HVsupply - Revision history

Thomas: /* Where to go from here */

2019-02-13T23:40:24Z

Where to go from here

← Older revision		Revision as of 23:40, 13 February 2019
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	Update February 2019: Temporarily storing an old lab-grade HV supply in the projectkast, 3d printing a custom HV connector for it and making it available for experiments at the space. Please don't use without permission, it bites!		Update February 2019: Temporarily storing an old lab-grade HV supply in the projectkast, 3d printing a custom HV connector for it and making it available for experiments at the space. Please don't use without permission, it bites!


			[[File:Brandenburg.jpg]]

Thomas: /* Where to go from here */

2019-02-13T23:37:13Z

Where to go from here

← Older revision		Revision as of 23:37, 13 February 2019
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	Update August 2018: Working on a manually switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.		Update August 2018: Working on a manually switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.

	Update February 2019: Temporarily storing an old lab-grade HV supply in the projectkast, 3d printing a custom HV connector for it and making it available for experiments at the space. Please don't use without permission, it bites!		Update February 2019: Temporarily storing an old lab-grade HV supply in the projectkast, 3d printing a custom HV connector for it and making it available for experiments at the space. Please don't use without permission, it bites!

Thomas: /* Where to go from here */

2019-02-13T23:37:01Z

Where to go from here

← Older revision		Revision as of 23:37, 13 February 2019
Line 67:		Line 67:

	Update August 2018: Working on a manually switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.		Update August 2018: Working on a manually switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.
			Update February 2019: Temporarily storing an old lab-grade HV supply in the projectkast, 3d printing a custom HV connector for it and making it available for experiments at the space. Please don't use without permission, it bites!

Thomas: /* Where to go from here */

2018-08-23T21:26:12Z

Where to go from here

← Older revision		Revision as of 21:26, 23 August 2018
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	==Where to go from here==		==Where to go from here==

	Update August 2018: Working on a ~~mechanically~~ switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.		Update August 2018: Working on a manually switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.

Thomas: /* Where to go from here */

2018-08-23T21:25:36Z

Where to go from here

← Older revision		Revision as of 21:25, 23 August 2018
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	==Where to go from here==		==Where to go from here==

	Update August 2018: Working on a mechanically switched capacitor bank to boost output by 5 times and create bigger sparks for the upcoming science weekend.		Update August 2018: Working on a mechanically switched capacitor bank to boost output voltage by 5 times and create bigger sparks for the upcoming science weekend.

Thomas: /* Where to go from here */

2018-08-23T21:25:06Z

Where to go from here

← Older revision		Revision as of 21:25, 23 August 2018
Line 66:		Line 66:
	==Where to go from here==		==Where to go from here==

	Working on a mechanically switched capacitor bank to boost output by 5 times and create bigger sparks for the upcoming science weekend.		Update August 2018: Working on a mechanically switched capacitor bank to boost output by 5 times and create bigger sparks for the upcoming science weekend.

Thomas: /* Where to go from here */

2018-08-23T21:24:44Z

Where to go from here

← Older revision		Revision as of 21:24, 23 August 2018
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	==Where to go from here==		==Where to go from here==

	~~There is~~ a ~~tentative plan~~ to ~~make a kit version of a similar high voltage supply, but then with a much improved inverter,~~ and ~~a pcb transformer instead of salvaged ccfl transformers, as designed by Mux. In order to gauge what features would be required, we're going to muck around with a few of~~ the ~~above supplies first~~.		Working on a mechanically switched capacitor bank to boost output by 5 times and create bigger sparks for the upcoming science weekend.

Thomastheo at 11:07, 25 August 2017

2017-08-25T11:07:36Z

← Older revision		Revision as of 11:07, 25 August 2017
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	==Circuit==		==Circuit==

	A small inverter, driving a ~~cockroft~~ walton voltage multiplier. Low voltage DC input is switched to drive a small step-up transformer, generating modestly high voltage AC (at around one kilovolt). This is then fed into a voltage multiplier, resulting in an output of many kilovolts DC. The inverter is driven at a high frequency (tens to hundreds of kilohertz), which means we can get away with relatively low-value capacitors.		A small inverter, driving a cockcroft walton voltage multiplier. Low voltage DC input is switched to drive a small step-up transformer, generating modestly high voltage AC (at around one kilovolt). This is then fed into a voltage multiplier, resulting in an output of many kilovolts DC. The inverter is driven at a high frequency (tens to hundreds of kilohertz), which means we can get away with relatively low-value capacitors.

	There are a number of ccfl inverter ~~toplogies~~ you might run across when you bust open an old lcd. More 'modern' backlight designs feature a controller of some sort to enable better power and brightness control, but the simplest kind you will ~~run across~~ is ~~just~~ a ~~classic~~ (resonant) royer oscillator. I found a couple of these old-style monitors on the RevSpace free stuff table over the past half-year, and salvaged the relevant components from their inverter board, which I then plonked on to a proto-board to make the heart of the high voltage supply. It's certainly not pretty, but seems to work just fine. The only change that I made to the circuit is the option to bypass the 22pF cap on the output, which helps pull more power out of the inverter.		There are a number of ccfl inverter topologies you might run across when you bust open an old lcd. More 'modern' ccfl backlight designs feature a controller of some sort to enable better power and brightness control, but the simplest kind you will find is nothing more than a (resonant) royer oscillator. I found a couple of these old-style monitors on the RevSpace free stuff table over the past half-year, and salvaged the relevant components from their inverter board, which I then plonked on to a proto-board to make the heart of the high voltage supply. It's certainly not pretty, but seems to work just fine. The only change that I made to the circuit is the option to bypass the 22pF cap on the output, which helps pull more power out of the inverter.

	The voltage multiplier is a bipolar ~~cockroft~~ walton, This seems to work the best, and has the added benefit of being visually more interesting that a single half-wave variant. A full-wave CW would be best, but unfortunately ccfl inverters just don't come with a center tap on the secondary. As for the components I used, they are the cheap kind, from aliexpress. The caps are ~~1nF~~ 3kV blue ceramics, available in packs of fifty for ~~under five~~ dollars. The diodes are just a series string of 1n4007 rectifiers. In the configuration I used, the components in the multiplier see about 2Vp (it would be 3Vp for a full-wave multiplier). I am not entirely sure exactly how high the output is on the secondary, especially when it is minimally loaded (as is the case when the multiplier is charged and open-circuit towards), and given their provenance I don't have much faith in the ratings of the capacitors, so I chose to be generous in terms of margins. I put two caps in series for a rating of 6kV, and in the case of the diodes, I started with four in series for a rating of 4kV. I ran out of 1n4007's at some point and cut back to series chains of three; I have not seen any failed diodes.		The voltage multiplier is a bipolar cockcroft walton, This seems to work the best, and has the added benefit of being visually more interesting that a single half-wave variant. A full-wave CW would be best, but unfortunately ccfl inverters just don't come with a center tap on the secondary. As for the components I used, they are the cheap kind, from ebay/aliexpress. The caps are 10nF 3kV blue ceramics available in packs of fifty for [http://www.ebay.com/itm/50pcs-High-Voltage-Ceramic-Disc-Capacitors-10000PF-10NF-0-01uf-3000V-3KV-103-NEW-/171427329091?hash=item27e9dd7443:g:W2cAAOSwDk5T8xRI three dollars]. The diodes are just a series string of 1n4007 rectifiers. In the configuration I used, the components in the multiplier see about 2Vp (it would be 3Vp for a full-wave multiplier). I am not entirely sure exactly how high the output is on the secondary, especially when it is minimally loaded (as is the case when the multiplier is charged and open-circuit towards), and given their provenance I don't have much faith in the ratings of the capacitors, so I chose to be generous in terms of margins. I put two caps in series for a rating of 6kV, and in the case of the diodes, I started with four in series for a rating of 4kV. I ran out of 1n4007's at some point and cut back to series chains of three; I have not seen any failed diodes.

	==Some notes on operation==		==Some notes on operation==
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	As for the multiplier, it is best to elevate it or prop it up on something non-conductive. It turns out that table-tops and other surfaces that you normally consider to be insulators are sufficiently conductive at these potentials to bleed a lot of charge. Avoiding sharp points helps, but given the construction technique I used for my multiplier, this was difficult to do. It turns out that separating the two halves of the multiplier in a V-shape and maintaining adequate distance reduces corona enough, and seems to work just fine. I guess you could use oil or potting, but at these potentials this seems overkill to me, and has the downside of obscuring the components.		As for the multiplier, it is best to elevate it or prop it up on something non-conductive. It turns out that table-tops and other surfaces that you normally consider to be insulators are sufficiently conductive at these potentials to bleed a lot of charge. Avoiding sharp points helps, but given the construction technique I used for my multiplier, this was difficult to do. It turns out that separating the two halves of the multiplier in a V-shape and maintaining adequate distance reduces corona enough, and seems to work just fine. I guess you could use oil or potting, but at these potentials this seems overkill to me, and has the downside of obscuring the components.

	Perhaps as a final note, I should say that being shocked by this thing is quite unpleasant, so please try to avoid it. Be especially careful not to shock yourself across the chest, and use only one hand when you mess with it. Things get scary very quickly when you ~~are attaching~~ any sort of capacitance to the output, and be mindful that at these voltages even small capacitance can represent significant hazard. Just keep your wits about you and use common sense. Take care to discharge the caps of the multiplier when you're finished (just shorting the output is not enough to dissipate the charge across all the caps in the chain, which may still have the potential to give you a nasty tickle) In conclusion, If you follow along, know that you are doing so at your own risk.		Perhaps as a final note, I should say that being shocked by this thing is quite unpleasant, so please try to avoid it. Be especially careful not to shock yourself across the chest, and use only one hand when you mess with it. Things do get scary very quickly when you attach any sort of capacitance to the output, and be mindful that at these voltages even small capacitance can represent significant hazard. Just keep your wits about you and use common sense. Take care to discharge the caps of the multiplier when you're finished (just shorting the output is not enough to dissipate the charge across all the caps in the chain, which may still have the potential to give you a nasty tickle) In conclusion, If you follow along, know that you are doing so at your own risk.

	== Pictures/schematics ==		== Pictures/schematics ==

Thomastheo: /* Requirements */

2017-08-24T14:05:16Z

Requirements

← Older revision		Revision as of 14:05, 24 August 2017
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	Robust, will survive short-circuit and open circuit indefinitely		Robust, will survive short-circuit and open circuit indefinitely

	Cheap!		Cheap!


	==Circuit==		==Circuit==

Thomastheo: /* Where to go from here */

2017-08-24T14:04:11Z

Where to go from here

← Older revision		Revision as of 14:04, 24 August 2017
Line 67:		Line 67:
	==Where to go from here==		==Where to go from here==

	There is a tentative plan to make a kit version of a similar high voltage supply, but then with a much improved inverter, and a pcb transformer instead of salvaged ccfl transformers, as designed by Mux. In order to gauge what features would be required, we're going to muck around with a few of the above supplies first.		There is a tentative plan to make a kit version of a similar high voltage supply, but then with a much improved inverter, and a pcb transformer instead of salvaged ccfl transformers, as designed by Mux. In order to gauge what features would be required, we're going to muck around with a few of the above supplies first.


	~~To be added: pictures, schematics, links, a section on experiments~~.