Cats love chasing prey. I'm sure the cat thought it a deal well worth while. You've been outsmarted by a cat. Lots of us are day after day. It's only human ego that insists we're smarter. In some ways we are, in some we're not.
NT
Just how do you mericans wire your buildings?
NT
The coax cabale shield is NOT grounded in 10base2. It's floating. If you look at the mating BNC connector, you'll see that it has a plastic insulator over the ground connection. Note the white insulators: Officially, one is suppose to ground the terminator at one end of the RG-58a/u coax run, which should take care of any real or imaginary power line leakage problem. However, if any of the "T" connectors along the coax run is disconnected, the ground is lifted, and there may be problems.
In the bad old daze when 10base2 was still in fashion, I installed and fixed a fair number of such installations. I've never been electrocuted, zapped, or tickled. I took no special precautions, like checking for voltage between the cable shield and AC ground. I guess I must have been lucky.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
This is the best squirrel proof feeder on the market, and at substantially less cost.
When the squirrel steps on the bar, it rotates down and blocks access to the seed trough.
The seed trough is compartmentalized, making it impossible for pest birds like starlings to dump the entire contents of the feeder on the ground as they are wont to do.
Sloppy.....
If it so good, why does it have a 1.4 our of 5 star rating? Maybe you should read the customer reviews.
Well, it is much easier to count a string of zeros than to count the long string of arbitrary numbers.
I got one, John, and I love it! My plan is to use it for logging mostly. It really has a nice, thoroughly done BLE application to use with it.
User manual is a bit wanting, but exploration of its capabilities is not painful.
Thanks for the link.
JohnS
Oddly, I haven't seen Pi written like this: 3.141,592,653,589,793,238,462,643,3 No zeros anywhere in sight.
If I multiply Pi by 1*10^6 3,141,592.6535897932384626433 becomes perfectly acceptable.
However, to be consistent, it should be written like this: 3,141,592.653,589,793,238,462,643,3 Ok, I'll grant that it's hard to read. So, I'll just add an extra decimal point making it easy to see. 3,141,592..653,589,793,238,462,643,3 There, that's better.
My theory is that our alphabet came from the Greeks and Romans, who wrote and counted from left to right. Our number system came from Hindu-Arab origins, who wrote and count from right to left. Actually, Roman Numerals are really screwed up, going both left and right at the same time. Somewhere, going back and forth between the left and right, and between big endian and little endian, we lost our way.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
We had one that had a switch on the hanger and a motor to spin the feeder. When the squirrel jumped on the feeder, its weight flipped the switch and round-n-round the contraption went until the squirrel was thrown off. They didn't tend to do it more than a couple of times.
This is not so much a problem in Americas.
In the rest of the world with higher distribution voltages, such as
230/400 V as in Europe, a single distribution transformer can feed tens or hundreds customers up to several hundred meters from the distribution transformer.In many countries, the TN-C-S wiring convention is used
In this system, four wires (L1, L2, L3 and PEN) leave the distribution transformer as TN-C and typically in each building entry panel, the PEN conductor is then split into separate PE (Protective Earth) and N (Neutral). In some system, the splitting of PEN into separate PE and N is done separately in each grounded mains socket.
With three phase loads and equal amount of single phase loads on each phase, no current should flow in the N wire (and in PEN towards the distribution transformer). The single phase neutral 50 Hz currents from different phases will cancel in the N conductor.
However, if the phase loads are unequal, some 50 Hz current will flow in the N conductor. However, with electronic loads with rectifier loads, there are large peak currents close to the positive and negative peak voltage. The conduction time is so short that the peak neutral current no longer overlap and no canceling occurs. The third harmonics (150 Hz) will add up from the different phases.
Now these strong 50 and 150 Hz currents will flow in the N and then into the PEN conductor. This current will also cause voltage drops in N and PEN conductor. The voltage drop in the PEN conductor between two customers will vary the entry panel PEN voltage and hence also the separate PE conductors within the two buildings.
If you connect a data cable between equipment in the two buildings each connected to the respective PE conductors, there can be several volt voltage different between the data cable shields of 50 and 150 Hz noise voltages. This is really problematic for unbalanced signaling such as RS-232, in which the signal ground is connected to local PE ground.
If you try to avoid this voltage difference by using very thick cable shields, part of the 50+150 Hz current will flow tough the cable shield instead o the mains PEN conductor between houses. This current can be several amperes and may also contain other frequencies from VFD loads etc. This strong shield current will cause induction into data cables.
So either you have a few voltage difference between data cable ends or a very strong current in the cable shield.
Using galvanic isolation and grounding the cable at one end only solves this problem.
No, it's isolated in every NIC. using a plastic bodied BNC connector.
photos here:
transciever data sheet:
--
?
You could be on to something here, Jeff. A potential Phd thesis for someone in the above. :)
-- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
+1, nice explanation of the problem. m
I just remembered one of my more amusing troubleshooting jobs. It was a small 10base2 network that looked like everything was installed correctly. However, it was very unstable and would crash or hang several times per day. I wasted a few hours chasing exotic problems and replacing good boards with other good boards. Eventually, I decided to walk the coax cable looking for physical damage. When I got to the far end, I found that the "grounded" termination wasn't exactly grounded very well. Instead of a ground clamp and wire, someone installed a 50 ohm terminator on a short chain. The chain looked like it was made for grounding, but obviously wasn't: Adding a hose clamp and running a ground wire to a better ground fixed the problem. I've seen the same thing maybe 3 times over the years.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
It would more likely be a suitable excuse for fighting a war between the Greek-Romans and Hindu-Arabs for control over the direction of writing and numbers. Plenty of other questions would need to be answered. Why do we add a comma every 3 digits, when our decimal system would suggest that every 5 digits would be a more useful separator? Why do we add separators only for base10 numbers, and not for binary, octal, or hex numbers? Why did we perpetuate the Hebrew, Greek, and Roman tradition of using letters for counting in base16 (hex) numbers, when it was obvious that base32 and higher would create an ugly mess? Like the screwed up QWERTY keyboard layout, some questions are best left unanswered for fear that the solution and transition to new and improved will be worse than the original problem.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Arabic is of course written from right to left, but numbers are entered with the most significant digits to the left.
One VT100 compatible terminal manufacturer thought that simple reversing the CRT horizontal deflection wires would solve this right to left issue. Unfortunately it also reversed the numbers with the most significant digit to the right :-).
Properly implemented terminals handled text and numbers correctly. Of course it required special processing for numbers. With such terminals, implementing bilingual data entry forms was easy. The Latin field labels at the left end of the line, while Arabic labels on the right end of the line. The operator could then enter the data values in the middle of the line, either with our digits or Indic digits depending of the operator's preference.
a few volts yes. I thought you meant a lot more.
NT
What, you mean I can't use bog chain for my building's grounding? Damn.
NT
IMHO "significant" means burning many RS-232 transceivers (1488/1489), not to mention RS-423 chips (which are supposed to be RS-232 compatible :-) on first generation VT220 terminals. Fortunately all RS-423 chips were burnt during the warranty period. The field service installed new chips on sockets and also installed external protection diodes cross the chips.
The voltage difference is significant, if it burns chips, no matter if the voltage different is a few volts or a hundred volts.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.