My thanks to Jason Harris for posting the web page. I have been off the
air for a while under the duress of starting a new project and
kick-starting my thesis work. Just a re-fresher: The web page Jason
referred to is the interactive robotics project I have written about over
the last 2 years. I worked with an artist named Yves Klein who designed
the sculpture and concept. He calls his work interactive autonomous
art. It uses PIC based PWM control to heat nitinol muscle
wires and move eight legs via closed loop control. Another PIC reads and
processes the absolute position sensor for all eight legs and sends that
info to the PWM PIC. A third PIC (the "brain") is generating leg set
points based upon optical input (eight "eyes") and pseudo neural net
learning algorithm.
Once again the web page can be viewed by clicking on Octofungi at:
An artist I know has created a sculpture consisting of a several
kilometers of pink wire rolled into a giant sphere of about 90cm
diameter. She wants me to make this sculpture interactive so that it
makes sounds when people touch or make gestures over an aura around
it. I thought it might be possible to make a hollow version of this
sculpture with speakers and electronics hidden inside, and to use
the two sides of the sphere like the aerials of a theremin. Theremin sounds
aren't exactly what she wants - its the gestural interactivity that is the
important bit.Is this likely to be possible? I don't know much about what
properties aerials have to have to make them work, will any old bit of wire
do the job? Will a large hemispheric tangle of copper wire with pink
plastic insulation do the trick? How will the electric field around
this aerial behave if so? And how difficult is it likely to be for me
(someone with basic electronics experience)to build a theremin
circuit.. Have also been considering hiding infrared proximity detectors
under the wire and using them to trigger/ increase volume of sound stored on
a chipCorder device.
Any advice, links or suggestions much appreciated! I'm not an electronics
expert so I'm looking for a fairly simple solution..
Sam.
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.
I would suggest getting the sculpture done as a matrix of wires, possibly
fairly open, and then driving some wires with signals, and using other wires
as detectors, a bit like a massive keyboard matrix.
I do not know how well the interaction between the driven wire and detection
wire would be with just placing a hand on it is, you may have to experiment
to find out. Get your artist friend involved in this so she has a good idea
of what is needed for the sculpture.
It may be that you will need to have some form of contact movement to get
sufficient cross coupling between the two, but I suspect that if you tried s
scheme like Hewlett Packard used in their early desktop calculators, you may
well achieve what she wants.
What HP did was to have "transformers" made of about two turns of PC track
on each winding under each key. All the windings in the X direction were
driven by a pulse, so there was 8 or 16 lines being sequentially scanned by
pulses. Windings in the Y direction were then wired in series and sufficient
pulse came out the windings for an amplifier to get a detectable pulse when
the X lines were driven. Under each key was a metal disc that became a
shorted turn on the winding when the key was pressed. A missing pulse during
a scan then represented a key press.
You may be able to do something similar by having coils of wire placed
around the sculpture, and have metal disks hanging that the public can place
against the coils. Worth a try on the bench, and the metal disk does not
have to be round - let the sculpture use her imagination on it, so long as
it will make a shorted turn on the winding.
> I would suggest getting the sculpture done as a matrix of wires, possibly
> fairly open, and then driving some wires with signals, and using other wires
> as detectors, a bit like a massive keyboard matrix.
>
> I do not know how well the interaction between the driven wire and detection
> wire would be with just placing a hand on it is, you may have to experiment
> to find out. Get your artist friend involved in this so she has a good idea
> of what is needed for the sculpture.
If you happen to have one of Synaptic's(*) TouchPads lying around, then
try cutting off the PCB traces that are connected to the TouchPad and
wiring them to this wire Matrix. It then should be possible to sense the
hand position and move a cursor around on a CRT. The API for the TouchPad
is exposed (for Window's) in such a way that you could write custom
software to capture the packets coming the TouchPad and interpret that
information anyway you see fit.
The biggest challenge will be in constructing a mesh that has similar
impedance as a TouchPad. You probably can do this with some 30AWG magnet
wire limited to < 1 meter lengthes. Each wire needs to be almost the same
length so that the capacitance matches quite closely.
Never used them myself - but plan on getting an eval board soon
>>> .....A.B.PearceKILLspam@spam@RL.AC.UK 06/13/02 01:02PM >>>
I would suggest getting the sculpture done as a matrix of wires, possibly
fairly open, and then driving some wires with signals, and using other wires
as detectors, a bit like a massive keyboard matrix.
I do not know how well the interaction between the driven wire and detection
wire would be with just placing a hand on it is, you may have to experiment
to find out. Get your artist friend involved in this so she has a good idea
of what is needed for the sculpture.
It may be that you will need to have some form of contact movement to get
sufficient cross coupling between the two, but I suspect that if you tried s
scheme like Hewlett Packard used in their early desktop calculators, you may
well achieve what she wants.
What HP did was to have "transformers" made of about two turns of PC track
on each winding under each key. All the windings in the X direction were
driven by a pulse, so there was 8 or 16 lines being sequentially scanned by
pulses. Windings in the Y direction were then wired in series and sufficient
pulse came out the windings for an amplifier to get a detectable pulse when
the X lines were driven. Under each key was a metal disc that became a
shorted turn on the winding when the key was pressed. A missing pulse during
a scan then represented a key press.
You may be able to do something similar by having coils of wire placed
around the sculpture, and have metal disks hanging that the public can place
against the coils. Worth a try on the bench, and the metal disk does not
have to be round - let the sculpture use her imagination on it, so long as
it will make a shorted turn on the winding.
Have you considered using a light sensitive sensor like a CdS cell to make
a light organ. It's a pretty simple and straight forward circuit that will
react
to varying levels of light falling on the sensor.
>An artist I know has created a sculpture consisting of a several
>kilometers of pink wire rolled into a giant sphere of about 90cm
>diameter. She wants me to make this sculpture interactive so that it
>makes sounds when people touch or make gestures over an aura around
>it. I thought it might be possible to make a hollow version of this
>sculpture with speakers and electronics hidden inside, and to use
>the two sides of the sphere like the aerials of a theremin. Theremin sounds
>aren't exactly what she wants - its the gestural interactivity that is the
>important bit.Is this likely to be possible? I don't know much about what
>properties aerials have to have to make them work, will any old bit of wire
>do the job? Will a large hemispheric tangle of copper wire with pink
>plastic insulation do the trick? How will the electric field around
>this aerial behave if so? And how difficult is it likely to be for me
>(someone with basic electronics experience)to build a theremin
>circuit.. Have also been considering hiding infrared proximity detectors
>under the wire and using them to trigger/ increase volume of sound stored on
>a chipCorder device.
>
>Any advice, links or suggestions much appreciated! I'm not an electronics
>expert so I'm looking for a fairly simple solution..
>Sam.
>
>
>_________________________________________________________________
>Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.
>
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>http://www.piclist.com hint: The PICList is archived three different
>ways. See http://www.piclist.com/#archives for details.
>
>
_____________________________________________________________
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University crisKILLspamclemson.edu
To report problems email: .....aah_computersKILLspam.....clemson.edu
> An artist I know has created a sculpture consisting of a several
> kilometers of pink wire rolled into a giant sphere of about 90cm
> diameter.
Is this wire electrically one piece - IOW is it all welded together ?
If so, you will have to add sensor wires of your own. I'd expect
those sensors would be compromised by such a large mass of
metal around them though
> Theremin sounds aren't exactly what she wants - its the
> gestural interactivity that is the important bit
At one time I too was asked about an interactive sculpture
and did some research into Theremins. There is a lot of
information around, as you've probably found out. Three
people I'd suggest you Google search for +theremin are
Clara Rockmore, Fred Nachbaur and Robert Moog. Most
of the circuits I found are valve - I think I found just two
solid state circuits and one of those IIRC was from the
University Of Glasgow
>.Is this likely to be possible? I don't know much about what
> properties aerials have to have to make them work, will
> any old bit of wire do the job ?
You might be better to look around for an RF alarm circuit.
I ended up using a 300MHz oscillator with a 1ft aerial and
amplifying the amplitude changes into an ADC to control
lighting. A single wire will give better spatial effects than a
a single hemispherical tangle of wire, I think. The HF osc
was a very simple 2-transistor thing. Basically you have
two aerials - one on the PCB as a reference and one in
free air. As the one in free air is interfered with it creates
a difference signal with the reference one. Any HF osc
is sensitive to bodiliy capacitance. I've made many touch
sensors using 80kHz from a 4001
> Have also been considering hiding infrared proximity
> detectors under the wire and using them to trigger/ increase
> volume of sound stored on a chipCorder device
That would work. You can buy domestic security lights very
cheaply these days. In fact I would not buy PIR units from
an alarm or electronics company - I'd get a whole twin-light
unit from a discount retailer and hack the PIR unit. The
PIR piezo element needs a lot of amplification and there
should be a quad op amp inside the PIR unit that will have
points at which you can take off a usable signal
Hmmmm... perhaps a spherical surround array of lights, with proximity and
motion controls on the surface of the sphere. Persons would see the lights
and their shadows, with the color additive effects .
A Deep blue light projected tangential to the globe with a bright red light
behind the observer.. A blue shadow with a Purple surround, with other
lights controlled by motion and nearness to the sphere. sound added to this
perhaps melodic bits rather than just theremin sounds.
One might even have projected movie clips triggered buy observer postition.
Jus t a few bizarre thoughts
At 10:18 AM 6/14/02 +1200, you wrote:
> > An artist I know has created a sculpture consisting of a several
> > kilometers of pink wire rolled into a giant sphere of about 90cm
> > diameter.
Hi everyone,
I've been designing the electronics for a rotating interactive sculpture.
There are two parts, a static base that acts as a turntable, and a revolving
pink blop that sits on top. The base contains a dc motor and mains
transformer. the top part contains a number of sensors (adapted from parking
sensors from http://www.velleman.be) that switch relays on and off when activated
to start the motor and change direction.
the problem is that wires between the revolving top-part and the static
bottom part get snagged and tangled as they are pulled round. There needs to
be two wires supplying power to the sensors and two wires from the sensors
to the relays. Can anyone suggest a solution to this problem... Surely
someone else must have encountered it before? I am imagining something like
rotating contacts but don;t know if these exist or what they'd be called if
they did. Or maybe I need to communicate wirelessly between the sensors and
the relays using RF?
Imho look into rotating contacts. You may be able to adapt parts from a
larger motor (the brushes). If you find a 3-phase squirrel cage motor with
wound rotor then you will get three heavy duty brush assemblies. The
fourth would be ground and you could add a brush set to work against the
axle itself.
If the device does not make full turns then you could pass the wires
through a hollow axle and sheath the free-standing part in flex conduit
with special grease inside. If done right this will last a long time.
Inductive power transfer over distances of mm to a few cm is quite easy.
Do you want continual rotation capability or just say 360 degree rotation
maximum?
Peter L. Peres wrote:
>
> Imho look into rotating contacts. You may be able to adapt parts from a
> larger motor (the brushes). If you find a 3-phase squirrel cage motor with
> wound rotor
Huh?? It's been almost 20 years since I did AC machines,
but AFAIK squirrel cage motors have a laminated iron
armature with copper or alloy "cage bars" and their main
distinquishing feature is they don't have brushes or
a wound rotor. Are you thinking of an AC synchronous
motor? :o)
-Roman
Hi Sam, "revolving pink blob"?? Now i've seen some
"revolting pink blobs" but let's not go there... ;o)
Try a web search for "slipring + brushes" etc.
Maybe you could use one simple ring to get power to your
top PIC and NiCds, then use IR for the top PIC to
send data to the bottom PIC. If the data is as simple
as clockwise/counter-clockwise then you may be able
to just use an IR pair, and reverse the motor if the
IR is on. No coding etc needed.
-Roman
>
> Hi everyone,
> I've been designing the electronics for a rotating interactive sculpture.
> There are two parts, a static base that acts as a turntable, and a revolving
> pink blop that sits on top. The base contains a dc motor and mains
> transformer. the top part contains a number of sensors (adapted from parking
> sensors from http://www.velleman.be) that switch relays on and off when activated
> to start the motor and change direction.
>
> the problem is that wires between the revolving top-part and the static
> bottom part get snagged and tangled as they are pulled round. There needs to
> be two wires supplying power to the sensors and two wires from the sensors
> to the relays. Can anyone suggest a solution to this problem... Surely
> someone else must have encountered it before? I am imagining something like
> rotating contacts but don;t know if these exist or what they'd be called if
> they did. Or maybe I need to communicate wirelessly between the sensors and
> the relays using RF?
Yes, rotating contacts do exist. They're called "Slip Rings" and are
used in motors and alternators quite extensively. They are also used
in machinery such as electric cranes to energize the magnet at the end
of the lifting cable.
> Hello Dave
>
> Firstly CONGRATULATION,
>
> have look at B.T, Thales Telecommunication, Siemen's,
> BBRM,
> JARVIS Rail, AMEY Rail,
> Serco Rail,
>
>
> Dave I am trying to learn pic programming (16F877) I am
> not
> bright student can you help. I like to know what the
> command means and what they do.
>
> regards
> Nash
>
> Yes, rotating contacts do exist. They're called "Slip Rings" and are
> used in motors and alternators quite extensively. They are also used
> in machinery such as electric cranes to energize the magnet at the end
> of the lifting cable.
>
>
> > Hello Dave
> >
> > Firstly CONGRATULATION,
> >
> > have look at B.T, Thales Telecommunication, Siemen's,
> > BBRM,
> > JARVIS Rail, AMEY Rail,
> > Serco Rail,
> >
> >
> > Dave I am trying to learn pic programming (16F877) I am
> > not
> > bright student can you help. I like to know what the
> > command means and what they do.
> >
> > regards
> > Nash
> >
Yes, there are rotating contacts, try a web serach to find them.
And, as this is a PIC related list, I'd put a PIC to read your sensors,
use three rotating contacts (power, ground common and serial
communication - RS232, maybe, for better noise rejection) and another
PIC to get the commands from the serial communication line and trigger
the relays.
> Hi everyone,
> I've been designing the electronics for a rotating interactive sculpture.
> There are two parts, a static base that acts as a turntable, and a
> revolving
> pink blop that sits on top. The base contains a dc motor and mains
> transformer. the top part contains a number of sensors (adapted from
> parking
> sensors from http://www.velleman.be) that switch relays on and off when
> activated
> to start the motor and change direction.
>
> the problem is that wires between the revolving top-part and the static
> bottom part get snagged and tangled as they are pulled round. There
> needs to
> be two wires supplying power to the sensors and two wires from the
> sensors
> to the relays. Can anyone suggest a solution to this problem... Surely
> someone else must have encountered it before? I am imagining something
> like
> rotating contacts but don;t know if these exist or what they'd be
> called if
> they did. Or maybe I need to communicate wirelessly between the
> sensors and
> the relays using RF?
>
> Any suggestions much appreciated.
>
> Sam.
>
> _________________________________________________________________
> MSN Photos is the easiest way to share and print your photos:
> http://photos.msn.com/support/worldwide.aspx
>
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> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
>
>
>
>
>
> I've been designing the electronics for a rotating interactive sculpture.
> There are two parts, a static base that acts as a turntable, and a
revolving
> pink blop that sits on top. The base contains a dc motor and mains
> transformer. the top part contains a number of sensors (adapted from
parking
> sensors from http://www.velleman.be) that switch relays on and off when activated
> to start the motor and change direction.
I would use a piece of copper laminate with circles engraved on the copper
with a scriber to make a slip ring unit. You could probably make wipers for
it using brass wire from a hobby store, depending on how permanent this
thing is going to be. This should give you enough current capacity for
sensors.
It involves some motor modifications but is an excellent idea.
Communications with the upper turning portion could be RF but then of
course, I'm slightly prejudiced there.
John
Wireless CAN with the CANRF module.
www.autoartisans.com/documents/canrf_prod_announcement.pdf
Automation Artisans Inc.
Ph. 1 250 544 4950
>Peter L. Peres wrote:
>>
>> Imho look into rotating contacts. You may be able to adapt parts from a
>> larger motor (the brushes). If you find a 3-phase squirrel cage motor with
>> wound rotor
>
>
>Huh?? It's been almost 20 years since I did AC machines,
>but AFAIK squirrel cage motors have a laminated iron
>armature with copper or alloy "cage bars" and their main
>distinquishing feature is they don't have brushes or
>a wound rotor. Are you thinking of an AC synchronous
>motor? :o)
Yes, except there is a class of synchronous motors that are exactly like
squirrel cage motors but have wound rotors (the squirrel cage) that is
connected to a rheostat or starting unit to reduce the immense required
starting current to bearable values (and to increase starting torque ?).
After the motor spins up the rotor contacts are shorted and the motor
becomes a squirrel cage motor. Some newer constructions embed the whole
starting system in the rotor using either NTCs or bimetal switches (?) or
active devices. I've never seen one with active devices though.
Russell McMahon wrote:
> How much power (watts) do you want to transfer?
> Inductive power transfer over distances of mm
> to a few cm is quite easy.
> Do you want continual rotation capability or just
> say 360 degree rotation maximum?
Navy guys have so-called "rotating transformers"
(translation from Russian). They have 2 ortogonal
windings on stator and 2 ortogonal windings on
rotor. May be used for AC 400 hz power transmission,
data transmission - varying frequency, determining
degree of rotation when rotating by simple motor,
also may be used as good rotating platform, as it
has strong bearings.
Mike.
-------
When responding, keep in mind, please,
this things may be under NDA.
Yes, a slipring would be the solution . You can buy (expensive) or try to
make your own. One possible cheap suggestion that works because you only
need 4 lines (and if your power requirements are low enough), pick up one
of those inline gizmos to keep the cord to a phone handset untangled.
Should only cost a couple of bucks, and should be readily available.
>Hi everyone,
>I've been designing the electronics for a rotating interactive sculpture.
>There are two parts, a static base that acts as a turntable, and a revolving
>pink blop that sits on top. The base contains a dc motor and mains
>transformer. the top part contains a number of sensors (adapted from parking
>sensors from http://www.velleman.be) that switch relays on and off when activated
>to start the motor and change direction.
>
>the problem is that wires between the revolving top-part and the static
>bottom part get snagged and tangled as they are pulled round. There needs to
>be two wires supplying power to the sensors and two wires from the sensors
>to the relays. Can anyone suggest a solution to this problem... Surely
>someone else must have encountered it before? I am imagining something like
>rotating contacts but don;t know if these exist or what they'd be called if
>they did. Or maybe I need to communicate wirelessly between the sensors and
>the relays using RF?
>
>Any suggestions much appreciated.
>
>Sam.
This lokks like a very nifty solution! You may have some strong magnets
fixed to the motor case and some coils at the moving part, so you can
get a variable magnectic flux in the coils to get some alternating
current (how much?). And you can add something like a transponder to
send high frequency serial data ;-)
>Russell McMahon wrote:
>
>
>>How much power (watts) do you want to transfer?
>>Inductive power transfer over distances of mm
>>to a few cm is quite easy.
>>Do you want continual rotation capability or just
>>say 360 degree rotation maximum?
>>
>>
>
> Navy guys have so-called "rotating transformers"
>(translation from Russian). They have 2 ortogonal
>windings on stator and 2 ortogonal windings on
>rotor. May be used for AC 400 hz power transmission,
>data transmission - varying frequency, determining
>degree of rotation when rotating by simple motor,
>also may be used as good rotating platform, as it
>has strong bearings.
>
> Mike.
>-------
> When responding, keep in mind, please,
>this things may be under NDA.
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics
>
>
>
>
>
>
>
No magnets, just feeding stator coils (or windings - what
is correct in English?) with 400 hz AC. Rotor coils produce
secondary 400 hz AC to feed moving part's electronics.
> This looks like a very nifty solution! You may have some
> strong magnets
> fixed to the motor case and some coils at the moving part, so you can
> get a variable magnectic flux in the coils to get some alternating
> current (how much?). And you can add something like a transponder to
> send high frequency serial data ;-)
>
> Francisco
>
>
> Mike Singer wrote:
>
> >Russell McMahon wrote:
> >
> >
> >>How much power (watts) do you want to transfer?
> >>Inductive power transfer over distances of mm
> >>to a few cm is quite easy.
> >>Do you want continual rotation capability or just
> >>say 360 degree rotation maximum?
> >>
> >>
> >
> > Navy guys have so-called "rotating transformers"
> >(translation from Russian). They have 2 ortogonal
> >windings on stator and 2 ortogonal windings on
> >rotor. May be used for AC 400 hz power transmission,
> >data transmission - varying frequency, determining
> >degree of rotation when rotating by simple motor,
> >also may be used as good rotating platform, as it
> >has strong bearings.
> >
> > Mike.
> >-------
> > When responding, keep in mind, please,
> >this things may be under NDA.
> >
Hi,
What Mike is describing is similar to a CT (control transformer) or a
synchro. If your project is a one-up, these are regularly available on
e-bay.
Regards,
Dave
>
> No magnets, just feeding stator coils (or windings - what
> is correct in English?) with 400 hz AC. Rotor coils produce
> secondary 400 hz AC to feed moving part's electronics.
>
> Mike.
>
> Francisco Ares wrote:
> > This looks like a very nifty solution! You may have some
> > strong magnets
> > fixed to the motor case and some coils at the moving part, so you can
> > get a variable magnectic flux in the coils to get some alternating
> > current (how much?). And you can add something like a transponder to
> > send high frequency serial data ;-)
> >
> > Francisco
> >
> >
> > Mike Singer wrote:
> >
> > >Russell McMahon wrote:
> > >
> > >
> > >>How much power (watts) do you want to transfer?
> > >>Inductive power transfer over distances of mm
> > >>to a few cm is quite easy.
> > >>Do you want continual rotation capability or just
> > >>say 360 degree rotation maximum?
> > >>
> > >>
> > >
> > > Navy guys have so-called "rotating transformers"
> > >(translation from Russian). They have 2 ortogonal
> > >windings on stator and 2 ortogonal windings on
> > >rotor. May be used for AC 400 hz power transmission,
> > >data transmission - varying frequency, determining
> > >degree of rotation when rotating by simple motor,
> > >also may be used as good rotating platform, as it
> > >has strong bearings.
> > >
> > > Mike.
> > >-------
> > > When responding, keep in mind, please,
> > >this things may be under NDA.
> > >
>
> --
> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
You could make a rotating slipring assembly with a jack plug and socket.
Depending on what the mechanical load is you can use the plug as the
pivot in the base, and the socket as the bearing and electrical
connection in the moving part. You can get 4-way jack plugs, or if you
have a common ground then a three way (stereo) might suffice. I would
suggest the 1/4" variety for strength, and I would imagine that this
construction would not last for long, but then, it might be ideal for
your application.
> I would use a piece of copper laminate with circles engraved on
> the copper with a scriber to make a slip ring unit. You could probably
> make wipers for it using brass wire from a hobby store, depending
> on how permanent this thing is going to be. This should give you
> enough current capacity for sensors
I made an angular sensor with 5 slip rings (2 power, 3 BCD) and
found that the springy contacts from an edge connector (from an
old motherboard) worked better than plain wire as they've multiple
contact points and are already shaped. A small PCB was made to
hold these, although Vero would do, and that PCB was rubber-mounted
to get optimum pressure between the wipers and the slip rings
The variable-pitch propellor I've been working on also uses slip rings
and carbon brushes to get power to the pitch motor. I'm told that even
after many hundreds of hours at high rpm the brushes are in good
condition and generate much less RFI than those against commutators
in eg an electric drill
>From: Kieren Johnstone <@spam@misterfugitKILLspamHOTMAIL.COM>
>Reply-To: pic microcontroller discussion list <KILLspamPICLISTKILLspamMITVMA.MIT.EDU>
>To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU
>Subject: Re: [ot]rotating sculpture tangled wire problem
>Date: Fri, 12 Jul 2002 22:31:46 +0100
>
>OK, well if no-one will change it to "[OT]:" (which means its filtered out
>for me), maybe "[EE]:", since its basically that anyway.
>
>Or maybe I'm just hot and bothered today...
>
_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com
David Minkler wrote:
>
> Hi,
> What Mike is describing is similar to a CT (control transformer) or a
> synchro. If your project is a one-up, these are regularly available on
> e-bay.
Rotary transformer! Fantastic idea, every vhs VCR
head assembly has a rotary transformer and precision
bearings... I can just imagine the next wave of
propellor clocks... :o)
-Roman
I'm pleased to see that after a longish digression into electromechanicals
(slip rings and ball bearings) we are starting to get back on track with
rotary transformers :-) (I mentioned inductive power transfer, Mike Singer
mentioned 400 Hz Russian military rotating transformers & Roman now mentions
video recorders).
Roman notes that all video recorders use rotary transformers in the heads -
something I was unaware of but it certainly makes sense. I assume this is
optimised for the several MHz video signal which is not a problem but I also
imagine the power that can be handled is very low.
So, I'll ask again -
???? How much power is this design meant to ????
???? transfer to the rotating head? ????
The answer probably has a significant affect on which is the best. solution.
Inductive power transfer is not very hard - especially if high efficiency is
not absolutely essential. As an alternative to sliprings and their ilk it
has many advantages.
>David Minkler wrote:
>>
>> Hi,
>> What Mike is describing is similar to a CT (control transformer) or a
>> synchro. If your project is a one-up, these are regularly available on
>> e-bay.
>
>Rotary transformer! Fantastic idea, every vhs VCR
>head assembly has a rotary transformer and precision
>bearings... I can just imagine the next wave of
>propellor clocks... :o)
>-Roman
You'd be hard pressed to pass enough power to light a LED with those.
> >You can also use a ball bearing assembly slid over the shaft. Solder a
> >wire to the inner race and a wire to the outer race.
>
> But depending on the precision class of the bearings only two of a set of
> several may make contact at any one time ...
>
> >Use as many as you need.
> >
> >Works for propeller clocks :)
>
> So it seems ;-). You were using decoupling caps on the coltages passed
> through the bearings, right ?
Yes, but Rickard Gunee has done it for serial communication as well
as power. Check out his cool web page:
Russell McMahon wrote:
>
> I'm pleased to see that after a longish digression into electromechanicals
> (slip rings and ball bearings) we are starting to get back on track with
> rotary transformers :-)
> So, I'll ask again -
>
> ???? How much power is this design meant to ????
> ???? transfer to the rotating head? ????
>
> The answer probably has a significant affect on which is the best. solution.
Peter L. Peres wrote:
>You'd be hard pressed to pass enough power to light a LED with those.
That would seem realistic at first thought, but i'm
not sure it's true. After doing that 2-transistor SMPS
using the tiny RF inductor I was surprised to get 150mA
and more with no problems.
Sure the VCR rotary transformer only carries uV and uW,
BUT it has a decent pair of coils, and beefy ferrite
cores that make what looks something like a standar round
ferrite former, but with tiny precision air gap (where
it rotates!). These are very precise units, with minimal
losses, and decent coil sizes, all because it HAS to
be efficient enough to get that tiny signal through.
Based on getting 150mA ok through an inductor 10x smaller,
and that i've used round ferrite cores a little larger good
for a couple of amps at 5v, i'm *guesstimating* you could
get 200mA to 500mA at 5v through these VCR units, maybe
considerably more. :o)
-Roman
The ferrites are actually fairly beefy. And the
wire size is not that small, larger than the wire
in the 1.5mH RF inductor I got an easy 150mA from.
I'm still betting on 200mA to 500mA @ 5v. :o)
-Roman
Jim wrote:
>
> 200 to 500 mA?
>
> "Beware the saturation of the magnetics."
>
> NEXT comes the I rating of the micro-wire they use...
>
> Jim
>
> {Original Message removed}
I build a few propeller displays, I collected a few tricks
and I'll throw you what I have learned.
I never gotten the coils from home VCR heads to push more then 100 ma
but I have heard of using big heads from professional VCRs to get more.
I have a feeling that this would be overkill for your project
You can make makeshift sliders from chopping up coin batter holders that
have the spring loaded tongs and make slide planes from copper
clad boards for making PCB. Draw circles on the Board were you want
the rings, and a cut them up with a dermal
I know it's been said but use the motor axial with a couple of tongs form
the coin batter holder,
one on each end
I guessing you have a H-bridge setup of some sort for the motor
you can save you self a wire by making up a tri state data line
example Vcc = Right, High Impedance = No movement, Ground = Left
if you get creative you can try to generate power in the globe
I have used a Thermoelectric pad ( Peltier junction ) on a over
heating barring once to generate power for a circuit
I all was wanted to try to generate power using the same trick a
self winding watch uses with a unbalanced fly wheel
Sam,
You might consider mounting the motor itself in the rotating "pink blob"
with the motor shaft held stationary by the base. Then you may get away
with only two wires going through the rotary joint to supply power. All the
control and sensor signals are within the rotary blob and don't move
relative to each other.
> sam woolf wrote:
> >
> > Hi everyone,
> > I've been designing the electronics for a rotating interactive
> sculpture.
> > There are two parts, a static base that acts as a turntable,
> and a revolving
> > pink blop that sits on top. The base contains a dc motor and mains
> > transformer. the top part contains a number of sensors (adapted
> from parking
> > sensors from http://www.velleman.be) that switch relays on and off
> when activated
> > to start the motor and change direction.
> >
> > the problem is that wires between the revolving top-part and the static
> > bottom part get snagged and tangled as they are pulled round.
> There needs to
> > be two wires supplying power to the sensors and two wires from
> the sensors
> > to the relays. Can anyone suggest a solution to this problem... Surely
> > someone else must have encountered it before? I am imagining
> something like
> > rotating contacts but don;t know if these exist or what they'd
> be called if
> > they did. Or maybe I need to communicate wirelessly between the
> sensors and
> > the relays using RF?
>
> --
> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
>
>
>
Bob Blick wrote:
>
> You can also use a ball bearing assembly slid over the shaft. Solder a
> wire to the inner race and a wire to the outer race.
>
> Use as many as you need.
>
> Works for propeller clocks :)
>
> -Bob
It didn't work on mine :-(
I am just about finished making one as a gift for the aero club that
helped me through my pilots licence.
I ended up machining up some small slip rings and it works like a charm
now.
I feed my clock with 9VAC through the slip rings using an internally
clocked 16F627. Using the mains frequency eliminates the need for a
crystal. I'm using a LED and detector out of an old slot sensor that I
had lying around as the signal to "fire" the message.
Setting the time was a problem because I wanted the GO and SET switches
outside the glass fronted case.
I ended up putting a diode in series with the AC supply with a normally
closed switch in parallel with it. This provides the circuit will full
wave rectification. When the SET switch is operated, the short across
the diode is removed and this cuts off the positive half cycles. This
has the effect of turning off the 50Hz clock input to the PIC but still
supplying enough half wave voltage to power the circuit.
The PIC software monitors the 50Hz input and as well as keeping time,
detects and uses the cutoff periods like a switch to set the time which
is done while the rotor is turning.
The display is not quite symmetrical top and bottom as the LEDs and PCB
spin in the vertical plane like a real propellor. The effect is still
quite stunning though.
The missus can't quite work out the time though because it's displayed
in Zulu.
You'll definitly have to post a photo of this clock on your web site...
Might be even more fun if you mounted the LEDs inside a wooden prop blade
so that the clock was even more 'aeronautical'. And what about sending
in temperature, wind and pressure information for it to display? Use
PAM of the supply voltage at some low baud rate (50baud in your case)
to get the data in (or IR for higher data rate, detector on the shaft end
so it doesn't move anywhere).
As for the original posters problem, a single slip ring carrying DC,
can be amplitude (or frequency) modulated a small precentage for communications.
Look at the various techniques used by the model railroaders to get their
information through to their engines on their noisy tracks.
>
> Bob Blick wrote:
> >
> > You can also use a ball bearing assembly slid over the shaft. Solder a
> > wire to the inner race and a wire to the outer race.
> >
> > Use as many as you need.
> >
> > Works for propeller clocks :)
> >
> > -Bob
>
> It didn't work on mine :-(
>
> I am just about finished making one as a gift for the aero club that
> helped me through my pilots licence.
>
> I ended up machining up some small slip rings and it works like a charm
> now.
>
> I feed my clock with 9VAC through the slip rings using an internally
> clocked 16F627. Using the mains frequency eliminates the need for a
> crystal. I'm using a LED and detector out of an old slot sensor that I
> had lying around as the signal to "fire" the message.
>
> Setting the time was a problem because I wanted the GO and SET switches
> outside the glass fronted case.
>
> I ended up putting a diode in series with the AC supply with a normally
> closed switch in parallel with it. This provides the circuit will full
> wave rectification. When the SET switch is operated, the short across
> the diode is removed and this cuts off the positive half cycles. This
> has the effect of turning off the 50Hz clock input to the PIC but still
> supplying enough half wave voltage to power the circuit.
>
> The PIC software monitors the 50Hz input and as well as keeping time,
> detects and uses the cutoff periods like a switch to set the time which
> is done while the rotor is turning.
>
> The display is not quite symmetrical top and bottom as the LEDs and PCB
> spin in the vertical plane like a real propellor. The effect is still
> quite stunning though.
>
> The missus can't quite work out the time though because it's displayed
> in Zulu.
>
> [ 03:49 z ]
>
> She asked me what is the Zulu time.
>
> I replied "Oomgalla banaswalla"
>
> Tch! Tch!
>
> Sad isn't it......
>
> --
> Best regards
>
> Tony
>
> mICros
> http://www.bubblesoftonline.com
> salesEraseME.....bubblesoftonline.com
I know a few people here will be interested in the artsy aspect of
this, but I love to think about the technical implementation.
Hundreds of balls suspended from string. Each ball is raised and
lowered independantly so you can make shapes in 3D space (although I
wouldn't call it 3D as you couldn't have a ball exactly below another
ball - maybe 2.5D... ;-)
Probably an interesting balance between weight of ball/effect of air
currents on ball/visibility of string/power, speed, size, and noise of
motors, and, of course, cost.
>I know a few people here will be interested in the artsy aspect of
>this, but I love to think about the technical implementation.
>
>Hundreds of balls suspended from string. Each ball is raised and
>lowered independantly so you can make shapes in 3D space (although I
>wouldn't call it 3D as you couldn't have a ball exactly below another
>ball - maybe 2.5D... ;-)
>
>http://www.youtube.com/watch?v=hlx-M53dC7M
>
>Probably an interesting balance between weight of ball/effect of air
>currents on ball/visibility of string/power, speed, size, and noise of
>motors, and, of course, cost.
>
>-Adam
I've seen this in person - truly amazing.
The most surprising thing is that it's completely silent - I suspect the strings pass through a
layer of sound insulation.
There are some making-of pics here
The PDF has a close-up of the winch, which appears to be a fairly simple stepper-motor & drum,
possibly with a controllable friction brake. If you look closely at the pic in the PDF, there is
something next to the stepper, which could be a brake actuator, or possibly an encoder.
As regards air currents, the room has clearly been carefully designed to avoid them - it's enclosed
except for a fairly small viewing doorway.
On Mon, Jun 22, 2009 at 9:17 AM, M. Adam Davis<RemoveMEstienmanEraseMEEraseMEgmail.com> wrote:
> I know a few people here will be interested in the artsy aspect of
> this, but I love to think about the technical implementation.
>
> Hundreds of balls suspended from string. Each ball is raised and
> lowered independantly so you can make shapes in 3D space (although I
> wouldn't call it 3D as you couldn't have a ball exactly below another
> ball - maybe 2.5D... ;-)
>
> http://www.youtube.com/watch?v=hlx-M53dC7M
Here's a more low tech way to get pretty moving shapes...
-j
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
-Douglas Adams
The wooden mirror is my all-time favorite tech+art piece, ever. It was
part of the inspiration for me to switch from windows application
programming (a serious yawn) to do freelance electronics design for
artists (and in general) back in 2001. I always played with it for a
few minutes every time I went to the ITP semester art+tech student
project show at NYU when I lived in new york.
J
Jinx wrote:
> Would be just so cool to add a camera to the floating balls, like
> the Wooden Mirror
>
> http://www.youtube.com/watch?v=8HqHg_GRhSU
>
> www.smoothware.com/danny/woodenmirror.html
>
asu.edu
