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Digital Output


frankm

Question

I am trying to generate a source of digital pulses for driving a stepper motor controller.

The controller needs pulses (logic levels) to make the motor move and also to dictate the direction of movement.

I have many USB-#### boards ( USB-1608G, USB-1024HLS, USB-1408, etc) that I am working with, but seem to be having the same issue with all of the units.

I am using a digital multimeter to try and confirm the logic level at the output of the board.

 

We also have many DASYLab licenses so that is the program I am using.  I have a ON/OFF switch connected to the digital output to simply turn the output on and off, while I am trying to confirm the logic level at the output.

I have used 10K resistors to pull up/pull down the outputs but still cannot reliably click the switch on and off and see the logic levels at the output.

At one point, it seemed to be working, and I was getting 4.2V at the high level, and 0 vdc at the low level.

 

I am reading the documentation for the USB-1024HLS about tying Port A, B, and C to either USB +5, or GND, depending on whether you want to pull up of pull down.

 

Do you have any recommendations as to how I can set up the simplest of circuits to test what I am trying to achieve?

I just want to be able to click on a switch to ON and see 4-5 VDC at the output, and click OFF to see 0 VDC again at the output.

 

Once I can reliable do this, then I plan to use a “generator” to generator a 10-20Hz signal that I will switch using a relay, and plan to use a PID control loop to drive the stepper motor based on an analog feedback signal.

I am just at the earliest of stages in this project and am starting with the simplest of circuits and then will work my way up to  a more complicated worksheet.

Any suggestions you have would be greatly appreciated.

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Hello,

The USB-1024HLS is a device that could be faster. DASYLab limits the speed to 100 updates per second, and each line counts as an update unless you set it to write the whole port as a number that is between 0 and 255. 

Regarding the logic levels on the USB-1024HLS, could you wire the pullup/pulldown terminals to +5 volts? This will ensure you get a logic high that is very close to +5 volts. See pages 3-5 & 3-6 in the user manual. https://www.mccdaq.com/pdfs/manuals/USB-1024HLS.pdf

Best regards,
John

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