Buffer as switch debounce

Feb 25, 2016 27 Replies

Dave's isn't static: it depends upon a cap holding state. If it's the one I'm thinking of.

If you prefer discrete, this could be implemented with four transistors (two for a Schmitt trigger/buffer, two for the divider -- a common-pulsed bistable multivibrator type), or a few more to get reasonable (TTL/CMOS) output logic levels or lower power consumption.

If you can arrange the bistable to exhibit hold-off (so it doesn't respond to extra input pulses for a duration), the Schmitt could be skipped. I'm not sure offhand if that can work.

Tim

Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com

As in...

...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

If I'm not wrong it looks like you could build Jim's circuit entirely out of the 4 sections of a 4093 Schmitt NAND gate.

The 4093 is pretty baller for a lot of things...

You don't need Schmitt. ...Jim Thompson

| James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Simple SPST or DPST. I'm using a C&K KMR4 series for one project now ( KMR432NGLFS ). In a previous project we wanted a reset for LPC1769, which I think you have used. But we wanted it such that holding the reset for a couple of seconds would put the device into programming mode.

I found an easier way for simple reset was to just use a POR chip like a TPS3809 with a 200ms td window. This reset drives more than just a uC.

Chisolm Republic of Texas

Thanks Jim, I'll try it.

Chisolm Republic of Texas

STM1818 is a cute reset chip. 3 pins, cheap. The pushbutton goes from the reset line to ground.

John Larkin Highland Technology, Inc lunatic fringe electronics

Thanks. I'll have to remember that one. I've used STM voltage monitors before but not their reset chips. This is cleaner than the TPS POR solution.

Chisolm Republic of Texas

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