schematic symbols
boneheadradio
Posts: 20
Im an old electrician and electronics tech.
while reading the schematic symbols page the image for the wires not connected is actually incorrect.
and could be very confusing to a new reader.
the following link contains the correct image .
https://www.allaboutcircuits.com/textbook/reference/chpt-9/wires-and-connections/
you would not believe how many students end up burning their projects up by misreading a schematic especially those schematics that are not clear enough to read
Comments
This is an old gripe of mine as well, and like the author, I use the “hybrid” notation method too. The worst offenders seem to be the small Taiwanese companies. I’ve seen different notational styles on the same data sheet. Really makes you appreciate the clarity and uniformity of the old TI datasheets.
yeah even though I'm retired now I still teach classes in Ham radio building (Not super complicated) but most of my students have never held a soldering iron before.
while I'm teaching them to be careful with reading a schematic many times they miss the difference between between the hybrid and the old standards
and its rough to keep them from getting discouraged when they make a mistake
many times they download a schematic to build from and their not very clear due to small size, When they expand or zoom in them the images get fuzzy and a hybrid notation can be easily misread
On pickiness, where is this offending page?
Deleted. After reading Evan’s question I can see he is talking about a page that wasnt provided in the original post. Good question.
It still shows in the OP for me:
https://www.allaboutcircuits.com/textbook/reference/chpt-9/wires-and-connections/
this was the page.
https://learn.parallax.com/support/reference/schematic-symbols
while its listed as such in a clear diagram a trained individual can make the distinction but it can confuse a novice.
i actually had college courses on it when i was in the navy (long, long, ago) (yeah Im an old fart)
I like, and will continue to use, the "newer convention" -- no jump-overs.
-Phil
I thought, as shown of the Parallax site, where a junction exists, it should only be 3 wires. If you have 4 wires joined (like a crossover) these should be joined as two sets of 3 wires. This way, even if you cannot make out the dot, you know 3 wires must be joined, and 4 wires should not be joined but are instead a crossover.
While on the subject, polarised capacitors can also be drawn with a +ve rectangle and straight line for -ve.
And if you look at some drawings, the resistors are drawn as rectangles with their value inside, and capacitors (non-polarised) as rounded rectangles with their values inside. This has been done to conserve space.
But don't get me started on the bad designs recommended to replace gates etc as just boxes with unknown symbols!
Cluso99,
Polarized capacitors are funny because the positive pin (+) is shown on the schematic but the negative pin (-) is identified on the part.
Most people know that + and - are opposites so it's easy to figure out.
In American schematics we make one of the sides curved but I can never remember whether that's the positive or negative pin.
@Genetix
I am fairly sure American schematics (well at least those from Singer Computers) in the 70’s used the rectangle for positive and a straight line for negative on polarised caps.
In my own experience, the curved side of the symbol is intended to denote where to connect the capacitor to the "nearest-to-environment" potential, and it refers to the "shield" (the outermost layer) of many kinds of non-electrolytic, "non-effectivelly-polarized" capacitors, such as film-foil ones.
Many of them (IMHO, the good ones) have a printed dot, strip (or diff-collored side) marking, near the terminal to where the "external shield" is connected, by construction.
Old examples can be found as paper and wax caps, used in tube radios and tv sets. Recent ones can be found in fancy capacitors used for "audiophile-grade" audio amplifiers, but they are not limited to such kind of application.
There was ever a lot of dispute, about the real effectiveness of following that line of thinking, when using non-polarized capacitor; kind of: I prefer 100% cotton socks, because they lay confortably over my feet mangled-skin.
That kind of construction technic and its meaning can be found at the following document, page 16, "identification and connection of external foil":
https://exxelia.com/uploads/PDF/59bac88997252.pdf
Hope it helps more than confuses...
Henrique
LADIES AND GENTLEMEN, THE WINNER IS...
A simple example of such mixed-feelings can be extracted from the following three datasheets, from three different (and well known) manufacturers, showing equivalent products, and each one's vision about the better way to express their symbols:
https://knowlescapacitors.com/getattachment/71d034d6-1378-440f-a101-f6e0c6f13a4a/SBSM-SBSMC-20A.aspx
https://catalogs.avx.com/MultilayerFeedthruCapacitorsAndArrays.pdf
https://search.murata.co.jp/Ceramy/image/img/A01X/G101/ENG/NFM18PS105D0J3-01.pdf
As usual, hope it helps "a cap"...
P.S. a bit of "pepper", from Farnell:
https://tr.farnell.com/capacitor-types-and-performance
not always for example the sprague orange drops and a few others are marked depending on the direction they are going through the machine.
using an o-scope to determine the shield end is easy.
here is a very good you tube on it:
Thanks for the update, and very informative video too!
I used to love that kind of paper capacitors, at the time (early 1967, and beyond).
It seems Sprague isn't the same, anymore; just take a look at the following thread:
https://vintage-radio.net/forum/showthread.php?t=163628
Actually you might also need the source/standard under which the schematic was drawn. When I was with Siemens, the schematics were drawn using the DIN standard. Some thing same, many different.
oh how true that is!
caused a bit of confusion when they brought in the Veritas inspection equipment into the factory, (No one bothered to tell us the difference)
i had to search it online from the manufacturer.
so it took a couple weeks to train all the techs on it.
Mildly related: This hoarder loves getting a million resistors from China for a buck, but what gives with the new color code? First, the background resistor color is light blue, which makes for poor contrast with stripe colors. Then the format has changed:
5.6K resistor is now green-blue-black-brown-brown, previously green-blue-red.
4.7K resistor is now yellow-violet-black-brown-brown, previously yellow-violet-red.
150-ohm (AKA 150R) is brown-orange-black-black-brown, previously brown-orange-brown.
Wassup with that? Now I have to check values with one of the 50 multimeters I have also hoarded.
That's crazy. That does not conform .
That particular one seems to be "stinky", at least.
Even at that new coding-style, there are two possibilities:
Time to pull those meters and do a check, in order to get the right meaning (or lenses
).
That colour code difference is old. What you're seeing is the difference between 5% and 1% resistors. The extra stripe is denoting the extra precision of the 1%'ers.
erco,
I have a mid-90's vintage Digital MultiMeter (DMM) full of "Blue" resistors.
I think they are Metal film instead of the standard Carbon composition.
I also have a late 80's to 90's vintage kit that has cylindrical resistors instead of the bumpy ones that you normally see.
Your resistors are 5-band precision (Brown = 1%)
5.6K resistor is now green-blue-black-brown-brown, previously green-blue-red.
... 560 x 10^1 1% = 560 x 10 = 5600 = 5.60K 1%
4.7K resistor is now yellow-violet-black-brown-brown, previously yellow-violet-red.
... 470 x 10^1 1% = 470 x 10 = 4700 = 4.70K 1%
150-ohm (AKA 150R) is brown-orange-black-black-brown, previously brown-orange-brown.
... 130 x 10^0 1% = 130 x 1 = 130 Ohm 1%
..... Orange is 3 while Green is 5 so double-check the color of the 2nd band or you got the wrong value.
https://www.mouser.com/technical-resources/conversion-calculators/resistor-color-code-calculator
As for the way the light-blueish background can be interfering with the perception of each band color, there is a good Interactive Java Tutorial, with full-colored waveforms, where one can fine-tune the two involved light frequencies, and watch the effective resulting construction/deconstruction.
https://micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/waveinteractions/index.html
Hope it helps the eyes...
Henrique
P.S. Sure, background light "tint" under which the observation is taken is also playing its role, but, as the tuning of the left-panel pair is based on human perception, the effective background contribution gets compensated too.
with the color differences in resistors i highly recommend double checking with a multimeter anyway.
even if the colors are clear background color can skew the band color enough to cause confusion
also while the odds are very high sometimes you can get a faulty component.
as was the case in a recent radio build, my customer received the kit built it and i walked him through the troubleshooting process.
tracing the tank circuit components we found 1 resistor that measured way below the marked value.
replaced it with a tested good one and alls well.
so no matter how good your eyes are double check with a meter!