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Inside view of camera. Note the Fresnel lens is still mounted in original sensor housing. This eliminates lens alignment problems. Hole in sensor housing is for "set-up" LED. One DPDT switch for "set-up" and "run".

Outside view of camera. Windows for flash and lens are plexiglas secured with small bolts.

View the basic timers' schematic (94k)

View a two-step version of this circuit.

View the timer PC board mounted inside the RS 49-425 (36k)

View Front (50k) and Back (55k) of the timer circuit board. Not super helpful - but it might give you some ideas.

This basic timer consists of two ICs and assorted discrete components. The ICs are: a 4538B dual monostable and a single NEC 2501 opto-isolator. On being triggered by the output of pin #2 from the "big IC" in the RS 49-425, "U1B" generates an adjustable time delay that inhibits multiple photos for the selected time duration. The time is set by adjusting the "POT". With component values shown, times can range from between ~15 seconds to 1.5 minutes. "U1A" generates a three second shutter time that drives the gate of "Q1", which then drives the input LED of the opto-isolator and trips the cameras shutter. During camera set-up, switch "SW1" to the "SETUP" position, which inhibits camera triggering and enables the set-up LED. The set-up LED will blink each time motion is detected when the switch is in "SETUP". In "RUN", the camera will be triggered and the "SETUP" LED will not blink, saving batt power.

Unlike the ever-popular TLC555's, the 4538B timers consume power only when active - a considerable savings in batt power. The use of an opto-isolator also reduces power consumption and is much cheaper and smaller than a relay. The 4538B's and opto's can be purchased for about 0.70 US$ each from Mouser Electronics.

Notes: Diodes "D1" and "D2" protect the IC from damage during power-down. Do not remove them. Do not use timing capacitors with a value over 100uF (as stated in the data-sheets for this part). Observe capacitor polarity marks. For accurate long duration time intervals between pics, see the "not-so-basic" circuit. A "dot" at the intersection of two lines denotes a connection.Two lines crossing without a "dot" means no connection.
The collector and emitter connections at the opto-coupler output have been tested and work with the Canon Owl series of cameras, the Canon Elph LT, and the Olympus Infinity Jr. These connections need to be reversed with some other camera models. The only known model that requires reversed connections so far is the Fuji 60-AF.

This circuit is small enough to fit inside the empty space above the original PC board in the RS 49-425. The time adjusting pot is mounted on the side of the case after removing the original speaker. View picture

I just recently finished this circuit and have not yet used it in the field. So far with indoor testing it's been working very well.
In case I drew it wrong, send corrections to: archilochus57@yahoo.com

A note concerning hardware / parts: The 100uF capacitor needs to be a very small type to fit in. These are fairly difficult to find in the retail market. I salvaged the one I used from a dead Infinity Jr camera. Cameras seems to have very small components. Since I like to make my projects as inexpensive as possible, I also salvaged the opto-coupler and diodes from a dead answering machine. The mounting standoffs are from an obsolete ISA card from an old computer. All of the wires are from a deceased VCR. The MOSFET and potentiometer are from some long forgotten equipment that I ripped apart.

View schematic for two-step timer.

This circuit was suggested by Richard Webb. The four 4538B monostable timers "A", "B", "C", and "D" are triggered in sequence. The first timer - "A" - is leading edge triggered by the output of the PIR sensor. "A"s time period is adjustable with "Pot1" from ~15 seconds to ~1.5 minutes. While "A" is high, no re-triggering of the timer circuit can occur - keeping the cam from being triggered many times in a row by the same subject. When "A"s output goes high, this leading-edge triggers "B", whose output goes high for ~2.2 seconds. "B"s output leading-edge triggers "C", and "C"s ouput goes high for ~4.7 seconds and turns on the 1/2 shutter press relay. When "B"s output falls, this falling-edge triggers "D" and "D"s output turns on the full press relay and a picture is taken. View picture of timing diagram. Use transistors to buffer the 4538 outputs from the relays or opto-couplers that drive the cameras shutter. The relays or opto-couplers should be returned to the input voltage before the regulator to avoid noise at the 4538's. The capacitors "C5" and "C6" should be placed as close as possible to the +V and ground pins of IC1 and IC2 to help reduce supply voltage spikes.

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