got your 74LS 92 to count properly now?