Detecting an ultrasonic beacon
By Radu Motisan Posted on April 7th, 2013 , 4176 Views (Rate 17.04)
An ultrasonic beacon and a ultrasonic receiver is very similar to a beam barrier circuit, the only difference is we don't sound an alarm when an object breaks the ultrasonic path, but instead we try to locate the ultrasonic beacon by moving the receiver. This can be useful in robotics, when we use ultrasounds to detect a target (which in fact is the beacon itself).
To generate or detect ultrasounds, we'll use "40KHZ Ultrasonic Transducer Sensors":
For the emitter (the beacon itself), all we need is an oscillator set for a 35-45KHz frequency. We can achieve this using a 555 timer, a microcontroller and PWM, or discrete components. The simple the better, even though we lack some control over the signal shape:
The receiver is two amplifying transistors and a detector diode:
The range is excellent, at about 4 meters, the receiver was returning more than 100mV, for the detected signal, while at less than 1 meter it was putting out 4 V. The emission cone's angle is almost 40 degrees wide. An excellent module for robotics!
Update: And speaking about robots, here are some neat ultrasonic detector modules, built for the differential rover robot I'm currently working on.
These modules can be hooked up to a microcontroller's ADC port, and will return distance dependent voltages. So not only you can use them to spot the direction the sound is coming from, but you can also estimate the distance. The output is via the "signal" pin, which will provide approximately 0..5V depending on the power level of the detected ultrasonic signal.
I built two, as I need differential data to be able to pinpoint the source beacon easier.
Circuit diagram and PCB layout
Eagle PCB layout available here: ultrasonic_beacon_receiver