The Simblee RFD77402 distance sensor (thanks to Victoria Stamps on Twitter for bringing it to my attention) is not very big and not very expensive (about $6).  It is the little black chip on the green carrier:


It is an IR time-of-flight device that will measure up to two metres with about 1 mm resolution.  It is interrogated using I2C.  It is pretty simple to wire up – above it’s shown attached to a Wemos D1 Arduino-like board; all that are needed are connections for SDA and SCL for the  I2C, the 3.3V supply and Ground.  I made a small modification to Nathan Seidle of SparkFun’s example program to get it to display a graph of the distances:

I’ve put the code here on Github.  It should work on any 3.3 volt Arduino (like the Due) or Arduino-like device.  But don’t use a 5 volt one; you’ll bust the RFD77402.

Next thing is to design a 360robot LIDAR with it.  This should be pretty simple: I’ll use a Wemos D1 Mini to drive the device, together with a couple of AAA cells to power it, a 3V DC motor, and a shaft encoder monitored by the D1 Mini to get the angle.  The D1 Mini will communicate by WiFi and the whole thing will spin with no electrical connection to the outside.  An HTTP request to the webserver on the D1 Mini will result in a 360o distance profile being returned as a comma-separated list of integer millimetres giving the ranges round the device.

Or, maybe more simply, make the whole thing static, point the sensor upwards, and spin a 45o mirror over it…

Watch this space!

Time-of-Flight Distances

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