From: wbrown@bevsun.bev.lbl.gov (Bill Brown)
Newsgroups: rec.models.railroad
Subject: Re: Command Control Standard Status Update
Date: 13 Aug 1992 15:04:17 GMT
Organization: Lawrence Berkeley Laboratory, California
NNTP-Posting-Host: 131.243.192.17

In article <1992Aug12.183901.14259@pixar.com> Bruce@Pixar.com (Bruce Perens) writes:
>In article <4649@blue.cis.pitt.edu.UUCP> ebe+@pitt.edu (Elmer Beachley)  
>writes:
>
>> with a open system, multiple sources and competition, will the demand
>> for this type of stuff every drive the prices low enough to meet the
>> goal of a $50 decoder?
>
>Gosh, I don't see why not. Let's look at the hardware we are talking about
>here:
>
>First, a simple embedded-controller microprocessor. Say a 4-bit controller
>with 512 bytes to 1K internal PROM. These cost about $2 in quantity.

I think an 8-bit, like one of the Motorola 68HC05 series might be a better
fit - if it had an a/d one might be able to "close the loop" on the motor.
A bit more spendy though - maybe $5 in qty.  An a/d might also be nice
for detecting maintenance mode.

Your also going to need a little bit of hardware in the front end - need
to be sure that noise doesn't get mistaken for a (real) transition.

>Then a few bytes of non-volatile RAM for the ID and throttle curve data.
>Either EAROM, or battery-backed RAM. Say $2 for the RAM and $2 for the
>battery.

There are 1-chip micros with NVRAM and eprom on-board, including several
68HC05xxx flavors.

>Then we have a zener diode (for the maintenance-mode-detect feature) and
>the power supply rectifier and filter capacitor. Say $4 .
>
>Then there's the power transistor to drive the motor (we'll use the
>microprocessor to pulse-modulate it, so it won't run hot). $1 .

One obvious omission is that with only 1 transistor you've no way to
reverse the motor.  A motor-driver chip (on the order of $3 or so)
is a more reasonable choice.  In any case, it takes the equivilent of
several transistors and a couple of diodes.  If one wanted to be fancy
and do an analog drive it would add a few bucks.

>
>And we need a double-sided PC board. $5.

Probably reasonable, but to get this price is gonna require a fairly
large order.  Ties up capital.
>
>$1 for copying the instructions, and you have a $14 parts cost for a kit.
>Mark it up to $20 to cover shipping and other expenses, and any model
>club could distribute them.
>
>Now, do this on a commercial scale. Use surface-mount components and
>a microprocessor with built-in EAROM, and it's going to be cheaper than
>that. Pot the whole thing to protect it from prying fingers, and you  
>should still be able to make a profit at $30.

I think your estimate is a bit on the low-ball side.  As a general rule,
the cost to produce an item can be assummed to be about twice the cost
of the components.  One problem here is that the "run sizes" are likely
to be too small for automated assembly, unless you can afford to tie up
a whole bunch of money for a long time.  Which adds to the cost.

I see Marklin 2-rail digital decoders, which I assume are what you are
proposing to duplicate, advertised for about $70.  Generally, the
distributor gets a mark-up of 20% of the retail cost; the retailer gets
another 40%.  The retail price is therefore 2.5 times the wholesale
price, which must include the manufacturing cost, including the manufacturers
profit.  It may be possible to beat this, but it's not gonna be easy.
Unless you consider your time and effort, and the use of capital, to
be worthless.

One can "cut out the middleman" by attempting to sell by direct mail order,
but there are significant costs invovlved in that route as well.

>Now, if you can find me a microprocessor with built-in EAROM that fits
>in an 18-pin DIP or smaller, I can get this to fit in a Z-gauge tender.
>I can do all of the software work and most of the hardware. Anyone want
>to help?

You bet!  It looks like you're located in Richmond. We should probably
move this to e-mail or telephone.

Disclaimer:  These opinions are my own and have	    |
    nothing to do with the official policy or the   |  -bill
    management of L.B.L, who probably couldn't      |   wlbrown@lbl.gov
    care less about employees who play with trains. |