Studio Ring Flash Xenon Tubes

[Pommie]

A way to keep the fast charge and make the flash tubes extinguish is to use the normally closed contacts of the trigger switch to make/break the charging circuit. In simple terms, connect the top part of the trigger switch in series with the 47Ω resistor. This does mean you will need a suitably isolated switch.

BTW, what does T2 do in that circuit?

Mike.

 

[schmitt trigger]

If I were to keep adding 50watt light bulbs in series with the resistor, am I not effectivly adding cheap resistors.


Jamie

The cold resistance of a light bulb is something like 20 times lower than its actual operating (hot) resistance...so this approach will not work.

As previous posters have mentioned, a Xenon tube, once that it fires, remains in conduction until the current reaches a point where the arc extinguishes itself; Therefore, your mains current limiting resistor should not allow a current higher than the minimum holding current of a single tube. Your best bet, as some other poster has already mentioned, is to use the contacts of a relay to open the mains while your flash is in the trigger mode.

But if you decide to do that, still keep the resitor to limit the inrush charging current to a safe value.

 

[Jamie Pocock]

BTW, what does T2 do in that circuit?

T2 was my attempt to enable the flash to run on 4 AA batterys.

It is a step up transformer, in multisim it got to about 240v with a 1 to 20 winding. However I have not built in the circuit I have running here.

 

[Pommie]

Transformers only work with AC and so can't be connected to a battery without additional circuitry.

Mike.

 

[Mr RB]

This flash is getting complex.

Sounds like you need an active charging circuit instead of just a charging resistor.

You could use something like a SCR (and 48 ohm resistor) to charge the caps. Then if the SCR gate is turned off (so SCR is off) you could fire the flash. Actually that might not work because of dVdT issues, you might need to go to a high voltage TV transistor instead of a SCR.

 

[imran khan]

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I'm doin ma B.E IN ELECTRONICS AND COMMUNICATION ENGINEERING,but my basic was very poor so pleas help to become strong in our field........... i'l thankful to u.........

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IMRAN:

 

[Jamie Pocock]

I have an idea I am going to try out today.

I am going to remove 3 capacitors and have each of the remaining 3 capcitors fire two tubes each, this I am hoping will pull the power down enough to put out the lamps when they are fired.

Do you think this will work?.

Its now an hour later..

I removed 3 caps and its exactly the same :-(

 

[Jamie Pocock]

Has anyone got a circuit diagram to show me how to cut of the main rail when the caps are fully charged, when they drop below 50v the rail turns back on again.

Jamie

 

[Jamie Pocock]

Its working

Finally after much playing around and a massive learning curve I got it working.

Really this project started over 2 months ago and I have put way to many hours on it when I should be doing my Cisco exam revision.

Anyway, I resolved the continuous burning of the Xenon lamps by removing the full wave bridge and replacing it with a half wave i.e. a single diode.
It also has the added benefit of not heating the power resistor as much as the circuit only uses one half of the wave......

Now to test it rigorously, I will post a follow up update after a few shoots with it in the studio for those wanting to build this.

Which by the way if you do build this you do on your own back, I take no responsibility for you killing yourself or burning your house down or whatever may happen if you are not careful . The caps can kill you when not even fully charged so be warned plus all other hazards that go with high voltage electronics.

Here is the final schematic.

**broken link removed**

If you have multisim 10 then here is the project file

**broken link removed**

 

[Pommie]

An interesting solution. The reason it extinguishes is because the power is being cut 50 times per second due to the half wave rectification. However, this could mean that the flash tubes are staying illuminated for up to 1/50th of a second. Hopefully, the initial flash will be much brighter than the after burn and this wont cause blurring on moving objects.

Mike.

 

[Mr RB]

Good solution Jamie! Going to half wave allows a much longer time for the gas to settle down in the tube so the arc will go out and was probably a better soltuion than just increasing the charge resistor value.

Obviously this has also doubled your charge time. If you hadn't noticed that charge time maybe you could even increase the charge resistor again, the lower that charge current is the longer your caps etc are going to survive.

(edit) Haha Pommie jumped me!

 

[schmitt trigger]

Jamie;
Rest assured that these last two months you have spent on the project have not been a waste of time....Quite the contrary, you have gained something very valuable: "EXPERIENCE".

Congrats on the succesful completition of your project. Please do post some pictures!

 

[andre_t]

I know this may be an old post but would it be possible to fire the 6 flastubes sequentially?

 

[KMoffett]

andre_t,
This thread is 10 years old. Please don't hijack other's threads. If you have a question, start your own thread. It will be less confusing for you and us.
Ken