Tacos Digest, Vol 127, Issue 5

[Chip Fetrow]

Funny thing was, we bought a carrier current device with our laundry pair.

It lets us know everything.

--chip

On Sep 4, 2013, at 5:32 AM, tacos-request at amrad.org wrote:

> Message: 4
> Date: Tue, 03 Sep 2013 20:31:43 -0400
> From: Rob Seastrom <rs at seastrom.com>
> To: tacos at amrad.org
> Cc: rs at seastrom.com
> Subject:Tacos Digest, Vol 127, Issue 5
> 
> Hey folks,
> 
> I'm on the cusp of throwing together something quick and dirty (and
> raspberry pi based probably; the price is right) that will talk to a
> couple of sensors hanging over the "cycle complete" LEDs on our washer
> and dryer and send appropriate text messages to a cell phone when
> they're done.
> 
> I was thinking about a CdS photoresistor (they're making 'em *tiny*
> these days!) with one leg hooked to Vcc, the other to a pull down
> resistor to ground, with the connection between the two hooked to a
> binary input pin of the Pi.  Kind of a quick and dirty "light
> controlled voltage divider".  Should work for a high impedence pin on
> the Pi with minimal fuss.
> 
> Tape the whole affair over the LED (maybe with a software controlled
> LED stuck to the back so that it can be lit to not lose having an LED
> on the front of the device when the cycle is done).
> 
> Only thing is, I'm not sure what the sensitivity of a typical CdS
> photoresistor is in the green band, and LEDs aren't very broadband so
> I can't get by on slop if this is a blind area for them.  Spec sheets?
> Ha.  That's like trying to find a datasheet on a 2.2k gold band
> resistor.  These things are buck-apiece commodities.
> 
> Can anyone shed some light (pun intended) on the receive passband of a
> typical CdS photoresistor?
> 
> Thanks,
> 
> -r