No, it was early dynamic RAM chips. The charge in the memory cells leaks off more quickly when exposed to light. Early DRAM chips had a refresh cycle that was separate from the read cycle. You'd write all 1's to the chip, then repeatedly read the array without refresh. The cells that changed to 0's first had the highest brightness. Byte Magazine even had a construction article and code to make a simple B&W imager, long before CCD's or web cams existed. http://members.tripod.com/RoBoJRR/techcorner.htm "The September and October 83 issues of Byte Magazine contain an in depth article on building a camera based on Micron's OpticRam. Technology guru, Steve Ciarcia, provides not only a highly detailed description of the technology involved, but complete schematics and software listings as well. This fine article is included in his Circuit Cellar Inc. series as well and may be easier to find than the original Byte articles." Marc Nicholas wrote: > > Actually, maybe it was ROM chips...but, anyways, back in ceramic casing days > you could file away the casing and make a crude imaging array. > > -marc > > On 9/7/03 15:56, "John Ferrell" wrote: > > > I had not heard of the the EPROM bit, Please enlighten me. > > > > I have used a LED as a photodiode. Oops, you just infringed an AT&T patent. Seems that a Popular (Radio?) Electronics columnist wrote in the late 70's an article about doing exactly that, to experiment with bidirectional communication over the 'new' optical fibre technology. AT&T lawyers showed up with the police to execute a search warrant on his home, claiming that he must have committed industrial espionage in order for him to have written about their yet to be obtained patent. The columnist was so pissed off that he dedicated half his column to slamming their strong arm tactics. I think it was Don Lancaster, but I'm not certain. R > > ----- Original Message ----- > > From: "Marc Nicholas" > > To: > > Sent: Wednesday, July 09, 2003 3:28 PM > > Subject: Re: [EE]: Phototransistors (*holding my head in shame*) > >> Shades of using EPROMs as crude input devices ;-) > >> -marc > >> > >> On 9/7/03 15:10, "Steve Smith" wrote: > >> > >>> A more simple soulition than sawing the top off :- > >>> OC71 scrape the paint off and you have an OCP71 > >>> > >>> (maybe 30 years ago) > >>> > >>> Steve...... > >>> > >>> -----Original Message----- > >>> From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU] On > >>> Behalf Of Peter L. Peres > >>> Sent: 09 July 2003 17:38 > >>> To: PICLIST@MITVMA.MIT.EDU > >>> Subject: Re: [EE]: Phototransistors (*holding my head in shame*) > >>> > >>> > >>>>>> If it had two pins it would be called a photo diode... > >>>>> > >>>>> 2-pin phototransistors were more common than 3-pin in my experience. > >>>> > >>>> I concur with that...I've only ever dealt with the 2-pin variety > >>>> before, which is why the 3-pin variety kinda had me wondering. > >>> > >>> Hehe. 3-pin phototransistors were the most common in hobbyist times > > because > >>> that's what you set if you carefully saw off the top of a metal can > >>> transistor like 2N2222 ;-) > >>> > >>> Peter -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu