Reliable Wireless Network

[richards]

Wireless networking and my Shopbot control computer caused me a great deal of grief a few years ago. On the day that I installed a Colombo 3hp spindle on my machine, I also installed a wireless network card in the Shopbot control computer. In the excitement of using a spindle, I totally forgot that I'd installed the wireless card. For several months, I had nothing but erratic performance from my PRT-Alpha. It would start a cut file and then, suddenly, it would move on its own, usually ruining the part. Of course, I blamed the spindle. Even after I had installed $750 worth of line, load and EFI filters, the problem persisted. Nothing worked. Late one night, while I was just air cutting and watching the machine, I noticed that the network icon turned red everytime the machine misbehaved. Lost communication! When I looked at the back of the computer, I saw that the network cable was disconnected from its port - and then I saw the wireless antenna. Five minutes later, I the the wireless card out of the computer, the network cable connected and eveything was good.

Well, I'm lucky enough to be able to connect the Shopbot to my home/office network via a standard CAT-5 cable. Not everybody has that luxury. Some 'botters have their machine in a separate building where it's impractical to run a network cable.

The solution is to set up a wireless network using a bridge and a station. The bridge, a Mikrotik RB433AH card with a R52 radio, is set to the AP-BRIDGE mode and connected to the wired network. The station, a Mikrotik RB411 card with an R52 radio is set to the STATION PSEUDOBRIDGE mode and connected directly to the network port on the Shopbot computer. The two Mikrotik routers form a wireless network, but to the Shopbot, everything appears to be a wired network. It works - without any glitches.

The Mikrotik routers are often used by WISP providers (Wireless Internet Service Providers) to provide Internet service to areas that don't have DSL or Cable. The Mikrotik routers can be mounted in "outdoor" enclosures to connect buildings without worry about the weather.

The RB411 router has a level 3 license, meaning that it can only be connected to ONE computer. If you have more than one computer in your shop, you'll need to use a router that has at least a level 4 license and you'll need to use STATION mode using MPLS instead of STATION PSEUDOBRIDGE. The RB411A, RB411AH, RB411AR, RB433AH all have at least a level 4 license.

Cost ranges from about $125 for the RB411 w/radio, indoor case and indoor antenna to about $200 for the RB433AH configured for indoor use. Outdoor enclosures and antenna would add $100 (or more) per router. It's not cheap, but for those who can't run cable to their shop, it is a reliable way to inter-connect the computers.

Manufacturers other than Mikrotik supply routers and radios, but I haven't tested any other brands.

Send me an email if this interests you (but be patient - some days I'm not able to spend much time at the computer).

-Mike Richards

[dlcw]

Having worked 18 years with computers (USCG, EDS, Microsoft - Mainframes, Unix, Apple, Windows, etc.) I can say that the following words should probably not be used in the same sentence:

"wireless" and "reliable" :rolleyes:
"computer" and "reliable" :confused:
"computer network" and "reliable" :rolleyes:

But that's just my opinion. :D

[ssflyer]

I find this discussion interesting - from stripping your computer to no internet access to no antivirus, etc...

I run my ShopBot computer with wireless internet, antivirus, and network sharing, and have never had a problem with collisions, reduced communication rate, interference, etc. I find my wireless connection to the internet and my development box to be invaluable. I transfer files from either end, and do quick web searches for help, or images/vectors.models. It allows me to easily sync my files between my main computer, or laptop, with the one running my ShopBot.

There are several things that can cause issues, but if you have a reasonable competent computer (I built the shop machine in 2005) I've usually found that it is a matter of insufficient shielding or grounding.

Of course every shop is different, so it can be a real bear to find out the real source of the problem. My wireless card on the shop machine is a real cheapie - $24 from amazon. They work in the 2.4GHz range, which shouldn't interfere, but sidebands can cause problems. Maybe the fact that my shop computer is away from the 'Bot helps, but I doubt it, since I run the wires overhead to the control box, which should make a great antenna! :rolleyes:

The only issue I've ever had with communication to the 'Bot was fixed by re-arranging the wire run from the steppers and spindle to the control box - I simply separated them as far as possible in the track, and made a rather haphazard mess under the 'Bot to the control box...

Don't know if this helps anyone, but it's my experience. I'd love to hear more on the subject, though - any info on what works for those with problems, helps us all!

Sorry for the long post,

Ron

[richards]

Using a standard Windows PC for process control can be tricky. Every user has his favorite programs that he likes/needs to run. On a normal home/office computer that wouldn't often be a problem because most of the time a home/office computer is waiting for the operator to do something, i.e. press a key or move the mouse. A computer used for process control is different. When a process is running, like sending 30,000 timing pulses per second to run the stepper motors, anything that disrupts those timing pulses can have dire consequences. Modems, wireless networks, standard networks and various other common devices and services can interrupt those timing pulses.

The only consistent problem that I've ever had has been wireless networking. As far as I can figure out, the wireless network card's software has higher priority than Shopbot's software when interrupt servicing is handled. I was able to duplicate the problem using a Netgear PCI wireless network card, a Netgear USB wireless network device and a D-Link PCI wireless network card. I've never had a problem with a variety of standard network cards that attach via CAT-5 cable, including the two network cards built into the motherboard on my computer.

Attaching a standard network device to a Mikrotik router board seems to have solved the problem of using wireless with my Shopbot.

[ed_lang]

I have been using NanoStation2 for my "bridge" between the house where the DSL line is and the shop and office. One NanoStation2 in the house setup as the AP, Access Point and the shop has a NanoStation2 setup as a Station. The office also has one NanoStation2 setup as a Station and then a router connects it to several devices. The NanoStation2 are about $80 each and come with a POE, Power Over Ethernet, device so you don't even need power close to the NanoStation2. They come in a case that is OK to mount outside and can cover a 20 or so mile range in clear site if I recall right. I have the power turned down quite a bit and use security to prevent me from supplying the local area with free Internet.

Works great for me, just Google NanoStation2 and pick your best price. There are bundles of three units for one price as well as buying them one at a time.

I have helped one other person close to me set up the same type of bridge and it worked great as well.

Ed

[richards]

Ed, the Ubiquity Nano units look good. I've never used them, but they are available locally. The next time I visit the local Streakwave store, I'll ask them for a demo. It looks like they cost about 1/3 as much as a Mikrotik unit configured for outdoor use.

(I use the Mikrotik units because the RB433AH is the unit that I use for my business customers as their main router to connect to the outside world. That unit has three ethernet ports and provisions for three radios. The RB411 series, which have only one ethernet port and provision for only one radio (except the RB411AR) are used as access points and stations wherever they're needed in those office environments. Sometimes I take the lazy way out because it's easier to be lazy and stick with a familiar family of devices rather than getting into the middle of a finger-pointing game when competing manufactures blame each other when devices won't communicate properly.)

[ssflyer]

I wonder if it would help to simply boost the priority of the SB3 process? Easily enough done from either task manager, or creating a shortcut to the program that does it...

Ron

[richards]

Changing the priority in the task manager may be a viable solution. Without access to the wireless driver and the Shopbot driver, it would be hard to know. The 802.11 standard doesn't allow a lot of latitude in timing, so a driver that closely properly follows the standard would need high priority.

In my case, the AP Point is only about 20 feet from the shop's computer, but the signal has to pass through a floor and two walls. Normally, the 2.4gHz B/G signal would be expected to handle that, but the Netgear program for the wireless card in the computer reported the signal as being low to extremely low. After using the 5gHz A band, which is a less crowded band (even though that frequency range should have more trouble passing through walls), the AP Bridge and the Station were able to communicate without dropping the signal. The standard network interface in the Shopbot computer was able to connect to the Station and the Shopbot computer acted as if it was hard-wired to the home/office network.

In a normal office environment, having occasional dropped wireless signals is not a big problem. Most of my office type software has provisions to handle those interruptions and the data is preserved; however, the Shopbot program is different. Because the computer generates the stepper motor pulse trains, any problem that delays timer interrupts can cause serious problems.

Changing the priority level of the tasks would seem to be an easy way to handle the problem, but if the wireless driver is constantly losing packets because it can't service the interrupt in the time allowed, those packets will have to be retransmitted and the problem can suddenly become multiplied. In essence, you might face the type of retransmital problem that can occur when you try to shoot a high frequency signal through trees where the leaves and limbs are being blown around by the wind, or when you try to shoot that signal between antennas in a rain storm or snow storm. Under those conditions, the signal can be reflected, and a deadly retransmission cycle starts. That type of problem used to happen at a customer's site. The local WISP operator used that customer's building to retransmit signals from a mountain side antenna to his roof mounted antenna. The customer's building had clear line-of-site to both antennas, but when the normally dry Utah weather was ruined by an occassional storm, throughput dropped to sub-modem speeds.

[danhamm]

If it wasn't for wireless, there wouldn't be much high speed up here in the Cariboo.
About 7 years ago I set up my own wireless link, 32 miles using Tranzeo Radios in a bridge point to point.
Tapped into a dsl Router on share.. and the only outages I have had are dsl routers, since that time have set up a few more for outlying places, they work well if you keep the radios to a minimum no more than 3 links and have a good line of sight, we use Google earths services such as line for point to point and then follow the line for elevations to see what height is needed tower wise.. 2.4 gig is fine up here not much for interferences, 5 gigs in the more settled areas as it can handle more connections and interference, they also make a radio in the low cell phone freq. that can handle a lot of trees and curvature of terrain, but its slower and narrow in bandwidth, they are good for extending telephone service to areas that can't get wire lines into..