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Overvoltage and reverse voltage protection
Dear all
I want to design a power supply for a low power rig with protection for reverse and overvoltage. The requirement would be about 1A at 12-14V. What is the best way of achieving this? I guess a diode would give reverse voltage protection but the 0.6V drop is a problem. Richard |
On Sun, 11 Jan 2004 19:44:19 +0800, Richard Hosking
wrote: Dear all I want to design a power supply for a low power rig with protection for reverse and overvoltage. The requirement would be about 1A at 12-14V. What is the best way of achieving this? I guess a diode would give reverse voltage protection but the 0.6V drop is a problem. Richard Rick, one way for reverse protection is to include a bridge recifier in the rigs power line ( internally fitted ), but this causes a drop in available volts. I prefer a diode into a relay coil, with the relay contacts enabling the power when the relay coil is correctly polarised and powered ( also internally fitted ). This enables full volts to the rig and also gives reverse protection, however this is at the cost of further ( and some may say excessive ) drain of the power source. Over voltage should be by fuse and a crowbar circuit. Do a search on crowbar for details. The diode + relay circuit should be obvious to you, I use a 9v relay coil with a 1N4001 in the activation side and a DPDT contact,in parallel, to switch the power. For the power you are talking about a 14pin DIL relay should be adequate. HTH, Mike W, G8NXD qthr |
On Sun, 11 Jan 2004 19:44:19 +0800, Richard Hosking
wrote: Dear all I want to design a power supply for a low power rig with protection for reverse and overvoltage. The requirement would be about 1A at 12-14V. What is the best way of achieving this? I guess a diode would give reverse voltage protection but the 0.6V drop is a problem. Richard Rick, one way for reverse protection is to include a bridge recifier in the rigs power line ( internally fitted ), but this causes a drop in available volts. I prefer a diode into a relay coil, with the relay contacts enabling the power when the relay coil is correctly polarised and powered ( also internally fitted ). This enables full volts to the rig and also gives reverse protection, however this is at the cost of further ( and some may say excessive ) drain of the power source. Over voltage should be by fuse and a crowbar circuit. Do a search on crowbar for details. The diode + relay circuit should be obvious to you, I use a 9v relay coil with a 1N4001 in the activation side and a DPDT contact,in parallel, to switch the power. For the power you are talking about a 14pin DIL relay should be adequate. HTH, Mike W, G8NXD qthr |
Mike W wrote:
Over voltage should be by fuse and a crowbar circuit. Do a search on crowbar for details. If you already have a fuse & crowbar circuit for overvoltage, wouldn't the easy way to handle reverse polarity be a diode hooked in the (normally) non-conducting direction across the output? -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com |
Mike W wrote:
Over voltage should be by fuse and a crowbar circuit. Do a search on crowbar for details. If you already have a fuse & crowbar circuit for overvoltage, wouldn't the easy way to handle reverse polarity be a diode hooked in the (normally) non-conducting direction across the output? -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com |
I'm not understanding something here. You want to design a power supply that protects against reverse voltage and overvoltage. OK. Is this power supply a battery or are you actually building a power supply that runs from the wall outlet? The requirements are quite different, depending on what you are trying to achieve. Jim Richard Hosking shared these priceless pearls of wisdom: -Dear all -I want to design a power supply for a low power rig with protection for -reverse and overvoltage. Jim Weir, VP Eng. RST Eng. WX6RST A&P, CFI, and other good alphabet soup |
I'm not understanding something here. You want to design a power supply that protects against reverse voltage and overvoltage. OK. Is this power supply a battery or are you actually building a power supply that runs from the wall outlet? The requirements are quite different, depending on what you are trying to achieve. Jim Richard Hosking shared these priceless pearls of wisdom: -Dear all -I want to design a power supply for a low power rig with protection for -reverse and overvoltage. Jim Weir, VP Eng. RST Eng. WX6RST A&P, CFI, and other good alphabet soup |
In article ,
says... Dear all I want to design a power supply for a low power rig with protection for reverse and overvoltage. The requirement would be about 1A at 12-14V. What is the best way of achieving this? I guess a diode would give reverse voltage protection but the 0.6V drop is a problem. Power Schottky diodes are available that have a forward voltage drop of 0.3 or less. More expensive, yes, but they really do work. -- Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute (Known to some as Bruce Lane, KC7GR) kyrrin a/t bluefeathertech d-o=t c&o&m Motorola Radio Programming & Service Available - http://www.bluefeathertech.com/rf.html "Quando Omni Flunkus Moritati" (Red Green) |
On Sun, 11 Jan 2004 14:05:21 GMT, (Mike W)
wrote: The diode + relay circuit should be obvious to you, I use a 9v relay coil with a 1N4001 in the activation side and a DPDT contact,in parallel, to switch the power. For the power you are talking about a 14pin DIL relay should be adequate. HTH, Mike W, G8NXD qthr I'd like to call it "the PYE method" since it is generally applied in those Westminster, Vanguard and Cambridge sets, while other manufacturers only use a diode. I've copied it for the larger sets which are often used in different places. The application of relay has the advantage that nothing happens if you use the wrong polarity - unless you have shortcircuit between two chassises, then you should apply a two-pole relay. Make sure that the relay stays operated under different operation, check that the relay operates with 9V. Remember to put a diode or other spark suppression across the coil, too. 73 LA8AK, http://home.online.no/~la8ak/c.htm -- Amount of SPAM is so large that MailWasher must delete 99% of the incoming mails Cannot check every email manually. Please use intelligent title for email. Mails without titles or using just "hi" is deleted |
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