I have a project that I want to encase in a handheld case, with LCD display.
Because it is likely going to kick around in a bag or toolbox, I want to make it delay to power on - so you have to hold down the power button for two seconds or such to get the unit to power on.
But I haven’t got a clue where to begin to do this.
My box contains a wifi board, a charging circuit, a Pro Mini, an LCD display, an SD card storage board, a battery, some buttons.
The application is a remote data acquisition app that contacts a sensor and downloads the data. Everything for the project works, but having an instant-on switch has flattened more than one battery
Ideally I would like to have to press two buttons to power it on - but one would be fine.
If anyone can point me to a solution, I would appreciate it. My budget has upwards of $15-20 left in it, so if I needed another MCU, that is doable.
Do you have a car? Is it a nice car? Does it have AC and a radio? Why not drive a horse and cart? Why not drive an old junker? Why not pedal a bicycle?
And, how am I to recess such a switch in a mass-produced ABS housing?
Or… do what I wanted to do in the first place and have delayed switch-on - which is obviously possible - says every cellphone ever.
LEDAero:
Do you have a car? Is it a nice car? Does it have AC and a radio? Why not drive a horse and cart? Why not drive an old junker? Why not pedal a bicycle?
And, how am I to recess such a switch in a mass-produced ABS housing?
Or… do what I wanted to do in the first place and have delayed switch-on - which is obviously possible - says every cellphone ever.
Do you often ask rhetorical questions when you don't get exactly what you want ?
Have you ever heard of the KISS principle ?
Do you realize they make coffee w/o caffeine these days ?
Do you want to press one button or two (unlike every cellphone ever) to turn it on ?
LEDAero:
Ideally I would like to have to press two buttons to power it on - but one would be fine.
Yeah a one shot (built with 555 or LS123) feeding a latch would work. But if he’s concerned about accidental activation in a bag then he’s better off with a turn-on sequence that can best be done with an MCU. The thing I said I’d give him for $50 was built to do exactly that: only turn on if it’s clicked twice within a second at the right speed.
I note that the OP has yet to tell the good EEVBLOG folks that there’s more to his system than just an ATMega. So sleeping, an interrupt and a (high side) FET switch are needed.
