# Build remote wireless Wake-Up with Attiny85

I'm building a ultra-low-power system (mainly composed by an attiny85) that's in sleep state most of the time in order to extend battery life.

I was wondering if there was any hack to wake up the attiny85 with a wireless signal. I know there are several interrupts in the attiny and I started searching a wireless (ultra-low-power absolutely needed) solution that triggered the interrupt and forced the microcontroller to wake-up, but I didn't find anything.

So, finally, my question: are you aware of any solution that could suit? The current needed should be under 100 uA. The least, the best.

• If you are okay with slightly more, it seems a IR receiver will only use 400 µA. Commented Feb 11, 2016 at 20:52

You haven't indicated any minimum distance requirements, so I'd consider using a pair of resonantly coupled inductive coils to wirelessly wake your ATTINY85.

This solution is particularly compelling because the receiver requires no power at all.

Here is a very simple circuit that could do the job...

simulate this circuit – Schematic created using CircuitLab

The transmitter could be as simple as a sine wave generator connected to a coil.

The AC current in the transmit coil will generate a magnetic field that will induce an AC voltage in the receiving coil. When this voltage rises above the threshold voltage on pin INT0 on the ATTINY then it can trigger that chip to wake from deep sleep. The zeener diode limits the maximum forward voltage that pin INT0 sees.

The distance between the transmitter and receiver will be dependent on the size of the coils, the number of turns they have, their geometric configuration (co-axial best), and the driving current and frequency on the transmit coil. You can google "resonant wireless power" for more info on these design factors.

In any case, it should be possible to achieve a transmit distance of 100cm or more with this very simple circuit and reasonably sized coils. Larger distances are possible with careful optimization.

There has been a new development in low no power wake up strategy!

Here is a chip that can use the power generated by a received IR or RF signal to wake up a device...

https://www.asapsemi.com/blog/university-of-bristol-develops-zero-power-standby-circuit/