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Best way to measure voltages above 3.3 — Parallax Forums

Best way to measure voltages above 3.3

pcleatspcleats Posts: 11
edited 2009-05-29 05:13 in Propeller 1
Hello all,

blush.gif·Just received my new propeller and have been playing with it a·bit. I have an application where I would like to measure voltages from 14.4 VDC·down to 10.5 VDC. Can this be done using the internal ADC's or would I be better off using an external chip. If external what would be a good choice? I need about .05 volts resolution.

Some sample code with be great also.

Thanks for the help

Patrick

Comments

  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-05-28 02:17
    You could do this with the make-shift ADC that is made using the Prop, or you can do it with an external chip. IMO, it's better to do it with an external chip since they tend to be a little more accurate, and if you fry that ADC with overvoltage or whatever the case, it's better than frying a Propeller.

    If you only want to measure a single voltage, you could go with the ADS7816 from TI. You can get a few as free samples, for tinkering, and there is code already for it. The code requires a cog, but samples 200,000 samples per second and does a running average, or allows you to grab individual samples. It's not in the OBEX, but I can post it if you want. Oh, this is a single channel, 12-bit ADC.

    Another chip is the TLV2543 from TI. It's a 11 channel, 12 Bit ADC from TI. Again, free samples and a SUPERB driver written by Tim Moore. This driver requires a cog, but samples ALL 11 channels at about 4,000 samples per second and does a running average. The code for this is in the OBEX.
  • Bill DrummondBill Drummond Posts: 54
    edited 2009-05-28 10:45
    I'm working a project using A Digital Pot, Here some examples that Digikey stocks.
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556350&keywords=IC%20Digital%20Pot&stock=1

    Post Edited (Bill Drummond) : 5/28/2009 10:50:33 AM GMT
  • hinvhinv Posts: 1,255
    edited 2009-05-28 11:23
    It's too bad Tim Moore doesn't hang out here. I would like to thank him publicly for the awesome contributions he has made.

    Kudos to Tim Moore!
  • northcovenorthcove Posts: 49
    edited 2009-05-29 05:13
    I've been using the MCP3208 8 channel, 12 bit ADC (http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556291&keywords=MCP3208) with excellent results on my project that has 64 channels of ADC (http://www.parallax.com/tabid/730/default.aspx). This chip half the price of the the TLV2543. The obex has interface code written by Chip Gracey (http://obex.parallax.com/objects/180/)
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