OK, I think that noise might be an issue-LSR's aren't known for being quiet. I use alot of the Burr-Brown opt201/301 photodiode/integrated amp=20 assembly's in my work, but I need low noise and high sensitivity. I have=20 not tried the Taos parts yet, but they are on my list of devices to try for= =20 less demanding aps. If you don't need extreme sensitivity, I suggest you=20 avoid the Burr-Brown parts and go with the TAOS units. The Taos parts have some hysterisis built into them and the photodiode=20 active area is small, so they are less expensive to manufacture. My guess=20 is that they would be just the ticket for you. I'd also guess that you will= =20 need some simple software hysterisis too, but you probably have a good=20 handle on that already. To do it right, you probably do need the A/D converter and the programmable= =20 hysterisis available from the pic software. Have fun and be sure to get the free samples from TAOS, they are good about= =20 that aspect as well. Regards, Art At 04:25 AM 4/19/04, you wrote: >Art, > >I just plan to use it for ambient light levels. Actually I'm only >interested in if there is lights on (sun, lamps) or if its dark. I need >the threshold to be user settable as "dark" is a subjective thing. The >thought is that a node send out a message (VSCP) when the transition >occurs (with hysteresis of course). This message can be used by other >nodes to turn on/off lamps or do other things. > >I found a Light to voltage sensor, TSL250 from TAOS, that was rather low >cost and I will probably use that instead of the LDR. > >For those interested I why I need this: >VSCP, stands for Very Simple Control Protocol and is a very, *very* >simple higher level protocol over CAN/TCP/UDP and such. It is event >driven and all that a node does is that it sends out its event when it >occurs or at even intervals. Other nodes can "do stuff" or react on >this event (light a lamp, log to a database) etc. It's really stupid but >makes a system that is very easy to configure. More information is >available at http://www.vscp.org > >I have been working with this since 1984 (yes I know I'm slow...) when >the node was a 6800 and I think the manufacturing cost was about $250 >and RS-232 was the only communication option. Now the node is based >around a 12F675 or 18F248/258 using CAN and the cost is very low. Still >this is may something that never will be finished but its a fun ride >soldering, thinking about it, trying it out... > >/Ake > >-----Ursprungligt meddelande----- >Fr=E5n: pic microcontroller discussion list >[mailto:PICLIST@MITVMA.MIT.EDU]F=F6r Art >Skickat: den 18 april 2004 22:21 >Till: PICLIST@MITVMA.MIT.EDU >=C4mne: Re: [EE:]Light detector > > >You didn't say what data rate you were trying to receive. LDR's have >really >poor frequency characteristics, don't expect much better than 5 to 20 >Hz, >especially with a 500k series resistor. > >When I first read you message, I thought you were just trying to detect >ambient light levels, but not sure. > >Phototransistors are good for low data rates, up to 10Khz or a tad >higher >if you are using them in small signal mode. Otherwise, look at a >photodiode >for big bandwidth and a very large dynamic range. > >Smile, it can always be worse:>: > >Art > >At 02:05 PM 4/18/04, you wrote: > >I am in need for a low cost light detector that has a use settable > >trigger point for the light/dark threshold. My first thought has been >to > >just set up a voltage divider in the following way. > > > > +5V > > | > > | | > > | | 500K > > | | > > | > > | > > |--------- PIC ADC > > | > > | > > | | > > | | LDR > > | | > > | > > | > > --- > > > >The LDR has >500K resistance in darkness and 3K-20K at 10 Lux. > > > >One could use a PIC output pin to feed the divider instead of the +5V > >and just activate this when a measurement is needed. > > > >Is there any drawbacks with such a scenario? Is there a better way to >do > >this in a low cost way? > > > >/Ake > > > > --- > >Ake Hedman (YAP - Yet Another Programmer) > >eurosource, Brattbergav=E4gen 17, 820 50 LOS, Sweden > >Phone: 46 657 413430 Cellular: 46 730 533146 > >Company home: http://www.eurosource.se Kryddor/Te/Kaffe: > >http://www.brattberg.com > >Personal homepage: http://www.eurosource.se/akhe > > > >-- > >http://www.piclist.com hint: The PICList is archived three different > >ways. See http://www.piclist.com/#archives for details. > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body