EVERYTHING FOR ELECTRONICS
In the November Q&A column,
Russell Kincaid designed an eight
channel thermocouple interface
circuit around the AD594 IC.
By coincidence, I helped another
hobbyist with a similar problem and
also chose the AD594 device.
According to the manufacturer,
this device can be used after an
analog MUX switch to select multiple
thermocouples, yet only use one
AD594. Quite a cost savings as the
AD594 retails for $10 to $20 each in
hobby quantities! The only requirement is that the MUX and related
interconnections are held at the same
temperature (isothermic) to get good
accuracy. The application note AN369
is very helpful (link: http://tinyurl.com/
256lzt). Keep up the good work!
— Peter J. Stonard
line, they shout “Bingo!” and halt the
game. So we have a third sub-set of
four or five ‘win’ numbers (four if the
free cell, if used). The win is declared
when these five numbers are verified.
The greatest number of the members
in the universe that can be called before
a Bingo! is 19 (plus that free space). So
the project firmware doesn’t need to store
all 75 possible universe members — just
an array of the sub-set called so far in the
current game. Most high-level languages
also include a pseudo-random number
generator that can be used to select the
next picker number.
This is an interesting mental
exercise in logic and well suited to a
uC project! It seems to me that the
firmware should vend random
numbers (from the universe set of 75)
on each PICKER button request until
a player shouts Bingo! Next, the
VERIFY button is pressed by the caller,
stopping the selection of new numbers, and then automatically scrolling
through the members of the called
sub-set (plus the free cell) slowly for
verification. The caller presses a third
button (CONFIRM) as each called
number is displayed and verified on
the win line of the player’s card.
If all five members of the called
sub-set are verified, we declare the
player the winner (perhaps we have a
flashing light and sounder?), and a new
game can begin. If the five numbers do
not match the called sub-set, we have
a denied win. The firmware continues
to scroll through the called numbers
again (in case one was missed during
initial verification) until the picker presses CONTINUE (the fourth button).
After a false win has been
disqualified, the same game progresses
and new numbers are picked at
random from the unused universe set
(and copied to the called sub-set)
until someone shouts the next Bingo!
A new game starts by cycling the
power switch, but care must be taken
to scramble the pseudo-random
number generator (typically by using
a new seed number for each game).
— Peter J. Stonard
Continued on page 91
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Response: Thanks for the feedback!
I wish I had found that application note
earlier. Anyone planning to measure
eight temperatures should read AN369
and install the isothermal block and
reference junction per Figure 11 of the
AN369. — Russ
Admittedly, I’ve never played
Bingo — it looks like fun! I’m having
trouble getting my head around the
user interface presented in Charles
Irwin’s project in the Oct. ‘07 issue.
What is the function of the “verify
plus one” and “verify plus 10” buttons?
I’m confused why we would add one
or 10 to any existing numbers?
As I understand it, the Bingo game
has a ‘universe’ set of integers (1
through 75 inclusive) and as the game
progresses, an unused number in the
universe set is selected at random and
given to the bingo caller. This forms a
sub-set of called numbers that can’t
be called again in this game and are
saved for verifying a winner. If a player matches five numbers on their win
8 February 2008
Lou Frenzel Marvin Mallon
Jeff Eckert Russ Kincaid
Fred Eady Vern Graner
Jeff Mazur Walter Lindenbach
Peter Hiscocks James Gaston
Larry Cicchinelli G. Y. Xu
George Steber Ron Hackett
Copyright © 2008 by T & L Publications, Inc.
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