Stepper Motor Driver/Controllers

	Unipolar Stepper Motor Driver WTSMD-M Drives a unipolar stepper motor which is rated between 8-30 VDC. Up to 1250 pps step rate. Single phase, dual phase, and half step drive modes. read more...
	Bipolar Microstep Chopper Driver WTMCD-M Drives a bipolar stepper motor using constant current chopper regulation. Up to 10,000 pps step rate and 64 microsteps per step. User programmable drive current and idle reduction current. read more...

 

Stepper Motor Definition

A stepper motor differs from a normal DC motor in that the movements consist of individual steps rather than a continuous rotation. These individual steps allow for precise positioning that can be repeated with accuracy. Examples of step-motor usage include the control of a paper feed in a printer, the movement of an automated drill press, milling machine, or lathe, etc. The stepper motor controller cards listed above are a complete stepper motor driver/controller unit built into one. Simple coordinate commands sent from the host will advance the motor to an exact position in the range of 0 to 16,777,215 using S-curve acceleration/deceleration slope profiles which reduce stall effects during ramping, and overrun effects during breaking. Host can also instruct the motor to accelerate to target velocity and continue to move until a limit switch triggers the deceleration curve.

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 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.