Power for US-040 ultrasonic ranger

Hello, everyone.
I am working on simple wireless sensor - ultrasonic ranger to measure water level in my home.
I made a quite simple prototyping board with ATtiny85, US-020 ultrasonic ranger and dirty-cheap and simple 433MHz radios.
Using Manchester library I established the communication with the receiver and everything seems fine.
However, I'd like to run the sensor from 3V battery.
Using the battery, the Tiny works fine, so does the transmitter (but the range is quite limited), but the US-020 refuses to measure the returning ping and returns no data.
Can anyone advice, how should I proceed? I have no simple way of adding 5V as far as I can see and I'd like to keep the sensor as small as possible.

If you can't find a 3V ultrasonic sensor, you could add a boost regulator to power the existing one, like this: http://www.pololu.com/product/2562 However you then have to use 5 to 3 volt level conversion on the inputs and outputs.

There are lots of other ways to measure water level, for example pressure sensors, or the etape, which comes in various lengths: Liquid Level Sensor - 8" - SEN-10221 - SparkFun Electronics

Thanks for the regulator tip - I didn't know they came in such a small package, keeping quite interesting efficiency. I'll dig deeper, but it seems as a solution I was looking for.
The water level measuring using the proposed sensor would not work - first of all the level difference is almost 2.5m (100") and the water is not exactly clean (output from bio-waste processing), therefore mechanical solutions will very quickly get dirty and stop being reliable - I know it as I do have similar and already non-working sensor in operation right now :slight_smile: