On Wednesday 30 October 2002 22:53, Bill Higdon wrote:
Keith Bowers wrote:
AD2S90-EB PRODUCTION Evaluation Boards - COMMERCIAL $89.06
AD2S90AP PRODUCTION PLASTIC LEAD CHIP CARRIER 20 COMMERCIAL $29.16
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I expect to need a 2-axis resolver to quadrature board, so I did a bit
more checking.
The evaluation board price above is quantity 1.
Unfortunately the above price for the chip is quantity 100 and is not
available for online purchase from Analog Devices WEB site.
Pioneer has ad2s90ap in stock with the quantity 1 price as $44.86. You
probably want an ad2s99 reference oscillator @$10.73 too, but out of
stock.
At a guess a 2-axis board with just quadrature output could probably be
hand wired for around $125 with all new parts.
More thinking is in order; such as serial out to a computer.
I have looked at these, and someone finally got smart! The cost for a
12 bit board back in 99 was very high. It took 2 8 bit converter chips,
a special chip to add their outputs together, and a high priced osc. The
8 bit chips were on the order of $300.00 each as I remember, and the
adder was about the same.
Bill Higdon
Another thing I have been contemplating is the Maxim MAX157/159 10/20 bit A/Ds
along with something like a DS89C420 (33 MHz clock) or maybe the Basic-X
stuff to do the arithmetic, but I haven't come up with a simple way to read
two signals at the same time since the samples must be perfectly synchronized
to the peak of the reference signal. By the time you add a sample and hold
chip in front and then read each sample things start to get complicated.
A really interesting solution would be the one TI has in a TMS324F240 DSP
application note. The approach could be really interesting if it was
completed. They don't appear to publish complete code for what they do and do
not include quadrature output in the design. The code for one axis, including
reference signal generation, used less than 25% of the processor, so it would
appear that a 2-axis board might be hand wired for about $50. As usual TI
wants a bundle for the associated compiler, but there is a GNU version at the
usual price 8o). One would also have to come up with a way to burn the
program into a chip. I have never gotten into DSP and would really prefer to
make chips with machine tools.
The more I write, the better the AD2S90s look <g>.
--
Keith Bowers - Thomasville, NC
