DIY studio strobe
in [Design]
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From: Ban on 30 Jan 2010 03:19 "El Loco Mateo" <ellocomateo(a)free.fr> schrieb im Newsbeitrag news:4b636ad8$0$5384$426a34cc(a)news.free.fr... > On 2010-01-29 15:19, MooseFET wrote: >> If you know about MOSFETs and bipolar transistors, you and think of an >> IGBT as an N channel MOSFET feeding a PNP transistor. >> >> You need to apply a pulse to the gate of the IGBT that is about 10V >> tall and lasts for as long as you want the current to flow. The gate >> of the IGBT must be moved from near zero to the near 10V and back >> quickly. Holding it high and low is the easy part. >> >> The IGBT must be in the path of the current through the tube. You >> can't control the tube via the trigger electrode once it is fired. >> The plasma inside the tube is a short circuit. You need to open one >> end connection of the tube by turning off the IGBT in that path. > > Thank you both for your comments! Is an IGBT the only solution to achieve > my goal? What other alternative do I have, should I want to reach currents > higher than say 150A? Wouldn't it be easier to fire an SCR in parallel to the tube to eat up the remaining charge? No floating grounds, can use the normal ignition transformer. ciao Ban Apricale, Italy
From: El Loco Mateo on 30 Jan 2010 07:49 On 2010-01-30 09:19, Ban wrote: > "El Loco Mateo"<ellocomateo(a)free.fr> schrieb im Newsbeitrag > news:4b636ad8$0$5384$426a34cc(a)news.free.fr... >> On 2010-01-29 15:19, MooseFET wrote: >>> If you know about MOSFETs and bipolar transistors, you and think of an >>> IGBT as an N channel MOSFET feeding a PNP transistor. >>> >>> You need to apply a pulse to the gate of the IGBT that is about 10V >>> tall and lasts for as long as you want the current to flow. The gate >>> of the IGBT must be moved from near zero to the near 10V and back >>> quickly. Holding it high and low is the easy part. >>> >>> The IGBT must be in the path of the current through the tube. You >>> can't control the tube via the trigger electrode once it is fired. >>> The plasma inside the tube is a short circuit. You need to open one >>> end connection of the tube by turning off the IGBT in that path. >> >> Thank you both for your comments! Is an IGBT the only solution to achieve >> my goal? What other alternative do I have, should I want to reach currents >> higher than say 150A? > > Wouldn't it be easier to fire an SCR in parallel to the tube to eat up the > remaining charge? No floating grounds, can use the normal ignition > transformer. > ciao Ban > Apricale, Italy > > That is a possibility, but I may adapt the design to be power-pack based, so that I would like spare electrons! Using a 2 SCR design, the storage capacitor would be emptied completely each time. Thank you anyway for highlighting this relevant point!
From: El Loco Mateo on 30 Jan 2010 07:53 On 2010-01-30 01:31, John Fields wrote: > On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo<ellocomateo(a)free.fr> > wrote: > >> On 2010-01-29 15:19, MooseFET wrote: >>> If you know about MOSFETs and bipolar transistors, you and think of an >>> IGBT as an N channel MOSFET feeding a PNP transistor. >>> >>> You need to apply a pulse to the gate of the IGBT that is about 10V >>> tall and lasts for as long as you want the current to flow. The gate >>> of the IGBT must be moved from near zero to the near 10V and back >>> quickly. Holding it high and low is the easy part. >>> >>> The IGBT must be in the path of the current through the tube. You >>> can't control the tube via the trigger electrode once it is fired. >>> The plasma inside the tube is a short circuit. You need to open one >>> end connection of the tube by turning off the IGBT in that path. >> >> Thank you both for your comments! Is an IGBT the only solution to >> achieve my goal? What other alternative do I have, should I want to >> reach currents higher than say 150A? > > --- > Not trying to be difficult, but are you sure you understand the comments > stating that in order to stop the discharge through the tube you must > interpose a switch between either the high or the low end of the tube > and what that end is connected to? > > JF Of course I do, but as you may have understood electronics is not a field I am heavily trained with and thus I call for readers'know-how. The concept is crystal clear, yet I have no perfect idea about the practical limit of the discussed devices.
From: MooseFET on 30 Jan 2010 10:54 On Jan 29, 3:10 pm, El Loco Mateo <ellocoma...(a)free.fr> wrote: > On 2010-01-29 15:19, MooseFET wrote: > > > If you know about MOSFETs and bipolar transistors, you and think of an > > IGBT as an N channel MOSFET feeding a PNP transistor. > > > You need to apply a pulse to the gate of the IGBT that is about 10V > > tall and lasts for as long as you want the current to flow. The gate > > of the IGBT must be moved from near zero to the near 10V and back > > quickly. Holding it high and low is the easy part. > > > The IGBT must be in the path of the current through the tube. You > > can't control the tube via the trigger electrode once it is fired. > > The plasma inside the tube is a short circuit. You need to open one > > end connection of the tube by turning off the IGBT in that path. > > Thank you both for your comments! Is an IGBT the only solution to > achieve my goal? What other alternative do I have, should I want to > reach currents higher than say 150A? You do have other options. (1) If you know before hand how much power you want in this pulse, you can connect only enough storage capacitance to give that flash. This could be done by having IGBTs, SCRs or bipolars switching in and out the capacitors before the shot is taken. (2) You can provide a second discharge path for the capacitor that takes away some of the energy and doesn't let it go towards the flash. (3) You can use some sort of semiconductor device to block the current in the tube. It doesn't need to fully block it It could have a capacitor across it so that it doesn't have to take the full current as it first turns off. (4) You can put a mechanical obstruction in front of the flash to block some of the light.
From: MooseFET on 30 Jan 2010 10:54
On Jan 29, 4:31 pm, John Fields <jfie...(a)austininstruments.com> wrote: > On Sat, 30 Jan 2010 00:10:06 +0100, El Loco Mateo <ellocoma...(a)free.fr> > wrote: > > > > >On 2010-01-29 15:19, MooseFET wrote: > >> If you know about MOSFETs and bipolar transistors, you and think of an > >> IGBT as an N channel MOSFET feeding a PNP transistor. > > >> You need to apply a pulse to the gate of the IGBT that is about 10V > >> tall and lasts for as long as you want the current to flow. The gate > >> of the IGBT must be moved from near zero to the near 10V and back > >> quickly. Holding it high and low is the easy part. > > >> The IGBT must be in the path of the current through the tube. You > >> can't control the tube via the trigger electrode once it is fired. > >> The plasma inside the tube is a short circuit. You need to open one > >> end connection of the tube by turning off the IGBT in that path. > > >Thank you both for your comments! Is an IGBT the only solution to > >achieve my goal? What other alternative do I have, should I want to > >reach currents higher than say 150A? > > --- > Not trying to be difficult, but are you sure you understand the comments > stating that in order to stop the discharge through the tube you must > interpose a switch between either the high or the low end of the tube > and what that end is connected to? .... or short out the tube, but good luck with that. > > JF |