avcctv Posted February 10, 2007 Share Posted February 10, 2007 Easy source would be a couple of old voltage requlators from an old panel or the four fitted after the transformer on a old alarm (fire) PCB. Jesus why not just use a zener diode. man you lot love to complicate things The older I get, the faster I was. Link to comment Share on other sites More sharing options...
luggsey Posted February 10, 2007 Share Posted February 10, 2007 Jesus why not just use a zener diode. man you lot love to complicate things You don't find 2/3A zenner diodes lying around very often for 5 volt as well.... ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
Drew Posted February 10, 2007 Share Posted February 10, 2007 Firstly, I'd advise strongly against opening or fiddling with switch mode PSU's. The hot side is likely to be up to 400V d.c. - not the sort of thing to lick to see if it's working. You need a 5V regulator Like an LM7805. It has three legs - Vin, 0V and Vout. Like this The left hand pin goes to +12V the middle pin to 0V (-Ve) and the output of 5V will appear between the right hand pin and the middle pin. Simple as that - Part UJ54J from Maplin, 77p Except.... If your load is 2A, this poor little regulator will develop the voltage difference X the current in heat. This is (12-5)V X 2A = 14W. In fresh air, the device will get very hot and shut down. It will have to be bolted to a heatsink in order to be stable. A 2.7 ohm 10W resistor in series with the Vin pin will improve its ability to go to 2A without going into thermal shutdown. Drew Hoggatt Managing Director Paxton Access Ltd Follow this link for important legal information Link to comment Share on other sites More sharing options...
Guest Posted February 10, 2007 Share Posted February 10, 2007 Having a bit more of a play with the old sat nav bit (now Drew has given me some slightly less bodgy sounding ideas!) it has in it a LM2576T-5.0, which is a 5V 3A regulator, and it has a heatsink fitted and has been running for a couple of hours and is not warm to the touch. All I need to do now is strip all the bits off that I don't need, pop it in a little box and that's another job done. Saves me taking the PSU to bits as well, as it's brand new. Link to comment Share on other sites More sharing options...
Drew Posted February 10, 2007 Share Posted February 10, 2007 An LM2576 eh? There's posh. It's a switching regulator and is therefore much more power efficient than the linear regulator I suggested. Drew Hoggatt Managing Director Paxton Access Ltd Follow this link for important legal information Link to comment Share on other sites More sharing options...
Guest Peter James Posted February 10, 2007 Share Posted February 10, 2007 It's likely that it is.I'm constantly amazed at what I have laying around! Ill give you a tenner for the garage door? Link to comment Share on other sites More sharing options...
luggsey Posted February 10, 2007 Share Posted February 10, 2007 Having a bit more of a play with the old sat nav bit (now Drew has given me some slightly less bodgy sounding ideas!) it has in it a LM2576T-5.0, which is a 5V 3A regulator, and it has a heatsink fitted and has been running for a couple of hours and is not warm to the touch. All I need to do now is strip all the bits off that I don't need, pop it in a little box and that's another job done. Saves me taking the PSU to bits as well, as it's brand new. I'm insulted! I've just been called a bodger in so many words. I'll have you know young man I suggested a power transistor in my first post so that makes Drew a bodger too! (Like that!) Drews detail was a "little" better then mine I conceed. Take back that bodger comment, I demand it, make it so! ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
Guest Posted February 10, 2007 Share Posted February 10, 2007 I'm insulted! I've just been called a bodger in so many words. I'll have you know young man I suggested a power transistor in my first post so that makes Drew a bodger too! (Like that!)Drews detail was a "little" better then mine I conceed. Take back that bodger comment, I demand it, make it so! You started out well, but then we got onto sticking 11 diodes in a line. Think that was where it started going wrong! Admittedly, you did mention power transistor, you get a point for that at least. Ill give you a tenner for the garage door? It doesn't work too well and it wants painting, and you have to remove it yourself, and you may as well fit the new one while you're at it. Link to comment Share on other sites More sharing options...
luggsey Posted February 10, 2007 Share Posted February 10, 2007 I don't know, I give you the advice you needed within two minutes and got called a bodger for my trouble. It's a cruel world..... ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
avcctv Posted February 10, 2007 Share Posted February 10, 2007 I don't know, I give you the advice you needed within two minutes and got called a bodger for my trouble.It's a cruel world..... A 5v6 zener The older I get, the faster I was. Link to comment Share on other sites More sharing options...
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