Post by thread:[EE]: using a PC power supply

Hello All, We are trying to use a power supply from an old PC, and it looks like it needs a certain amount of load in order to operate. Our application involves switching between several loads, and since some of the loads don't consume much power, the power supply simply shuts off. Does anybody know of a way to modify the circuit, to avoid wasting energy? Thank you for your help, Vitaliy -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> -----Original Message----- > From: Vitaliy M [SMTP:spam_OUTpiclist2001TakeThisOuTHOTMAIL.COM] > Sent: Monday, March 24, 2003 8:56 AM > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: [EE]: using a PC power supply > > Hello All, > > We are trying to use a power supply from an old PC, and it looks like it > needs a certain amount of load in order to operate. Our application > involves switching between several loads, and since some of the loads > don't > consume much power, the power supply simply shuts off. Does anybody know > of > a way to modify the circuit, to avoid wasting energy? > > Thank you for your help, > > Vitaliy > You are correct in that many of them do require a minimum load. Sorry this isn't very hellpfull but if you cannot provide the minimum load then a more suitable power supply should be used. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to postmasterKILLspambookham.com. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> We are trying to use a power supply from an old PC, and it looks like it > needs a certain amount of load in order to operate. Our application > involves switching between several loads, and since some of the > loads don't > consume much power, the power supply simply shuts off. Does > anybody know of > a way to modify the circuit, to avoid wasting energy? Doubtful. A switched power supply of that type REQUIRES a load to function normally. An unprotected switched power supply can blow up if it doesn't have a load of some minimal amount, yours obviously has minimum load protection. In order to get what you want you'd have to modify the supply such that your minimum load is enough to satisfy it's minimum load. Considering the priorities while designing a PC power supply the odds that you'll be able to do this are very low. You will either have to live with the power being wasted, or get/build another power supply instead. TTYL -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

x-no-archive:yes If I am using the old PC supply for this purpose, it is because it is cheap, easy and convenient. Maximum efficency and more trouble would not be what I desire. Under this condition, I would just parallel a load (resistor) to the lightest load that was the problem. This would also mean you can replace the PC supply with another one without modification if it is breakdown. So ease future tasks in support and maintenance. Ling SM "x-no-archive:yes" as your first line to avoid Google archiving. > > We are trying to use a power supply from an old PC, and it looks like it > > needs a certain amount of load in order to operate. Our application > > involves switching between several loads, and since some of the > > loads don't > > consume much power, the power supply simply shuts off. Does > > anybody know of > > a way to modify the circuit, to avoid wasting energy? > > Doubtful. A switched power supply of that type REQUIRES a load to function > normally. An unprotected switched power supply can blow up if it doesn't > have a load of some minimal amount, yours obviously has minimum load > protection. > In order to get what you want you'd have to modify the supply such that > your minimum load is enough to satisfy it's minimum load. Considering the > priorities while designing a PC power supply the odds that you'll be able to > do this are very low. You will either have to live with the power being > wasted, or get/build another power supply instead. TTYL -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hello everyone, Thank you all for your feedback. In case this could be useful to someone: we ended up connecting a 1 watt 47 Ohm resistor to the 5V output, plus added an LED in series with a 1k resistor connected to the 12V output, and the power supply is now working fine. This is what we intended to do in the first place, but I hoped there was a way to make it work without converting electrical energy to heat. Here in Phoenix, it is pretty warm as it is. Again, thank you very much for your help. Best regards, Vitaliy {Original Message removed}