Newsgroups: comp.robotics
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!news.mathworks.com!news.kei.com!eff!wariat.org!malgudi.oar.net!picker!central.picker.com!sam
From: sam@colossus.stdavids.picker.com (Sam Goldwasser)
Subject: Re: Q: Strobe FLASH
In-Reply-To: onat@turbine.kuee.kyoto-u.ac.jp's message of 31 Oct 1994 03:46:08 GMT
Message-ID: <SAM.94Oct31131057@colossus.stdavids.picker.com>
Sender: news@picker.com
Nntp-Posting-Host: 144.54.160.15
Organization: Picker International, St. Davids
References: <391pa0$5em@hemp.imel.kyoto-u.ac.jp>
Date: Mon, 31 Oct 1994 18:10:57 GMT
Lines: 48

In article <391pa0$5em@hemp.imel.kyoto-u.ac.jp> onat@turbine.kuee.kyoto-u.ac.jp (Onat Ahmet) writes:

   I have built a strobe flash to be used as a part of a vehicle guidence
   system. It forks fine, except that it has a simple flashing pattern;
   only once every second. I would like to build one which flashes a couple
   of times in rapid succession in each cycle; and pause for a time. This 
   pattern is similar to the strobe flashes used in modern cameras to reduce
   the red eye syndrome. 

   Building such a circuit to be powered by a high voltage supply is not
   a problem, but I have to use batteries, so I am looking for something 
   powered by four cells to give around 6 volts. The most obvious way 
   to do it is to use as many large capacitors as the necessary number
   of flashes, charge them at the same time and trigger each of them
   in sequence; but there MUST be a more clever solution (such as
   interrupting the current going to the flash lamp before the charge is
   used up and retriggering).

   The circuit will be a standalone application, so I do not really consider 
   using any microprocessor power in it, but if that is the way to go, I will
   use one!

First idea: rip the unit out of a defunct camera.

Second idea:

What you could do  easily is charge a large capacitor slowly
from your DC-DC converter, then have its output feed a smaller flash energy
storage capacitor through a resistor small enough to give you a fast recharge.

Building the DC-DC converter is pretty easy and you should be able to
make it run off of 6V without any problem.  You can use a simple power
oscillator feeding a home-wound step-up transformer.

How big is your flash?

A small unit using a 100 uF 330 V capacitor for the flash could say use a
1000 uF cap. for storage separated by a 500 ohm power resistor.  That would
give you a 100 ms or so recharge time.  The 1000 uF cap provides a buffer
between the relatively low power DC-DC converter and the tube as long as you 
do not flash too quickly - faster than your DC-DC converter can supply.

I would think that this would be easier than trying to interrupt the 10s-100s
of amperes of current flowing in the tube during the flash.

Email for any additional ideas.

--- sam
