sergio masci wrote: > Hi Phil, I've looked at the datasheets again and see nothing about the > SFH309 being an IR filtered part. I did note that it has a response range > from 380nm to 1180nm while the SFH300 has a response range from 420nm to > 1130nm. > > What am missing / misreading? Take a look at the photo at and the PDF datasheet at . You have to read between the lines a bit: - Especially suitable for applications from 380nm to 1180nm (SFH309) and of 880nm (SFH309FA) Note the black colour of the SFH309FA illustration of the datasheet, and the severely limited spectral response. The spectral response alone indicates some form of IR filtering package; the black case confirms it. The standard SFH309 has a clear resin (or plastic) package and will respond to just about any wavelength in the visible light spectrum, and most of the near-IR range too. I tend to use SFH300s because they're very sensitive to red light, especially laser light. I've got a 1mW Maplin "experimenter's laser module" and an SFH300 rigged up on a breadboard to measure the rotation speed (in RPM) of a motor's drive shaft. It works pretty well - most of the limitations are on the PIC side (mostly the CCP bottoming out when the speed goes below ~600RPM). Optical alignment is a bit of a pain, but easier when the laser's collimator lens is deliberately set slightly out of focus. -- Phil. piclist@philpem.me.uk http://www.philpem.me.uk/ -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist