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how to connect variable frequency driver with NI 9263

Hi guys,

 

I have a variable frequency driver to control brushless dc motors.In manual it is explained how to control the driver with a potentiometer. There is no problem for controlling with a potentiometer, however, now, I want to control it with NI 9263 +/- 10V analog signal generator. At this point, I confused about how to connect NI 9263 to the driver. It is explained how to connect it with a potentiometer as below,

     

  1) First ,you link the COM to EN

  2) and link the COM ,.SV ,5V to the potentiometer

  3) when you link the power , the scrn will show the P000 then you need use the _ button change the 01 to 00

 4) then you will use the potentiometer control the speed

 

I have attached a photo of the driver.

 

edit: "SV" abb means "analog signals" written in the manual of the driver..

 

Egemen
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Egemen,

 

Most likely you can connect the COM on the driver to COM on the NI 9263 and SV to one of the AOx lines.

 

Check the manual of the driver to see what the input impedance is, or how much current is required at the SV input. The AO lines are limited to 1 mA.  If the driver will work with a pot of 10000 ohms or more, the NI 9263 can probably drive it. If the pot is required to be 1000 ohms or less, then the current drive may be an issue.

 

Lynn

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Thank you Lynn.

 

The manual that I have is not explanatory well. It has no knowledge about ohm of the pot. What is ohm of a pot basically? Can I measure it or get the knowledge of it? Or is it enough to connect NI 9263 to the driver and just do a trial? If the driver requires more than 1 mA to drive with analog voltage signal, can I adapt it to drive with 1 mA via adding a device or sth like that? I have asked a lot of questions, sorry for that but actually, I am far away from electric/electronic stuff, that's why it happened. Thanks in advance.

Egemen
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Egemen,

 

I will give a very basic discussion of resistances, pots, and input currents.  This is based on your comment about being far from electric.electronic stuff. If I have oversimplified, it was in an attempt to help you understand.

 

The resistance of any conductive device, like the pot, is measured in ohms. One ohm is the resistance of a device which has one volt across it when one ampere flows through it.

 

Potentiometers (pots) are adjustable resistors with 3 terminals. One terminal is connected to each end of the resistive material and the third terminal is connected to the movable part called the wiper. As the wiper is moved from one end ot the other, the resistance between the wiper and the end terminals varies. One part increases while the other part decreases.  The pot can be considered to be electrically equivalent to two resistors in series with both resistors variable. Two resistors in series are sometimes called a voltage divider. The voltage at the junction of the two resistors is a fraction of the voltage connected across the ends. The resistance of a pot is the total resistance measured between the fixed ends wiht nothing else connected to the pot.

 

Consider your motor driver. To use it with a pot the +5 V terminal is connected to one end of the pot. COM is connected to the other end of the pot. The wiper is connected to SV. As the pot is adjusted mechanically the voltage at SV will vary from COM to +5 V. However, the SV input also behaves as though it has an internal resistor connected from SV to COM. That resistor is connected in parallel to the corresponding part of the pot. Without getting into the mathematics of parallel resistances I will point out if the resistance of the internal resistor is comparable to or lower than the resistance of the pot, then the voltage will not vary in a nice linear manner as the pot is adjusted.

 

When you try to use the motor driver with the NI 9263 the votlage output  of the 9263 must flow through the internal resistance of the driver.  The driver can only produce 1 mA. At 5 V a resistance of 5000 ohms will draw 1 mA. If the input resistance is lower than that, then the NI 9263 will not be able to control the driver over the full speed range.

 

Somewhere the manufacturer of the motor driver should either specify the resistance range for the external pot or the input resistance (or input impedance) at the SV input. Otherwise, no one would know how to connect it.

 

You probably cannot measure the input resistance directly. If you have a voltmeter, try this simple test. It can be done two different ways, depending on what you have available.

 

1. If you have a resistor with a value between 1000 ohms and 100000 ohms, connect the resistor to the positive end of a 1.5 V battery (AA cell, C cell - whatever you have). Connect the negative end of the battery to the COM terminal of the driver. Also connect the negative input of the voltmeter to this point. Connect the other end of the resistor to the SV terminal. (Caution! If a motor is connected to the driver, it may start running!) Make two measurements with the voltmeter. Measure the voltage at the positive battery terminal and at the SV input.

 

If the voltages are within a few percent of each other, then you can likely use the NI 9263. Otherwise a more careful calculation will need to be made.

 

2. No resistor. Set your meter to measure current, probably on a milliampere range. On most meters this requires connecting the leads to different inputs than for measuring voltage. Connect the negative end of the battery to COM. connect the positive end of the battery to the negative lead of the meter. Connect the positive lead of the meter to SV. (Caution! If a motor is connected to the driver, it may start running!) Record the current. If it is too small to measure, you may need to set the meter to microampere ranges.  

 

If the current is less than 0.3 mA, then you can probably use the NI 9263.

 

Why 0.3 mA? Because the test is run with a 1.5 V battery. At 5V it may draw more current.

 

Lynn

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Hi Lynn,

 

I am working on the connection of the driver now. As you said, I wired COM of NI 9263 to the COM of the driver and the 5V output to the SV port of the driver. As explained for pot connection, do I have to shortcut between COM and SV ports on the driver? Do you have any idea? There is no info about this on the manual 😞

Egemen
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Egemen,

 

This is very basic electrical connections. Perhpas you should get an electrical technician to assist you so that you do not damage any equipement get anyone hurt.

 

Here is the way you connect the motor driver to a pot:

 

Motor Driver with Pot.png

 

Here is the way to connect it to the NI 9263:

 

Motor Driver with NI 9263.png

Note that n/c means "no connection." You do not connect anything to the 5 V terminal on the motor driver.  Of course you could use any of the AO lines you choose, not just AO1 to connect to the SV input.

 

Lynn

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I mentioned about the shortcut between COM and SV, but it must be between COM and EN. I tried it after you asked taking the risk. I have wired COM to COM and AO to SV as you mentioned and shortcut on the driver ports COM to EN. In this way, it works. Thank you very much for your help. However, when I drive the compressor under load driver stopped and pops up errors. I will ask about this errors to the manufacturer.

Egemen
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