NI PCI7344 host +5V for ORIEL motor encoder

[Q_ND]

I have 3 ORIEL motors (Model: 18277, 18215) to drive an x-y-z station. All of 3 motors require +5V 24mA for the Mike encoder. Right now, the +5V pins connected through an amplifier board to the "Host +5V" pin#59 in Motion I/O Connector of PCI-7344 board. But the MAX couldn't read the current trajectory position, which means the encoder didn't work at all. I measure the voltage connected to the encoder, when one axis connected, it's 3.8V, when two axes connected, it's 1.7V instead of 5V. I am wondering why the Host +5V from the PCI-7344 couldn't be used to drive the encoder? I look the manual of PCI-7344, and found "Caution: The Host +5V signal is limited to < 100mA and should not be used to power any external devices, except those intended in the host bus monitor circuits on the UMI and drive products." What should I do to fix it? Thanks.

[DJ_L.]

Hey Q_ND,

If you are wondering why the Host +5V connection from the PCI 7344 could not be used to drive the encoder, then the answer would be that the Host +5V connection is the host computer’s internal +5 V supply. It is used to detect when the host computer is powered and as an interlock to shut down external motion system components when the host computer is turned off. Like you found in the user manual, it should not be used to power any external devices, including encoders.

Therefore, in order to fix this, you should really be using an external power supply to drive your encoder.

Let me know if you have any further questions. Thanks, and have a great day.

Regards,
DJ
Applications Engineer
National Instruments

[Q_ND]

Hi, DJ,

Thank you for your reply and suggestion. Then, my current concern is: can I use the +5V and GND of the PC power supply to drive the encoder? The ground for the encoder is pretty tricky in order to minimize the noise. The PCI 7344 is connected to an amplifier board to drive the motors, and the amplifier board is driven by the +12V from PC power supply, there is a +5V is spare. If this 5V is feasible, I may rewire them. Thanks again.

Best,

Q @ ND

[DJ_L.]

Hey Q @ ND,

You can use the +5 Volt from your computer's power supply to power your encoder. You will have to look into the specs of your computer and the specs of your encoder to determine if this will work or not. The computer's power supply should have enough current to drive your encoder, but that will be dependent on your computer's specifications. I can only tell you that the PCI 7344 will not be able to drive your encoder.

Good luck with this, and have a great day.

Regards,
DJ
Applications Engineer
National Instruments

[ChadE]

Hello Q @ ND,

Both of NI's UMI's (Universal Motion Interfaces), the UMI-7774 and the UMI-7764, supply power for powering encoders. I suggest that you use one of these in your solution.

Regards,

[AnalogKid2DigitalMan]

I would suggest a stand alone supply (even a wall wart might do) rather than using the PC's 5V. PC supplies can tend to be noisy (they are switchers) and a lot of high frequency signals with fast rise/fall times are running around in there.

[Buechsenschuetz]

We have been using the 5V supply of the host PC as power supply for our subsystems for some time, The subsystems included digital circuitry and encoders, and we had no problems related to the PC power supply. You should always use a suitable fuse since the 5V rail of a PC can supply 10 or 20 amperes - a short circuit on your system may blow up the PC power supply and wiring of your system.

A wall transformer is not a good solution, Usually they have no regulated output, and if they have it sometimes is poorly regulated. Power supplies with common output voltages such as 5VDC and 12VDC and good regulation are available from several manufacturers.

[fumitake]

How can I do to fine out the diagram about tha CVI7344  I/O ? And read or write the data between the program and the 7344 ? Example : use the C language to read the data or send the order to perform.

[jamrite]

Hi Fumitake,

You can find the PCI 7344 pin-out on page 28 of the user manual for the card. Here is a link to the manual: http://www.ni.com/pdf/manuals/370838a.pdf.

If you want to use CVI to write programs for the 7344 card, please look at som of the examples that ship with the NI-Motion driver. These are typically installed at "C:\Program Files\National Instruments\CVI<version number>\samples\Motion".

Please let me know if you have any other questions.

Thank You,

Jaidev Amrite

National Instruments