control stepper motor using digital outputs -凯发k8网页登录

this example shows how to control a stepper motor using digital output ports.

discover devices supporting digital output

use daqlist to discover devices. this example uses a national instruments® elvis ii with id dev2.

d = daqlist

d =
  12×5 table
    vendorid     deviceid                 description                    model             deviceinfo     
    ________    ___________    __________________________________    _____________    ____________________
      "ni"      "cdaq1mod1"    "national instruments ni 9205"        "ni 9205"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod2"    "national instruments ni 9263"        "ni 9263"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod3"    "national instruments ni 9234"        "ni 9234"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod4"    "national instruments ni 9201"        "ni 9201"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod5"    "national instruments ni 9402"        "ni 9402"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod6"    "national instruments ni 9213"        "ni 9213"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod7"    "national instruments ni 9219"        "ni 9219"        [1×1 daq.deviceinfo]
      "ni"      "cdaq1mod8"    "national instruments ni 9265"        "ni 9265"        [1×1 daq.deviceinfo]
      "ni"      "dev1"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]
      "ni"      "dev2"         "national instruments ni elvis ii"    "ni elvis ii"    [1×1 daq.deviceinfo]
      "ni"      "dev3"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]
      "ni"      "dev4"         "national instruments pcie-6363"      "pcie-6363"      [1×1 daq.deviceinfo]

d{10, "deviceinfo"}

ans = 
ni: national instruments ni elvis ii (device id: 'dev2')
   analog input supports:
      7 ranges supported
      rates from 0.0 to 1250000.0 scans/sec
      16 channels ('ai0' - 'ai15')
      'voltage' measurement type
   
   analog output supports:
      -5.0 to  5.0 volts,-10 to  10 volts ranges
      rates from 0.0 to 2857142.9 scans/sec
      2 channels ('ao0','ao1')
      'voltage' measurement type
   
   digital io supports:
      39 channels ('port0/line0' - 'port2/line6')
      'inputonly','outputonly','bidirectional' measurement types
   
   counter input supports:
      rates from 0.1 to 80000000.0 scans/sec
      2 channels ('ctr0','ctr1')
      'edgecount' measurement type
   
   counter output supports:
      rates from 0.1 to 80000000.0 scans/sec
      2 channels ('ctr0','ctr1')
      'pulsegeneration' measurement type

hardware setup description

this example uses a portescap 20m020d1u motor (5 v, 18 degree unipolar stepper). the ttl signals produced by the digital i/o system are amplified by a texas instruments uln2003ain (high voltage, high current darlington transistor array), as shown in this schematic:

add digital output-only channels

create a dataacquisition and add 4 digital channels on port 0, lines 0-3. set the measurement type to outputonly. these are connected to the 4 control lines for the stepper motor.

dq = daq("ni");
addoutput(dq,"dev2","port0/line0:3","digital")

warning: added channel does not support clocked sampling: clocked operations are
disabled. only on-demand operations are allowed.

define motor steps

refer to the portescap motor wiring diagram describing the sequence of 4-bit patterns. send this pattern sequentially to the motor to produce counterclockwise motion. each step turns the motor 18 degrees. each cycle of 4 steps turns the motor 72 degrees. repeat this cycle five times to rotate the motor 360 degrees.

step1 = [1 0 1 0];
step2 = [1 0 0 1];
step3 = [0 1 0 1];
step4 = [0 1 1 0];

rotate motor

use write to output the sequence to turn the motor 72 degrees counterclockwise.

write(dq,step1);
write(dq,step2);
write(dq,step3);
write(dq,step4);

repeat sequence 50 times to rotate the motor 10 times counterclockwise.

for motorstep = 1:50
    write(dq,step1);
    write(dq,step2);
    write(dq,step3);
    write(dq,step4);
end

to turn the motor 72 degrees clockwise, reverse the order of the steps.

write(dq,step4);
write(dq,step3);
write(dq,step2);
write(dq,step1);

turn off all outputs

after you use the motor, turn off all the lines to allow the motor to rotate freely.

write(dq,[0 0 0 0]);