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Generate PWM with 24V signal

Hi,

 

I have the following equipment:

- PXI-6259 M-Series 

- SCC-RLY01 1-channel relay module 5A 30VDC

 

Can I generate a PWM signal with 24V amplitude?

 

I read the tutorial "Pulse Width Modulation (PWM) Using NI-DAQmx and LabVIEW" but this is done with counters that give a 5V signal.

Any help on this?

 

Thank tou! 

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Is your SCC fast enough to handle the PWM?

It will fit to your DAQ output, however mechanical relays are a bad choice for PWM. You should use a solid state relay. 

Do you need the 24V as a power output or to control another switch/amplifier?

What PWM frequency do you want to use?

 

 

 

 

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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In the SCC specifications I have:

Switching time - Operate - 5ms (10ms max)

Switching time - Release - 4ms (5ms max) 

 

I need the 24V to control a solenoid valve.

 

I need to use 100Hz for the PWM frequency.

 

Thank you! 

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At 100 Hz (10 ms pulses), you would have a very poor PWM signal.  By your specs, typically 9 ms out of 10ms will be used for switching time.
Randall Pursley
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100Hz for a relay (and your valve) is hard and due to the delays, bouncing, jitter I would claim it a bad solution. However, it's not impossible. 

Even more you have to look at the solenoid valve! Do you have a datasheet/spec of it? 

What medium? Air, water .... at which pressure ?  Needed flow rate range and resolution, ripple?   

 

 

Another point is the live time of your mechanical relay and valve. Consider 10E6 cycles live time at  100Hz will give you only 166 hours runtime!

 

My suggestion: Use a small solid state relay to drive your valve. Depending on the solenoid/valve spec I would use a simple optocoupler with  a transistor and a free running diode. In principle a rebuild of your relay driver (see schematic in the NI doc) or replace the NI relay solenoid with the valve solenoid and use their driver circuit 😉  and go down to one pulse every 5 seconds.

 

If you tell us more about your goal, maybe I or someone else can make a better suggestion.

  

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Hi Henrik,

 

I have a similar Question related to driving the Brushed DC motor of a small air pump.

 

The pump need to be controlled with a ramping up and down of voltages using PWM with a max PWM voltage of 24VDC.  

 

I would like to control the pump with an Arduino or similar device that operates PWM outputs at 5DVC.

 

Is there a rapidly switching (~15kHz) solidstate relay that you might recomend using to supply the higher voltage and current to the air pump motor?

 

Best Regards,

 

-Andy

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Andy,

 

It would be pretty easy to implement with a 9474 inside a 9171.  This would give you eight channels with microsecond resolution at the voltage level you require.

J Newk
Systems Engineer
National Instruments
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Andy,

 

Most solid state relays are not that fast. I would recommend a suitably rated power MOSFET or IGBT and a MOSFET driver IC. The drivers can easily be driven by the 5 V logic signals. These devices are designed for switching power supplies, motors, and similar circuits working to 100 kHz or faster.

 

Lynn

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