CNC Shark Forum

Hello all,

I just moved to Florida, and since I have been here have lost momentary power a couple of times, ruining my projects.

I figure a UPS would be my best bet, but what size? I run a porter cable 890 series 12 amp router and the cnc 60th anniversary shark as well as a old pc...

Thanks!

Tony:

Power issues can be nightmareish with these machines, to be sure!

The Biggest issue is going to be powering that router. Not something your typical computer-oriented UPS is going to do well, if at all.

Because of the spinning router being a motor, you're going to have a hard time getting enough. 12A @120VAC = 1440W. UPS unit capacity is rated in WH (Watt Hours), which is how much BATTERY charge they hold. For the PC and Controller (and thus steppers) you could probably get by with a "standard" 0.5-1.0 KVA unit. But, to handle the router, you're wanting something that can supply somewhere in the 20A @ 120VAC range, and that's a rating of how powerful the converter from battery-to-line-voltage is. Converters that can supply 1.5 KW and up are NOT cheap. Typical 1.5KVA units can only support a load in the 500+ Watts. For example, here's one:

http://www.apc.com/shop/us/en/products/ ... /P-BX1500M

That's a 1.5KVA unit, but can only power devices up to 900W, barely 2/3 what just the router will take, never mind the controller and PC.

My personal recommendation is to NOT put the CNC on a UPS, but rather just a good power filter. Why? Because overall, in the times it's happened to me, it's "best" that when a power hit occurs, the machine just stops in its tracks. If you keep the controller powered, then it's going to move the spindle, and if you can't afford a "real" UPS for that spindle/router, then it's going to move a non-spinning bit. At least if it just stops, you can restart it, likely without anything but lost time.

Now, if you had a 120V non-router spindle motor, you'd have a much better luck with it, since the Variable Frequency Drive (VFD) isn't an inductive load in the usual sense, like the router is. UPS devices do not like inductive loads. And, IIRC, my VFD shuts down the spindle completely when it detects a brownout (low input voltage) or a blackout (total dropout).

And, just because, "pure sine wave" UPS units are better than the modified-square wave units. That is, they produce less powerline noise, it's better for modern electronics in computers (especially power-factor correction circuits). But, they do tend to cost more.

In my case, I have a UPS on the computer, the network, and the Silex USB-over-ethernet device server. The controller is on a good power strip with no UPS, and the spindle is directly connected into the 208VAC power line, no support in the middle.

For the computer, an easier option might be to use a laptop. It has the bonus of taking up less space, too.

I'm with Rando here. Powering your router is the bigger problem. The control box should be able to continue even if it loses contact with the PC, so I'm not sure backup PC power is even critical.

If you are running a business or are a very serious woodworker then a small backup generator (typically one that automatically kicks in when there is a power outage) might be the best option. But there may still be a small delay caused hiccup in the carving.

Just a thought!

Have a Great Day!!!

Be SAFE around those AWESOME machines!!!

Sharkcutup

sharkcutup wrote: But there may still be a small delay caused hiccup in the carving.

That "hiccup" would reset the control box, which would halt any carving in process unless you have a way to keep uninterrupted power on the control box.

Kayvon wrote:

sharkcutup wrote: But there may still be a small delay caused hiccup in the carving.

That "hiccup" would reset the control box, which would halt any carving in process unless you have a way to keep uninterrupted power on the control box.

totally, Kayvon and Sharkcutup. I wonder if it would work to have a UPS for the non-motor loads AFTER the generator, so that first second or so wont kill the controller. Probably a good idea anyway, since generator power isnt typically the cleanest, electrically. That way, spindle rundown would be the primary issue. Not as much a problem in wood, but I'd cringe if it happened on some hard roughing. Even if the bit doesn't break, it would call for at least a check of alignments, for me, anyway.

If you could get <0.5s switchover, that might be okay (with the UPS), but faster switchover is likely exponentially proportional to cost . You can get <1 cycle (16ms) switchover if the generator is running constantly....

I wonder if one of those Tesla PowerWall units would have enough ooomph? Hopefully it won't become fooom!

Thom

Thanks for the good info. I agree I would rather have it stop in its tracks rather than running without the spindle running.

Thanks!

I used to have a system, before UPS units were available, that had to live in a similar power situation: good, but would ocassionally have a glitch, and having the system continue would cause potential damage. And for short drop-outs, the power could cause the system to operate in unpredictable ways. To solve this, I got a "contactor", which is a high-current "relay". It takes like 120VAC into a low-current coil, and the relay contacts were huge. The 220VAC model had 3 switched "poles". Since I was only switching 120VAC, I essentially had a spare set of contacts. What I then did was wire the coil energizing circuit through one of those sets of normally-open contacts. To energize the system, there was a momentary switch parallel to those contacts. Pull the switch and current flows to the coil. Once the contactor is "ON", that set of contacts maintains the coil circuit, so it stays energized. The other two sets of contacts were used to switch the load.

This worked really well because if a power-glitch came in that was enough to even momentarily let the contacts open, it would NOT re-energize. And so with that first hit to the power-line, the whole system went dead and didn't even try to come back on. Worked great. Took a bit to draw in PowerPoint (about all I have at the moment), but below is a schematic of how I remember it. Note that NC and NO mean Normally-Closed and -Open (NC can also mean No Connection).
The contactor is pretty cheap, too, $15 to $35 depending. Be sure to get the 120VAC coil.

https://www.amazon.com/Eaton-C25DND330A ... tor+3+pole

For the purposes of this application, the difference between a "contactor" versus a "relay", even of the same current spec, is that the contactor has positively-engaging contacts, that wipe against each other to make a new bare-metal contact each time. Also, they have better arc suppression on the contacts so they won't someday weld themselves closed. They're the right thing; a general-purpose relay is the wrong thing for this kind of high-current application.

To the above you can add line-voltage indicator lamps so you can tell if input and output power are on. Also, a fuse/circuit breaker in the high-current circuit is a Good Idea(TM).

Regards,

Thom

Anyway, just an idea.

A little pricey, but a Tesla Power wall can be a great investment, especially if your power rates vary between peak and off-peak consumption times.