[WoodSpinner]

I'm going to be adding a relay to my hobbycnc board to control my shopvac, the only cable I have is shielded. Is there any benefit grounding the shield for this aplication?

John

[Fastest1]

It wont hurt and wire is cheap.

[Al_The_Man]

You don't say which conductors? From Board to power relay coil, or relay contacts to shopvac power?
If you intend using shielded cable, there would be no harm done in earth grounding the shield.
Al.

[WoodSpinner]

You don't say which conductors? From Board to power relay coil, or relay contacts to shopvac power?
If you intend using shielded cable, there would be no harm done in earth grounding the shield.
Al.

Thanks Al, what I am refering to are from board to power relay coil.

I just didnt know if it would be worth the effort. I guess its a good time to arrange a star "-" point in my controller.

John

[Al_The_Man]

I guess its a good time to arrange a star "-" point in my controller.
John

Definitely!
If using a relay with DC coil a reverse diode should be used across the coil, if AC a R/C snubber should be used.
Al.

[Fastest1]

If you dont have the star ground now, then by all means do it. Also I misunderstood the electronics when I was building my HCNC Pro board and chased noise issues until I finally tied the Ve- into the star ground. Of course Al told me in the first or 2nd reply but I didnt understand it. It took me over a year of doing other things to eliminate noise til I finally did it. No problems since.

Thanks Al, what I am refering to are from board to power relay coil.

I just didnt know if it would be worth the effort. I guess its a good time to arrange a star "-" point in my controller.

John

[WoodSpinner]

If you dont have the star ground now, then by all means do it. Also I misunderstood the electronics when I was building my HCNC Pro board and chased noise issues until I finally tied the Ve- into the star ground. Of course Al told me in the first or 2nd reply but I didnt understand it. It took me over a year of doing other things to eliminate noise til I finally did it. No problems since.

I'm looking for a bus bar to use for my star connections at present, maybe I'll find one at radio shack tomorrow when I'm in town.

Sorry for having to ask what is probably a silly question to you guys, but what is this Ve- you refer to, would it be the - connection from the pp?

John

Definitely!
If using a relay with DC coil a reverse diode should be used across the coil, if AC a R/C snubber should be used.
Al.

I'll be using a C37 - Single Relay Board from cnc4pc

I think its a dc coil, does this need the reverse diode?

John

[Fastest1]

This not a silly question. This is the item I misunderstood the most. In my case IIRC the HCNC was a cap and rectifier set up for the power supply. I had to take a jumper from the - on the cap to the star ground. In my case the star ground is a simple bolt running thru my case (surface around the hole was sanded to remove any finish and to allow an electrical bond). Also I used a repurposed metal case to house my HCNC electronics whereas Dave specifies a PacTec enclosure from plastic.

[Al_The_Man]

The coil should have a reverse diode, 1n4003 - 7 is a candidate.

With the Ve-, strictly speaking all supply commons should be identified in a way similar to this.
Unfortunately the term Common on its own to describe all power supply reference point has become all too "common"
I have seen it used in documentation when in in fact there are more than one supply negative reference described as Common in this way which can promote confusion.
Also Earth is used indiscriminately, where normally it should be used when describing Earth Ground.
There is also at least four different drawing symbols to indicate the type of various Common reference sources.
Al.

[WoodSpinner]

The coil should have a reverse diode, 1n4003 - 7 is a candidate.

With the Ve-, strictly speaking all supply commons should be identified in a way similar to this.
Unfortunately the term Common on its own to describe all power supply reference point has become all too "common"
I have seen it used in documentation when in in fact there are more than one supply negative reference described as Common in this way which can promote confusion.
Also Earth is used indiscriminately, where normally it should be used when describing Earth Ground.
There is also at least four different drawing symbols to indicate the type of various Common reference sources.
Al.

Thank you Al, so you think I need to add a diode? and it should be connected to the power supply connections to the coil?

John

This not a silly question. This is the item I misunderstood the most. In my case IIRC the HCNC was a cap and rectifier set up for the power supply. I had to take a jumper from the - on the cap to the star ground. In my case the star ground is a simple bolt running thru my case (surface around the hole was sanded to remove any finish and to allow an electrical bond). Also I used a repurposed metal case to house my HCNC electronics whereas Dave specifies a PacTec enclosure from plastic.

I bought a 36v power supply from ebay, so if I understand correctly I should include a link to my power supply's - side to the star?
I thought that it and the pp's - were joined on the driver and didnt think it would be necessary.

John

[Al_The_Man]

The diode is connected 'reversed biased' across the coil connections, IOW the banded end goes to supply +Ve.
Al.

[WoodSpinner]

The diode is connected 'reversed biased' across the coil connections, IOW the banded end goes to supply +Ve.
Al.

Thank you Al,

I have some 1N4004s laying around, I'm make sure to add one.

John

[Fastest1]

Yes the - of the power supply should also tie into the star ground. In my case, I have all of my shields, the V- and the earth ground from my power cord all tied to the star ground. Oddly enough I am not sure about the PP's ground. It might be grounded thru the case. Again mine is metal and presents different issues than the plastic one suggeseted. Al will chime in on the PP's ground.

Thank you Al, so you think I need to add a diode? and it should be connected to the power supply connections to the coil?

John



I bought a 36v power supply from ebay, so if I understand correctly I should include a link to my power supply's - side to the star?
I thought that it and the pp's - were joined on the driver and didnt think it would be necessary.

John

[Al_The_Man]

The P.P. common is usually at earth ground, unless you use a lap-top.
The P.C. P.S. common is grounded through the M.B. ground plane mounting screws.
Al.