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Old 19th May 2008, 07:49 PM   #1
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Default Esl Battery Bias

I've soon finished building my new electrostats, and I want
to bias them with a battery driven supply.

I know there is many battery driven high voltage devices out there, like mosquito killers and ionizers, but they all pull to much
juice out of the batteries.

I want a device that pulls almost no current, as it shall feed almost no current to the esl membrane.

My idea is to place one hundred (to avoid the energy pulling switch transformer) AA batteries in series, switch those 150 volts on and off at 20 KHz with a fet or transistor, also placed in series to avoid pulling battery power to ground.

Then I feed this AC to a 15-stage voltage multiplier ladder to get 5-6 kilovolts.

Now, I wonder , is this a plausible approach?

regards, Jonas
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Old 19th May 2008, 07:57 PM   #2
SY is offline SY  United States
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500 of these will run about $350-400 and save you from building a supply.
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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Old 19th May 2008, 08:20 PM   #3
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Sorry for being negative but why not just use a normal AC HT supply?

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Old 19th May 2008, 08:38 PM   #4
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I also say why not a standard hv supply? I have nothing against
batterys in fact I built a battery powered 5w Son of Zen using
about 50lbs of batterys that lasted about 2 hours. I am about
to build another amp and use a 9v battery instead of a zener but
for a hi voltage supply I would definitly just go to a ac supply.
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Old 20th May 2008, 04:02 AM   #5
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If you must use batteries, why use such a high voltage stack of them? That's going to be VERY expensive and very large.

There are DC-DC and DC-AC converters that run with battery friendly input voltages/currents and they are very cheap. CCFL lamps require 200VAC or so which is usually derived from a low voltage 5-12VDC source. You can pick up surplus CCFL lamp inverters for about $5. Then you still need your voltage multiplier.

Low voltage DC to HV DC converters are also available for about $50 or so that convert 2-12VDC input up to 5-6 kVDC. Emco and Pico make such modules.

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Old 20th May 2008, 07:05 AM   #6
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Thanks for the replies!

Why I want a battery bias supply:

Cost of 100 AA batteries, swiitch fet and multiplier stops
at 50-60 $, less cables laying around, and hopefully, I only
have to change the batteries every second year.

One more reason: The custom made aluminium sidepanels are hollow, and makes two perfect compartments for non-lethal 2 x 100 AA:s.

regards, Jonas
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Old 20th May 2008, 07:25 AM   #7
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Jonas är du för optimistisk.

Avvara sig yourself mycket en besvära, genom att använda en enkel AC PSU.

Upptagen förmiddag I refurbishing en uppsättning av Martin Logan högtalare och PSU är så liten och enkel. Jag kan även leverera dig med diagrammet.

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Old 20th May 2008, 07:56 AM   #8
Calvin is offline Calvin  Germany
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You won´t find a circuit that "pulls almost no current".
The expected lifetime of the batteries will not be reached, not even will it come close. The efficiency of a cascade isn´t that high, especially not a 15-stage-cascade (I wouldn´t recommend using more than 10stages at all anyway!)
The stacked batteries will have a rather high impedance value and be rather ´slow´. Without a charging cap, You´ll probabely not be able to switch with 20kHz and get enough out of them to feed a cascade properly. I think the costs and size and effort of wiring will be considerably higher than needed. It´ll probabely not ok to just put a chain of batteries somehow into a aluminium tube and expect this to exhibit good, stable and lasting contacts.
The cascade needs rather high cap-values with this high number of stages-count. So You face a space-problem.
A classical approach with a transformer and cascade will work properly, will be smaller, will be more reliable, will be cheaper, will have a much reduced parts-count.
To me it doesn´t look like a plausible approach. It might be so with
lower voltages in the 1kV-1.5kV-range but not with such high values You want to work with.

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Old 20th May 2008, 09:24 AM   #9
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But I'll do some experiments, and let You know
how things are going!

regards, Jonas
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Old 20th May 2008, 07:26 PM   #10
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I would expect to have about 5 watts of leakage. So your going to need 2kw/hours per year to keep a bias on the panels. So your going to need close to 700 AA battery's at 2 amp hours per 1.5 volt battery.

Battery are not really practical even if you make a circuit to turn off the bias when there is no music playing. If you use the speakers two hours a day 60 battery's are going to last you a year. This is all assuming 100% of the battery energy is getting to the diaphragm.
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