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How do I calculate resistor sizes for capacitors?

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Randy13

New Member
I'm extremely new to all of this (I'm learning as I go!) and I've decided to build a 300V Xenon Strobe for fun and as a learning experience. I will be building it according to the diagram below, with a 12V to 300V step-up converter, a bank of 6x 300V capacitors totaling 60uF (Cs), and with a 300V 0.22uF trigger capacitor (Ct).

Now, the diagram calls for a resistor between the input voltage and the 0.22uF trigger capacitor. How do I calculate what size resistor I need? I have searched for hours and can't find anything that explains this. Also, do I need a resistor on each of the 6x 10uF main capacitors (Cs)?

Thank you for the help!!

**broken link removed**
 

alec_t

Well-Known Member
Most Helpful Member
First of all, be aware that the charge stored in Cs at 300V will be enough to KILL YOU! This circuit should only be built by someone who fully understands the dangers of high voltage and takes all due safety precautions.
The value of R1 will depend on how much time you can allow between successive triggerings. A value of 10kΩ, for example, will give a time constant of 10k x Ct = 2.2ms, hence Ct will be charged in ~ 10ms. The power rating of the resistor would depend on both its resistance and the triggering period.
do I need a resistor on each of the 6x 10uF main capacitors (Cs)?
That would depend on the source impedance of your power supply. One series resistor would probably be ok to serve all caps.
 
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