Post by thread:amphometer

Hi all, I don't know if anyone remembers, but awhile ago I built a PIC based amphometer cct. The way that it worked was to detect the light level change as a vehicle passed over two LDR's. This arrangement worked quite well and gave consistent and accurate results as verified with high speed video. The only problem was varying light levels which may be caused by artificial lighting and/or clouds moving around temporarily blocking the sun. I have played around quite a bit trying to erradicate this problem because due to the nature of it's use, it needs another person to adjust the threshold levels prior to using it. I have come up with a simple ALC circuit, (Automatic Level Control). The problem is that my op amp knowlege is not what it should be, so if anyone has some time to have a quick peek at it I would appreciate someone checking if it is ok. I have posted the detector cct on my web site at http//http://www.picnpoke.com/sch.gif It works (I hope) by the fact that the (+) input is always 1 diode drop below the (-) input until a rapid reduction in light level occurs, thus briefly changing the comparators output state. -- Best regards Tony http://www.picnpoke.com Email spam_OUTsalesTakeThisOuTpicnpoke.com