# circuit help

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#### Nigel Goodwin

##### Super Moderator
batman said:
https://www.aaroncake.net/circuits/strobe2_1.gif
if L1 and Q1 were removed, would the capacitors charge until they exploded, or would they charge and max out and wait until discharge?
thanks

They should just charge up - and sit there waiting for someone to put their fingers across them :twisted:

#### k7elp60

##### Active Member
As long as the working voltage on C2 is greater than 2X the AC input peak nothing would happen. Looks like a 1/2 wave doubler circuit to me.
Sometimes the load on a power supply is meant to keep the charge on the
filter capacitor below a certain level, so the working voltage of the capacitor is lower than what one would expect. If the working voltage is below 2X the peak it could be damaged and the fuse would blow.

#### batman

##### New Member
thanks k7elp60

how do the capacitance values of C1 and C2 affect the rest of the circuit?

and also, how does the variable resistor affect C3?

i appreciate it!

#### Nigel Goodwin

##### Super Moderator
batman said:
thanks k7elp60

how do the capacitance values of C1 and C2 affect the rest of the circuit?

and also, how does the variable resistor affect C3?

i appreciate it!

C1 and C2 are part of a voltage doubling circuit, the current output is dependent on their value - the lower the value, the smaller the current. When the strobe fires it discharges the energy stored in C2 through the strobe tube - so it's important that C2 charges fully in between flashes.

R2 and R3 charge C3 from the high voltage DC supply, once the charge on C3 reaches the trigger point of the neon bulb it conducts turning the SCR on - this triggers the strobe tube. The neon bulb conducting also discharges C3 partially, it then starts charging again repeating the cycle.

It's a VERY! old circuit called a neon relaxation oscillator.

#### batman

##### New Member
Alright, im understanding this more and more...
So i want the values of C1 C2 and C3 to all be very low, so that they can charge and discharge as quickly as possible, allowing for higher flash rates? like 1 uF?

would the circuit work like this
http://www.geocities.com/tgohan/triggerflash.JPG
so that instead of the flash occuring spontaneously, it would flash when the button is pressed?
thanks

error

#### Nigel Goodwin

##### Super Moderator
batman said:
Alright, im understanding this more and more...
So i want the values of C1 C2 and C3 to all be very low, so that they can charge and discharge as quickly as possible, allowing for higher flash rates? like 1 uF?

NO!, C3's value is dependent on the flash rate you require, presumably the value is already specified along with the resistors that charge it.

C2 holds the charge for the flash, 1uF sounds rather low, the bigger this capacitor the larger the flash - C1 is part of a voltage doubling circuit (for primitive countries on 110V mains!) and should be a similar value to C2. These values depend on the flash rate required, there's no point having huge values if they can't charge up betwen flashes.

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