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2010-03-09 by logicresearch
Hi, I have two photos at <http://www.logicresearch.co.nz/pcbfuse.html> of the pcb tracks being used as a fuse. I've not seen this before, and I thought you might like to see how it worked. Has anyone here got the maths on track widths and thickness for this?. Daryl Mills LogicResearch
2010-03-09 by Paul Mateer
Here's one calculator I found: http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/ On Mon, Mar 8, 2010 at 10:47 PM, logicresearch <logicresearch@...>wrote: > > > Hi, > > I have two photos at <http://www.logicresearch.co.nz/pcbfuse.html> of the > pcb tracks being used as a fuse. > I've not seen this before, and I thought you might like to see how it > worked. > Has anyone here got the maths on track widths and thickness for this?. > > Daryl Mills > LogicResearch > > > -- Paul Mateer, AA9GG Elan Engineering Corp. www.elanengr.com NAQCC 3123, SKCC 4628, FPQRP 2003 [Non-text portions of this message have been removed]
2010-03-09 by Stefan Trethan
That's a good calculator, they also have a very good via calculator there. The question is what temperature rise do you calculate for? You mustn't go over the max. PCB temperature during normal operation (something like 130°C). I would size the fuse trace so it can carry the normal current with some good safety margin (esp. trace manufacturing tolerances) and then experiment at which current it fuses in which time. Stuff like inrush currents must be accounted for, but are probably fine. But then, I would not do this at all! Another weird thing I've seen is in a Tektronix logic probe. A little wire of springy material is fixed on one end, and then bent down for soldering on the other end. If you overload the input the wire gets hot and unsolders itself, springing away from the joint. The manual stresses you must not add any solder to re-set it, a bit like those old temperature fuses which had a "rivet" of low melting alloy. ST
On Tue, Mar 9, 2010 at 6:07 PM, Paul Mateer <paul.aa9gg@...> wrote: > Here's one calculator I found: > http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/ >
2010-03-09 by Derk Steggewentz
I have seen pcb-trace fuses on a power supply PCB in a Tektronix 577 curve tracer, which I think is from the '70s. So, this technique seems to be around for a while and to me it can makes sense for certain uncritical applications (e.g. tripping extremely unlikely and only for full shorts, delay time uncritical etc.... ) Derk logicresearch wrote:
> > > Hi, > > I have two photos at <http://www.logicresearch.co.nz/pcbfuse.html > <http://www.logicresearch.co.nz/pcbfuse.html>> of the pcb tracks being > used as a fuse. > I've not seen this before, and I thought you might like to see how it > worked. > Has anyone here got the maths on track widths and thickness for this?. > > Daryl Mills > LogicResearch >
2010-03-09 by David Griffith
On Tue, 9 Mar 2010, Derk Steggewentz wrote: > I have seen pcb-trace fuses on a power supply PCB in a Tektronix 577 > curve tracer, which I think is from the '70s. So, this technique seems > to be around for a while and to me it can makes sense for certain > uncritical applications (e.g. tripping extremely unlikely and only for > full shorts, delay time uncritical etc.... ) I'm curious why someone would want to use such a fuse in the first place. How do you replace it? Are there pads for adding a fuse holder after the PCB fuse blows? -- David Griffith dgriffi@... A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail?
2010-03-09 by Stefan Trethan
You appear to be under the impression that fuses should be replaceable? Usually this is not the case, fuses are there to prevent fire and/or other danger if something goes wrong. Changing the fuse will not solve the problem, since it blew for a reason. You are supposed to throw the thing out once it is broken, not repair it. ;-) The only situation where a replaceable fuse makes some sense is if you have like an outlet or something to which the user can connect stuff. But more and more the trend goes towards not providing a user replaceable fuse because people can't be trusted to replace with the same rating, no matter how many warnings you print on. ST
On Tue, Mar 9, 2010 at 9:57 PM, David Griffith <dgriffi@...> wrote: > I'm curious why someone would want to use such a fuse in the first place. > How do you replace it? Are there pads for adding a fuse holder after the > PCB fuse blows? > > -- > David Griffith > dgriffi@... >
2010-03-09 by awakephd
I'm not sure what the big deal is about printed-on fuses. I've done that many times -- in fact just the other day, when I made a bone-headed connection on the 170V PWM motor control board I was working on, several traces turned into instant fuses! I'm embarrassed to confess that I forgot that the "ground" on the board was NOT at the level of ground in the wall when I attached the ground lead from the o-scope. Fortunately the board "fused" rather than the o-scope. It destroyed two IC's on the board in the process, but that was a small price to pay compared to fixing or replacing the scope! And yes ... the board went in the trash and I started over -- much more carefully this time! And yes, the new board works perfectly. --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
> You appear to be under the impression that fuses should be replaceable? > > Usually this is not the case, fuses are there to prevent fire and/or > other danger if something goes wrong. > Changing the fuse will not solve the problem, since it blew for a reason. > You are supposed to throw the thing out once it is broken, not repair it. ;-) > > The only situation where a replaceable fuse makes some sense is if you > have like an outlet or something to which the user can connect stuff. > But more and more the trend goes towards not providing a user > replaceable fuse because people can't be trusted to replace with the > same rating, no matter how many warnings you print on. > > ST > > > On Tue, Mar 9, 2010 at 9:57 PM, David Griffith <dgriffi@...> wrote: > > > I'm curious why someone would want to use such a fuse in the first place. > > How do you replace it? Are there pads for adding a fuse holder after the > > PCB fuse blows? > > > > -- > > David Griffith > > dgriffi@... > > >
2010-03-09 by Paul Mateer
zzzzzzZZZZZZAAAAAPPPPPP!!!!!!!!!!!!!!!!! On 3/9/10, awakephd <a_wake@earthlink.net> wrote: > I'm not sure what the big deal is about printed-on fuses. I've done that > many times -- in fact just the other day, when I made a bone-headed > connection on the 170V PWM motor control board I was working on, several > traces turned into instant fuses! > > I'm embarrassed to confess that I forgot that the "ground" on the board was > NOT at the level of ground in the wall when I attached the ground lead from > the o-scope. Fortunately the board "fused" rather than the o-scope. It > destroyed two IC's on the board in the process, but that was a small price > to pay compared to fixing or replacing the scope! > > And yes ... the board went in the trash and I started over -- much more > carefully this time! And yes, the new board works perfectly. > > --- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> > wrote: > >> You appear to be under the impression that fuses should be replaceable? >> >> Usually this is not the case, fuses are there to prevent fire and/or >> other danger if something goes wrong. >> Changing the fuse will not solve the problem, since it blew for a reason. >> You are supposed to throw the thing out once it is broken, not repair it. >> ;-) >> >> The only situation where a replaceable fuse makes some sense is if you >> have like an outlet or something to which the user can connect stuff. >> But more and more the trend goes towards not providing a user >> replaceable fuse because people can't be trusted to replace with the >> same rating, no matter how many warnings you print on. >> >> ST >> >> >> On Tue, Mar 9, 2010 at 9:57 PM, David Griffith <dgriffi@...> wrote: >> >> > I'm curious why someone would want to use such a fuse in the first >> > place. >> > How do you replace it? Are there pads for adding a fuse holder after >> > the >> > PCB fuse blows? >> > >> > -- >> > David Griffith >> > dgriffi@... >> > >> > > > -- Paul Mateer, AA9GG Elan Engineering Corp. www.elanengr.com NAQCC 3123, SKCC 4628, FPQRP 2003
2010-03-09 by James
--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote: > > You appear to be under the impression that fuses should be replaceable? > > Usually this is not the case, fuses are there to prevent fire and/or > other danger if something goes wrong. > Changing the fuse will not solve the problem, since it blew for a reason. > You are supposed to throw the thing out once it is broken, not repair it. ;-) > > The only place I've seen a "fuse" like this is in some compact fluorescent lamps, others use a low ohm fusible resistor for the same purpose. I've repaired them just because I can, using a replacement fuse of 0.5A or so or a small fusible resistor, naturally one also has to locate and replace the shorted component that blew the fuse in the first place. The actual value is not so critical, it needs to be high enough to not blow under normal use, and low enough to blow before heavier traces or wires heat up, since the typical fault is a direct short, anything under a couple amps or so will blow in that condition.
2010-03-09 by James
--- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@...> wrote: > > I'm not sure what the big deal is about printed-on fuses. I've done that many times -- in fact just the other day, when I made a bone-headed connection on the 170V PWM motor control board I was working on, several traces turned into instant fuses! > > I'm embarrassed to confess that I forgot that the "ground" on the board was NOT at the level of ground in the wall when I attached the ground lead from the o-scope. Fortunately the board "fused" rather than the o-scope. It destroyed two IC's on the board in the process, but that was a small price to pay compared to fixing or replacing the scope! > > And yes ... the board went in the trash and I started over -- much more carefully this time! And yes, the new board works perfectly. > > Been there, done that. *ALWAYS* use an isolation transformer when testing "hot chassis" equipment. It may save some expensive test gear, or yourself! If you don't have one, it can be made in a pinch with a pair of back to back power transformers.
2010-03-10 by awakephd
--- In Homebrew_PCBs@yahoogroups.com, "James" <jamesrsweet@...> wrote: > > > > --- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@> wrote: > > > > I'm not sure what the big deal is about printed-on fuses. I've done that many times -- in fact just the other day, when I made a bone-headed connection on the 170V PWM motor control board I was working on, several traces turned into instant fuses! > > > > I'm embarrassed to confess that I forgot that the "ground" on the board was NOT at the level of ground in the wall when I attached the ground lead from the o-scope. Fortunately the board "fused" rather than the o-scope. It destroyed two IC's on the board in the process, but that was a small price to pay compared to fixing or replacing the scope! > > > > And yes ... the board went in the trash and I started over -- much more carefully this time! And yes, the new board works perfectly. > > > > > > > Been there, done that. *ALWAYS* use an isolation transformer when testing "hot chassis" equipment. It may save some expensive test gear, or yourself! If you don't have one, it can be made in a pinch with a pair of back to back power transformers. > I'm glad I'm not the only one. I had intended to test the board out feeding in power to the logic section from an isolated power source (and that is what I did after I re-made the board). But I had had to set the project aside for several weeks, so I when I finally got back to it I was overly eager ... and it was late, and I was tired, and I wasn't thinking. But hopefully the lesson is now burned into my brain! Errr ... no pun intended. :)
2010-03-10 by awakephd
You left out the next sound that occurred. It began with "oh" ... :) --- In Homebrew_PCBs@yahoogroups.com, Paul Mateer <paul.aa9gg@...> wrote:
> > zzzzzzZZZZZZAAAAAPPPPPP!!!!!!!!!!!!!!!!! > > On 3/9/10, awakephd <a_wake@...> wrote: > > I'm not sure what the big deal is about printed-on fuses. I've done that > > many times -- in fact just the other day, when I made a bone-headed > > connection on the 170V PWM motor control board I was working on, several > > traces turned into instant fuses! > > > > I'm embarrassed to confess that I forgot that the "ground" on the board was > > NOT at the level of ground in the wall when I attached the ground lead from > > the o-scope. Fortunately the board "fused" rather than the o-scope. It > > destroyed two IC's on the board in the process, but that was a small price > > to pay compared to fixing or replacing the scope! > > > > And yes ... the board went in the trash and I started over -- much more > > carefully this time! And yes, the new board works perfectly. > -- > Paul Mateer, AA9GG > Elan Engineering Corp. > www.elanengr.com > NAQCC 3123, SKCC 4628, FPQRP 2003 >
2010-03-10 by Donald H Locker
More like reflashed, perhaps? Donald. Pun completely intended. ----- "awakephd" <a_wake@...> wrote:
> --- In Homebrew_PCBs@yahoogroups.com, "James" <jamesrsweet@...> > wrote: > > > > > > > > --- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@> wrote: > > > > > > I'm not sure what the big deal is about printed-on fuses. I've > done that many times -- in fact just the other day, when I made a > bone-headed connection on the 170V PWM motor control board I was > working on, several traces turned into instant fuses! > > > > > > I'm embarrassed to confess that I forgot that the "ground" on the > board was NOT at the level of ground in the wall when I attached the > ground lead from the o-scope. Fortunately the board "fused" rather > than the o-scope. It destroyed two IC's on the board in the process, > but that was a small price to pay compared to fixing or replacing the > scope! > > > > > > And yes ... the board went in the trash and I started over -- much > more carefully this time! And yes, the new board works perfectly. > > > > > > > > > > > > Been there, done that. *ALWAYS* use an isolation transformer when > testing "hot chassis" equipment. It may save some expensive test gear, > or yourself! If you don't have one, it can be made in a pinch with a > pair of back to back power transformers. > > > > I'm glad I'm not the only one. I had intended to test the board out > feeding in power to the logic section from an isolated power source > (and that is what I did after I re-made the board). But I had had to > set the project aside for several weeks, so I when I finally got back > to it I was overly eager ... and it was late, and I was tired, and I > wasn't thinking. But hopefully the lesson is now burned into my brain! > Errr ... no pun intended. :)
2010-03-10 by Sz G
Sorry for the inline comments. It wouldn't make any sense otherwise. Hope it does this way :) > ________________________________ > From: Stefan Trethan <stefan_trethan@...> > To: Homebrew_PCBs@yahoogroups.com > Sent: Tue, March 9, 2010 10:25:58 PM > Subject: Re: [Homebrew_PCBs] PCB fuse > > > You appear to be under the impression that fuses should be replaceable? > He's not alone. Not sure if anyone cares, but I also think it's a much better idea to have a fuse enclosed in an electrically and thermally (!) isolated container rather than a trace on the PCB itself. I'd find it hard to find any reason to choose the latter over the former. Any defect in the manufacturing process (or a minor difference in the choice of materials, like using another laminate with slightly different properties) could render a "PCB fuse" worthless. Not to mention that it could aggravate the issue by creating another possible source of fire hazard and damaging the PCB if higher currents are involved. > Usually this is not the case, fuses are there to prevent fire and/or > other danger if something goes wrong. > Changing the fuse will not solve the problem, since it blew for a reason. > You are supposed to throw the thing out once it is broken, not repair it. ;-) > I'm pretty confused now. Sure thing: fuses (in the majority of cases) blow because the POS behind them drew more current than it should have. But I certainly don't feel like wasting hundreds or thousands of $'s worth of fine electronics if an electrolytic capacitor decides to give up in a SMPS, even if I'm supposed to. In fact, I believe that no one should, at least as long as repairs are (financially) feasible. Most people won't even attempt repairing a faulty component on their own and if they do, they're aware (or at least they should be) of the risks associated with the procedure. A skilled technician or engineer on the other hand would find it _really_ annoying if they were expected to find a way to "replicate" a blown PCB fuse. In fact, the only thing they could responsibly tell the customer is to throw it away, because it's clearly not meant to be repaired. > The only situation where a replaceable fuse makes some sense is if you > have like an outlet or something to which the user can connect stuff. > But more and more the trend goes towards not providing a user > replaceable fuse because people can't be trusted to replace with the > same rating, no matter how many warnings you print on. > I couldn't agree more. People with no experience working with electronics shouldn't be trusted with this. That's why they came to mount the fuse holder inside the case on the PCB (or somewhere else where it's inaccessible from the outside) - still replaceable, but only by those who make an explicit decision to disassemble it. Gabor
> ST > On Tue, Mar 9, 2010 at 9:57 PM, David Griffith <dgriffi@.... edu> wrote: > I'm curious why someone would want to use such a fuse in the first place. > How do you replace it? Are there pads for adding a fuse holder after the > PCB fuse blows? > > -- > David Griffith > dgriffi@.... edu >
2010-03-10 by Donald H Locker
I'm a fan of PPTC (Polymer Positive Temperature Coefficient) fuses for on-board protection. Quick enough for most purposes, self-resetting after the fault is removed, available in many sizes and ratings. Try a web search for such trade names as: PolySwitch, OptiFuse, Multifuse, Polyfuse or for PPTC Donald. ----- "Sz G" <the6hu8b@...> wrote:
> Sorry for the inline comments. It wouldn't make any sense otherwise. > Hope it does this way :) > > > ________________________________ > > From: Stefan Trethan <stefan_trethan@...> > > To: Homebrew_PCBs@yahoogroups.com > > Sent: Tue, March 9, 2010 10:25:58 PM > > Subject: Re: [Homebrew_PCBs] PCB fuse > > > > > > You appear to be under the impression that fuses should be > replaceable? > > > > He's not alone. Not sure if anyone cares, but I also think it's a much > better idea to have a fuse enclosed in an electrically and thermally > (!) isolated container rather than a trace on the PCB itself. I'd find > it hard to find any reason to choose the latter over the former. Any > defect in the manufacturing process (or a minor difference in the > choice of materials, like using another laminate with slightly > different properties) could render a "PCB fuse" worthless. Not to > mention that it could aggravate the issue by creating another possible > source of fire hazard and damaging the PCB if higher currents are > involved. > > > Usually this is not the case, fuses are there to prevent fire > and/or > > other danger if something goes wrong. > > Changing the fuse will not solve the problem, since it blew for a > reason. > > You are supposed to throw the thing out once it is broken, not > repair it. ;-) > > > I'm pretty confused now. Sure thing: fuses (in the majority of cases) > blow because the POS behind them drew more current than it should > have. But I certainly don't feel like wasting hundreds or thousands of > $'s worth of fine electronics if an electrolytic capacitor decides to > give up in a SMPS, even if I'm supposed to. In fact, I believe that no > one should, at least as long as repairs are (financially) feasible. > Most people won't even attempt repairing a faulty component on their > own and if they do, they're aware (or at least they should be) of the > risks associated with the procedure. > A skilled technician or engineer on the other hand would find it > _really_ annoying if they were expected to find a way to "replicate" a > blown PCB fuse. In fact, the only thing they could responsibly tell > the customer is to throw it away, because it's clearly not meant to be > repaired. > > > The only situation where a replaceable fuse makes some sense is if > you > > have like an outlet or something to which the user can connect > stuff. > > But more and more the trend goes towards not providing a user > > replaceable fuse because people can't be trusted to replace with > the > > same rating, no matter how many warnings you print on. > > > I couldn't agree more. People with no experience working with > electronics shouldn't be trusted with this. That's why they came to > mount the fuse holder inside the case on the PCB (or somewhere else > where it's inaccessible from the outside) - still replaceable, but > only by those who make an explicit decision to disassemble it. > > Gabor > > > ST > > > On Tue, Mar 9, 2010 at 9:57 PM, David Griffith <dgriffi@.... > edu> wrote: > > > I'm curious why someone would want to use such a fuse in the first > place. > > How do you replace it? Are there pads for adding a fuse holder > after the > > PCB fuse blows? > > > > -- > > David Griffith > > dgriffi@.... edu > > > > > > > > > > ------------------------------------ > > Be sure to visit the group home and check for new Links, Files, and > Photos: > http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links > > >