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Can NI 9474 be used to control injectors and 4-pin fans?

Hello,

 

I am trying to control 3 banks of four 4-wire, pwm fans, as well as 3 fuel injectors. I want to use pwm to control both the fuel injectors and the fans.

Here is the fan I am trying to use: http://www.mouser.com/ds/2/471/9SG1224P1G01-10596.pdf

 

My first question - can I connect the digital output of this module directly to the control wire of the fan?

I believe the NI9474 is a source, so it provides cuurrent, and the fan spec says that it acts as a sink at 1mA @ 0V.

Can I just connect the 4 control wires from a bank of fans into one digital out?

 

If I supply 5V to the NI9474, do I need to add a resistor or something in line to the control wire?

 

Would the NI9474 be capable of outputting 6 different pwm signals at different frequencies?

 

Thanks,


Mitchell

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Can I connect the digital output of this module directly to the control wire of the fan?

You can connect the module's digital output directly to the fan control wire.

 

Can I just connect the 4 control wires from a bank of fans into one digital out?

As long as the current demanded by the fan bank does not exceed 1A, you can connect it to a single channel. If the current is higher at any point, you can simply connect as many channels in paralel to the load as required to go up to the load current demand.

 

If I supply 5V to the NI9474, do I need to add a resistor or something in line to the control wire?

You don't need to add a resistor to drive the fans.

 

Would the NI9474 be capable of outputting 6 different pwm signals at different frequencies?

The NI 9474 cannot do that by itself. If you have it connected to a compact DAQ chassis, you cannot either as the chassis will provide just one Digotal Output Timing Engine. The only way would be using a compact RIO chassis to take advantage from the FPGA.

 

You can find additional information the document liked below:

http://www.ni.com/pdf/manuals/373509e.pdf

Camilo V.
National Instruments
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Hmmm.... taking another look into the last question, there might be a workaround. You could try to do a multi channel task and generate a different waveform for each channel (this might be what you asked, I think I didn't fully understand the question the first time). The sampling rate would be the same for all the channels as it would be a single task, but you can for example play around with the Square Waveform.vi and the Analog to Digital.vi to generate custom waveforms for each channel, build an array of those waveforms and wire that array to the DAQmx Write.vi (if using a compact DAQ chassis).

Camilo V.
National Instruments
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Caraval, I appreciate your insight. I did some research on FPGA and I think that's the route I am going to take. However, I think you missed a subtle part of my question.

 

I am intentionally buying 4-pin fans with the pwm hardware inside of them. The fans have 2 wires for power (always on), 1 for tach, and then 1 for control. It is my understanding I have to output a digital pwm signal to the control wire to control the fans. The spec sheet for the fan lists a current spec for the control wire (http://www.mouser.com/ds/2/471/9SG1224P1G01-10596.pdf). So I can just use FPGA to create the waveform, but what module would I use to output said waveform to the control pin of the fan? Or am I missing something?

 

Thanks for your help so far!

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bieniekm,

 

You can use a Compact RIO chassis (cRIO) to take advantage from the FPGA, but you will need a module to actually do the output. In this case, as the NI 9474 module can be used on the cRIO chassis, you can do the output with it, as well as with any other digital output module able to reach the required voltage.

Camilo V.
National Instruments
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Hi

Similar issue-

I have a 9474 module in a 9074 cRIO.

I need to generate a 20Hz PWM signal.

I am already using my FPGA for timing tasks.

Is there a NON-resource intensive way to run the 9474 off of a custom clock source to give me my 20 signal?

 

Thanks

joe

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You should just be able to build and run a real time program to perform that task, especially if it is only 20 Hz.

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But in PWM mode, the NI9474 will run at 1Hz or 50Hz (and other higher frequencies).  I need PWM at 20Hz,

The application has too many other needles, gages, plots, etc to keep updated.

I tried to run a brute force, flat sequence structure (a timer for "period" and another for "ON" time).

The PC (scan mode) and the FPGA (FPGA mode) are not allowed to do other tasks during the wait periods. 

I'm at a loss...

joe san

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Hello Joe,

 

The PWM mode makes easier implementing a pulse train using scan-mode, but just as you mentioned, it only allows using the predefined frequencies (see PWM-Specific Features) . If you need a different frequency, you will need to either use the FPGA or scan-mode without the specialty digital option.

 

Agamemone is right about scan mode being able to provide a PWM of 20 Hz with a very high accuracy, but you will need to do it manually. Please refer to this example and this document (see 2. PWM). I actually like the second option better because it is fairly simple and just as effective.

 

If you don't need the duty cycle control and just want a constant 50% high / 50% low pulse train, you can just remove the High Pulse and Low Pulse controls from the article's example and use a constant value on the loop timer (notice the period from the while loop should be half of the period from the expected PWM).

 

Hope it helps.

Camilo V.
National Instruments
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