Triboelectric amplifier

[Ian Macmillan]

I am interested in a possible application of an old technology which is
seemingly ignored by common texts.

This is the tribo-electric amplifier as exemplified by Edison's
Electromotograph telegraphic relay and Chalk telephone, and as I
remember, a WW2 German loudspeaking megaphone, which may have used a dry
mineral rotor (Agate?).

In the Chalk telephone, a small dampened chalk cylinder is rotated quite
slowly. A spring leaf connected to a diaphagm is pressed quite hard on
the chalk. A voltage between the spring leaf and the chalk varies the
friction acting on the spring leaf, causing the diaphagm to move in and
out in accordance with the applied voltage. Evidently quite low voltages
and currents are effective.

A certain amount of basic information can be Googled, but I'd like to
find out more about the effect and it's principle, and I'd appreciate it
if anyone can offer any references.

All the best

Ian Macmillan

[Ian Macmillan]

"Ian Macmillan" <iandmac@tpg.com.au> wrote in message
news:4461ecda$1@dnews.tpgi.com.au...
> I am interested in a possible application of an old technology which is
> seemingly ignored by common texts.
>
> This is the tribo-electric amplifier as exemplified by Edison's
> Electromotograph telegraphic relay and Chalk telephone, and as I
> remember, a WW2 German loudspeaking megaphone, which may have used a dry
> mineral rotor (Agate?).
>
> In the Chalk telephone, a small dampened chalk cylinder is rotated quite
> slowly. A spring leaf connected to a diaphagm is pressed quite hard on
> the chalk. A voltage between the spring leaf and the chalk varies the
> friction acting on the spring leaf, causing the diaphagm to move in and
> out in accordance with the applied voltage. Evidently quite low voltages
> and currents are effective.
>
> A certain amount of basic information can be Googled, but I'd like to
> find out more about the effect and it's principle, and I'd appreciate it
> if anyone can offer any references.
>
> All the best
>
> Ian Macmillan
>

Further to the above, I have found that this was the subject of patent No.
158787 by Thomas Edison on January 19th 1877, in which a paper sleeve
dampened with one of a variety of solutions including alcohol was mounted on
a metal cylinder, with a platinum probe providing the frictional contact.

The chalk cylinder appears in Edison's patent No. 221957 of Nov. 25, 1879 as
a later development using mainly KOH.as the electrolyte.

Elisha Gray, in letters to the "American Electrical Society" in 1875 and
1878 described an apparatus in which current passing through the fingers of
an operator in contact with a rotating diaphragm, produced sound in
accordance with an alternating current. Gray proposed this as a means of
transmitting music, as mentioned in pp 151-205 of "The Speaking Telephone"
by George B.Prescott (London 1879).

Edison thought that hydrogen evolved at the pressure point reduced friction,
and that reversing the potential produced oxygen which tended to increase
friction. However it is difficult to reconcile this explanation with Gray's
finger-on-the-diaphragm system, or the German device with the agate
cylinder.

I continue to hope that someone can cast a bit more light on this for me...

All the best

Ian Macmillan

[Ian Macmillan]

"Ian Macmillan" <iandmac@tpg.com.au> wrote in message
news:44688b47$1@dnews.tpgi.com.au...
> "Ian Macmillan" <iandmac@tpg.com.au> wrote in message
> news:4461ecda$1@dnews.tpgi.com.au...
> > I am interested in a possible application of an old technology which is
> > seemingly ignored by common texts.
> >
> > This is the tribo-electric amplifier as exemplified by Edison's
> > Electromotograph telegraphic relay and Chalk telephone, and as I
> > remember, a WW2 German loudspeaking megaphone, which may have used a dry
> > mineral rotor (Agate?).
> >
> > In the Chalk telephone, a small dampened chalk cylinder is rotated quite
> > slowly. A spring leaf connected to a diaphagm is pressed quite hard on
> > the chalk. A voltage between the spring leaf and the chalk varies the
> > friction acting on the spring leaf, causing the diaphagm to move in and
> > out in accordance with the applied voltage. Evidently quite low voltages
> > and currents are effective.
> >
> > A certain amount of basic information can be Googled, but I'd like to
> > find out more about the effect and it's principle, and I'd appreciate it
> > if anyone can offer any references.
> >
> > All the best
> >
> > Ian Macmillan
> >
>
> Further to the above, I have found that this was the subject of patent No.
> 158787 by Thomas Edison on January 19th 1877, in which a paper sleeve
> dampened with one of a variety of solutions including alcohol was mounted
on
> a metal cylinder, with a platinum probe providing the frictional contact.
>
> The chalk cylinder appears in Edison's patent No. 221957 of Nov. 25, 1879
as
> a later development using mainly KOH.as the electrolyte.
>
> Elisha Gray, in letters to the "American Electrical Society" in 1875 and
> 1878 described an apparatus in which current passing through the fingers
of
> an operator in contact with a rotating diaphragm, produced sound in
> accordance with an alternating current. Gray proposed this as a means of
> transmitting music, as mentioned in pp 151-205 of "The Speaking
Telephone"
> by George B.Prescott (London 1879).
>
> Edison thought that hydrogen evolved at the pressure point reduced
friction,
> and that reversing the potential produced oxygen which tended to increase
> friction. However it is difficult to reconcile this explanation with
Gray's
> finger-on-the-diaphragm system, or the German device with the agate
> cylinder.
>
> I continue to hope that someone can cast a bit more light on this for
me...
>
> All the best
>
> Ian Macmillan
>
Further to the above, I have discovered a reference to a practical
application of this as follows:

http://www.research.ibm.com/journal/rd/011/ibmrd0101H.pdf

I also found a reference to a simple explanation of the Johnsen - Rahbek
effect:

http://www.iop.org/EJ/abstract/0022-3727/2/3/303

It's not high faluting physics, but it's interesting.

Isn't it?

All the best

Ian Macmillan