Ultrasonic transducers ordered

Ultrasonic Wave TCT40-18R from dx.com

Last night I ordered a pair of Ultrasonic Wave Transmitter and Receiver heads. These are driven at 40kHz compared to the 4.8kHz I run the current radio beacons at. My hope is that I can use these to improve the accuracy of the radio beacons. The idea is not to measure distance to an object but to measure distance between two specific entities, the robot and a radio-beacon.

I have tried using two HC-SR04 units and tried measure the distance between them but the echo cannot be detected before the trigger has been activated.

A schematic for ultrasonic range finder from micro-examples.com

I intend to build one sending circuit for the robot and one receiver circuit for the radio-beacon with these. I found the above schematics from micro-examples.com with PIC example code. That circuit looks easy to connect and I just need to divide it into two parts. The code needs to be adapted to Arduino but that sounds even more easy, PWM at 40kHz, delay to avoid false readings and wait for the response... easy as pie. I can probably use the pulseIn Arduino function or a interrupt trigger.

USB-HUB

Not really related but I also ordered a 4-port USB HUB with individual switches for the new workshop. I hope that will save me from the wear and tear of pulling those USB cable out and press them in all the time.