I'm trying to drive transistors with just a push of a button without using a MCU. The circuit I drawn drives different transistor on every button push and resets back. First part is a debounce circuit and the other is a counter which drives the transistors.

  1. Is this circuit enough?
  2. Do I need to add more passives like pull-downs?
  3. Can you recommend a schmitt trigger with lesser I/O?
  4. Is there a better circuit that does this? without using MCU ofcourse.


simulate this circuit – Schematic created using CircuitLab

  • 2
    \$\begingroup\$ It's usually a good idea to put resistors between the driving circuitry and the transistor bases. \$\endgroup\$
    – Hearth
    Mar 10 '19 at 12:21
  • \$\begingroup\$ As smaller Schmitt trigger ICs, try here. \$\endgroup\$
    – Hearth
    Mar 10 '19 at 12:26
  • \$\begingroup\$ or a counter with built-in schmitt trigger input \$\endgroup\$ Mar 10 '19 at 12:29
  • 2
    \$\begingroup\$ @JFetz2191 digikey.com -> Active components - Integrated Circuits (ICs) -> Logic – Counters, Dividers -> select "in stock", "View Prices at" = 1, Logic Type = "Binary Counter || Counter, decade || Binary Counter, decade", Direction = "Up || Up, Down", number of bits per element = All that have enough outputs (in your figure, at least 4), apply the filters. Maybe restrict by the packages you want to work with, and the supply voltage. Sort by price. Look through the datasheets until you find one with schmitt trigger input \$\endgroup\$ Mar 10 '19 at 12:39
  • 1
    \$\begingroup\$ The fourth or so is MC14024B, which has a "clock input with increased immunity due to hysteresis" – jackpot. Bonus: can drive up to 10 mA per pin, so if your load is small enough, you might not even need the transistors. \$\endgroup\$ Mar 10 '19 at 12:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.