kebloks Posted September 12, 2006 Report Share Posted September 12, 2006 http://www3.telus.net/chemelec/Projects/Power-Supply/Power-Supply.htmschematics:will it work? Quote Link to comment Share on other sites More sharing options...
ante Posted September 12, 2006 Report Share Posted September 12, 2006 Hi kebloks,Welcome to our forum!Looks good, try it! Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 12, 2006 Report Share Posted September 12, 2006 The resistor from the output to the ADJ terminal of the voltage regulating IC is 240 ohms when it should be 120 ohms so the output voltage doesn't rise without a load, as per the datasheet. Then the value of the voltage adjustment pot should also be reduced to half also. Quote Link to comment Share on other sites More sharing options...
ante Posted September 12, 2006 Report Share Posted September 12, 2006 Hi AG,Well, Gary built and tested it without any problems! Quote Link to comment Share on other sites More sharing options...
audioguru Posted September 12, 2006 Report Share Posted September 12, 2006 Hi Ante,Gary made one or two.The datasheet has a max rating for the IC's idle current which is 10mA for the LM317 in a large case and only 5mA for the more expensive LM117. The reference voltage of 1.25V flows through the resistor which is only 5.2mA for a 240 ohm resistor. Since the max idle current for the LM317 is 10mA then you can expect some of them to have more than only 5.2mA so the output voltage will rise without a load.Unfortunately, the datasheet shows a circuit with a 240 ohm resistor on its 1st page and that is the circuit most people use. It uses an LM117. Quote Link to comment Share on other sites More sharing options...
ante Posted September 12, 2006 Report Share Posted September 12, 2006 Yes I know what you are getting at; it’s not the first time this discussion has been up! ;DLet’s do it your way; let’s change the resistor for a 120R and we’re really safe! ;) Quote Link to comment Share on other sites More sharing options...
kebloks Posted September 14, 2006 Author Report Share Posted September 14, 2006 Will it work for 3A?and... ( from the site )"NOTE:  R2 is determined by the voltage across the 220 uF Cap. (Volts - 1.2) R2 = ------------- .015 Any Resistor close to the calculated value should be fine. Its only purpose is for an approximate 15 mA current flow which will create a quite stable -1.2 volt supply. "does it mean voltage across the cap of the complete circuit? Quote Link to comment Share on other sites More sharing options...
ante Posted September 14, 2006 Report Share Posted September 14, 2006 Yes with the LM350 Quote Link to comment Share on other sites More sharing options...
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