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stevejferry
Posts: 52
Joined: Tue Mar 11, 2014 6:57 pm
Location: Seaham, UK
Contact: Website

8 Channel ADC board

Sun Jun 01, 2014 4:40 pm

Image

The Baart ADC-8 is an 8 channel ADC board which can be connected to the Raspberry Pi SPI interface via a ribbon cable. The SPI interface can obtain much higher samples per second than the I2C ADC boards (I'm getting 25 ksps by bit-banging and possibly higher if the code can be optimised). A quick shuftie through the Raspberry Pi forum or Google will reveal just how many programming examples there are for this type of ADC chip in C++, Python and a host of other flavours. Eventually, it is intended to have a repository of examples on our own website http://www.baart.co.uk (coming soon)

The boards were originally designed for an industrial use monitoring gearbox vibrations remotely via the internet but it was designed to be very versatile and accept a range of sensors rather than re-inventing the wheel for future needs.

The board features a very stable 3.3V supply and reference voltage from the Pi's 5V supply using a regulator and smoothing capacitors as the Pi's own 3.3V line tends to be unstable. Each input has a voltage divider in the form of a 23turn trimmer so input voltage ranges are from 0-3.3V to 0-25V. They are also overvoltage and reverse polarity protected so you won't accidentally fry the chip. Calibration of the trimmer for any given voltage range is a simple process and is included in the instructions.

Several of the Pi's GPIO lines are accessible via 3pin SIL connectors on the board for easy access. The chip supplied is a 12 bit MCP3208 which would be capable of 100k samples per second if the Pi would let it but using the conventional SPI, speeds of 10-20k SPS should be manageable and MUCH higher speeds using 'bit-banging' The board will also accept the 10 bit MCP3008 and the 13 bit MCP3304 if you fancy a 'bit' of a change!

Connection of sensors to the ADC is by terminal blocks.

Finally, the board has a selectable chip enable line so two boards can be used with a multi socket ribbon cable giving 16 channels in total however, if you are familiar with the 'bit-banging' technique mentioned earlier, many boards can be coupled in parallel giving over a hundred channels - almost as many as SKY but much cheaper and fewer repeats!

The cost per board on eBay is £19.50 with £3.20 first class signed for delivery but I'm open to offers for a worthy cause!

Email me if you have any questions. [email protected] dont forget to mention where you read this please.
There are 10 types of people. Those who understand binary and those who don't.

User avatar
stevejferry
Posts: 52
Joined: Tue Mar 11, 2014 6:57 pm
Location: Seaham, UK
Contact: Website

Re: 8 Channel ADC board

Fri Jun 06, 2014 7:58 pm

I now have a C++ library of ADC (using SPIDev) and GPIO routines to support this board.
There are 10 types of people. Those who understand binary and those who don't.

User avatar
stevejferry
Posts: 52
Joined: Tue Mar 11, 2014 6:57 pm
Location: Seaham, UK
Contact: Website

Re: 8 Channel ADC board

Sat Jun 28, 2014 8:09 pm

The PiMon board now comes with either voltage divider trimmers for sensors on the range 0-3.3 up to 0-20V or links to connect the ADC to the terminal block or to ground to prevent erroneous readings caused by unused channels.

The library now also includes FFT and windowing routines.

Also available are 300mV/g mems accelerometers and hall effect rpm sensors. Please email me for details. s.ferry @ efftek-uk.com
There are 10 types of people. Those who understand binary and those who don't.

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