1
\$\begingroup\$

enter image description here

I'm trying to get the following circuit to work. It says to:

Connect the circuit as shown in the block diagram in Figure 2 by adding a NAND gate followed by a CD4029 connected as a decade counter. For the CD4029, connect one of the lab station’s switches so that it will reset the counter, and connect the four outputs of the counter to LEDs on the lab station.

Input a TTL signal from the signal generator that has a frequency somewhere between 2 Hz and 9 Hz and verify this frequency using the oscilloscope. Note that you will have to measure the frequency. The frequency readout of the scope will not help.

View the LED that is monitoring the 1 second pulse, and reset CD4029 counter while the frequency divider output voltage is low. Then, when the same signal goes high, verify that the CD4029 counts the signal pulses being output by the generator. When the divider signal again goes low, read the final count in the CD4029. It should be the same as the output frequency of the signal generator.

enter image description here

enter image description here

Using the function generator of the NI myDAQ, I've set the frequency to 5 Hz and connected it to one input of the NAND gate and connected the 0.5 Hz signal to the other input of the NAND gate. The output of the NAND gate is then connected to the clock input of the CD4029 counter. A switch is connected to the PRESET of the CD4029. All of the Q outputs of the CD4029 are on when the board is first powered on.

When the LED on the 1 Hz signal goes low I press the button switch and all four of the LEDs turn off. However, none of the LEDs turn back on unless I turn on and off the power supply; then all four of the Q output LEDs turn back on. The output frequency should be the same as the 5 Hz signal frequency, which means that the output of the four LEDs should be 0101, but they're all off. Can someone help me figure out what is wrong?

The waveform I'm getting at the clock input of the CD4029 looks like this:

enter image description here

The frequency at this point varies up to around 2 kHz on my oscilloscope.

\$\endgroup\$

2 Answers 2

1
\$\begingroup\$

Your clock circuit is incomplete, and you need bypass capacitors on the power supply rails, directly across the IC pins. Show the waveforms you observe on the clock.

(edit) That waveform looks like just noise. Probably bad connections on the breadboard and lack of bypass capacitors. Here are the recommended clock circuits for the CD4060, from the datasheet:

CD4060 Clock

\$\endgroup\$
4
  • \$\begingroup\$ How is the clock circuit incomplete? I've included the waveform I'm getting at the clock input of the CD4029. I've tried adding 0.001 uf capacitors between the ic power inputs and gnd but it still doesn't work. \$\endgroup\$
    – Licentia
    Oct 22, 2022 at 1:44
  • \$\begingroup\$ Pin 11 of U1 needs to be connected to C2, not GND. \$\endgroup\$
    – PStechPaul
    Oct 22, 2022 at 7:58
  • \$\begingroup\$ That was an error on the schematic I drew as I think I confused it with the RST pin in Multisim. The breadboard however had it set up correctly. My lab handout made no mention of bypass capacitors and I'm unsure of how to choose the correct capacitance as I've never used bypass capacitors before. \$\endgroup\$
    – Licentia
    Oct 22, 2022 at 16:31
  • \$\begingroup\$ For most purposes, 10 nF to 470 nF ceramic is sufficient, and also something like 10-100 uF near the power supply. Can you get a good clean scope trace now? I see you have asked another question about this circuit. Hopefully you have gotten this working correctly first. \$\endgroup\$
    – PStechPaul
    Oct 23, 2022 at 0:23
1
\$\begingroup\$

I was finally apply to get it to work by setting the Vpp on the function generator to 5V.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.