Simple circuit for the ADAM-4050
The ADAM-4050 is an inexpensive module that has the digital outputs needed to drive certain external devices, such as the Sable gas stream multiplexers.  However, attaching these devices is trickier than with a Sable UI2 A-D converter.   This is because the Sable multiplexers require digital high (+5 volts) on their control lines, and the ADAM-4050 does not provide positive voltages on its digital outputs.   Instead, they are open-collectors that can 'drive' a digital high signal to digital low (~ 0 volts) on command: when active, they are low-resistance paths to ground; when inactive they have very high restance.   You need to provide the +5 volts on three digital leads.

You can get one 5V source from the Sable multiplexer itself (consult the Sable manual to identify this and other pins on the multiplexer's DB-15 connector).   I provided the other 5V sources by reducing the 12V DC main supply voltage to the ADAM units with voltage dividers, one for each of the two remaining digital leads.   If you use a different supply voltage -- ADAM modules accept DC supplies from +10 to +30 volts -- adjust the resistors in the voltage divider to provide +5 volts, using this calculator.

Once you have a +5V source for each of the three digital leads, connect them as follows (see this page, which shows a very similar circuit for other A-D converters).

  • Connect the GND terminal on the 4050 to the digital ground on the multiplexer (pin 3 on the DB-15).
  • Connect a 5V source to Digital Input 1 (optically isolated) on the multiplexer (pin 1 on the DB-15).  Then also connect this line to the DO0 terminal on the 4050.
  • Connect the second 5V source to Digital Input 2 (optically isolated) on the multiplexer (pin 9 on the DB-15).  Then also connect this line to the DO1 terminal on the 4050.
  • Connect the third 5V source to Digital Input 3 (optically isolated) on the multiplexer (pin 2 on the DB-15).  Then also connect this line to the DO2 terminal on the 4050.

  • If you want to use the 5V source on the multiplexer, it is pin 4 on the DB-15.
  • Make sure there is a substantial resistor (300 ohms or so) between the 5V source and the 4050 terminals, to limit any possible current draw.
  • NOTE:   you may have to build a cable between the multiplexer and the ADAM-4050 to ensure the connections are correct)
This circuit keeps the digital lines high (+5 V) unless they are 'pulled' low by activating the open collectors on the 4050.

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