Ultrasound rx/tx device

Projects General Guidance
1

I am wanting to make a pair of ultrasound rx/tx devices. One which a fixed detector on a toy car which receives a continuous pulse from a source at the front. The car needs to time between receiving each pulse and if the car does not receive a pulse after 30 seconds an loud sound alarm on the car goes off and doesn't stop until it receives a pulse from the fixed detector at the front.

I need the fixed detector to be small so it can be made into a watch. It doesn't matter how big the fixed detector is.

How would I go about doing this?

Thanks

2

The size of the send and receive elements of ping sensors is subject to the wavelength of the sound.

You need to make a working transmitter and receiver that fit your description.

3

GoForSmoke:
The size of the send and receive elements of ping sensors is subject to the wavelength of the sound.

Is that true?
The microphones and speakers in my mobile phone are very much smaller than the wavelengths of audible sound.

I agree though, that you need to make a working proof-of-concept device, before worrying about form-factor.

4

You can run at fractions of the wavelength just as radio antennae may be whole, half, quarter wave or even less as I'm sure you know. Which antenna is going to have the longer range given the same watts out and same boost on input?