Ryan Kremser wrote:

First of all the actual project is an bowling arcade game type thing
(http://www.pinrepair.com/bowl/goldmed3.jpg) its easier to see than to
explain. So the updates would only occur to update scores which aside from
when it happens isn't a huge time issue. (ex takes a second to update) The
solution that you mentioned before would definatly work for me, I"m just
wondering what kind of prices i should expect to pay for that setup. Just
to clarify all the inputs are going to be incoming through a ps2 port to the
computer and i'll be updating scores / lighting background / strike lights
ect. with these outputs.

The price from the Maxim website for the MAX6958AAPE (16 pin DIP) is about US$6 ea,
and they're ex-stock. The displays are common garden variety common-cathode types
that should be picked up from your local electronics shop for a couple of dollars each.
Discounts should apply if you're buying 18 of them. Larger displays, well, you
may be able to source them from an electronics discount warehouse.

As for controlling the whole shebang, I think using a PC would be overkill.
Personally, I'd use a controller, such as a PIC, or 8051, or something
similar. But then again, I like a challenge. I'd also break the project
down into subsystems. This is done for a couple of reasons.

1. Each element of the overall project has a large amount of control detail
associated with it. Each of the 7 segment displays has to be refreshed, changed,
etc, all within a certain timeframe, and each of the 7 segment displays have to
be turned on for an equivalent amount of time, otherwise some displays will be
brighter than others. A single controller that updates the displays, responds to
inputs, responds to interrupts, waits on timers, waits for electro-mechanicals
to complete their actions, etc, will all affect how the displays will appear.
However, a RTOS (Real Time Operating System) may take care of the majority of these
issues.

2. Subsystems can be easier to replace/debug.

Subsystems.
1. Scoring Display -This has already been dealt with, so no further discussion
is warranted.

2. Lighting - These may be low voltage/low wattage incandescent lamps, or white
or coloured leds, as required. Since they only need to be turned on and off,
they can use an I2C bus decoder such as a Philips PCF8574, and some buffers.
The PCF8574 has 8 channels, and you can hook up to 3 of these using different
hard-wired addresses on the same I2C bus, thus gettting up to 24 channels of
on-off control. These can be leds or relays, thus wiring is kept to a mimumum by
the inherent serial bus nature of I2C.

3. Inputs - A keyboard decoder that can debounce a pushbutton, encode the button,
issue an interrupt, and send the data to the microcontroller when requested,
takes much overhead off the ucontroller.

4. Central controller - This little baby sits in the middle and manages the
whole project.

5. Power supply - The current consumption of the individual subsystems can be
added up, and a suitable PSU can be purchased or designed, as required.

Simple, innit.

--

David