![[-]](https://theultimatetone.com/images/collapse.png "[-]")
10-14-2021, 12:36 AM
Hi Strelok
With the less expensive normally-open/closed push buttons a debounce circuit is required. Our QRK-LATCH kit incorporates this, using three BJTs per switch. You can also use CMOS inverters for the task, or try to go passive. In all cases, a small capacitor is required to provide the controlled rise without noise.
One form of the passive circuit capacitively couples the switch to the chip input. On the chip side of the cap is a resistor to ground to assure a LO input as standard. The switch closes and ties the cap to V+, making a pulse into the gate of the chip.
An alternative form uses a NC switch in parallel with the cap to ground. A resistor to V+ charges the cap when the switch opens.
In both passive cases the CMOS threshold voltages for recognition of a HI or a LO determine the point at which the chip changes its status.
The active circuits provide a narrow square pulse hits the latch chip.
Have fun
With the less expensive normally-open/closed push buttons a debounce circuit is required. Our QRK-LATCH kit incorporates this, using three BJTs per switch. You can also use CMOS inverters for the task, or try to go passive. In all cases, a small capacitor is required to provide the controlled rise without noise.
One form of the passive circuit capacitively couples the switch to the chip input. On the chip side of the cap is a resistor to ground to assure a LO input as standard. The switch closes and ties the cap to V+, making a pulse into the gate of the chip.
An alternative form uses a NC switch in parallel with the cap to ground. A resistor to V+ charges the cap when the switch opens.
In both passive cases the CMOS threshold voltages for recognition of a HI or a LO determine the point at which the chip changes its status.
The active circuits provide a narrow square pulse hits the latch chip.
Have fun
