On 7/4/06, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
> Obviously you might well not be able to do this. In which case, you
> either have to buffer the port lines (to reduce the output impedance
> there) or add a buffer amplifier on the analogue output. Either solution
> involves active components that need power.
I know that the "right" way to do it involves active components...
given my 95% success with passive components, I was hoping to squeak
by. If I could get power and data from the same source (see below), I
wouldn't be quite so picky.
> Can't you grab power from the computer? Obvious places would be either
> the keynoard connector or the joystick port.
Keyboard connector is a possibility. This (server-class) computer
doesn't have a joystick port. As I mentioned in another message, my
breadboard is extracting power for projects from the USB port (cable
came from a dead keyboard), but I really don't think the mechanical
arrangement is viable in a user environment. We've lost three of
these machines in 12 months by static discharge when plugging in USB
devices - you can see the resultant hole in the epoxy of the gate
array that does the USB... the machine is totally fried after a
spark... I'd prefer to glue the cover shut to keep users out; I
certainly don't want to leave a device behind that encourages them to
fiddle with the front USB ports. No... we don't have any powered USB
hubs here - the ports the vendor designs in are the ports we have to
I'd probably be best served by rigging up a back bracket with a custom
power cable - that way, at least, it'd be out of sight, out of mind
> I have never forgivven IBM for not putting a +5V line on the parallel
> port. It would be so useful for homebrew add-ons. I have modified a few
> parallel cards (cut and jumper in the obvious way) so that pin 25 is a
> +5V output, the problem then is that any normal printer cable will short
> the 5V line to ground.
That's a nice hack, and one I might have done for myself back in the
ISA days, but as I mentioned in another message, an official +5V
output pin on the Amiga 1000 caused lots of people lots of grief and
C= relented with the A500 and A2000 and went with a totally
PC-printer-cable-compatible port after the A1000.
I've seen some goofy designs for getting power to an external device -
molded DB25s with integral coaxial power connector (for an early
powered mouse), and more than one design for a male/female keyboard
power connector (Xircom did one for their PE3 Pocket Ethernet
Adapters)... it would have been so much easier if there had been an
official way to tap power.
> > two, because I'm at the South Pole and I have to work with what I have
> > on hand - there won't be another plane for nearly 4 months.
> Ah, and you don't have any DACs in the junk box...
We have many, many parts in drawers (I probably have access to 20-25
parts bins), but DACs are not among them. I might be able to scrounge
something off of a dead board (we have some Vaisala weathersonde
boards and some UPS boards in the scrap pile - I did manage to score
16 IRF510s from a dead UPS a couple of months ago, perfect for a
thermo-controlled fan ;-)
> But do you have suitable resistors? I've not done the calculations, but intuitively, you
> need the R's and 2*R's all to agree to better than 0.5% for an 8 bit
> converter. 0.5% resistors are not common.
Ah... we have quantities of 1% resistors, but no 0.5% resistors that I know of.
As for my simple 8-value DAC, I used 5% resistors and hand-sorted them
for a (nearly) consistent 1:2 ratio up the line. We have a number of
the ancient Ohmite red drawers with a dozen values per tray (there are
lots of components here from the 1960s, including a bucket full of
I've heard rumors that an RK05 suitcase exercisor exists. Has anyone
ever seen one or used one? Does anyone have one?
I assume it would connect via the "unibus" connector and exercise the
drive (seek, read, write, etc...)
I need one plastic part to make this one complete.
E-mail me offlist please. Thankee.
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I turned these up looking for something else this morning
Related to Billy's postings a while back about ESD issues in disc drives and
why it is more of an issue in modern drives.
I've been skimming the recent threads on microfiche scanning with some
interest. Just out of curiosity, has anyone tried scanning
microfilm/microfiche with a film scanner?
Just interested, because VueScan (free trial from www.hamrick.com, $50 for
the basic licence, $90 for the 'professional' licence) seems to have a setting
for microfilm scanning. Unfortunately I don't have any microfilm to try it
out, but my film scanner (a Minolta DiMAGE Scan Dual IV) only takes mounted
35mm slides and 35mm strip film, so anything I put in would have to meet those
I could (in theory at least) bodge up a cardboard carrier for my flatbed
scanner (an Epson Perfection 2400 Photo) and use that, but I don't rate its
optical quality for transparency film very highly.
I was just curious if anyone had considered trying it... I'd love to but
like I said, I haven't got any film to test with.
Phil. | Kitsune: Acorn RiscPC SA202 64M+6G ViewFinder
philpem at dsl.pipex.com | Cheetah: Athlon64 3200+ A8VDeluxeV2 512M+100G
http://www.philpem.me.uk/ | Tiger: Toshiba SatPro4600 Celeron700 256M+40G
I have this Kensington Expert Mouse here (c. 1995), and I'm wondering
if I'm missing an external adapter box... it has a Mac-style DIN-8 for
a connector, and inside, I see 3 chips - an LM358 near the DIN-8, an
LP339N (quad comparator?) and a 24-pin Motorola SC417907P with an
adjacent 4.00MHz crystal resonator, clearly some sort of
microcontroller being used as a mouse protocol encoder. One
mysterious part is the optical receiver, an SD6150... it's an
acrylic-housed device with a visible silicon die, and 5 leads. It's
positioned to catch the light off of the marked roller that catches
light from an IR diode, so it's got to be something like a
multiple-element photodiode (they are marked "DTC1" and "DTC2"), but
googling isn't not revealing any hard details on the part. I _think_
I can see 4 "panels" on the die, so it might be a Common lead and 4
light sensitive patches that the board would use to turn a strobed
light from the roller into both phases of the quadrature waveform.
I don't think the folks that once used this had old Macs (perhaps they
did 10 years ago), so my first thought is... what protocol might this
speak and am I missing an external adapter to, say, a PS/2-style mouse
cable? Another possibility I can think of is that it is designed to
hook to a Microsoft Bus Mouse board (probably have one of those
hanging around here somewhere).
I did some googling on it and can't find any internals info or any
"hack" articles. Honestly, I could use this even if I have to extract
raw quadrature and do something with that. It's a single-sided board,
so reverse-engineering it is not impossible, but I thought I'd ask
first and see if anyone knows some technical details on it.
Very likely that it uses an adaptor box. Almost all Macs (exclusive of the Plus) with MiniDIN-8 serial also had MiniDIN-4 ADB interface, which would be what a mouse would use.
Even on a Plus I don't see why anyone would go to the trouble of rewriting enough drivers to use the serial ports for a mouse when the mouse port is available and SSW expects its use.
Could this be a NeXT trackball?