Computing stuff tied to the physical world


Meet the new Analog Plug

In Hardware on Nov 25, 2009 at 00:01

Here’s the revised Analog Plug (AP2):

DSC_0780.jpg

Still the MCP3424, i.e. from 12- to 18-bit (!) resolution, depending on configuration, supporting 4 differential inputs with an input range of -2.048V to +2.048V. The plug is I2C based and can be daisy-chained with other I2C plugs on the same port.

Here’s a hookup to measure the voltage of a NiCd battery:

DSC_0782.jpg

Note: I did not forget the solder jumpers. With this chip, floating inputs are ok. The I2C address is 0x68 (which is actually not such a good choice because it conflicts with the RTC plug).

The following code turns the JeeNode into a 4.5’ish-digit voltmeter:

Screen shot 2009-11-23 at 18.21.27.png

And here is the sample output:

Screen shot 2009-11-23 at 18.05.39.png

Is it precise? You bet.

Is it accurate? Well, my multimeter says 1.265…