Connecting a MESA 7i76 card to JMC iHSV57 servos

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26 May 2022 15:40 - 26 May 2022 15:51 #243907 by knipknap
Hi,I am currently setting up my 7i76 with iHSV servos, and for the connections took hints from this thread  as well as this YouTube video , since the manual is pretty hard to follow and actually seems to have some errors in it (e.g. W8 is referred to incorrectly on page 24, as well as other inconsistencies listed below).

There are however some questions that I was unable to answer:
  • According to the 7i76 manual, if W1 is set to the left, field power does not need to be connected. The guy in the video on the other hand says it is needed, and that's also how it is in the connection diagram in the thread linked above. Is it needed in this situation?
  • Why would I want to separate field power? Is it to avoid interference problems like they are common with some machines like plasma cutters? Will it protect the board in case of shortage in the "field" cables/servo controllers?
  • According to the 7i76 manual, jumpers W10, 11, and 13 should be set to the right if the encoder is differential, and to the left if it uses TTL. In both, the video and the connection sheet, the jumpers are set to the left - but the iHSV use differential mode according to this site , so I would have set the jumpers to the right. Am I wrong? Is the manual wrong?
  • What is the right position of W6? According to the 7i76 manual: "Jumper W6 selects the pull-up resistor voltage, When W6 is in the UP position the 4.7K I/O pullup resistor common is connected to 5V, When W6 is in the down position, The 4.7K I/O pullup resistor common is connected to 3.3V"
  • I know how to connect STEP+/- (=PUL+/-) and DIR+/-. But how should you connect the other wires (ENA+-, PED+-, Alarm+-)?
  • How should I size the field power supply? Are 24V/4A (=~100W) enough? (I am using 4 servos. These have a separate power supply, of course.)
  • Should the servo power and field power share a common ground? I am unsure if my power supply is potential free.
  • Should the control cables to the servos use shielding + twisted pair?

And I guess a word of warning to others: The 7i76 manual seems to have an error regarding IP address configuration, saying "The 7I76E has 3 IP address options: Default, EEPROM, and Bootp, selected by jumpers W1 and W2." - but elsewhere in the document, W1 is referred to as a jumper to configure the power mode. That seems ... dangerous. I think W2 and W3 are meant here, as described on page 4.

Anyone knows the answers? I'm trying not to fry anything, this time...
Last edit: 26 May 2022 15:51 by knipknap.

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26 May 2022 16:15 - 26 May 2022 16:16 #243919 by PCW

According to the 7i76 manual, if W1 is set to the left, field power does not need to be connected. The guy in the video on the other hand says it is needed, and that's also how it is in the connection diagram in the thread linked above. Is it needed in this situation?
The manual says:
Note: When W1 is in the default left hand position, VIN is connected to VFIELD, so only VFIELD need be supplied to the 7I76E to power its field IO

According to the 7i76 manual, jumpers W10, 11, and 13 should be set to the right if the encoder is differential, and to the left if it uses TTL. In both, the video and the connection sheet, the jumpers are set to the left - but the iHSV use differential mode according to this site , so I would have set the jumpers to the right. Am I wrong? Is the manual wrong?
The manual is correct, these jumpers are set to the right for differential mode and to the left for single ended mode, HOWEVER
the 7I76E encoder input would normally be used for spindle feedback and would not connect at all to step/dir drives

What is the right position of W6? According to the 7i76 manual: "Jumper W6 selects the pull-up resistor voltage, When W6 is in the UP position the 4.7K I/O pullup resistor common is connected to 5V, When W6 is in the down position, The 4.7K I/O pullup resistor common is connected to 3.3V"
It makes no difference unless you are using the parallel expansion connectors. Normally it should just be left in the default
(5V) position

How should I size the field power supply? Are 24V/4A (=~100W) enough? (I am using 4 servos. These have a separate power supply, of course.)
1A would typically be more than enough

I will fix page 24 of the manual (the IP address select options)

Last edit: 26 May 2022 16:16 by PCW.

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26 May 2022 16:18 #243920 by PCW
In other news, I would like to personally punish whoever wrote the forum editor...
The following user(s) said Thank You: Todd Zuercher

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26 May 2022 16:30 - 26 May 2022 16:37 #243921 by knipknap
Haha, yeah, I was fighting with the editor as well for 15 minutes earlier...

Note: When W1 is in the default left hand position, VIN is connected to VFIELD, so only VFIELD need be supplied to the 7I76E to power its field IO

Ah ha. But I still need to feed 24V into TB1 and TB3? Should that be a separate power supply?Thanks for the other clarifications, that helps!
Last edit: 26 May 2022 16:37 by knipknap.

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26 May 2022 16:39 #243923 by PCW
The 7I76E has 2 separately powered sections (the logic section and field I/O section)
In most cases the can be powered by the same supply but in any case they both need
power.

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26 May 2022 19:28 #243940 by knipknap
Ok, I will try it that way, Thank you!

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