Question on 300V indicator or switch

[ks]

Hi,

I was wandering if any one would be able to help me here? I am building a
flash (strobe) that uses several 330V 120uF capacitors. So in order for the
flash to maintain the same light intensity need a simple circuit that will
allow the capacitors to only discharge when they reach about 300V or some
thing like that.



So if anyone could help me with this it would be greatly appreciated.



Thanks

 

[Mark Jones]

Hi,

I was wandering if any one would be able to help me here? I am building a
flash (strobe) that uses several 330V 120uF capacitors. So in order for the
flash to maintain the same light intensity need a simple circuit that will
allow the capacitors to only discharge when they reach about 300V or some
thing like that.

So if anyone could help me with this it would be greatly appreciated.

Google is your friend:
http://www.google.com/search&q=strobe+trigger+schematic

-- "I cannot say for certain over-unity is possible. All the laws of
physics seem to indicate that it is not. But these laws are only laws
in the minds of man; the universe knows no such law. Being only but a
man, I can't say but what I have observed, and that entails
incomprehensibly little of the universe." MCJ 2003

 

[ks]

well not really, genrally most people that use the internet know about
google.

Which also means that I've tried it with many different words or phrases
and apart from getting many usless pages of advertising or unrelated topics
the closest I've found was a 5 to 9V battery tester. So my problem is that I
can build it however I'm no really shure what most of the stuff may be doing
so I cannot even adapt it for use it with 300V DC.

 

[John Fields]

Hi,

I was wandering if any one would be able to help me here? I am building a
flash (strobe) that uses several 330V 120uF capacitors. So in order for the
flash to maintain the same light intensity need a simple circuit that will
allow the capacitors to only discharge when they reach about 300V or some
thing like that.

 

[Nicholas O. Lindan]

well not really, genrally most people that use the internet know about
google.

Which also means that I've tried it with many different words or phrases
and apart from getting many usless pages

It is rare that this group knows more than what can be found through Google.

 

[ks]

Do you want something that absolutely keeps the strobe from
discharging the caps below 300V or would something like a flashing LED
to let you know they're charged up to 300V be OK?

I think that I could work with both. I'm just not sure how to go about
getting the something to switched on and partically at that voltage, as I've
said all I've found so far goes up to 30V or is too complicated.
if it were to do both it would be great however the main thing I'm looking
for is for it to be simple, so a light would do as long as it goes on after
a specific voltage is reached.

 

[Fred Bloggs]

Hi,

I was wandering if any one would be able to help me here? I am building a
flash (strobe) that uses several 330V 120uF capacitors. So in order for the
flash to maintain the same light intensity need a simple circuit that will
allow the capacitors to only discharge when they reach about 300V or some
thing like that.



So if anyone could help me with this it would be greatly appreciated.



Thanks

You are talking about a simple comparator. Use a resistor divider from
the 300V to GND to divide the comparator voltage down. Then use the
comparator output to inhibit your discharge trigger until the divided
input voltage crosses threshold corresponding to 300V. The CMOS versions
of the 555, such as the LMC555 or TLC555, make excellent Schmitt trigger
comparators when you tie TRIG/THRESH inputs together and to the junction
of your voltage divider. If you power the 555 with Vcc, then OUT goes
from Vcc to 0V when the input exceedS 0.67 x Vcc. So you size your high
voltage divider so that 300V=0.67*Vcc*(1+R2/R1), where R2 is connected
to 300V, R2/R1 junction to TRIG/THRESH, and other end of R1 to GND. For
example, if Vcc=5, the R2/R1= [300/(0.67*5)]-1=89. If 10uA is a
reasonable current drain on your charge circuit, then this fixes R1+R2
to 300V/10uA=30Meg ohms. Then R1~ 30M/89=330K, using standard values. So
your R2 would 3x 10Meg resistors in series, and R1 would be 330K. These
resistors can be 1/8Watt or more in rating. It would also be a good idea
to add a transient suppression capacitor like so:
View in a fixed-width font such as Courier.

 

[amdx]

Hi,
I was wandering if any one would be able to help me >here? I am building a

flash (strobe) that uses several >330V 120uF capacitors. So in order for the

flash to maintain the same light intensity need a simple >circuit that

will allow the capacitors to only discharge >when they reach about 300V or
some thing like that.

So if anyone could help me with this it would be greatly >appreciated.

Thanks

How about just a simple timer (RC network) that has the same charge timing
as your 120uf capacitor? If your 120uf cap takes 6 seconds to charge to
300v, set your RC to take 6 (or 6.5) seconds to charge to whatever trigger
voltage you need .
Seems like 555 would work great, reset after each flash.

Mike

 

[Mark Jones]

well not really, genrally most people that use the internet know about
google.

Which also means that I've tried it with many different words or phrases
and apart from getting many usless pages of advertising or unrelated topics
the closest I've found was a 5 to 9V battery tester. So my problem is that I
can build it however I'm no really shure what most of the stuff may be doing
so I cannot even adapt it for use it with 300V DC.

Look, if you're not going to even try to find the answer yourself...

If you actually looked at that google link, you'd see there were
plenty of schematics and text available discribing most if not all
details of strobe unit design, not 9v battery testers. It's all there,
do your homework! Learn how to be resourceful, not dependent.

Since I'm so kind, (really, I am), here's that link again:
http://www.google.com/search?&q=strobe+trigger+schematic

If you don't understand what the others here have said about
comparators and 555's (like Fred Blogg's excellent solution) then may
I suggest a great [free] place to brush up on electronics:
http://www.ibiblio.org/obp/electricCircuits/



-- "Hawking theorized that the matter swallowed by a black hole
radiates outward along its periphery in the form of elementary atomic
particles. Perhaps what is really going on is the anomaly simply
'compresses' all matter into the last of the 11 spatial dimensions
described in string theory, and thus far outside our visual range."
MCJ 20050120