We have a rowing machine at home, which has a small built-in computer
thingy with a small LCD display, which unfortunately has got smashed.

Although I know sweet FA about electronics, I decided to dismantle the
computer to see if the screen was a readily replacable standard item.
Extracted the computer from the machine - it just comprises a circuit
board about 1" x 2" screwed to a casing, and below the circuit board is
the offending screen, about 1.5" x 3".

So I unscrew the PCB and lift it off, expecting there to be some form of
wires connecting it to the LCD display. But no, there isn't - absolutely
no evidence of any physical connection to the display whatsoever.

The display drops out of the casing and I can see it comprises 2 thin
sheets of glass (the front one being smashed), with a silvery-white,
non-conductive sheet covering the back. No markings of any description.

So...

First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?

Second - presumably these displays will typically be bespoke to whatever
equipment they come from? Or not...? (you'll have gathered it's not
possible to obtain one from the original manufacturer of the rowing
machine).

Thanks
David

wrote:
Common connection methods include flat foil ribbon cables, and direct
contact along the edges of the lcd (which yours probably has) - you
should be able to see corresponding contact pads on the pcb.

That's what I thought - but I swear to God there's absolutely *nothing*
there... no wires, no possible way to connect them, nada...

David

On 02/02/2008 08:16, Lobster wrote:
wrote:
Common connection methods include flat foil ribbon cables, and direct
contact along the edges of the lcd (which yours probably has) - you
should be able to see corresponding contact pads on the pcb.

That's what I thought - but I swear to God there's absolutely *nothing*
there... no wires, no possible way to connect them, nada...

sometimes they use a zebra strip of which is just a small block of
silicone "rubber" with alternate conducting/insulating layers

http://www.gsweb.com.tw/silicone_products_no.php?id=13

In message , Lobster
wrote

First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?

The connecting strip is conductive.

There are some contacts on the printed circuit board with matching
contacts on the display. The two items are joined with what looks like a
small strip of foam rubber. This strip is made a multi-layer sandwich
(running length wise) of an insulator , an electrical conductor, an
insulator, a conductor etc. The pitch of the conducting bits is much
finer than the pitch of the connectors on the board and display so no
matter how the strip is aligned it is guaranteed that there is least one
conducting path between the contacts on the board and on the display,
and with at least one insulating area between any two contacts. It is a
cheap and effective way of manufacture for a one off assembly process.
The strips are not designed to be reused but in practice you can
probably dismantle and reassemble the cheap ones used in your equipment
10s of times without too much problem.

These strips come with conductive layers being made of carbon, silver or
gold with the precious metal ones having a lower resistance. The ones in
your device will be the low cost carbon type and if you measure the
resistance of the foam between the shorter sides you will probable find
a resistance of a few ohms (maybe the low 10s of ohms)


Second - presumably these displays will typically be bespoke to
whatever equipment they come from? Or not...? (you'll have gathered
it's not possible to obtain one from the original manufacturer of the
rowing machine).

They will be bespoke items.

--
Alan
news2006 {at} amac {dot} f2s {dot} com

Andy Burns wrote:
On 02/02/2008 08:16, Lobster wrote:
wrote:
Common connection methods include flat foil ribbon cables, and direct
contact along the edges of the lcd (which yours probably has) - you
should be able to see corresponding contact pads on the pcb.

That's what I thought - but I swear to God there's absolutely
*nothing* there... no wires, no possible way to connect them, nada...

sometimes they use a zebra strip of which is just a small block of
silicone "rubber" with alternate conducting/insulating layers

http://www.gsweb.com.tw/silicone_products_no.php?id=13

Ah right... that'll be it. I have two of those, and thought they were
just mounts. Very odd - they just look like homegenous blocks or rubber
to me: can't see any conductors running through them. However, there
are some incredibly faint striations on the glass where these strips
touch, which must be contacts, and I can now see that there are 2 rows
of 13, what must be contacts on the base of the PCB which must match up.

Am I right in thinking that providing the PCB is registered accurately
versus the LCD display (which it is, via screws in the casing) that the
position of these zebra strips isn't crucial providing they cover the
area where the contacts are? Although it looks a bit academic now as I
can't see any chance of replacing the display. :-(

Thanks
David

On 02/02/2008 09:40, Lobster wrote:

Andy Burns wrote:

sometimes they use a zebra strip
http://www.gsweb.com.tw/silicone_products_no.php?id=13

Ah right... that'll be it. I have two of those, and thought they were
just mounts. Very odd - they just look like homegenous blocks or rubber
to me: can't see any conductors running through them.

the conductors are strips of carbon impregnated rubber

Am I right in thinking that providing the PCB is registered accurately
versus the LCD display (which it is, via screws in the casing) that the
position of these zebra strips isn't crucial providing they cover the
area where the contacts are?

yes the pitch of the zebra strip is finer than the pcb/lcd contacts, so
long as it is roughly in the right place it'll work

Although it looks a bit academic now as I
can't see any chance of replacing the display. :-(

bound to be a custom part.

"Lobster" wrote in message
...
First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?
Did you happen to notice two strip of rubber like material between display
and PCB? These are conductive, in than there are multiple tracks linking the
front to the rear.


Second - presumably these displays will typically be bespoke to whatever
equipment they come from? Or not...? (you'll have gathered it's not
possible to obtain one from the original manufacturer of the rowing
machine).

Very unlikely you will be able to find anything to replace it. Most are now
custom units.

In message , Lobster
writes
Andy Burns wrote:
On 02/02/2008 08:16, Lobster wrote:
wrote:
Common connection methods include flat foil ribbon cables, and direct
contact along the edges of the lcd (which yours probably has) - you
should be able to see corresponding contact pads on the pcb.

That's what I thought - but I swear to God there's absolutely
*nothing* there... no wires, no possible way to connect them, nada...
sometimes they use a zebra strip of which is just a small block of
silicone "rubber" with alternate conducting/insulating layers
http://www.gsweb.com.tw/silicone_products_no.php?id=13

Ah right... that'll be it. I have two of those, and thought they were
just mounts. Very odd - they just look like homegenous blocks or
rubber to me: can't see any conductors running through them. However,
there are some incredibly faint striations on the glass where these
strips touch, which must be contacts, and I can now see that there are
2 rows of 13, what must be contacts on the base of the PCB which must
match up.

Am I right in thinking that providing the PCB is registered accurately
versus the LCD display (which it is, via screws in the casing) that the
position of these zebra strips isn't crucial providing they cover the
area where the contacts are? Although it looks a bit academic now as I
can't see any chance of replacing the display. :-(

yes, a fairly standard way of connecting an LCD display

Where were you thinking of getting the correct LCD display from ?

or did you think that they are all the same ?

--
geoff

In message , Lobster
writes
We have a rowing machine at home, which has a small built-in computer
thingy with a small LCD display, which unfortunately has got smashed.

First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?
No, generally they use conductive rubber strips called (generically)
Zebra strip because they're stripey. I'd suspect they fell out, are
still in the case or attached to either the PCB or the display.

Second - presumably these displays will typically be bespoke to
whatever equipment they come from? Or not...? (you'll have gathered
it's not possible to obtain one from the original manufacturer of the
rowing machine).
Highly unlikely to be off the shelf but find somewhere to post pics of
it, you never know...

Thanks
David

--
Clint Sharp

Alan wrote:
In message , Lobster
wrote

First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?

The connecting strip is conductive.

There are some contacts on the printed circuit board with matching
contacts on the display. The two items are joined with what looks like a
small strip of foam rubber. This strip is made a multi-layer sandwich
(running length wise) of an insulator , an electrical conductor, an
insulator, a conductor etc. The pitch of the conducting bits is much
finer than the pitch of the connectors on the board and display so no
matter how the strip is aligned it is guaranteed that there is least one
conducting path between the contacts on the board and on the display,
and with at least one insulating area between any two contacts. It is a
cheap and effective way of manufacture for a one off assembly process.
The strips are not designed to be reused but in practice you can
probably dismantle and reassemble the cheap ones used in your equipment
10s of times without too much problem.

These strips come with conductive layers being made of carbon, silver or
gold with the precious metal ones having a lower resistance. The ones in
your device will be the low cost carbon type and if you measure the
resistance of the foam between the shorter sides you will probable find
a resistance of a few ohms (maybe the low 10s of ohms)


Second - presumably these displays will typically be bespoke to
whatever equipment they come from? Or not...? (you'll have
gathered it's not possible to obtain one from the original
manufacturer of the rowing machine).

They will be bespoke items.


No they wont..LCD factories have HUGE investments in auto plant, and
churn out a few standard sizes in massive quantities.

Sadly these are seldom sold in any kind of retail market.

You are probably reduced to getting it off the machine manufacturer, or
finding an indentical unit from something else.

In article The Natural Philosopher
wrote:

No they wont..LCD factories have HUGE investments in auto plant, and
churn out a few standard sizes in massive quantities.

While this is probably true for a standard matrix like a computer monitor or
TV I don't think it applies for the smaller displays on other devices such
as the OP's rowing machine. These often have faint outlines of all the
icons and digits visible on the screen even when the power is off. I
imagine these are all custom devices with the relevant graphic elements
embedded into the display. I expect this makes for much simpler logic
circuitry in the control system and the extra tooling cost when the panels
are bought in the tens of thousands will be relatively low.

--
Mike Clarke

In article ,
Mike Clarke writes:
In article The Natural Philosopher
wrote:

No they wont..LCD factories have HUGE investments in auto plant, and
churn out a few standard sizes in massive quantities.

While this is probably true for a standard matrix like a computer monitor or
TV I don't think it applies for the smaller displays on other devices such
as the OP's rowing machine. These often have faint outlines of all the
icons and digits visible on the screen even when the power is off. I
imagine these are all custom devices with the relevant graphic elements
embedded into the display. I expect this makes for much simpler logic
circuitry in the control system and the extra tooling cost when the panels
are bought in the tens of thousands will be relatively low.

I worked for a company which had some custom LCD panels manufacturered
back in the 1990's. At that time, you had a choice of using about
3 different types of display, and looking around, that still seems to
be the case today. The most basic is a 2 line by 40 character display
(and variations, but the chip they use always assumes it's driving a
2 line by 40 character display even where there are fewer characters
displayed, or a bigger display with multiple display chips, or is it
2 x 20 -- I forget now).

The second type is a graphic display made of pixels from which you can
create your own characters, glyphs, pictures, etc. I've never used one
of those, but I expect they're like the character displays in that there
are just a few similar driver chips with a reasonably common interface.
These first two are common off-the-shelf parts with equivalents from
many manufacturers.

The third type is where you have the display areas custom manufacturered
to your own image specifications. We supplied the image layout, and it
was etched (don't know the details of the process). ISTR a laser etch
was done for a couple of prototypes and some other process for the
bulk manufacture. The units are supplied with the zebra strip and a
connection board pre-assembled -- reliable assembly of the display
with the zebra strip is a specialist job. Usually the connection board
has the driver chip(s) on it too.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In message , The Natural
Philosopher writes
Alan wrote:
In message , Lobster
wrote

First - how on earth does the display work? Induction from the PCB
or something? Is what I'm seeing 'normal'?
The connecting strip is conductive.
There are some contacts on the printed circuit board with matching
contacts on the display. The two items are joined with what looks like
small strip of foam rubber. This strip is made a multi-layer sandwich
(running length wise) of an insulator , an electrical conductor, an
insulator, a conductor etc. The pitch of the conducting bits is much
finer than the pitch of the connectors on the board and display so no
matter how the strip is aligned it is guaranteed that there is least
one conducting path between the contacts on the board and on the
display, and with at least one insulating area between any two
contacts. It is a cheap and effective way of manufacture for a one
off assembly process. The strips are not designed to be reused but in
practice you can probably dismantle and reassemble the cheap ones
used in your equipment 10s of times without too much problem.
These strips come with conductive layers being made of carbon,
silver or gold with the precious metal ones having a lower
resistance. The ones in your device will be the low cost carbon type
and if you measure the resistance of the foam between the shorter
sides you will probable find a resistance of a few ohms (maybe the
low 10s of ohms)


Second - presumably these displays will typically be bespoke to
whatever equipment they come from? Or not...? (you'll have
gathered it's not possible to obtain one from the original
manufacturer of the rowing machine).
They will be bespoke items.


No they wont..

Of course they will

Do you think that the same display would be used for an exercise machine
as a CH programmer, for one CH programmer as another, for a GPS as a TV
remote?

I don't think so

LCD factories have H
UGE investments in auto plant, and churn out a few standard sizes in
massive quantities.


And ... ?

--
geoff

On Sun, 03 Feb 2008 09:33:49 +0000, The Natural Philosopher wrote:

Alan wrote:
In message , Lobster
wrote

First - how on earth does the display work? Induction from the PCB or
something? Is what I'm seeing 'normal'?

The connecting strip is conductive.

There are some contacts on the printed circuit board with matching
contacts on the display. The two items are joined with what looks like a
small strip of foam rubber. This strip is made a multi-layer sandwich
(running length wise) of an insulator , an electrical conductor, an
insulator, a conductor etc. The pitch of the conducting bits is much
finer than the pitch of the connectors on the board and display so no
matter how the strip is aligned it is guaranteed that there is least one
conducting path between the contacts on the board and on the display,
and with at least one insulating area between any two contacts. It is a
cheap and effective way of manufacture for a one off assembly process.
The strips are not designed to be reused but in practice you can
probably dismantle and reassemble the cheap ones used in your equipment
10s of times without too much problem.

These strips come with conductive layers being made of carbon, silver or
gold with the precious metal ones having a lower resistance. The ones in
your device will be the low cost carbon type and if you measure the
resistance of the foam between the shorter sides you will probable find
a resistance of a few ohms (maybe the low 10s of ohms)


Second - presumably these displays will typically be bespoke to
whatever equipment they come from? Or not...? (you'll have
gathered it's not possible to obtain one from the original
manufacturer of the rowing machine).

They will be bespoke items.


No they wont..LCD factories have HUGE investments in auto plant, and
churn out a few standard sizes in massive quantities.

As well as millions of specials. It's all done on big sheets for most of the process so having lots
of different designs is no big deal.

Consumer products like this will almost always use a custom LCD with whatever icons & other display
layout etc. they want. Tooling costs for this type of LCD are trivial (£ mid-hundreds to very low
thousands) compared to things like plastic mouldings.

In article , Lobster davidlobst
writes

Am I right in thinking that providing the PCB is registered accurately
versus the LCD display (which it is, via screws in the casing) that the
position of these zebra strips isn't crucial providing they cover the
area where the contacts are?

Yes.

--
(\__/) Bunny says NO to Windows Vista!
(='.'=) http://www.cs.auckland.ac.nz/~pgut00...ista_cost.html
(")_(")