1. Ask them if they have ever sent the PIClist $20 or bought a mug. If no, then they are a cheap person indeed. (sips coffee smugly from his shiny new PIClist mug...) 2. In a constantly lit environment, such as a grocery store, just use a phototransistor, and look for a decrease in light or even a large change either way. Below a certain threcshold, the lights are out and the device can sleep. When the person walks in front of the sensor, presumable light levels will change, mostly darker unless they have on a white shirt. Any big variation from ambient would do. 3. For a one-off, hack into a PIR motion detector, $20US. --Lawrence ----- Original Message ----- From: "Spehro Pefhany" To: Sent: Thursday, March 14, 2002 9:03 AM Subject: Re: [EE]: Cheap Person Sensor > At 09:35 AM 3/14/02 -0500, you wrote: > >If you wanted to trigger a small point of sale device to talk to > >passerby's in the shopping market what sensor would you use that was > >inexpensive? > > Probably a PIR sensor, but you could consider a photoconductive cell if the > passerby would shade the sensor. > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the reward" > speff@interlog.com Info for manufacturers: http://www.trexon.com > Embedded software/hardware/analog Info for designers: http://www.speff.com > 9/11 United we Stand > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics