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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

Master Category List - Dave's Circuits

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Camera Circuits

9v Powered Xenon Photoflash Controller  -  This 9v battery powered circuit is designed for remote control flash needs. A charge control circuit turns off the high voltage generator when the photoflash capacitor is fully charged. A neon lamp is included to indicate when the system is ready to flash . . . [Circuit by David A. Johnson P.E.,  06/03/00]


Camera Shutter Time Measurement  -  A while back I received an email from someone who needed a simple way to measure the speed of a photographic camera.  I thought about this and suggested the method below.  It relies on an oscilloscope and a cheap photodiode to measure the speed . . . [Hobby Circuit designed by David Johnson P.E.,  08/14/11]


Cheap Close-Up Camera Lens  -  I often use my digital camera to take photos of some electronic projects. At times, I need to get in close to capture some details. But, without some additional optics, my camera just could not maintain focus, as I received closer to an object. Being a cheap . . . [Hobby Circuit designed by Dave Johnson P.E.,  04/01/05]

Controller for a 9v Powered Xenon Photoflash  -  This 9v battery powered circuit is designed for remote control flash needs. A charge control circuit turns off the high voltage generator when the photoflash capacitor is fully charged. A neon lamp is included to indicate when the system is ready to flash . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/03/00]


Darkroom Camera Shutter Timer  -  This circuit was designed to control a film exposure shutter for a darkroom. It has 8 time steps ranging from 0.35 seconds to 4 seconds. It is activated by a foot switch and draws power from an external 12-volt DC supply . . . [Circuit by Dave Johnson P.E.,  06/11/00]


DVD Recorder + TV Camera Make Cheap Data Logger  -  Sometimes recording the results of a test requires as much ingenuity as designing the product. Consider a situation which requires the collection of many different variables over a long period of time . . . [Hobby Circuit designed by David A. Johnson P.E.,  04/01/05]


Remote TV Camera Power  -  A while back I received an email from a company with a problem. They needed a security camera installed at some remote location.  The camera was a high quality color camera sending out standard NTSC video through a long 500 foot 50 ohm coax cable.  With some difficulty they got the coax strung.  They were told that there would be AC power near the camera location to power that device.  But, they then learned that in fact, there was no power available.  They thought about using a solar panel and a battery but they decided to call me for help instead.  Was there some way to power the camera without stringing another cable? . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/03/11]


Solar Powered Infrared 1W Security Camera Illuminator  -  Many security cameras are equipped with an array of infrared LEDs to illuminate an area in front of the camera with invisible light for night time surveillance.  However, there are times when a remote area, well away from the camera, needs additional infrared light.  The circuit below uses a modified solar powered path light to bathe a fairly large area with 850nm infrared light . . . [Circuit by David Johnson P.E.,  06/22/14]


Timer for Darkroom Camera Shutter  -  This circuit was designed to control a film exposure shutter for a darkroom. It has 8 time steps ranging from 0.35 seconds to 4 seconds. It is activated by a foot switch and draws power from an external 12-volt DC supply . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/11/00]


Xenon Photoflash Controller  -  This 9v battery powered circuit is designed for remote control flash needs. A charge control circuit turns off the high voltage generator when the photoflash capacitor is fully charged. A neon lamp is included to indicate when the system is ready to flash . . . [Circuit by Dave Johnson P.E.,  06/03/00]


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