Expanding Inputs on BSII

Archiver

Hi there,

I need to measure the resistance of 64 LDR close to
simultaneously with my BSII. Does anybody know how I can do this kind
of thing?

Thanks,

Daniel W

Archiver

Hi,

Please specify a bit more on the following:

- your ultimate goal, i.e do you want the light vs. resistance curve, or
just find matched pairs, or what?
- The maximum allowed timeframe
- Are the LDR in-circuit or free

Greetings peter

---

Oorspronkelijk bericht

---

Van: danielixto@y... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mhI4KxUTpGJzDTz0UoRPimOpyanzgjeXj3ncRfMLP3cxfbjS9d5qkeBB528WL7TXdz2D0qsS3FMzJw]danielixto@y...[/url
Verzonden: vrijdag 2 november 2001 7:36
Aan: basicstamps@yahoogroups.com
Onderwerp: [noparse][[/noparse]basicstamps] Expanding Inputs on BSII

Hi there,

I need to measure the resistance of 64 LDR close to
simultaneously with my BSII. Does anybody know how I can do this kind
of thing?

Thanks,

Daniel W




To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.


Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

Archiver

That's a tall order. The Stamp really likes to do one thing at a time.
Even with a PAK-III or IV (which has RCTime commands) they will only do
1 at a time too. I guess it depends on what your idea of "almost
simultaneous" is.

If the Stamp is fast enough, but just not enough I/O, I wonder if you
could do this:

What if you had 17 I/O (either a BS2P40 or a regular Stamp with a PAK).
Could you put your resistors and capacitors in an 8x8 array? You'd have
8 "resistor drive pins" and 8 "sense pins". Each drive pin would connect
to 8 resistors. These 8 resistors would connect together on the other
side and go to the sense pin. Then 1 of 8 capacitors would connect
between the sense pin and ground. You'd leave all 8 drive pins as inputs
until you want to measure. Then you'd turn one drive bin on, pause, turn
it back off, and read the correct sense pin. Not sure that would work,
but it should.

Another possiblity would be to use 8 hex schmitt or CMOS inverters as RC
oscillators. You'd put the LDR (and maybe a fixed resistor) between
input and output. Then you'd put a capacitor from the input to ground.
The output would become a square wave you could measure with PULSIN. Now
you need 64 inputs (you'd have to go with a PAK or a multiplexer to get
that). You could use PAK 7's to measure the pulses simultaneously and
then the only thing is how fast you can read the PAK 7's.

Just some random, early-morning ideas :-)

Regards,

Al Williams
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm



>

---

Original Message

---

> From: danielixto@y... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=k5D0e_FTqpgSWxbGCkW8CbRRYiG0Qn9JXsQULc3TCrQRev3ImEmvlKiLbLbxbLoIdYhXEB_iYs7GKvE]danielixto@y...[/url
> Sent: Friday, November 02, 2001 12:36 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Expanding Inputs on BSII
>
>
> Hi there,
>
> I need to measure the resistance of 64 LDR close to
> simultaneously with my BSII. Does anybody know how I can do this kind
> of thing?
>
> Thanks,
>
> Daniel W
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>