The first command sets the first digital output, which would cause the LED in example 1 above to glow. The second
command clears the output, turning off the LED.
TTL Outputs
Additional circuitry is required to get TTL signal levels from the X-MCC, as shown below.
The 74LS04 contains 6 inverters so it is possible to convert all of the digital outputs with one IC. In order to maintain
isolation, it is recommended that the 5 V and GND supply connections come from the device requiring the TTL
signalling. It is, however, possible to use the 5 V and GND connections from the Analog Output connector on the X-
MCC to power the external device, as long as the current limits are adhered to.
Analog Inputs
The analog inputs on the X-MCC accept and display voltages in the range of 0 – 10 V. In order to measure other
analog variables, a transducer or sensor is required that outputs an appropriate voltage range. As transducers
typically provide low voltage signals, an amplifier and buffer circuit is required to interface a transducer to the X-
MCC.
The reference circuit below demonstrates how to connect a wheatstone bridge to one of the analog inputs on the X-
MCC. Various instruments are configured in a wheatstone bridge arragement, including load-cells and strain
guages.
R_GAIN's value should be chosen so that a positive full scale of the instrument produces 10 V at the analog input of
the X-MCC and a negative full scale produces 0 V. The OP97 op-amp provides an offset of 5 V to the amplified
value so that no load on the instrument produces an output of 5 V.