Thanks! That did the trick. This would be a pulldown resistor correct? I had to use a 330k to not loose the 0.6v input threshold for activation. Here is the new data... Smaller values are baseline and larger consecutive numbers are with alarm activation. If I want to get it cleaner I suppose I would have to supply a larger threshold voltage from the smoke detector and use a smaller resistor.
pin AIN6 value is 0 pin AIN6 value is 0 pin AIN6 value is 3 pin AIN6 value is 117 pin AIN6 value is 14 pin AIN6 value is 20 pin AIN6 value is 0 pin AIN6 value is 3 pin AIN6 value is 116 pin AIN6 value is 12 pin AIN6 value is 16 pin AIN6 value is 0 pin AIN6 value is 5 pin AIN6 value is 131 pin AIN6 value is 11 pin AIN6 value is 754 pin AIN6 value is 122 pin AIN6 value is 137 pin AIN6 value is 264 pin AIN6 value is 145 pin AIN6 value is 146 pin AIN6 value is 68 pin AIN6 value is 753 pin AIN6 value is 264 pin AIN6 value is 763 pin AIN6 value is 147 On Friday, December 19, 2014 10:07:05 AM UTC-6, TJF wrote: > > Hi! > > Am Donnerstag, 18. Dezember 2014 18:44:14 UTC+1 schrieb > [email protected]: >> >> I am trying use the Beaglebone Black to monitor a smoke detector >> activation. I have two wires coming from the smoke detector, ground and >> positive lead. The voltage on the wires will go to 0.6v when the detector >> is activated. I have the ground connected to the P9 header GNDA_ADC and the >> positive wire from the detector going to AIN6. When monitoring the base >> values of AIN6 without the detector being activated I get a wide range of >> values. Example output below... >> > > Post more information about the sensor if you want a concrete answer. > > >> pin AIN6 value is 2 >> pin AIN6 value is 105 >> pin AIN6 value is 0 >> pin AIN6 value is 0 >> pin AIN6 value is 687 >> pin AIN6 value is 195 >> pin AIN6 value is 29 >> pin AIN6 value is 1799 >> pin AIN6 value is 182 >> pin AIN6 value is 0 >> > > Where does these values come from and how are they scaled (ADC digits or > mV)? > > >> When the detector is activated the AIN6 value will just be above 1000. >> However the random base values frequently exceed 1000 as well resulting in >> a lot of false positive activations. >> >> My questions.. >> >> 1. Why is there so much variance in the base AIN values when no voltage >> is being applied? Should it not be near or at zero? >> > > 1. An open ADC input has high impedance, meaning any input will rise the > signal, even with low current. The connectors and cables act like an > antenna, you're receiving "Radio Erivan". -> Connect a resistor (~100 k) > between the AIN-6 pin and AGND to force the signal down. (You can use the > example oszi > <http://users.freebasic-portal.de/tjf/Projekte/libpruio/doc/html/_cha_examples.html#SubSecExaOszi> > > in the package libpruio <http://beagleboard.org/project/libpruio/> to > study the behaviors of the ADC subsystem.) > > 2. What can I do to remedy this so I can get consistently low baseline AIN >> values so I do not generate false positive activations? >> > > 2. Send a circuit diagram to get concrete answers. > > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
