Having fun with disposable digital camera
This is the place contain some information and project related to Pure Digital PV2 camera!
The camera I'm targeting is the second version of the Pure Digital's digital disposable
camera. This one has a preview LCD on the back of the camrea. An excellent place to
find background information on this camera is at
www.maushammer.com
WARNING: The flash unit in the camera contain high voltage. Execise care when working
with the flash unit. DISCHARGE the photocap before working with the unit!
The best way to discharge the photocap is to use a 1K to 10K ohm resistor to short out the cap.
Do not short out the two photocap's leads directly, as that would create a large spark.
FLASH unit information
The PV2 contain a compact flash unit that runs off two AA batteries. This flash unit is
supprisingly complicated such a low cost camera. For most disposable camera, the flash unit
is often designed to discharge the photocap completely when triggered. But for the PV2,
the camera is actually designed with a TTL (Through the lens) metering system. This means,
the camrea will fire a short metering flash to measure the brightness of the flash and calculate
the brightness of the main flash that is required. The time between the metering flash
and the main flash is short enough that the eye can not tell them apart. To achive this,
the flash unit contain an extra switch to turn off the current flowing to the
xeon flash tube.
The Pinout of the FLASH unit is:
1: GND
2: PWM - Charge control (46Khz with 28% duty cycle)
3: TRIGGER (Low to trigger)
4: GND
5: Charge level - (280V charge gives a reading of 1.25V)
6: Shutter release switch. (Active low)
7: 3.3V power supply
8: Vbattery (Connected to the battery terminal directly)
You can see the pinout from the picture of the FLASH unit.
The first pin is the pin closest to the photocap. It is also marked by the square pad
instead of the normal round pad.
The 3.3V power supply can be connected directly to Vbattery. I have tested the unit
with a supply voltage down to 2.4V and the unit still work normally.
Control the FLASH unit through computer
This is my attempt to control the flash unit using a computer through RS232. The PWM signal
required to charge the photocap is generated by the PIC processor. The processor also sense
the voltage of the photocap and stop charging if the voltage reaches around 280V. The duration
of the FLASH is controlled by the host PC. When triggered with a reduced duration, the
photocap will reach chaged state faster. At 1/32 duration, it is possible to fire two times
with a full charge.
Firmware is located here: FlashControl.asm
Schematic is located here: Click
A picture of the setup is here: Click
Afterthought: It should not be hard to make the unit into a slave flash.
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Page last updated: September 16, 2006
Email: rihuang ([at]) gmail (*dot*) com
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