Grounding on 16PC ???

[Dr_Aplet]

Hello forum friends,

i have a 16pc board that i am putting into a irrigation timer box.  should i connect my ground to the metal Heatsinc that the triacs are connected to?  i see that right and left side are isolated.  with that much metal it seems like it should be grounded as it could build up a charge otherwise.

[TheDucks]

54 minutes ago, Dr_Aplet said:

Hello forum friends,

i have a 16pc board that i am putting into a irrigation timer box.  should i connect my ground to the metal Heatsinc that the triacs are connected to?  i see that right and left side are isolated.  with that much metal it seems like it should be grounded as it could build up a charge otherwise.

I just looked at mine, built by LOR. NO ground on the Heat sink. 

Static? This is not (really) high voltage. Besides, if an insulator on a triac fails, it might fry traces. It would not hurt to measure to ground to see if there IS voltage where it does not belong. 

Sprinkler control box? Is it big enough?

 

[Orville]

4 hours ago, TheDucks said:

I just looked at mine, built by LOR. NO ground on the Heat sink. 

Static? This is not (really) high voltage. Besides, if an insulator on a triac fails, it might fry traces. It would not hurt to measure to ground to see if there IS voltage where it does not belong. 

Sprinkler control box? Is it big enough?

 

Depends on the box, the sprinkler control box that was installed at my late mother-in-laws would have had enough room to install 2 fully assembled CTB16PC Controllers inside it and still had a little room to spare.

[Dr_Aplet]

Below is a image of the board and box.  what is not on the board is a place for a ground.  I have neutral but not ground. I dont know how to embed images into this forum since the max total for file size is 4kb which is not possible to to make.

https://drive.google.com/file/d/1bZEWXZYHOcMKkeS2M-kSoVc_TelguY9B/view?usp=drive_link

 

 

[Dr_Aplet]

<img src="https://drive.google.com/file/d/1bZEWXZYHOcMKkeS2M-kSoVc_TelguY9B/view">

Edited November 19, 2023 by Dr_Aplet

[Orville]

22 minutes ago, Dr_Aplet said:

<img src="https://drive.google.com/file/d/1bZEWXZYHOcMKkeS2M-kSoVc_TelguY9B/view">

Here's what and where the grounds connected inside a RTG CTB16PC Controller. Well, I'll have to post a photo later so I can get it to a size I can load to the forum.

But, on my CTB16PC controller there is a seperate metal plate mounted at the bottom of the controller case.  There are 2 large screws with a nut on them, all green ground wires are connected to that metal plate. Ch.1-8 to one screw, and Ch.9-16 on the other screw.

Now this is in a PLASTIC LOR supplied case. And this metal plate makes absolutely NO CONTACT with the PCB Heat Sinks connected to the Triacs.

I believe you stated your box is metal, if so, you CAN connect all your grounds to the metal box itself. 

However, if you do this, make sure YOUR TRIAC HEAT SINKS ARE INSULATED FROM THE METAL BOX! 

I'd highly recommend plastic stand offs, because metal ones would still be connecting the heat sinks to ground, and even if you placed some form of insulating film under the heat sinks, metal screws could still become an issue. 

With plastic standoffs the screws holding them to the case on the bottom would be insulated from screws going through the heatsinks going to the top of the plastic standoffs.

This is about the safest way to ground your cords in a metal box.

[Dr_Aplet]

18 minutes ago, Orville said:

Here's what and where the grounds connected inside a RTG CTB16PC Controller. Well, I'll have to post a photo later so I can get it to a size I can load to the forum.

But, on my CTB16PC controller there is a seperate metal plate mounted at the bottom of the controller case.  There are 2 large screws with a nut on them, all green ground wires are connected to that metal plate. Ch.1-8 to one screw, and Ch.9-16 on the other screw.

Now this is in a PLASTIC LOR supplied case. And this metal plate makes absolutely NO CONTACT with the PCB Heat Sinks connected to the Triacs.

I believe you stated your box is metal, if so, you CAN connect all your grounds to the metal box itself. 

However, if you do this, make sure YOUR TRIAC HEAT SINKS ARE INSULATED FROM THE METAL BOX! 

I'd highly recommend plastic stand offs, because metal ones would still be connecting the heat sinks to ground, and even if you placed some form of insulating film under the heat sinks, metal screws could still become an issue. 

With plastic standoffs the screws holding them to the case on the bottom would be insulated from screws going through the heatsinks going to the top of the plastic standoffs.

This is about the safest way to ground your cords in a metal box.

I have a plastic box so i will make a post to gather the grounds to continue them through the plugs.  It seems unusual to be to not have the boards grounded in some way.  I work on a lot of medical equipment and almost all are grounded to the board.  Thank you all for your input. 

[Orville]

31 minutes ago, Dr_Aplet said:

I have a plastic box so i will make a post to gather the grounds to continue them through the plugs.  It seems unusual to be to not have the boards grounded in some way.  I work on a lot of medical equipment and almost all are grounded to the board.  Thank you all for your input. 

Just find a good piece of metal for your grounds.  Probably something about 2-3 inches wide and at least about 8 to 12 inches long. 

If you're using the LOR Grounded dangles, they won't be long enough to be centered or have them all on one side all together.  You need 2 screws through the metal plate and 8 grounded cords per channel bank side hekd down with a nut.

Edit: btw  I know what you mean  most PCB's do have a ground.  I built medical equipment at one point too, also built PCB's for Military contracts and NASA, they always had grounds on them as well.  But, I think the LOR boards are "specialized" in some way, so they don't need a ground on the PCB.  Yes, it does seem a bit strange, but it works.

Edited November 19, 2023 by Orville