Question on 300V indicator or switch

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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?

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

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

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Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer:  Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

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:

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:

-- "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

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.

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

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

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

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.