The dataTaker 50 has 5 digital input/output channels, and the dataTaker 500/600 series loggers have 4 digital input/output channels, which can be used to output digital states. The Channel Expansion Module (CEM-AD) has 10 digital output channels, implemented as 5 open collector outputs and 5 change over relay outputs.

The digital output channels can be addressed either as digital bit outputs, or as digital byte outputs.

The digital output channels are powered down when the dataTaker is operating in the low power mode or asleep. Therefore the digital output channels will not hold their output state while the dataTaker is asleep. However when the logger wakes, the pre-sleep condition of the digital outputs is restored.

The digital output channels of the loggers are implemented as open collector outputs, able to sink up to 200 mA at 30 VDC. The outputs are buffered, and able to directly drive low voltage relays. Each output has a 15 KOhm pull up resistor to 5 Volts.

The digital output channels 6 - 10 of the Channel Expansion Module (CEM-AD) are also implemented as open collector outputs, able to sink up to 200 mA at 30 VDC. The outputs are also buffered, and able to directly drive low voltage relays. Each output has a 15 KOhm pull up resistor to 5 Volts.

The digital output channels 1 - 5 of the Channel Expansion Module (CEM-AD) are implemented as single pole change over relays, able to switch 240 VAC at up to 5A.

A schematic for the open collector digital output channels is illustrated in Figure 121.

Open Collector Digital Outputs

The open collector digital outputs are TTL/CMOS compatible, and can be used to directly interface to TTL or CMOS circuits. Each channel has a 15 KOhm pull up resistor to 5 Volts.

The open collector outputs are active low. Setting a channel ON results in the voltage at the digital output going to a low state of approximately 0.6 Volts.

The open collector digital outputs are designed to drive relays, solenoids, etc. directly. The actuator device is connected between an external power supply of up to 30 Volts maximum, and a digital output channel. The negative side of the external power supply is connected to the dataTaker ground.

The output drivers are not current limited, and so care must be taken to avoid shorting a supply line directly to a digital output.

 

 

Figure 121 - Digital Input/Output Channel Circuit Schematic

 

Connecting to Open Collector Digital Outputs

The open collector digital outputs can be connected directly to TTL/CMOS interfaces, and can drive up to 2 TTL loads. The outputs are active low, and are referenced to dataTaker ground.

The open collector digital outputs can also be connected directly to low voltage relays, solenoids, etc. The device is connected between the digital output channel and the positive pole of a power supply.

The power supply can be an external power supply of 5 - 30 VDC, or the 5 Volt switched sensor power supply of the dataTaker.

 

 

Figure 122 - Connecting Relays to Open Collector Output Channels,
Powered from the dataTaker

 

 

Figure 123 - Connecting Relays to Open Collector Output Channels,
Externally Powered

 

The relay, solenoid, etc. must have a coil voltage/resistance rating which matches the power supply used to drive the device.

While the open collector digital outputs incorporate transient protection for inductive loads, it is a sound practice to place a reversed diode across such loads.

The output drivers are not current limited, and so care must be taken to avoid shorting a supply line directly to a digital output.

Setting Digital Bit Output Channels

The digital output channels are set to required states by assignment commands.

Assigning a 0 to the output channel turns the channel OFF, and the output goes high to approximately 5 Volt (the open collector becomes non-conducting).

Assigning a 1 to the output channel turns the channel ON, and the output goes low to approximately 0.6 Volt (the open collector becomes conducting).

Using DeTransfer, the commands for example

switches the digital output channels as follows

turns the digital output 1 ON, which goes to a low state of approximately 0.6 Volt

turns the digital output 3 OFF, which goes to a high state of approximately 5 Volt

Using DeLogger, the digital output channels can be set from the Program Builder as part of a program as follows. In this case the state of the digital outputs is managed by the Triggered Schedules. The digital output state is selected directly from the channel selection walking menu.

 

 

Using DeLogger, the state of digital output channels can also be set directly from the Text View. The appropriate commands are installed behind the User buttons at the bottom of the Entry Screen, and whenever a User button is clicked the corresponding command is sent to the dataTaker to change the state of the digital output channel. This switching is independent of the schedules.

 

 

Caution :  While a digital output channel of the dataTaker is turned ON, it cannot be used to monitor digital inputs. However the current state of the output can be read as a digital input.

Use of the digital output channels is described in greater detail in Section III - Commands for Digital Output Channels.

Setting Digital Byte Output Channels

The digital output channels can be set singularly to provide bit outputs, or in groups of channels to provide byte outputs.

The digital byte output channel is set to bit patterns, which are represented by decimal values assigned to the byte channel.

Using DeTransfer, the command for example

instructs the dataTaker to set the digital output channels to a bit pattern 01101 which corresponds to the digital channels in the order 5 4 3 2 1. This sets the digital output channels as follows

channels 1, 3 and 4 are turned ON

channel 2 (and 5 for dataTaker 50 and CEM-AD) are turned OFF.

Caution :  While the  digital output channels are turned ON, they cannot be used to monitor digital inputs. However the current state of the digital outputs can be read as a digital byte input.

Before using the digital channels for monitoring digital states or low speed counting, it is good practice to enter the command

to ensure all outputs are OFF.

The digital byte outputs are not directly supported by the Program Builder of DeLogger. However digital byte outputs can be managed

from the User buttons of the Text View as described above

from the User channel type (DeLogger Version 4.2.15 or later) in the Program Builder as follows

 

 

Setting of digital output channels is described in greater detail in Section III - Commands for Digital Output Channels.

Channel Expansion Module Digital Output Channels

The Channel Expansion Module (CEM-AD) has 10 digital output channels, configured as 5 open collector outputs and 5 relay contact outputs.

The 5 open collector digital output channels are implemented in the same way as the digital output channels of the dataTaker (see above). The open collector digital output channels are channels 6 to 10.

The 5 relay output channels are implemented as contact closures which will switch  240 VAC/DC at 5 Amps. The relay output channels are channels 1 to 5.

The current draw from each digital output relay when switched ON is 35 mA. The relays are automatically switched off when the dataTaker enters low power mode (sleep), and the previous relay state is resumed when the logger next wakes.

A circuit schematic for the Channel Expansion Module (CEM-AD) relay digital output channels is illustrated in below

 

 

Figure 124 ñ Relay Output Channel Circuit Schematic for the CEM-AD

 

Setting Digital Output Channels of the CEM-AD

The digital output commands for the Channel Expansion Module (CEM-AD) are the same as those for the dataTaker data loggers. However all digital output commands for the Channel Expansion Module (CEM-AD) are prefixed by the module number.

Using DeTransfer, the commands for example

instruct the dataTaker to set the state of the digital outputs of the CEM-AD as follows

CEM-AD module number 1 will switch relay 3 ON

CEM-AD module number 2 will switch open collector output 1 (channel 6) ON

Using DeLogger,

 

 

the digital output channels on the CEM-AD can be set from the Program Builder as part of a program. This is done as follows

firstly set any digital output channel of the logger, say digital output 1, to the required state as described above

then reassign this channel to the CEM by right clicking on the new ëpseudoí channel icon, and select Channel Options:Channel Number:CEMn:channel number

Setting of digital output channels for the Channel Expansion Module (CEM-AD) is discussed in greater detail in Section III - Commands for Digital Output Channels, and Section II - Operation of the Channel Expansion Module).