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Ultrasonic Radar using PIC16f877

Ultrasonic Radar using PIC16f877

Using a modified Devantech SFR04 Ultrasonic Range Finder in an ultrasonic radar application. Displays radar data on a PC with a Visual Basic program.
The Devantech SFR04 Ultrasonic Range Finder indicates the distance to the closest object within range. Echo’s that arrive later are received and processed, but subsequently ignored. For a true radar all signals should be taken into account. So, time to heat up the old soldering iron and make some modifications to the Devantech SFR04 circuit board. We will add a wire to the ‘raw signal line’ and process the incoming data ourselves.


I have to admit I am a bit disappointed by the results. The ultrasonic signals appear to be bouncing back and forth through the office and give a lot of ‘false’ readings. It is very unclear what the signals on the screen actually represent. Out in the field (where a normal radar would be used) I assume this is less of a problem but in a my office area with lots of books and objects around it surely is.

I think that for indoor use Devantech made the right decision to only measure the first pulse and ignore the rest. This makes it ideally suited for robotics applications (as was shown in the Subsumption Robots section). It was a fun project to do however and if I ever get a portable PC I’ll built it again and see what outdoor measurements look like.

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