After mucking around with multiple exposures during the eclipse, and\nforgetting more than once where i was at with the timing, I decided to\nhasten a project that I've had in the back of my mind for a long time. Canon\nmake a timed remote for the 20D and upwards but it is hideously expensive. I\nhave a Samsung GX10, and I couldn't find the existence of a similar beast to\nsuit, so I was planning on rolling my own. I had been planning on designing\na timer that would allow both control of Bulb exposures, and control of\nmulti-exposures. I no longer have access to things like a PIC programmer etc\nso it would have been a time consuming, and possibly expensive project.\n\nBrowsing a bit on the net indicated that quite a few astronomers use a\nlaptop computer to control time exposures. I wanted something more portable,\nand able to run longer without mains power, and so I started thinking about\nmy palm pda. I have an old M100 which has a serial port interface which I\nthought would be easier than using the USB port on a modern Palm. A bit of\ndigging around and I found it. New batteries, and it still worked.\n\nI discovered that the program "FotoTimer", which I've previously used to\ntime film development, also allows control of hardware through the serial\nport of the palm. It is intended to turn on enlargers etc. A few minutes\nlater, and I had a LED flashing under control of the Palm.\n\nA few more google searches and I found various circuits for controlling a\nCanon SLR from a palm. The Samsung GX10 uses basically the same remote\ninterface as the 300D/350D/400D series Canon cameras (I use a canon RS60 as\nmy remote) so the information to suit them should be relevant. I found a\nsmall circuit on one of the websites, which I knocked up as a prototype, but\nfound I had a problem - the GX10 goes into sleep mode after a couple of\nminutes, and the remote wouldn't wake it up. A bit of experimentation and I\nfound the GX10 requires the "ring" connector of the remote to be grounded to\nwake the camera up, so a slight modification and I came up with the\nfollowing circuit:\n[URL]http://www.flickr.com/photos/gdaj/1317816870/[/URL]\nIt all fits together neatly on a tiny piece of stripboard which fits neatly\ninside the plug backshell.\n\nIt works like a little beauty :-) With the FotoTimer software it is possible\nto control both the time the shutter is open and the delay between opening.\nA complete sequence of timings can be created, so for example I could do a 2\nminute exposure, pause for 2 minutes to wait for the noise reduction, take a\n4 minute exposure, pause for 4 minutes etc. Or I could do do multiple\nexposures where the shutter is triggered momentarily every x seconds for y\nsequences. The FotoTimer software also allows manual control and displays a\ntimer when working manually.\n\nWhile I can't be sure, this circuit should also work on 300D/350D/400D\nseries canon's in addition to the Samsung/Pentax DSLRs. It would probably\nonly need a suitable plug to work with other cameras.\nParts Cost (in Aussie Dollars):\nPalm M100 collecting dust (bought 2nd hand several years ago for . M100's\nand similar can be had on Ebay for around ).\nD9 Backshell </body>.85\nD9 Plug .01\n2.5mm Stereo Plug </body>.28\n1m Twin core Shielded Audio Wire </body>.89\n2 x 47k Resisters </body>.04ea\n2 x BC547 Transisters </body>.13ea\n2 x 1N4148 Diodes </body>.04ea\nTotal Cost .45 plus a few cents worth of solder stripboard etc, plus the\npalm which I already had. If I had to buy another palm off ebay the cost\nwould probably run to about . Compared to the Canon TC-80N3 which has an\nAussie RRP of 9, this is a bargain!\n\nI haven't taken it out for anything serious yet, but experimenting with it\nshows it to work like a little beauty. Hope this info is helpful for someone\nelse out there.