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Analog input module, need some input


#1

One of the modules we want to offer is an analog input module. One problem, there are thousands to ADCs to chose from, ranging from few dollars to $$$ and from 8bit to 24bit!

So what is on your wish list for an analog input module?
Input voltage levels?
Resolution?
Differential inputs?

Adding A-type sockets for input will increase cost and over complicate things. Is 0.1" header or terminal block okay?

How will you use it? An example application will help very much.


#2

I guess there’s still a need to have 5v input but I’d sacrifice that if needed. If it was switchable to work as a 3v3 or 5v reference that would be a great feature too.

connections: personally with Analog Input I sometimes think that even .1" headers are not flexible enough, and it might be more suitable to have screw down connections (depending on use cases)

Actually talking about use cases, I can’t think of any ???


#3

The lowest cost solution I’ve played with is Microchip’s MCP3304. It can do 4 differential or 8 single ended, runs off 5V through and through and costs ~$5. It’s 13 bit and of course SPI.

Uses. Read all those IR distance sensors, or measure back emf on your robots motors. So many sensors so few analog inputs…

The Linear Technology’s LTC1867 is similarly capable but it’s 16 bit and supports Bipolar conversions all for ~$16.

Bipolar is great for small signals near ground. The LTC1863 is the 12 bit version for ~$8.


#4

Hello Dennis. Thanks for feedback and welcome to the community.


#5

I’d like to see a programmable analog front end. Something with 1M or more input impedance and an auto range function for voltages from -50V to +220V with x0.01 x0.1x1 x10 x100 amplification.

It is easier than it sounds. Just a good op amp with a digital pot or R2R ladder. There are plenty in DIY oscilloscope designs.

There are such nice analog sensors to read but the analog conditioning is always such a pain. In Gadgeteer style I’d like to plug and play.

Use cases:

  • Oscilloscope
  • audio power meter
  • battery charger
  • energy meter
  • lightning detector
  • lux meter
  • weather station
  • solar monitor
  • earthquake monitor
    Etc etc etc

#6

@ realiser: take a look to the AD7608
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7608/products/product.html

Not cheap but nice product.


#7

Funny you should mention teh AD7608, I’m working on a design with it now.

Here are the issues.

  1. Noise sensitivity (anything more than 12 bits is going to be sticky this way).
  2. Multiple power supplies.
  3. More control signals than a single Gadgeteer connector.
  4. Cost.

Here are the solutions I am looking at.

  1. Digital isolators and isolated DC/DC power. (takes care of #2 as well.
  2. Dual connector with default pullup/down if not used.
  3. No way around this and the above solutions only aggravate the situation.

As far as connecting to the real world I’m inclined to use a miniature terminal strip. This would include provisions for external power.