Review - Hardware Design

[davidlee11]

As a newbie, Switch section is designed according to my knowledge. Please let me know the review for this section.

Switch is connected with the microcontroller. I have tried to protect microcontroller from positive & negative spike. The distance of switch from microcontroller is approx. 6 Inches. Here Vcc is 3.3V & microcontroller also works on 3.3V.
The schematic for the switch section is attached.

 

[D.A.(Tony)Stewart]

A similar R/CR diode structure is built into every input. See ESD protection current. Ensure switch is isolated from finger discharges to signals with 15 mm clearance for 15kV isolation. Do you want cap at 0V on power up then pulled up with switch to ground and power up closure? DOes it have software controlled pullup on input?

Choose RC >> debounce time for switch depending on size /quality 1~10ms typ.switches.

 

[davidlee11]

The microcontroller will measure 0V when switch is pressed. It has software controlled pull up resistor.

 

[KlausST]

Hi,

the switch ON time constant is about 110us (falling)
the switch OFF time constant is about 22ms (rising)

These values are OK even for debouncing.

The protection seems to be OK as well.

if a high energy positive pulse comes in, then it may lift the VCC voltage. Use an adequate bulk capacitor at vcc.

Klaus