Which to Turn on First or Not

[Mr.Chips]

Have a questions and haven’t seen any comments on this, and it may be a mute point but I’m gonna ask any way. Don't want to loose the magic blue smoke after waiting for so long.

There are three components to my electrical system, and each is on a separate plug.
1. Computer.
2. 28V DC power supply.
3. Control box containing a PS for the 5V I need for the various components in the control box.

Does it matter in which order I turn them on?

Hager

[NC Cams]

Sometimes yes, sometimes no.

If your circuitry is designed properly, any DC circuits should fall naturally into a benign state when the circuit is not under power - any circuit that requires power to go benign is dangerous.

Empirically, I'd be inclined to turn on the computer first then the other stuff. You might find however, that your collage of stuff may want a different sequence.

I would hope that the three items would be plugged to the same power socket to prevent ground loop potenial problems. If the three are plugged into different outlets, you could let the smoke out no matter what sequence you use to turn them on.

[Al_The_Man]

A separate plug can mean a different circuit, although that should not ordinarily matter as long as the system is designed right, it is very rare to have any equipment that is not isolated from the 120vac supply, if all of the components are, then there should be no problem, it is important that any component in the system that need to be grounded should share an identical ground point, together with the incoming system ground, this ensures there is no potential between equipment, as this usually is the only common point between each.
There are two differing camps as to grounding and isolation, some believe in total power isolation between all items of equipment, and others believe in all power supplies, including PC all be made common to one ground point.
For many years I have used the second approach as it works for me.
But you generally have to adopt one or the other, mix and matching can lead to problems.
In most commercial systems, components like drives are disabled untill the Controlling element (CNC) is ready, this is known as orderly start-up, this avoids random action of servo's etc untill the CNC has controll, observation will tell if you need to do this depending on your system.
Al.

[Mr.Chips]

Originally Posted by NC Cams Sometimes yes, sometimes no. If your circuitry is designed properly, any DC circuits should fall naturally into a benign state when the circuit is not under power - any circuit that requires power to go benign is dangerous. Empirically, I'd be inclined to turn on the computer first then the other stuff. You might find however, that your collage of stuff may want a different sequence. I would hope that the three items would be plugged to the same power socket to prevent ground loop potenial problems. If the three are plugged into different outlets, you could let the smoke out no matter what sequence you use to turn them on.

Hmmm benign state, dangerious, ground loop problems, let the smoke out no matter what sequence you use to turn them on, OK you have my attantion!

I wholeheartedly admit that I am electronically challenged, yet I’m not in the 12 step program yet.

I have attached a drawing of my overall electrical system showing how they interconnect with each other. Also a little more detailed version of the electrical system and how it connects to the control boards.

Yes I am plugging all three components into a power strip.

Can you tell from these drawings if it would be in the “Benign state”?

What sequence should I turn them on?

Thanks
Hager

[Jay C]

Per Mach3's Mill user guide, it warns that PC's can sometimes output spurious signals on port pins as it boots. Thus to be safe:

1. turn the PC on first
2. load Mach3
3. turn on the breakout board
4. turn on your stepper power supply
5. turn on the machine spindle

At least that's my plan

FWIW,
Jay

[NC Cams]

Grounding is a critical issue when it comes to operating low and high voltage ciruits that interface with each other.

Let's hypothetically you have a 220 feed to your house and your computer is fed from one of the 110 volt legs and your power supply that feeds your CNC on the other 110 volt leg.

The PC is in the garage and the P/S is fed via an extension cord out of the kitchen window - things like that happen.

It is possible that the "ground" on the one outlet may NOT be at the same voltage potential as the ground on the other (resistance, loose wire, not grounded due to bad wiring, whatever).

The net result is that you COULD end up with a possibility of current flowing thru the ground leg from the PC to or from the P/Swhich should never happen.

This is essentially why they put GFI circuits into bathrooms anymore - to protect a badly grounded plug from seeking ground thru you via the water pipe.

Should current inadvertently flow thru the ground, you can toast stuff - especially low voltage stuff mounted thru parallel ports. How bad can this happen? Expensive bad.

We had some 3 phase powered 220 volt equipment that was wired thru some 440 to 220 step down transformers. A guy needed to hook up a PC to transfer data. So he simmply ran an extension cord across the shop and plugged in the PC and hooked a jumper cable between parallel port and the motherboard on some Fanuc powered lathes.

Did this to the first one and shortly afterwards, the lathe went DOA. Hmmm. That's strange. So he then did the same identical thing to the second one. You guessed it. Smoked the second one too.

About $3000 later later in repairs not to mention close to $20K loss due to unloading the now useless/inoperative machines, the machines were eventually returned to serviceable condition. But the contracts were lost and the machines now lie there looking/hoping for work 99% of the time. Why? there was a voltage differential between the ground of the 3 phase equipment and that of the extension corded PC and the difference caused current to flow thru the ground which ultimately fried the M/B on the Fanuc's.

When stuff is wired right, it doesn't make much difference in the order that it is plugged in. When the wiring is home brewed and not necessarily to National Electric code due to lame wire hacking and/or improperly grounded, you can let the smoke out with little regard for any/all good intentions.

If you don't know to do properl wiring, especially industrial wiring of single and 3 phase with interconnected or isolated transformer connected circuits, get help or learn how to check for proper grounding.

A licensed electrical inspection can save you big bucks in damage avoidance, or perhaps even save you your life, when it comes to making sure home and/or industrial circuits are properly connected.

Or, you can plug it in, see if the smoke flies and then wonder what the hell happened? But, by now, you already should know...

[BobWarfield]

They make a gadget called a "Delay On Make" relay that I have found useful for this problem:

http://www.thewarfields.com/cnccookb...CNCDrivers.htm

The delay on make will wait a predetermined length of time (potentially adjustable with a screwdriver) after it gets current before passing that current along. For my CNC lathe electronics, I use this to give the breakout board and low voltage stuff enough time to "wake up" before I let power through to the spindle or the DC supply to the steppers.

I put my E-stops in series with the same circuit, so that if any are tripped, the spindle and steppers immediately lose their power, but the computer stays live and doesn't need to be rebooted.

Best,

BW

[Al_The_Man]

Originally Posted by BobWarfield They make a gadget called a "Delay On Make" relay that I have found useful for this problem:

There is also special E-stop relays that condition the start-up/shut-down, there was a post just recently, someone was trying to give a couple away.
Al.

[Mr.Chips]

Originally Posted by BobWarfield They make a gadget called a "Delay On Make" relay that I have found useful for this problem: http://www.thewarfields.com/cnccookb...CNCDrivers.htm The delay on make will wait a predetermined length of time (potentially adjustable with a screwdriver) after it gets current before passing that current along. For my CNC lathe electronics, I use this to give the breakout board and low voltage stuff enough time to "wake up" before I let power through to the spindle or the DC supply to the steppers. I put my E-stops in series with the same circuit, so that if any are tripped, the spindle and steppers immediately lose their power, but the computer stays live and doesn't need to be rebooted. Best, BW

BW.

The link to your CNC electrical site is really nice, good sharp pictures and text detail. I would like to see your build, it must be as good.

I looking at your schematic of the “Delay on Make” it looks like it only delays at the initial power on. And doesn’t have any influence after that, when the steppers are starting, stopping, and idle. Is this correct?

If this is so then the sequence that Jay gave me is in essence a manual version of “Delay on Make” control. And would work for me.

1. turn the PC on first
2. load Mach3
3. turn on the breakout board
4. turn on your stepper power supply
5. turn on the machine spindle

Thanks

Hager

[BobWarfield]

Originally Posted by Mr.Chips BW. The link to your CNC electrical site is really nice, good sharp pictures and text detail. I would like to see your build, it must be as good. I looking at your schematic of the “Delay on Make” it looks like it only delays at the initial power on. And doesn’t have any influence after that, when the steppers are starting, stopping, and idle. Is this correct? If this is so then the sequence that Jay gave me is in essence a manual version of “Delay on Make” control. And would work for me. 1. turn the PC on first 2. load Mach3 3. turn on the breakout board 4. turn on your stepper power supply 5. turn on the machine spindle Thanks Hager

The build isn't done yet, so time will tell if it is as good. I tend to over engineer and take too long just to get things working because I enjoy learning and building as much as getting done. I guess that is the definition of a hobby.

You are correct, my circuit only delays initial power on and essentially automates the manual procedure you describe.

Al, the E-Stop relay sounds a handy gadget. I'll have to be on the lookout. Learn something new every day!

Best,

BW

[Mr.Chips]

Originally Posted by BobWarfield The build isn't done yet, so time will tell if it is as good. I tend to over engineer and take too long just to get things working because I enjoy learning and building as much as getting done. I guess that is the definition of a hobby. You are correct, my circuit only delays initial power on and essentially automates the manual procedure you describe. Al, the E-Stop relay sounds a handy gadget. I'll have to be on the lookout. Learn something new every day! Best, BW

Thanks BW.

I started building 3 years ago and finished everything except the electrical connections, gave up in frustration, people just didn't answer questions, they would tell a story or give me some 4th year electrical explanation. And I wanted to know where do you connect this wire to. Tackled it again recently and had some good help occasionally. If the diagrams are OK I'm ready to spin the motors.

I checked out your web site. all I can say is SUPER.
Thanks
Hager
Tucson AZ