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man, they really changed focus after inventing the synthesizer
I was actually researching something about slip rings, and found this lovely picture.
Want some ethernet you can rotate 360 degrees? NOW YOU CAN!
Want some ethernet you can rotate 360 degrees? NOW YOU CAN!
they call these "pancake slip rings" and this one has a nice exploded view.
although now I want to make one that uses them for making pancakes. mmm, pancakes.
although now I want to make one that uses them for making pancakes. mmm, pancakes.
They also make fiber optic ones, which are... different.
They& #39;re not actually a slip ring, because they don& #39;t slip: instead they just terminate the two fiber optic cables real near each other and have them held in place.
The light just skips the gap, with no contact.
They& #39;re not actually a slip ring, because they don& #39;t slip: instead they just terminate the two fiber optic cables real near each other and have them held in place.
The light just skips the gap, with no contact.
there& #39;s also HIGH SPEED SLIP RINGS which can keep working up to 12,000 RPM
and high-current slip rings, for when you need to transmit 3 kilo-amps to a rotating device.
fun fact: the ones which produce the least interference work by having a conductive liquid inside.
Guess which one?
MERCURY!
Guess which one?
MERCURY!
and high temperature slip rings, for when you need your slip rings to keep working at 250 degrees Celsius
they mention low cost carbon slip rings, then just show off one that& #39;s TALLER THAN A HUMAN with no explanation:
OK SO there& #39;s like four types of slip rings, and the 4th one is the most interesting because it makes no sense at first.
First, there& #39;s "Drum style":
There& #39;s a cylinder with contacts, and a brush on the outside.
First, there& #39;s "Drum style":
There& #39;s a cylinder with contacts, and a brush on the outside.
Then there& #39;s pancake slip rings: closely related, just instead of a cylinder, it& #39;s a disc.
then there& #39;s mercury slip rings: these don& #39;t have a brush, instead they just have liquid mercury that maintains a continuous contact with less interference.
but the final type... is the wireless slip ring.
What. Wireless? The whole point of a slip ring is to electrically connect a stationary thing with a rotating thing!
If you could do wireless, why would you need a slip ring?
What. Wireless? The whole point of a slip ring is to electrically connect a stationary thing with a rotating thing!
If you could do wireless, why would you need a slip ring?
and it turns out the reason is: POWER!
You have a device that needs to rotate, and it needs power (and signals)
So you need a way to get power and data in and out... but regular slip rings are too electrically noisy, and wear out, and mercury is too dangerous...
You have a device that needs to rotate, and it needs power (and signals)
So you need a way to get power and data in and out... but regular slip rings are too electrically noisy, and wear out, and mercury is too dangerous...
So the answer is WIRELESS SLIP RINGS!
Also known as a rotary transformer.
Basically, you build a bunch of little coils around each other, and this becomes the primary side of the transformer, with the secondary side being in the rotating part.
Also known as a rotary transformer.
Basically, you build a bunch of little coils around each other, and this becomes the primary side of the transformer, with the secondary side being in the rotating part.
the quick TL;DR of how a transformer works is that you have some magnetic core, and two coils of wire with different numbers of windings. The varying current in the primary creates a magnetic field which creates another varying current in the secondary.
but the core can be all sorts of things, including just... air.
It won& #39;t work as well (because an iron/steel/whatever core has less loss at lower frequencies), but it& #39;ll work.
You& #39;re just turning an AC signal into a magnetic field and back.
It won& #39;t work as well (because an iron/steel/whatever core has less loss at lower frequencies), but it& #39;ll work.
You& #39;re just turning an AC signal into a magnetic field and back.
This, btw, is how the wireless charging in your phone works.
There& #39;s a coil inside your phone, and the matching coil inside the charger creates a magnetic field that gets turned back into a current inside your phone.
There& #39;s a coil inside your phone, and the matching coil inside the charger creates a magnetic field that gets turned back into a current inside your phone.
but back to wireless slip rings... do you know where they were primarily used, and why you might have had one?
There was something very common, in most households, which needed to have a part spin very fast for a long time (without breaking), with power and data...
There was something very common, in most households, which needed to have a part spin very fast for a long time (without breaking), with power and data...
Here& #39;s a zoomed-out hint.
It& #39;s the head of a VCR!
VCR heads have to spin (unlike cassette tape heads) because they& #39;re using helical-scan recording to fit more data onto the tape, so they use a wireless slip ring to take power and data into the head, and to bring data back out.
helical-scan is the thing where the head drum is tilted and spinning, so there& #39;s a bunch of diagonal-line tracks across the length of the tape, instead of being stacked horizontally like in a cassette tape.
for comparison on a cassette tape they& #39;re just flat lines on the tape.
Which is much simpler but it limits how much data you can store. For audio, this is fine. For video, you& #39;d have to make the tape move REALLY FAST to get all the data on there.
Which is much simpler but it limits how much data you can store. For audio, this is fine. For video, you& #39;d have to make the tape move REALLY FAST to get all the data on there.
and faster moving tape means your cassettes are bigger and more expensive.
So helical-scan may make the players more complicated, but the added bandwidth makes the tapes able to store a lot more, which is a good trade off for the customer.
So helical-scan may make the players more complicated, but the added bandwidth makes the tapes able to store a lot more, which is a good trade off for the customer.
expensive VCRs and cheap tapes makes way more sense than cheaper players and expensive tapes.
helical scan also gives you the ability to make your tracks closer together cheaply: you can always spin the head faster while the tape moves at the same speed, so the "slices" the head sees are now closer to each other
with a linear system like a cassette tape head, the only way to move the heads closer together is to redesign the tape head and add more and smaller heads in the same area.
That& #39;s certainly possible (check out a 4-channel tape deck sometime!) but it& #39;s tricky and expensive
That& #39;s certainly possible (check out a 4-channel tape deck sometime!) but it& #39;s tricky and expensive
spinning the drum faster, on the other hand, is relatively easy to do. So you can figure out what speed you need to encode enough data on it for a NTSC/PAL video frame, and design it to run at that rate.
fun fact: these two styles of magnetic tape recording? They& #39;re not incompatible!
In fact, VHS tapes use both, at once.
The video is helical scan, but the two audio channels (for stereo) are linear, and so is the control (synchronization) track.
In fact, VHS tapes use both, at once.
The video is helical scan, but the two audio channels (for stereo) are linear, and so is the control (synchronization) track.
There& #39;s another fun trick in how the heads work:
So there& #39;s (at least) two heads on the drum, on each side, and instead of being identical, they& #39;re tilted, but in different directions.
(from this page on betamax heads: https://mrbetamax.com/DAHeads.htm )">https://mrbetamax.com/DAHeads.h...
So there& #39;s (at least) two heads on the drum, on each side, and instead of being identical, they& #39;re tilted, but in different directions.
(from this page on betamax heads: https://mrbetamax.com/DAHeads.htm )">https://mrbetamax.com/DAHeads.h...
this is called slant azimuth recording, and it prevents one head from reading the neighboring tracks (because they& #39;re at a different angle) and the tracks interfering with each other.
the reason I say "at least 2 heads" is because later VCRs added more heads so they could better record for EP/SLP tapes and for hi-fi audio, which encoded another audio track at higher quality than the original linear track.
the different tape speeds were just running the tape slower, btw.
half speed for LP, and 1/3rd speed for EP/SLP.
half speed for LP, and 1/3rd speed for EP/SLP.
because more tracks are being stuffed into the same length of tape, this resulted in the resolution going down and the audio quality becoming much poorer.
a fun fact about stereo types:
since JVC added Hi-Fi audio in a backwards compatible way (tapes using it would still play just fine on an older VCR), it was very commonly used on pre-recorded tapes, since it just provided "free" extra sound quality.
since JVC added Hi-Fi audio in a backwards compatible way (tapes using it would still play just fine on an older VCR), it was very commonly used on pre-recorded tapes, since it just provided "free" extra sound quality.
but an interesting thing is that even home recordings on hi-fi VCRs were made of TV shows in stereo, even before those areas implemented stereo TV audio. How?
And it turns out that some VCRs had a simulcast mode, where you could pipe in stereo audio from an external source to be recorded onto the tape, instead of the actual over-the-air audio.
And because this existed, sometimes TV stations would arrange for a radio station to broadcast the audio of certain events (like concerts and music videos) over FM-stereo!
MTV, for example, did this in their early years.
anyway, slip rings, won& #39;t you?
BTW, one of the pre-helical-scan video tape tests was the BBC VERA format, developed (but never implemented) in the early 50s.
It used a linear head, so the tape had to move much faster to record the higher frequencies of video.
Very much faster.
It used a linear head, so the tape had to move much faster to record the higher frequencies of video.
Very much faster.
the tape was 20 inches wide (52cm), and moved at SEVENTEEN FEET PER SECOND (5m/s) past the read head.
so it worked, technically, but it also meant they needed five kilometers (3 miles) of tape to record 15 minutes worth of black and white video.
So the BBC never implemented it, instead using Ampex& #39;s 2" Quadruplex video.
That used transverse encoding (which is basically helical but fully vertical instead of diagonal) but only needed to move at 7.5/15 inches a second (19cm/38cm)
That used transverse encoding (which is basically helical but fully vertical instead of diagonal) but only needed to move at 7.5/15 inches a second (19cm/38cm)
also, whoops: the tape wasn& #39;t 20cm wide, it was stored on 20cm open reels.
and to go back to the joke that started the thread:
That Moog company, the one who does defense stuff?
That& #39;s Moog Inc, founded in 1951 by Bill Moog.
They do actuators, servo valves, and slip rings, mainly for aerospace uses.
That Moog company, the one who does defense stuff?
That& #39;s Moog Inc, founded in 1951 by Bill Moog.
They do actuators, servo valves, and slip rings, mainly for aerospace uses.
The famous synth is from R. A. Moog Co, later called Moog Music.
That Moog was founded by Robert Moog, not Bill Moog. They& #39;re cousins.
Fun fact: Their HQ is in Asheville, NC, my hometown.
Fun fact: Their HQ is in Asheville, NC, my hometown.
Robert Moog moved to NC in the late 70s, and at one point was a professor of music at my college, the University of North Carolina at Asheville. (He& #39;d retired before I started there, however)
