Shop OBEX P1 Docs P2 Docs Learn Events
Quad Sum and Difference Amplifier — Parallax Forums

Quad Sum and Difference Amplifier

WhatamINutsWhatamINuts Posts: 6
edited 2009-08-26 12:37 in Accessories
·Greetings
·· I need to interface a pacific silicon quad sum and difference amplifier to stamp.
···· its part number is QP154-Q-HVSD
·· Anyone have any expierence here?
··· Thanks
····· Have Fun
··········· Tim

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2009-08-21 13:40
    Tim,

    It looks like you will need to level-shift your voltages from +/-15V down to +5V/0V ... You will need to do this at least three times for each output. Once you have done that, the Stamp would be able to read the signal through an ADC.

    www.parallax.com/StoreSearchResults/tabid/768/txtSearch/ADC/List/0/SortField/4/ProductID/574/Default.aspx

    I'm about ready to board a plane, or else I would show you how to do the level-shift. If I don't see a reply, I will try to provide one later tonight.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • WhatamINutsWhatamINuts Posts: 6
    edited 2009-08-21 16:14
    Thanks looking forward to your voltage shifter

    ·hope you had a good flight

    ·· Have Fun

    ····· Tim
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2009-08-22 16:54
    Tim,

    Maybe Beau is at UPENE?

    One option would be to use the MAX1270 analog to digital converter, which accepts inputs in the range of +/- 10 volts even when operating on a single 5 volt power supply. Parallax sells the MAX1270 for use with the StampPLC. The QP154-Q-HVSD outputs swing to within 3 volts of the rails, so with a +/-12 V supply for the QP154-Q-HVSD, you would have +/-9 volts into the ADC.

    The MAX1270 uses a simple scheme at the inputs to extend the range beyond the +5 volt level. You can use the same technique with a different ADC.
                                                 12.5k            8.67k
       signal +/- 10 volts   -------/\/\---o------/\/\------ Vss common
                                                       |
                                                       o----/\/\------- Vref 4.096 Volts
                                                       |    5.12k        
                                                       `----------------ADC input 0 to 4.096 Volts



    The way this work is, yes, a voltage divider. When the input is at -10 Volts, the ADC sees 0 Volts. When the input is +10 volts, the ADC sees 4.096 Volts. And it is linear in between those limits. Those are the same resistor values that are used by the MAX1270, and I verified for myself that the math does work out with those ratios.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2009-08-26 05:45
    Yes Tracy you were correct... I was at the UPENE with Chip, Jeff, and many forum friends along the way. smilewinkgrin.gif


    WhatamINuts,

    Sorry I did not get back to you sooner. The method that Tracy posted was what I had in mind, but the values should be re-calculated for +/- 15V

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • WhatamINutsWhatamINuts Posts: 6
    edited 2009-08-26 12:37
    Guys
    · Thanks for· the help.
    ·· I think I wil use the Max1270 with a +/- 12 Volt supply as suggested by Tracy.
    · less wires.
    ·· For the appllication see Space elevator Blues here.
    http://www.spaceelevatorgames.org/
    · Page down to the article on NSS space elevator.· We are building the tracking system for the mirror in the video
    ·· Have Fun
    ········ Tim
Sign In or Register to comment.