really controlled by both MCU and push button

Community PCB Design
1

Hi

I would like to use really board

the relay should be connect disconnect using the MCU (simple board like this http://www.sparkfun.com/tutorials/119)

and also disconnect using push button (not through the MCU) making it hardware red big disconnect button

I can only think about connecting the MCU and push button using flip-flop

is there any other simple way?

thanks

2

Why not put the “red big disconnect button” in series with the MCU contol line?

If you open that circuit with the button then resistor R1 (see schematic on page to which you linked) ensures Q2 turns off, opening the relay. If you close the circuit, control returns to the microcontroller pin.

If the pushbutton you envision is a momentary, say, NC (normally closed) switch then the relay will be disabled as long as the button is pressed. Consider a toggle-type switch if you need it to be disabled even without the operator depressing the switch.

3

thanks

I understood what you suggested

but I need it as momentary button that keep the relay close until a command from MCU open it

for example

relay open->button pressed->relay close->button released->relay kept close … MCU high->relay open->MCU low->relay closed

(to use flip-flop?)

any ideas how to do it?