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Forum Index : Electronics : Variable power supply update
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Doug Regular Member  Joined: 11/05/2010 Location: New ZealandPosts: 41 |
Hi all Was looking through a web page on electronic projects, specifically power supplies and came across the variable power supply cct that glen has posted in the projects page with one change. The LM317 transistor is only good for about 1.5 amps maximum current flow. Apparently if you change it for a LM338T it will handle up to 5 amps. In my mind that makes it a much more usable type of power supply. Doug May The Power Be With You |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Good info Doug. I've used a LM338K in the past, same chip but different case. One tip I have is to use a BIG heatsink if you plan to draw a few amps, since its a series regulator and they can get very warm. The LM338 has built in protection against overheating, a big heatsink will mean better regulation at high current loads. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| VK4AYQ Guru  Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glen Have you seen the switchmode regulator its got four leads in the same package as a normal regulator 5 amps I think and very low loss I cant find the number at the moment. All the best Bob Foolin Around |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glen I found the details on the regulator, is 3 amp not 5 as I thought but maybe able to be used as a controller for a high power fet, what do you think. All the best Bob Manufacturer: National Semiconductor Manufacturer P/N: LM2576T-ADJ Output voltage adjustable from 1.23V to 37V Guaranteed 3A output current Input voltage up to 40V High efficiency Thermal shutdown and current limit protection Package: TO-220 http://www.national.com/ds/LM/LM2576.pdf http://www.national.com/ds/LM/LM2576.pdf Foolin Around |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Bob I've been tempted to build a switch mode variable power supply for some time. Something different to my trusty old series regulators, with a smaller heat sink 
The LM2576 looks pretty good, easy to use. Jaycar sell them for $17.oo I also like the TL494, its just the IC, and needs a MOSFET and other parts, but does include neat features like soft start and current limiting. The TL494 is used in many PC power supplies and I've used one in a motor controller. http://www.datasheetcatalog.org/datasheet/motorola/TL494.pdf http://focus.ti.com.cn/cn/lit/an/slva001d/slva001d.pdf Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glen I have found some on ebay Seller information green21century ( 4584) 99.8% Positive feedback Ask a question Save this seller See other items Visit store: green21century 10 units for $13 free post have ordered some to try them, do you think they could be used as a controller for a couple of fets, I have a nice 1.2 kw transformer 36 volt I would like to build a big power supply with but didn't want to create a workshop warmer with 3055 in parallel. All the best Bob Foolin Around |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glen Had a look at the spec sheet, it is an interesting option. Bob Foolin Around |
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