So, I got my 74190 counter shows number like this 9-8-7-6-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0-5-4-3-2-1-0 and so on.

My questions:

  1. What can I do to change the output count down into 5-4-3-2-1-0-5-4-3-2-1-0 and so on?
  2. When it changes 0 into 5 it moves so fast. How could I fix this one?

enter image description here

  • \$\begingroup\$ the output of U8A is short-circuited by the switch S3. move the switch into the input circuit of U8A. \$\endgroup\$ – Jasen May 4 '18 at 10:40
  • \$\begingroup\$ the schematic could be improved by simplifying the ground net so that ground wires do not cross other ground wires. \$\endgroup\$ – Jasen May 4 '18 at 10:43
  • \$\begingroup\$ i dont know about how to move switch into the input circuit of u8A because it causes error on my circuit :( \$\endgroup\$ – Evangelina Tessia P May 4 '18 at 11:48

You cannot predict the initial state of the counter.

You must make a reset circuit that brings the counter to a known state at powerup.

Replace U8A with a NOR gate with one pin to an RC reset circuit or you can use a spare OR gate with U8A to make a NOR gate:


simulate this circuit – Schematic created using CircuitLab

On powerup the capacitor will drag the second input to "1" for a short time forcing a a counter load. This will make the counter start from 5.

From the additional comment I understand that the technology used is really LS which has an 1 mA input current, I thought it was just the schematic.

A fix is to use a negative reset like this:


simulate this circuit

R can be higher that 2k2 since the input high current is of uA order and also the capacitor if the reset does not work properly

  • \$\begingroup\$ But, it makes counter goes from 5-4-3-2-1-0-9-8-7-6-5-4-3-2-1-0-9-8-7-6-5-4-3-2-1-0-9-8-7 so on :( \$\endgroup\$ – Evangelina Tessia P May 4 '18 at 11:45
  • \$\begingroup\$ How can be possible ? With the reset input to '0' it should act as an inverter as in the original schematic. Are you sure you wired the MAX/MIN output to the gate? \$\endgroup\$ – Dorian May 4 '18 at 11:58
  • \$\begingroup\$ @EvangelinaTessiaP You actually use the old 74LS version , not 74HC or 74HCT version? \$\endgroup\$ – Dorian May 4 '18 at 12:04
  • \$\begingroup\$ Yes. I use the old 74LS version \$\endgroup\$ – Evangelina Tessia P May 4 '18 at 12:27
  • \$\begingroup\$ @EvangelinaTessiaP Oh, I didn't know that are still used, the LS have a higher input current that make the voltage on R to be higher than input low level. You should use a negative reset, i will update my answer right away \$\endgroup\$ – Dorian May 4 '18 at 12:50

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