Hi, Did you realize the power dissipation in the transistor? Better is to use a tranformer with several taps in a circuit like this.
eric -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of jb-electronics Sent: maandag 25 juli 2011 19:00 To: [email protected] Subject: Re: [neonixie-l] Nixie Tube Power Supply: 0..300V @ 30mA max. Hi, thanks for the hint. See the reviewed circuit: http://www.jb-electronics.de/tmp/400v_adjustable.png Yes, the feedback loop will be included, I forgot to mention that my power supply will have both a volt- and amperemeter built in. This way I will be able to check the voltage, as well as to completely shut off the PWM stage when the current is too high. Is this safe? Does anyone know a good PNP transistor for this purpose? Regards, Jens Am 25.07.2011 18:08, schrieb Frank Bemelman: > I would (at least) add some feedback. Voltage divider and opamp to > compare against set value. > Without feedback, the cap would charge to 400V in no time. > Plus a current limiting resistor of 1K in series with the emitter, > which makes a lousy protection but still better than nothing. > > ----- Original Message ----- From: "jb-electronics" > <[email protected]> > To: <[email protected]> > Sent: Monday, July 25, 2011 5:11 PM > Subject: Re: [neonixie-l] Nixie Tube Power Supply: 0..300V @ 30mA max. > > >> Hi, >> >> thanks a lot for all these replies. I am not an engineer, so I am not >> familiar with power supply circuitry. >> >> These modules on Ebay are nice, but I would like to build my own >> meters around that supply, that would be a waste of these units I >> think. They are a tad too powerful for me as well ;-) >> >> I like the PWM idea because it is so simple: Why not rectify some AC >> (after two transformers of course) to say 400V. Then use some suited >> PNP transistor (which would that be?) that switches the +400V on and >> off, and then a cap to smoothen the signal. Probably a rather Spartan >> design yet, any improvements? I can tell it is not protected against >> shorts. >> >> http://www.jb-electronics.de/tmp/400v_adjustable.png >> >> The maximum current is then limited by the transformers that are >> used, isn't it? >> >> Thanks again, >> Jens >> >> >> >> Am 23.07.2011 02:36, schrieb Charles MacDonald: >>> On 11-07-22 06:51 AM, Tidak Ada wrote: >>>> The background is this: I would like to build a universal power >>>> supply that can be used to drive all kinds of display devices: VFD >>>> tubes with their 50-60V anode voltage, as well as larger Nixie >>>> tubes with 300V anode voltage and 25mA current. >>>> >>>> >>>> Any other ideas are quite welcome, too. >>> >>> Do you really want to BUILD such an item? They are common on test >>> benches and with fewer test benches using High Voltage devices, they >>> are found in surplus. >>> >>> I recently got a nice looking unit with 1-400 volts at about 100ma >>> as a science lab item. Dial the voltage limit, Dial the current >>> limit. I have not tried it with an audio amp yet, but it should run >>> fine for Nixie use. >>> >>> For example have a look at Ebay >>> Item number: 230649564649 >>> Item number: 150634915051 >>> >>> >>> >>> If you want to look at the OLD school way, My old school test bench >>> as a Stark Regulated supply, which is one of the schematics at >>> Pacific TV tubes site. It uses a 6l6 as a pass regulator. The C >>> supply would cover your VFD requirements. This was surplus from an >>> Old High School lab. >>> >>> >> >> -- >> You received this message because you are subscribed to the Google >> Groups "neonixie-l" group. >> To post to this group, send an email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]. >> For more options, visit this group at >> http://groups.google.com/group/neonixie-l?hl=en-GB. >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
