PWM to continuous voltage

[David1982]

Hello,

I am using maxon motor control PWM servoamplifier ADS 50/10 for my application. It has PWM frequency of 500kHZ. I want to generate continuous, instead of PWM signal, (2-3VDC) at the output . Is it possible to do through software or hardware?

Thanks

[Jochen]

PWM is the recommended way to control DC motors, as this reduces stick-slip effects and other issues. I don't know the drive that you are talking about, but typically the power signal generation is done in hardware (or maybe in the firmware of an FPGA or DSP and there is typically no way to change this. If such a feature is available or not depends solely on the design of the drive, so you should contact Maxon for this question.

Regards,

Jochen Klier

National Instruments

[David1982]

Thanks Jochen for reply.

I am no more intersted to get a continuous signal. However, I have additional questions. How can I measure pulse frequncy and width using PCI 6040E and BNC 2090. I am using labview 8.5.1. The voltage output of the said PWM servo amplifier is plus minus 15VDC. Which I have reduced to plus minus 7.5 V using  resistors. My application is just a wire and not a motor, the wire has resistance of 10 ohm only.  Also can I control the pulse frequency, width and level through software? The data sheet for the amplifier I am using is attached. The PWM frequency and  switching time mentioned in the datasheet are 50kHz and 500 microseconds. Can I change those through LabVIEW?

Many thanks.

[Rich_Silley_NIUK]

Hi

In response to your first question about the frequency and pulse width measurements, please see the DAQmx examples. Assuming you have the DAQmx driver installed (see here if not), from LabVIEW go to 'Help >> Find Examples'. Then, form the 'Browse' tab, navigate to:

Hardware Input and Output >> DAQmx >> Counter Measurements >> Digital Frequency

Hardware Input and Output >> DAQmx >> Counter Measurements >> Period or Pulse Width

The examples here should give you what you need to get going with these types of measurements.

With regards to your question about programatically controlling the servo amp from LabVIEW, I am not sure if this is possible. I have only had a very quick look at the spec sheet and it is clear there is no communications bus present (eg. serial). This means the only way to configure it is will passing raw signals to the inputs of  the amp. If you find that the PWM frequency is set by a voltage level, then you could generate an analogue output from your 6040E that controls the frequency. If it is one of the potentiometers that set the frequency then this will be a lot more difficult. 

I hope this information helps.

Rich

NI | UK