Hardware Design using TI ADS1115 analog to digital converters

For those that don't need or want all the IO and additional memory that the Beaglebone Black offers I see no reason why this project could not be run on the various models of the Raspberry Pi including maybe even the Raspberry Pi Zero which could cut the cost to below $50, or any Linux computer which has an accessable built in I2C bus, might even be possible to run it on your router running OpenWRT or something similar.

This project requires some electronics knowledge and some soldering skills unless you use a breadboard. Some knowledge about the Linux operating system and the Python programming language is useful but not essential.

Rather than the more typical approach of a dedicated circuit I have chosen the Beaglebone due to flexibility, ease of use, software availability, cost (US$55) and reasonable power consumption. As the Beaglebone is a full blown Linux computer with networking capability and a USB host, not only can it just log data either in its own flash memory or on microSD, if connected to the Internet either via a 3G dongle or cable ethernet or WiFi the information can be accessed via the internet and of course the Beaglebone can also be controlled and reprogrammed via the Internet.

Using the ADS1115 four channel 16 bit A/Ds makes the interface between the battery and the Beaglebone easy, requiring just a resistor divider circuit, yet the 15 bit resolution in single ended mode gives a resolution of around 1mV for a 24 volt battery. The ADS1115 also has an on chip op amp with up to 8 times amplification which when used if differential mode gives 16 bit resolution with an input of +/- 256mV which makes it possible to measure battery current easily and accurately using just a 50mV shunt . Added to this, Adafruit make a PCB with this chip which costs only US$14.95 which means you don't have to solder a chip with 0.5mm pin spacing.

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