Slip Rings

[colin]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once an
hour for a few days.

However it now seems I now need to run the thing continuously for several
days, the slip rings make an awefull noise and the contacts wear out too
fast (theyr rather stiff) although the pcb seems to hold up fairly well wich
is the opposite of what I expected. contact lube/grease makes a big
difference but not for very long.

Im just wondering if anyone has sucesfully made any slip rings, Im going to
ramake them but this time I think I will have to make them axialy instead of
radialy, (the shaft is 15mm diameter on the end of an induction motor), Ive
taken apart some relays, I might try and use the contacts from them, and
make the rings out of the contact strip.

Im also considering other options like tramsiting the data via wireless,
just one ring for the power would be a lot easier,
Is there an easy setup to go from usb to pc via wireless? or a (cheap) data
logger that conects to a pc wirelessly ?

I also could do with monitoring a few more signals, I already have a USB
data logger wich has many inputs, would the USB signals actualy cope with
going through slip rings ?

Colin =^.^=

 

[[email protected]]

You got it half right. Slip rings are usually copper but the brushes
are usually carbon because they are softer than copper and self
lubricating.

 

[colin]

You got it half right. Slip rings are usually copper but the brushes
are usually carbon because they are softer than copper and self
lubricating.

Yeah like in motor brushes, it was only meant as a short term thing to start
with, I didnt have any suitable motors I was prepared to sacrifice to use
the brushes from though.

maybe some car dynamo/alternator brushes would suffice but would be tricky
to mount.

I did just have a brainwave though, if I uses a second identical pcb instead
of the brushes and have some brass discs making contact between the two pcbs
free to rotate but guided by a spider, bit like an axial roller bearing.

thanks
Colin =^.^=

 

[[email protected]]

I think it would be simpler to just use pencil led, just measured the
resistance of a .5mm, it is low, but fragile, so why not use a
carpenters pencil? Just shape your point and cut to length, cost
negligible. Remove 3/8" of the wood from one side and drill a small
hole for a small screw to fasten your wire.

Rolf

 

[Paul Hovnanian P.E.]

Yeah like in motor brushes, it was only meant as a short term thing to start
with, I didnt have any suitable motors I was prepared to sacrifice to use
the brushes from though.

maybe some car dynamo/alternator brushes would suffice but would be tricky
to mount.

I did just have a brainwave though, if I uses a second identical pcb instead
of the brushes and have some brass discs making contact between the two pcbs
free to rotate but guided by a spider, bit like an axial roller bearing.

That might be better than a slips ring/brush, since the rollers will not
be sliding over the ring surface. On the other hand, the sliding effect
does keep the surfaces clean. A roller will just roll across any crap
that may settle on the ring surface.

For the data, you might want to consider some sort of low range RF
(BlueTooth, ZigBee, etc.) so as not to be subject to noise on the data
slip ring (if that's a problem). The power on the moving pat can be
filtered and a big cap or two can carry the system over the od slip ring
glitch.

 

[colin]

That might be better than a slips ring/brush, since the rollers will not
be sliding over the ring surface. On the other hand, the sliding effect
does keep the surfaces clean. A roller will just roll across any crap
that may settle on the ring surface.

Yes thats a point, still there wont be any need for grease to get gumed up
with dust etc.
maybe a felt pad to clean the surface .. and multiple narrow rollers (brass
washers) to cut through any debris.

For the data, you might want to consider some sort of low range RF
(BlueTooth, ZigBee, etc.) so as not to be subject to noise on the data
slip ring (if that's a problem). The power on the moving pat can be
filtered and a big cap or two can carry the system over the od slip ring
glitch.

Theres a 5v headroom on the power line with ULDO regulator and rechargeble
batteries to cope with interruptions, the data is very low frequency, a .1uf
cap and high impedance ip on the stationary side is enough to smooth out any
glitches, a seperate reference ring is used rather than power 0v.

Yes I havnt waded through all whats available in the short range RF stuff
yet. I think my mothorboard has some kind of wirless LAN facility. maybe
even a ring of leds and a sensor would be a solution.

Colin =^.^=

 

[Don Lancaster]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once an
hour for a few days.

However it now seems I now need to run the thing continuously for several
days, the slip rings make an awefull noise and the contacts wear out too
fast (theyr rather stiff) although the pcb seems to hold up fairly well wich
is the opposite of what I expected. contact lube/grease makes a big
difference but not for very long.

Im just wondering if anyone has sucesfully made any slip rings, Im going to
ramake them but this time I think I will have to make them axialy instead of
radialy, (the shaft is 15mm diameter on the end of an induction motor), Ive
taken apart some relays, I might try and use the contacts from them, and
make the rings out of the contact strip.

Im also considering other options like tramsiting the data via wireless,
just one ring for the power would be a lot easier,
Is there an easy setup to go from usb to pc via wireless? or a (cheap) data
logger that conects to a pc wirelessly ?

I also could do with monitoring a few more signals, I already have a USB
data logger wich has many inputs, would the USB signals actualy cope with
going through slip rings ?

Colin =^.^=

What happens if you try the super mangy slip rings on telephone cords?


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com

 

[Mike Monett]

What happens if you try the super mangy slip rings on telephone cords?

Many thanks,

Don Lancaster voice phone: (928)428-4073

Put a dab of plain vaseline on the contacts. This removes the grime and
gives true metal-to-metal contact. It leaves a thin film that keeps the
surface clean. This reduces the contact resistance by a factor of ten and
stabilizes it. Works on most electrical connections that operate at room
temp.

Try it on the CMOS clock battery, pcb and ram connectors, flashlight
battery connections and on/off switch, intermittent and scratchy noises in
telephone connectors, electric light bulb sockets (also makes them much
easier to remove when they burn out), car battery terminals, and any other
connection that operates at room temperature. Repeat every six months or so
when the connections start acting up again.

This is an old trick used by transmitter radio engineers since the 30's.
When the antenna wouldn't tune properly, they would unbolt the feedline
bars, clean the connections, apply vaseline, and reassemble. This solved
the tuning problems.

Regards,

Mike Monett

 

[Tim Wescott]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once an
hour for a few days.

However it now seems I now need to run the thing continuously for several
days, the slip rings make an awefull noise and the contacts wear out too
fast (theyr rather stiff) although the pcb seems to hold up fairly well wich
is the opposite of what I expected. contact lube/grease makes a big
difference but not for very long.

Im just wondering if anyone has sucesfully made any slip rings, Im going to
ramake them but this time I think I will have to make them axialy instead of
radialy, (the shaft is 15mm diameter on the end of an induction motor), Ive
taken apart some relays, I might try and use the contacts from them, and
make the rings out of the contact strip.

Im also considering other options like tramsiting the data via wireless,
just one ring for the power would be a lot easier,
Is there an easy setup to go from usb to pc via wireless? or a (cheap) data
logger that conects to a pc wirelessly ?

I also could do with monitoring a few more signals, I already have a USB
data logger wich has many inputs, would the USB signals actualy cope with
going through slip rings ?

Colin =^.^=

If you have the $$ see if you can find out what happened to Litton --
before they got bought up by Northrop-Grumman they had some 'budget'
12-contact slip rings for $200 ea. Whatever N-G division they've become
they may still sell them.

Even if you don't want to spend that much for slip rings they had a
pretty educational website on how the things were manufactured. If I
recall correctly they used real brushes -- bundles of silver wire that
rode in a 'v' slot in a disk to make contact. There's obviously a great
deal of science behind what they do, but their sliprings last forever.

Alternately, what's keeping you from going to Radio shack and buying
some DC motor brushes? They come wrapped in a cheap DC motor that you
have to take off and throw away, but they'll be designed to run against
copper which is what you're using now. If you can mount them so they
maintain pretty good contact you should be OK.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[Jamie]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once an
hour for a few days.

However it now seems I now need to run the thing continuously for several
days, the slip rings make an awefull noise and the contacts wear out too
fast (theyr rather stiff) although the pcb seems to hold up fairly well wich
is the opposite of what I expected. contact lube/grease makes a big
difference but not for very long.

Im just wondering if anyone has sucesfully made any slip rings, Im going to
ramake them but this time I think I will have to make them axialy instead of
radialy, (the shaft is 15mm diameter on the end of an induction motor), Ive
taken apart some relays, I might try and use the contacts from them, and
make the rings out of the contact strip.

Im also considering other options like tramsiting the data via wireless,
just one ring for the power would be a lot easier,
Is there an easy setup to go from usb to pc via wireless? or a (cheap) data
logger that conects to a pc wirelessly ?

I also could do with monitoring a few more signals, I already have a USB
data logger wich has many inputs, would the USB signals actualy cope with
going through slip rings ?

Colin =^.^=

if your really serious about it then maybe using a inductive method will
work for you?

 

[colin]

If you have the $$ see if you can find out what happened to Litton --
before they got bought up by Northrop-Grumman they had some 'budget'
12-contact slip rings for $200 ea. Whatever N-G division they've become
they may still sell them.

Even if you don't want to spend that much for slip rings they had a
pretty educational website on how the things were manufactured. If I
recall correctly they used real brushes -- bundles of silver wire that
rode in a 'v' slot in a disk to make contact. There's obviously a great
deal of science behind what they do, but their sliprings last forever.

I found a site that sold slip rings but my local distributers didnt stock
anything like it, and they were quite expensive. dont recall seeing any
details of how they were constructed, maybe they want to keep that a secret
to themselves, also very interesting was fibre optic slip rings

However the 'real brush' idea is quite interesting, wonder if a brush made
from copper wire aka 'a short bit of ordinary stranded wire' will do

Alternately, what's keeping you from going to Radio shack and buying
some DC motor brushes? They come wrapped in a cheap DC motor that you
have to take off and throw away, but they'll be designed to run against
copper which is what you're using now. If you can mount them so they
maintain pretty good contact you should be OK.

Good idea dont know why I didnt think of that before, oh I tend to just try
and use what I have at hand, just looked for some cheap motors on ebay found
5 quite cheep, stil dont like trashing new stuff, however found 4 cheap
motor brushes. they have round carbon type brush and coil spring wich is a
challenge to try and mount, however the brushes have a shoulder on them wich
i might be able to mount in a hole in the end of the contact strip.

thanks
Colin =^.^=

 

[Jim Thompson]

Put a dab of plain vaseline on the contacts. This removes the grime and
gives true metal-to-metal contact. It leaves a thin film that keeps the
surface clean. This reduces the contact resistance by a factor of ten and
stabilizes it. Works on most electrical connections that operate at room
temp.

Try it on the CMOS clock battery, pcb and ram connectors, flashlight
battery connections and on/off switch, intermittent and scratchy noises in
telephone connectors, electric light bulb sockets (also makes them much
easier to remove when they burn out), car battery terminals, and any other
connection that operates at room temperature. Repeat every six months or so
when the connections start acting up again.

This is an old trick used by transmitter radio engineers since the 30's.
When the antenna wouldn't tune properly, they would unbolt the feedline
bars, clean the connections, apply vaseline, and reassemble. This solved
the tuning problems.

Regards,

Mike Monett

For about two years now I've been applying Silicone Spray on light
bulb threads. No more getting out the 15' ladder to remove
frozen-in-the-socket bulbs.

...Jim Thompson

 

[Jim Thompson]

if your really serious about it then maybe using a inductive method will
work for you?

I used rotating transformers for the Hubble 'scope mirror electronics.
(The mirror floats on a magnetic field.)

...Jim Thompson

 

[John Larkin]

I used rotating transformers for the Hubble 'scope mirror electronics.
(The mirror floats on a magnetic field.)

...Jim Thompson

Good book: The Hubble Wars by Chaisson.

John

 

[Jim Thompson]

Good book: The Hubble Wars by Chaisson.

John

Haven't heard of it. Quick synopsis?

...Jim Thompson

 

[[email protected]]

Brushes are usually used when conduction path has more than one route,
like in armatures and variacs, otherwise they would short. I have seen
big slip rings before. Had some analog DC servo stuff around here some
time ago. High currents and low voltage are not really good in slip
ring use. An AC to DC supply would probably work better as a supply
with HV AC on the rings say 48 volts.
gs

 

[Rich Grise]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once an
hour for a few days.

....

Take apart a scrap car alternator?

Good Luck!
Rich

 

[Don Cleveland]

Hi,
I have a device that is rotating fairly slowly (1-5rps) and I need to
supply
power (atm 12v at 1amp, possibly needing 24v at 4 amps peak) and read a
couple of vlf signals,
At the moment I have tried to make some slip rings using (4) concentric
circular tracks on a pcb and some springy contact strip, I didnt expect it
to last forever but the experiment only has to run for a few minutes once
an
hour for a few days.

However it now seems I now need to run the thing continuously for several
days, the slip rings make an awefull noise and the contacts wear out too
fast (theyr rather stiff) although the pcb seems to hold up fairly well
wich
is the opposite of what I expected. contact lube/grease makes a big
difference but not for very long.

Im just wondering if anyone has sucesfully made any slip rings, Im going
to
ramake them but this time I think I will have to make them axialy instead
of
radialy, (the shaft is 15mm diameter on the end of an induction motor),
Ive
taken apart some relays, I might try and use the contacts from them, and
make the rings out of the contact strip.

Im also considering other options like tramsiting the data via wireless,
just one ring for the power would be a lot easier,
Is there an easy setup to go from usb to pc via wireless? or a (cheap)
data
logger that conects to a pc wirelessly ?

I also could do with monitoring a few more signals, I already have a USB
data logger wich has many inputs, would the USB signals actualy cope with
going through slip rings ?

Colin =^.^=

Colin:

Check out the Rotating connectors at:

http://www.mercotac.com/index.html

I don't know the cost, but they claim to have lower noise than slip rings.

Don Cleveland

 

[colin]

Colin:

Check out the Rotating connectors at:

http://www.mercotac.com/index.html

I don't know the cost, but they claim to have lower noise than slip rings.

wow they look cool, liquid metal .. mercury ?

Colin =^.^=

 

[Richard Henry]

Colin:

Check out the Rotating connectors at:

http://www.mercotac.com/index.html

I don't know the cost, but they claim to have lower noise than slip rings.

Will the application permit the use of mercury?