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Series or Parallel

 
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George B



Joined: 05 Jun 2008
Posts: 33
Location: Northern New Jersey

PostPosted: Tue Aug 18, 2009 3:55 am    Post subject: Series or Parallel Reply with quote

When using two or four bulbs for a one or two stop increase in exposure should the bulbs be wired in series or parallel ? I'm using a Kalart gun with three "C" cells.
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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Tue Aug 18, 2009 11:25 am    Post subject: Reply with quote

With just typical D batteries, run them in parallel.

If you have a Battery Capacitor circuit, usually running 22.5v run them in series.

At least that's what Graflex said.
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C. Henry



Joined: 13 Dec 2005
Posts: 356
Location: North East Georgia, USA

PostPosted: Tue Aug 18, 2009 12:43 pm    Post subject: Reply with quote

The critical factor is the current through the primer in the flash bulb! With three "D" cells four bulbs wired in parallel should work well however since you are using "C" cells there may not be enough current available to fire four bulbs. The voltage only matters in there being enough to push the needed current through the resistance of the primers. While I do not know what the minimum voltage to fire a flash bulb is, I do know that 3 volts with a sufficient current available will reliably fire one.
If you wire the bulbs in series you need 3n volts (where "n" is the number of bulbs) or 12 volts for four bulbs. your three "C" cells (or three "D" cells) only have a total voltage of 4.5 volts. The "D" cells have the same voltage as "C" cells but have more current available before the internal resistance of the cells causes an unacceptable voltage drop.
If the bulbs are wired in parallel there will be the total voltage across each bulb and the current available from the batteries will be divided between the bulbs.
A "B-C pack" has a much greater momentary current available than a battery so that the voltage to which the capacitor is charged governs how many bulbs wired in series can be fired with it.

C. Henry
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George B



Joined: 05 Jun 2008
Posts: 33
Location: Northern New Jersey

PostPosted: Wed Aug 19, 2009 6:22 am    Post subject: Reply with quote

Now I get it... thanks guys.

My plan... tape a 22,000uf/10v cap to the gun and feed it with a series isolation diode and current limiting resistor connected to the focuspot terminals for charging purposes. From the cap feed the bulbs in parallel with an extension cord connected in series to the shutter sync terminals. I'll be using four clamp on Edison base reflectors and No.2 bulbs plugged into a household line strip. At 20' that should give me f32 with Plus-X... perfect exposure.

On the other hand maybe I should just use a 6 or 12V lantern battery in a shoulder bag and be done with it.
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glennfromwy



Joined: 29 Nov 2001
Posts: 903
Location: S.W. Wyoming

PostPosted: Sun Aug 23, 2009 10:47 pm    Post subject: Reply with quote

Use a battery. Do not use household current. It's a very hazardous thing to do.
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George B



Joined: 05 Jun 2008
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Location: Northern New Jersey

PostPosted: Fri Aug 28, 2009 1:11 am    Post subject: Reply with quote

I will use a 6V lantern battery with bulbs in parallel.

Thanks
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