Tilt sensor - low power / interrupt

Other Hardware Sensors
1

I am playing with a tilt sensor on my Arduino Pro Mini (328p) - this sensor is sensitive to all kind of small vibrations (Tilt Sensor - AT407 - SEN-10289 - SparkFun Electronics) which is real fun

Have the sensor as such working via an interrupt ISR. Now in my next step I want to reduce power and make the circuit low power. What I would like to do is to put the Arduino into a sleep mode (Power down) and be awaken by the tilt sensor interrupt.

However what I am puzzled about it how to minimize the power consumption by the tilt sensor itself. I was thinking about a NAND gate (LOW output when tilt is not triggered, and HIGH when tilt is triggered). However this solution also uses power (range of 0.x mA) .. so when you have some ideas it would really help me.

Thanks

2

However what I am puzzled about it how to minimize the power consumption by the tilt sensor itself.

The AT407 sensor is just a switch, and consumes no power. It will not conduct current unless activated.

3

Is the tilt sensor in the circuit below consuming no power at all?

3.3V ---> TILT SENSOR (NC) ---> D2 (INT1)

  • INT1: triggered by HIGH to LOW / falling edge

Sensor activated once the ball "breaks the contact"

4

You need a pulldown resistor in that circuit, and some very basic understanding of electrical circuits.

5

Thanks. I know the basic stuff and trying to find a way to reduce consumption to a couple of uA (to have a battery operated solution for a couple of years)

6

Use a 1M pullup or pulldown resistor (5uA only when the switch makes contact, zero otherwise).
Adding a 1nF capacitor to reduce sensitivity to electrical noise would be wise.

7

to have a battery operated solution for a couple of years

Lots of tricks are needed to get to that place. Nick Gammon wrote a great tutorial on power saving techniques.

8

Thanks for the link, really contains a good overview. There are some tricks which I did not know yet.
Will work on my sensor and drop some lines when done

9

With the suggestions I got yesterday from you I have been playing and reading up on some 328 stuff. I realize now that an input PIN has an big internal impedance of 100 Mohm. So the monitoring itself already does not consumes too much power.

So the current of just having the tilt sensor trigger an interrupt is already very low (3.3V / 100 Mohm) ... or?

10

The current required by the tilt sensor is the power supply voltage divided by the pulldown or pullup resistor value, and then only when the switch is conducting.

For all practical purposes you can ignore the current into or out of the Arduino input, unless the internal pullup resistor is enabled.

11

Thanks for your clear answers. Appreciated!