6v & 90v DC Power supply
in [Design]
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From: John Crighton on 27 Dec 2005 00:58 On Tue, 27 Dec 2005 02:02:15 GMT, "James F. Mayer" <jfma(a)ix.netcom.com> wrote: > I need to generate 6v DC and 90v DC from a 12v DC automotive electrical >system to power an RT-70A/GRC surplus military radio. I need about 250 mA >at +6 volts and about 75 mA at +90 volts. I was thinking about using the >guts from an old battery back up but it would be a bit of a kluge. Are >there any 90 volt regulators in the 78xx series? How do I get the voltage >up to where I can get something that I can get the 90 volts from. Getting >the 6 volts doesn't seem to be a problem. A 7806 off the battery should >work for that unless any of you can see a problem doing that. Maybe the >common common would be a problem. Right now I'm running it off of an HP6299A >and an HP6236B with commons jumpered. I'd like to be able to go portable >with it. > > Hello James, Speaking as a cheapskate ham/hobbyist, how about salvaging parts from a computer power supply. Find a dud power supply for free at computer shops/dumpsters/rubbish tips/roadside etc. Salvage the TL494 integrated circuit that can be found in many computer power supplies. You could build a 90 Volt power supply as Ray Robinson has down here http://www.shlrc.mq.edu.au/~robinson/Information/Inverter_4W.html Here is a link to the TL494 Data sheet http://focus.ti.com/lit/ds/symlink/tl494.pdf This link tells you how to use the TL494 IC http://focus.ti.com/lit/an/slva001d/slva001d.pdf Use another TL494 in a buck converter for your 12 Volts to 6Volts power supply module. Look at the bottom of this page for more info. http://focus.ti.com/docs/prod/folders/print/tl494.html Your 7806 is probably a better idea, saves a lot of messing about. Or you could use the guts of a mobile phone car charger. The charger that fits into the cigarette lighter in a motor car. You can find them in pawn shops for a dollar or two. Dud ones even cheaper. Usually just a broken connection from rough handling. http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF Look at page 7 Figure 10 Step down converter. In the few car phone chargers that I opened, the IC was a MC34063 and the schematic was very similar to that shown in figure 10 Just change R1 or R2 slightly so that you get 6 Volts out. You may have to check/change the value of resistor Rsc to be closer to that shown in figure 10 You might even get away with not changing the inductor. Try it and see if the original inductor works well enough for you. A ton of reading, bits and pieces for free or dirt cheap. What a great hobby, this is James, eh! Regards, John Crighton Sydney
From: John Crighton on 27 Dec 2005 03:25 On Tue, 27 Dec 2005 02:02:15 GMT, "James F. Mayer" <jfma(a)ix.netcom.com> wrote: > I need to generate 6v DC and 90v DC from a 12v DC automotive electrical >system to power an RT-70A/GRC surplus military radio. I need about 250 mA >at +6 volts and about 75 mA at +90 volts. I was thinking about using the >guts from an old battery back up but it would be a bit of a kluge. Are >there any 90 volt regulators in the 78xx series? How do I get the voltage >up to where I can get something that I can get the 90 volts from. Getting >the 6 volts doesn't seem to be a problem. A 7806 off the battery should >work for that unless any of you can see a problem doing that. Maybe the >common common would be a problem. Right now I'm running it off of an HP6299A >and an HP6236B with commons jumpered. I'd like to be able to go portable >with it. > > Hello again James, I just came across this site while looking for something else. http://web.telia.com/~u85920178/use/tubepsu.htm Look at the the 6V AC from 12 V DC. Nifty! Here is another http://www.i4at.org/lib2/inverter.htm You want DC out so you will have to fit a bridge rectifier and filter capacitors to the output of the transformer just like Harry Lythall's circuit above. Regards, John Crighton Sydney
From: Bill Turner on 27 Dec 2005 09:32 ORIGINAL MESSAGE: On Mon, 26 Dec 2005 21:11:35 -0800, Highland Ham <abcgm0csz.kn6whxyz(a)dsl.pipex.com> wrote: >Those 'inexpensive inverters' might need some attention in respect of >the 'hash' they create , possibly causing interference in the receiver. > >Frank ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ True for any kind of inverter. 73, Bill W6WRT
From: Bill Turner on 27 Dec 2005 09:38 ORIGINAL MESSAGE: On Tue, 27 Dec 2005 05:58:18 GMT, john_c(a)tpg.com.au (John Crighton) wrote: > >Hello James, >Speaking as a cheapskate ham/hobbyist, how >about salvaging parts from a computer power supply. >Find a dud power supply for free at computer >shops/dumpsters/rubbish tips/roadside etc. >Salvage the TL494 integrated circuit that can >be found in many computer power supplies. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Excellent info, John. Thanks!! 73, Bill W6WRT
From: RST Engineering on 27 Dec 2005 11:16
Do it the way the original radio did it -- dynamotor. You can still find them in the back room at a lot of military surplus electronics junk stores. Jim |