Since this question has come up more than once, here is another example
of a small electronic flash design - This time in ASCII.
--- sam
Photoflash from pocket camera (model unknown):
---------------------------------------------
This schematic was traced from an electronic flash unit from an inexpensive
pocket camera (110 film size probably). Errors in transcription are possible.
I have not entirely determined how the Ready Light functions as it is not in
the usual place monitoring the energy storage capacitor voltage. It seems to
operate on the principle that once nearly full charge is reached and the
invertor is not being heavily loaded, enough drive voltage is available from
an auxiliary winding on the invertor transformer to light the LED. It is
also interesting that the trigger circuit dumps charge into the trigger
capacitor instead of the other way around but the effect is the same.
Invertor Flashtube
+------------------------------+---------------------+--+--------+---+
| 1 K Ready LED | | | | |
| +--/\/\-----+--|<|-----+ | ______ On | +-+ +-+ |
Batt. _ | | | | | \___| )||( |
3 V ___ | +------|--/\/\/---+ | | __ Off )||( +|
2-AA _ | ||(2 .4 | 10 | Energy | | )||( _|_
___ | || +-------------+ | Storage | +-------+---+ ||( | | |
| | ||(5 .2 | | +| 280 uF | | ||( || |
+---+ || +------+ | __|__ 330 V | Fire -| ||( || |
| ||(1 | | _____ | (Shutter) | +--|| |
+---+ ||( | | | | +-----+ Trigger || |
3)||( 142 -|47 uF | -| | | | || _ |
<.1 )||( _|_ 6.3 | | | \ _|_ Trigger |_|_|
)||( ___ V | | | 1 M / ___ .02 uF |
+-+ || +-+ | | | | \ | 400 V -|
C| 4 6 | +| | | | / | |
B|/ | | | | | | | |
+--| 2SD879 +--------------|<|--+----------------+-----+--------------+
| |\ | | HV Rect. |
| E| | | |
| +-------------+------|------------------+
| |
+-------------------------+
Note: the polarities of the 47 uF capacitor and/or LED do not seem to make
sense but these were confirmed on a working flash removed from a dead camera.
There is almost no DC voltage across the capacitor at any time.
Invertor transformer winding resistances measured with a Radio Shack DMM.
Primary resistance was below .1 ohms.
| |
---+--- are connected; ---|--- and ------- are NOT connected.
| |
Date: Sun, 17 Mar 1996 02:13:18 GMT
Original Subject: Another photo strobe schematic