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Isolated/Stackable DAQ Module HMI SCADA Software
 

Isolated Stackable DAQ
Modules with Free Software

  • Digital Inputs
  • Dry Contact Inputs
  • Counter Inputs
  • Quadrature Encoder Inputs
  • Tachometer Inputs
  • Digital Outputs
  • Timer Outputs
  • PWM Outputs
  • Relay/Solenoid Control
  • Analog Inputs
  • Analog Outputs
  • Thermocouple Inputs
We offer a full line of low-cost Data Acquisition and Control modules which can be daisy chained together and connected to a single communications port of a PC or Laptop. Our HMI Software as pictured above is specifically designed to communicate with these modules and can be set up very quickly and easily by the novice with little or no programming skills. Advanced programmers can utilize the power of this software by writing complex scripts, conditional statements, and control logic that will run in the background.
 

Relay/Solenoid Controller Modules

WTX4 Isolated DAQ Module WTX4
Up to 32 high current open collector outputs which can directly drive relays, solenoids, DC motors, or other equipment of up to 1.0 Amp each. Can also include a combination of digital input channels, analog input channels, analog output channels, and thermocouple input channels. read more...
WTDOT-M Digital Output Card WTDOT-M
8 high current open collector outputs can directly drive relays, solenoids, DC motors, or other equipment of up to 1.0 Amp each. Also includes 2 digital input channels. read more...
WTDIN-M Digital Input Card WTDIN-M
2 high current open collector outputs can directly drive relays, solenoids, DC motors, or other equipment of up to 1.0 Amp each. Also includes 8 digital input channels. read more...
WTSSR-M Solid State Relay Card WTSSR-M
5 optically isolated solid state relays can be wired directly to in-circuit buttons and switches to allow software control of their operation. Built-in sequence generator. read more...
DIO-SSR Relay Controller Card DIO-SSR
Used as the host to the Solid State Relay Module. Switches wired to it's inputs will control the on/off states of the WTSSR relays via a remote data link. read more...

 

Stackable Capability

Stackable refers to the ability to connect multiple units together and share a single communications port of a host PC, laptop, or Single Board Computer (SBC). The DAQ modules are offered in two different footprints as shown above, enclosed in a case with full electrical isolation, or a non-isolated bare OEM circuit board. Both of these versions are stackable and can be mixed together if desired. The communications bus uses a stratagem based on the Carrier Sense Multiple Access (CSMA/CD) protocol. Carrier Sense (CS) is the monitoring of the data bus for a period of inactivity before a DAQ module is allowed to begin its own transmission. Multiple Access (MA) means that once the bus is free, every DAQ module in the network has an equal opportunity to transmit a frame. And Collision Detection (CD) uses non destructive bit wise arbitration to preserve the integrity of a data frame when two or more DAQ modules try to transmit at the exact same time. And since the data frame that wins arbitration remains intact during a collision, there is no additional communications delay when a collision occurs no matter how often it happens.

Host Communications

To communicate with the DAQ modules, commands are sent to the individual units by including a header character at the beginning (the address) so that it can be routed to the appropriate unit. If using multiple units connected together, the DIP switch for each unit should be set to a different position so that it will be assigned a different header character. Each DAQ module has its own command set used to configure it, operate the functions, and to read data from it. These commands are listed in the product data sheets. A typical command string looks like this:

HCNV{cr}

H = Header Character
C = Command Character
N = Channel Number (if applicable)
V = Value (if applicable)
{cr} = Carriage Return

If using our ModCom HMI software, the carriage return is not necessary because ModCom automatically inserts this at the end of each command string. ModCom has a communications dialog box which can be used to transmit individual commands to the DAQ modules and see the data coming back. This is helpful in learning the style of the command-set protocol and testing the hardware that's attached to the DAQ module. It is highly recommended that this testing be done prior to setting up any complex control programs.

Output Current

The output channels of the WTX4, WTDOT-M, and WTDIN-M series uses an open-collector configuration which can sink up to 1.0 amps per channel allowing them to directly drive relays, solenoids, DC motors, magnetic latches, flow valves, etc. To attach the outputs to a device such as a relay or solenoid, connect one side of the coil to the positive side of an appropriate power source, the other side of the coil to one of the output channels of the Digital Output module, and the COM or GND terminal of the Digital Output module to the negative side (or ground) of the power source. Then use the LOW command to pull the output channel to ground which will complete the circuit and current will flow through the coil activating the relay or solenoid. The HIGH command can be used to release the output channel from ground and deactivate the relay or solenoid.

Output Timer Function

Each of the output channels of the Digital Output modules incorporate its own independent count-down timer which can be used to control the length of time that a HIGH or LOW function holds the output at a specific state before returning it to the previous state. This timer can be re-loaded on the fly before it times out which provides a valuable feature. Suppose the output channel is being used to turn on a piece of machinery but ideally you would want that machine to turn back off automatically if the host PC shuts down or for any other reasons the communications has failed. By activating the channel using the HIGH or LOW command including a time value and then re-transmitting that command repeatedly at a rate faster than the timer can expire, will keep the machine active only as long as those commands are being received from the host.

This same procedure can be used to turn on an external alarm or warning light if there are any communications problems by having the host continuously transmitting a deactivation command instead of the activation command mentioned above. When using this method, the DEFAULT command should be used to make sure the output channel is set to the deactivation state upon power up.

PWM Output Function

The WTX4, WTDOT-M, and WTDIN-M series incorporate a special function that will produce a PWM (Pulse Width Modulation) output using the PWM command. In this mode, the output is a continuous square wave with a variable duty cycle which is controlled by the host. Duty Cycle represents the percentage of high time to low time of each pulse and can be used to control the current flow through a load such as a DC motor or flow control valve, for instance. The duty cycle can be adjusted in 0.1% increments from 0 to 1000.

Output Overload Shutdown

Each of the output channels of the WTX4, WTDOT-M, and WTDIN-M series incorporate a resettable fuse which protects it from excessive current flow. If the current being sunk by an output channel exceeds 1.0 amps for an extended period of time, the output will automatically shut down to prevent damage to the output drivers. Once this happens, the current must be removed from the output channel before it will return to normal operation.