VME board layout. Below is a sketch of the custom ADC readout board. Essentially this is a copy of the hardware on the MVD motherboard. We will use this board to read out the sensors (temperature, flow, humidity) around the MVD cooling system.

The top 8 lines on the front panel are driven by a digital I/O board in the VME crate (such as one of these). This board in turn is driven by a C-routine (using existing examples from TC) running in the MVME162, [which in turn is activated as an EPICS subroutine record.]

As a general-purpose Phenix board, we can design it for the maximum of 128 single-ended or 64 differential analog inputs. For the MVD, we use 64 differential.

Postscript version

Postscript version

On the final board the 16-pin connector is at the top and the two condo connectors are below it. On the backplane the bottom connector is unused, and is not installed on one of the 2 boards that were built.

Links:Maxim,

Parts

                part              value              have     need
  -----------------------------------------------------------------
  D1                              green diode        many BNL  0
  D2                              red diode          many BNL  0
  R1, R7                          150                 2        0
  R2                              24K                 1        0
  R3,4,5,6                        24                  4        0
  C01,02,03,04,06,08,09,10,12,13,                                
   14,16,17,18,20,21,22,24,25,26,                               
   28,29,30,32,33,34,36,37,38,40,                                
   41,42,44,45,46,48,49,50,52,53,                                
   54,56,57,58,60,61,62,64,65,66,                               
   68,69                          ?? (DECOUPLING)     -       52
  C5                              22 uF               1        0
  C07,11,15,19,23,27,31,35,39,43,                               
   47,51,55,59,63,67              4.7 uF              16       0
  U1,2                            74ACT138PC          1        0
  U3                              DM74123N            1        0
  U4                              74ACT244PC          1        0
  U05,06,07,08,09,10,11,12,13,14,                               
   15,16,17,18,19,20              MAX186_CPP          -       16
                   17             20-pin socket       -       17
                    3             16-pin socket       3        0
  P2                              VME backplane      many      0
  P3                              16-PIN RH HEADER   some BNL  0
  P4,5                            2X34-PIN CONDO      0        2
                                  FRONT PANEL         -        -

             pulldown resistor    13M (?)             0       64
             pulldown cap         .22uF               ?       64
  ------------------------------------------------------------------

1. On the board, the backplane connectors P1 and P2 were reversed. All we use from the backplane is +5V and ground, and these are picked off the top connector P1 with fat wires and brought down to where they connect to the board by the P2 connector.
   
   
2. The 64 input lines were floating, and they need to be terminated to ground. A little daughter board on the back pulls the input to ground via 2 (4, 13)Mohm resistors, plus .22 uF caps to ground:

   
   First the connector pins, where they stick out through the back of the
   board:
   
                      top of board
   
                      four columns
                      of 17 pins:
   
    b                  1  2  3  4       f
    a                  2                r
    c                  3                o
    k                  4                n
                       5                t
    o                  6
    f                  7
                       8
    b                  9
    o                 10
    a                 11
    r                 12
    d                 13
                      14
                      15
                      16
                      17
    
                    bottom of board
   
    
       Every pin except the top row in columns 1 and 3 has a similar
    looking arangement:
    
    
    Cap   2Mohm resistor?      4Mohm resistor?    Cap --> Ground on this side
    ^ ^   ^             ^      ^            ^     ^                            
    | |___|             |      |            |_____|
    g     |             _______|            pin from column 3 attached here
    r     |                    |            
    o     |                    ground (I think) here
    u     |
    n     pin from column 1 attached here
    d
    
    Some of the conections are on the back of a small breadboard so
    it is confusing. There are also three ground (I assume) wires
    from the breadboard to points on the back of the ADC board.
    I do not understand the values of the resistors. I give you
    what I measure across them. However, by their colors, th 2 and 4
    Mohm resistors should be the same (or maybe I can't tell the colors).
    yellow - gold? - blue - orange - brown.
    
    The caps say:
    224
    35K
    548
    on them. In each case, the brown band on the cap is towards the
    middle of the arrangement above.
    
    Is that enough?
    John (Feb 16 2000)