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DC power supply for a Canon 350D

The battery span on an imaging night for a standard Canon or imitation battery on my 350D was about an hour. this meant I had to go outside every hour and change the battery while in the meantime charging the other one that had been exhausted. This didn't work, as I was starting to go for longer total exposure times, and didn't want to have to go outside and stop my session every hour to change the camera battery. So I decided to make my own 12V DC to 8 V DC power converter in order to supply my Canon 350D from my regulated 13.8 V DC power supply that also my NEQ6 mount runs off. I used a very nice datasheet by Damiel McCauley, similar to this page by Renzo del Rosso who has the same idea, although Daniel's design has some better safety build in to prevent frying the camera in case of messing up the (+) and (-) in the dark, as well as reducing high frequency occilations by putting condesators over the input and output of the linear voltage regulator, ;-). Basicly you need to sacrifice an old battery to act as the camera connector and then make the DC-DC convertor as shown by Daniel using an LM 7808. On other modifcation I did to make the old battery usable as a connector is putting a 10 k resistor over the minus- and T-connectors inside the old battery casing. This then fools the camera in thinking it has a full battery, as otherwise the camera firmware may kick in and tell you that you need to replace your battery. The images below illustrate the final product in action.


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