I would like to turn on an active buzzer TMB12A05 using the decimal place output channel of a TM1638 display driver that is designed to drive LEDs using a PWM signal.

I considered using a passive buzzer but then the sound would vary dependent on the brightness of the display, plus the buzzer likely requires more current than an LED and may damage the TM1638 so i went off the idea.

Would this circuit activate the buzzer correctly, and if so, how would i calculate the capacitance required for C2 to hole Q1 on for the duration the PWM signal is off.

If the buzzer continued to sound for a few milliseconds or so after TM1-SEG10 was deactivated it wouldn't be a any bother.

Am I barking up the wrong tree or is this feasible?

I am struggling to test this before paying to print the circuit since to my knowledge there is no through hole equivalent of a TM1638 and the pins are to small to see never mind solder.

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  • \$\begingroup\$ A turn-off latency of only a few milliseconds is very short. The value of C2 depends on the frequency of the input. What is that? Also, if you are trying for something like buzzer on when pwm is greater than 50%, and off below 50%, one transistor is not a good enough comparator. You will need at least a differential pair, and probably should go with an analog comparator. \$\endgroup\$
    – AnalogKid
    Aug 5 at 13:41
  • \$\begingroup\$ a few hundred milliseconds would be fine, i dont think its that important if the buzzer was a bit late going off, anything less than half a second i doubt anyone would notice as long as it actually stops when asked to. no im not bothered what the duty cycle actually is, if there is one, sound the buzzer. that said a TM1638 chip uses the same pins to read button states, there is a very brief negative voltage while it reads the button states, but i don't think it is an issue as the LED in the EL3H7 Optocoupler should block it out. \$\endgroup\$
    – Jay Dee
    Aug 5 at 17:27


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