Strobe light
Jeff
it PCB looks a lot like the schematic at
http://www.aaroncake.net/circuits/strobe2.htm. What is the part on here
that actually fires the capacitors? I was thinking it was the neon tube and
heard it has about 90V going through it. Would I just be able to get a
(solid state?) relay rated at around 90V that would be put in place of it?
I plan to eventually hook it up to a serial port on my computer to remotely
control it. Thanks,
--Jeff
Roger Hamlett
"Jeff" <com.home@jeffv111> wrote in message
news:neoL7.62451$XJ4.36...@news1.sttln1.wa.home.com...
The problem is that the voltage on the firing circuit will keep rising
towards the supply voltage, till the system is fired. With the neon
trigger, this is allways at a safe level for the drive parts, but if you
don't trigger it, the voltages can rise to the point where parts in this
area could be damaged...
It is worth understanding, that there is no circuit to 'fire the
capacitors'. The main supply generates a DC rail, presented across the
Xenon tube, that is below the breakdown volatage of the tube. This can sit
there indefinately. The small transformer (T1), has a massive ratio, and
when a pulse of current is delivered through it's primary, a very high
voltage is generated to an extra pin on the side of the flash tube. This
ionises the gas in the tube, and a spark forms, discharging the
capacitors. The spark ends, when the endpoint voltage drops below the
value needed to sustain it. So it is the tube itself, that does the
'triggering'.
You can amend the circuit like this:
Remove the neon.
Instead install the neon, across C3.
Remove Q1, and instead fit a opto-coupled thyristor across here (source to
ground, drain to the transformer).
Now the existing pot, will adjust the _maximum_ rate that can be achieved,
setting the time taken for the voltage across C3 to rise.
Once this voltage is present at a sufficient level, triggering the
thyristor, will fire the tube. The neon will light if the tube is not
triggered, and help prevent the voltage from rising too far.
All your printer port needs, is a simple resistor drive to the LED in the
opto-coupler, and this provides the safetly needed.
Best Wishes
Mikey
Jeff wrote:
Maybe a photoflash unit, easy enough to salvage from a disposable camera, would be better for this type of application.
Since it charges up then waits for the shutter button to activate the
trigger contact.
You could then drive that trigger input on the flash with an opto
coupler from your puter.
I don't think these can rapid-fire and you'd have to replace the battery
with a power supply, but it might be less trouble than redesigning the
strobe light's circuits.
BE CAREFUL AROUND THAT HIGH VOLTAGE !!!
Jeff
specs are we looking at? Any part #'s? ;-) Thanks,
--Jeff
"Roger Hamlett" <ro...@ttelmah.demon.co.uk> wrote in message
news:DspL7.211$7z3.2...@news6-win.server.ntlworld.com...
Roger Hamlett
"Jeff" <com.home@jeffv111> wrote in message
> Where would you recommend getting an opt-coupled thyristor? What kind
of
> specs are we looking at? Any part #'s? ;-) Thanks,
These are small thyristors, used in quite a few bits of kit for mains
control and isolation. About 0.3A, 400V rating, and cost pennies. :-)
Sam Goldwasser
> Where would you recommend getting an opt-coupled thyristor? What kind of
> specs are we looking at? Any part #'s? ;-) Thanks,
Digikey, Mouser, etc.
See the Strobe FAQ at the site below. Plenty of info and circuits.
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