Hello everyone
I'm a student in the international master degree of electroacoustic at LE MANS in France.
Currently, I'm doing my first master year's project which is, design, model and build an ESL.
I'm doing a push-pull ESL with a membrane with the following dimension 25cm x 50cm coated with graphite powder. The gap between the membrane and the plates will be around 2mm.
In order to biased the diaphragm, I wanted to use a voltage multiplier circuit directly connected to an outlet (230V AC 50Hz in France) to transform it around 1500V DC.
I use the following components
capacitor:
564R30GASS10 Vishay / Cera-Mite | Mouser France
diode:
1N4007GP-E3/54 Vishay Semiconductors | Mouser France
I use those components in a classic eight-stage Cockcroft–Walton multiplier.
My problem is, the voltage multiplier works well with the 2 first stages
I get first 420V and then around 550V DC but after this stage, the voltage keeps dropping of about 60V for each stage.
Does somebody have any idea why?
Regards
I'm a student in the international master degree of electroacoustic at LE MANS in France.
Currently, I'm doing my first master year's project which is, design, model and build an ESL.
I'm doing a push-pull ESL with a membrane with the following dimension 25cm x 50cm coated with graphite powder. The gap between the membrane and the plates will be around 2mm.
In order to biased the diaphragm, I wanted to use a voltage multiplier circuit directly connected to an outlet (230V AC 50Hz in France) to transform it around 1500V DC.
I use the following components
capacitor:
564R30GASS10 Vishay / Cera-Mite | Mouser France
diode:
1N4007GP-E3/54 Vishay Semiconductors | Mouser France
I use those components in a classic eight-stage Cockcroft–Walton multiplier.
My problem is, the voltage multiplier works well with the 2 first stages
I get first 420V and then around 550V DC but after this stage, the voltage keeps dropping of about 60V for each stage.
Does somebody have any idea why?
Regards
Oui, très probablement parceque vous n'utilisez pas un voltmètre ayant une résistance d'entrée suffisante. Ce genre de multiplicateur, avec les valeurs de capacité choisies, ne peut débiter que des courants très faibles (ce qui convient parfaitement pour l'utilisation que vous voulez en faire.
Il faut bien vous représenter qu'à 50 Hz, un condensateur de 0.01 µF représente une impédance de 320 kilohms à peu près. C'est à dire que la résistance interne du montage multiplicateur se compte en mégohms. La résistance interne du voltmètre que vous devez utiliser devra se compter en centaines de mégohms. Ces appareils ne sont pas courants du tout. Usuellement on se contente de vérifier que tous les composants sont bons et on prend comme valeur le résultat du calcul.
Il va de soi que l'isolement du support de la membrane par rapport aux grilles et à la masse doit être irréprochable, même en atmosphère humide. Je vous conseille le Téflon, ou encore le Plexiglas. Les grilles doivent être bien polies, absolument exemptes de bavures, sinon il pourra se produire des étincelles...
(Google translation....
Yes, most likely because you do not use a voltmeter with sufficient input resistance. This kind of multiplier, with the chosen capacity values, can only deliver very low currents (which is perfectly suitable for the use you want to make of it).
It must be remembered that at 50 Hz, a capacitor of 0.01 μF represents an impedance of approximately 320 kilohms. That is, the internal resistance of the multiplier assembly is in megohms. The internal resistance of the voltmeter that you should use should be counted in hundreds of megohms. These devices are not common at all. Usually we just check that all the components are good and we take as value the result of the calculation.
It goes without saying that the isolation of the support of the membrane with respect to the grids and to the mass must be irreproachable, even in a humid atmosphere. I advise you the Teflon, or the Plexiglas. Grilles must be well polished, absolutely free of burrs, otherwise sparks may occur ...)
Il faut bien vous représenter qu'à 50 Hz, un condensateur de 0.01 µF représente une impédance de 320 kilohms à peu près. C'est à dire que la résistance interne du montage multiplicateur se compte en mégohms. La résistance interne du voltmètre que vous devez utiliser devra se compter en centaines de mégohms. Ces appareils ne sont pas courants du tout. Usuellement on se contente de vérifier que tous les composants sont bons et on prend comme valeur le résultat du calcul.
Il va de soi que l'isolement du support de la membrane par rapport aux grilles et à la masse doit être irréprochable, même en atmosphère humide. Je vous conseille le Téflon, ou encore le Plexiglas. Les grilles doivent être bien polies, absolument exemptes de bavures, sinon il pourra se produire des étincelles...
(Google translation....
Yes, most likely because you do not use a voltmeter with sufficient input resistance. This kind of multiplier, with the chosen capacity values, can only deliver very low currents (which is perfectly suitable for the use you want to make of it).
It must be remembered that at 50 Hz, a capacitor of 0.01 μF represents an impedance of approximately 320 kilohms. That is, the internal resistance of the multiplier assembly is in megohms. The internal resistance of the voltmeter that you should use should be counted in hundreds of megohms. These devices are not common at all. Usually we just check that all the components are good and we take as value the result of the calculation.
It goes without saying that the isolation of the support of the membrane with respect to the grids and to the mass must be irreproachable, even in a humid atmosphere. I advise you the Teflon, or the Plexiglas. Grilles must be well polished, absolutely free of burrs, otherwise sparks may occur ...)
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For safety reasons it is better to use an isolation transformer. You can also use two small transformers back to back, for example 230 V to 12 V and 12 V back to 230 V.
By the way, you can find lots of information on the theory of electrostatic loudspeakers on this site:
Elektrostatic Loudspeakers - Frank Verwaal
By the way, you can find lots of information on the theory of electrostatic loudspeakers on this site:
Elektrostatic Loudspeakers - Frank Verwaal
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Are you sure you are not loading it harder then it can deliver current for the meter ? sometimes the meter alone is a to big of a load when you go further into the stages. might want to look for a voltage divider with very high resistors. ? and go from there ? with my multimeter i cant get above 800 volt but looking at the arcs it pulls
it is way higher then 800 - Status
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