Some RCX400 internals images

"Tim Killian" wrote in message
...
yes, the linear, absolute strip encoders would be nice, but putting
three or four of them into the system would cost at least $200, and
probably bump the retail price up by $500. Meade already uses the rotary
discs in their other products, so the cost is minimal.
I was thinking of the relative encoders, not absolute units. If you look
at the designs used on digital vernier calipers, these use a pair of PCB
strips, with fractionally different pitches, to produce a sinusoidal
coupling change as the strips are moved relative to one another. Since the
signals involved are low frequency (normlly 32K 'watch' crystals), you can
run the strip continuously, using a 'watch' battery. I use these in a
system here. The strips cost less than $2 in PCB 'real estate', and the
detector is an off the shelf IC, costing $1.65. These give 0.0005"
position detection, and finer strips can be made if needed. This in 10 off
quantities.
These typically run for a couple of years on a single SR44 cell. I use one
of the rechargeable Lithium cells, that is rated for 90mA/Hr, to run four
of these, and a clock. These systems have been in use for about five
years, without a single failure in this area, with an enviroment, that
makes the scopes look positively 'friendly' (the units live beside
streams/rivers, as part of a pollution measurement system).
Add an 'index' point, with a single optical switch at the end of the
travel, and the system can reset itself, even if power is lost.

It may be a shock to some, but I suspect a major goal of these RCX
scopes is to increase Meade's profits.
Yes. The key is that there was no development cost involved in using the
existing system, and no extra parts to buy.... :-(

Best Wishes

Roger Hamlett wrote:

"Chris L Peterson" wrote in message
...

On 14 Jan 2005 04:37:59 -0800, "Peter [astro.mp]"
wrote:


Thanks to some posters in the RCX400 Yahoo group, here's some images
of
the insides of the RCX400:

http://astroskys.com/v-web/gallery/t...00_0817?full=1
http://astroskys.com/v-web/gallery/t...00_0812?full=1
http://astroskys.com/v-web/gallery/t...00_0818?full=1

and many more he
http://www.tv-shopper.com/MEADE/

Hmmm... looks like the same cheesy pseudo worm gears they use in the
LX200 line.
That doesn't make me too optimistic that this will compete with high
end mounts.
We'll see- maybe some of the internals here are just prototypes.

The ones that worry me, are the three focusser motors. These have the
same 'mouse' encoders used on most of the other Meade motors, which
implies there is no real positional feedback for the corrector (they
are dependant on the accuracy of the threads, and the slop in the
gears). After some wear, the 'zero backlash' claims will begin to look
poor. I had been hoping, that they might have taken a lesson out of
most inkjet printers, and used a linear 'strip' optical encoder, to
actually allow the secondary/corrector position to be read. Then as
play starts to appear in the mechanism, and if there is any iregularity
in the threads, the system would compensate for it. Given how cheap
such encoders now are, this seemed the logical way to design the system
to be really accurately repeatable...

Best Wishes

Roger Hamlett wrote in message ...

I was thinking of the relative encoders, not absolute units. If you look
at the designs used on digital vernier calipers, these use a pair of PCB
strips, with fractionally different pitches, to produce a sinusoidal
coupling change as the strips are moved relative to one another. Since the
signals involved are low frequency (normlly 32K 'watch' crystals), you can
run the strip continuously, using a 'watch' battery. I use these in a
system here. The strips cost less than $2 in PCB 'real estate', and the
detector is an off the shelf IC, costing $1.65. These give 0.0005"
position detection, and finer strips can be made if needed. This in 10 off
quantities.
Best Wishes


I'm interested in which is the off the shelf $1.65 IC that does the digital
caliper function . If you know the chip maker, vendor, distributor, chip
designator , would be greatly appreciated.
Most of these work based on patents owned by Mitutoyo , I wasn't able to
find any standard part for the function.
While the electrodes configuration is something that can be circumvented due
to multiple layout possibilities, I don't know of any Western IC maker that
has an IC for this .
I have seen Chinese copies but the chip is bonded to the pcb directly so no
way to identify it . I have worked with more high end devices from Renishaw
and Heidenhain but they're in a much higher price class.

best regards,
matt tudor