Ultrasonic Range Finders: My Top 5

An ultrasonic range finder is a device that emits ultrasonic waves as a medium for distance measuring - it works much similar to a bat's sonar ability to know their position. It is used as a common sensor in robotic systems, automotives or simply for measurements in the industrial or home environment.

Devantech SRF235

One of the best and most expensive ultrasonic range finders around, the SRF235 uses a 235KHz transducer with a very narrow beamwidth (only 15 degrees) to measure ranges from 10cm to 120cm. It also cycles much more quickly than comparable sensors, taking up to 100 measurements per second. At this speed and its small size, the price of around $130 - $150 is well worth what you get.

Devantech Ultrasonic Range Finder SRF10

Billed as the "world's smallest ultrasonic range finder," this doesn't really seem to be drastically smaller than other sensors - but it is definitely a small little thing. Communication comes via the I2C bus, available on popular controllers like the BASIC Stamp 2 module. The SRF10 lets you know the exact distance of any obstacle, ranging from 3cm to 6m, with little room for error. With more advanced programming, you can take it to new levels by designing compensators to control motors to keep your robot at a set distance from the obstacle. The price range for this is between $60 and $80.

Devantech Ultrasonic Range Finder SRF08

The SRF08 can identify obstacles from 3cm to 6m, using a digital pot to vary the gain as the range increases - allowing a higher overall gain to be set and therefore providing an even better range. This range finder uses an I2C bus interface, allowing it to easily connect to such microcontrollers as the BasicX or BasicATOM. Not as quick as the SRF235 or SRF10, but giving a drastically faster recharge time than previous models, multiple echos can also be received, storing the first 16 of them in memory. A light sensor is also included. The price for this small sensor is around $65.

Maxbotix LV-EZ1

This easy-to-use range finder is also a small, lightweight device, offering very accurate range detection from 0 to 255 inches (0 to 6.45m) in 1 inch increments. Its power consumption is very small, operating from only 2.5 - 5.5 volts, with a low 2mA supply current. Included interface output formats are ansynchronous serial digital, pulse width, and analog voltage outputs. This is a great sensor to have for just around $25.

Parallax SRF04

The $35 Parallax SRF04 uses PING))) technology for measurements between either moving or stationary obstacles. It comes with an LED to easily make readouts and uses just 1 I/O pin, where other devices generally use more. It is easy to connect the SRF04 to such microcontrollers as the BASIC Stamp or other popular ones.