On Fri, 08 May 2015 12:19:38 -0700, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno ><DLU1@DecadentLinuxUser.org> wrote: > >>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >><jlarkin@highlandtechnology.com> Gave us: >> >>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>><DLU1@DecadentLinuxUser.org> wrote: >>> >>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>> >>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>that? >>>>> >>>> >>>> Absolutely presents a problem... >>>> >>>> This will let the smoke out. No question. >>> >>>That's only 8 volts above the Vceo spec. No problem. >> >> >> Pretty fucking unprofessional statement, Larkin. > >I pointed out to him that he should not leave the base open, which is >what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >application, but if he already has them, the risk of using them is >nil. > >Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >don't have any in stock. > >> >> I ran two to drive the front end of my HV switcher drives into >>transformer. >> >> One designs within the spec, not over it, dipshit. > >One designs things that work and can be sold. > > >> >> A 1N4001 can do 1000V, but there is no way I would use them in a >>multiplier. > >Too slow, mostly. And thru-hole axial! > >> >> Folks spec EL and even solid state caps at just over half their rated >>voltage. You seem to not even know, much less understand why. > >Sometimes I derate caps, and sometimes I use them at over their rated >voltages. Low voltage ceramic caps can stand 10x or 20x their rated >voltages; you just lose capacitance. Tantalums can run at rated >voltage in some cases, or should be derated 3:1 in others. > >We were just yesterday discussing how much power we can dissipate into >standard surface-mount resistors. It's safe to go way over their >ratings if you put decent power pours on the end caps. > >Datasheet specs are sort of arbitrary anyhow.Speaking of which, I have 15 volts available. Should I use a 12 volt fan, or a 24 volt fan? -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
2N3904 maximum ratings Vceo Vcbo
Started by ●May 2, 2015
Reply by ●May 8, 20152015-05-08
Reply by ●May 8, 20152015-05-08
On Fri, 08 May 2015 12:52:17 -0700, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 08 May 2015 12:19:38 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > >>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno >><DLU1@DecadentLinuxUser.org> wrote: >> >>>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >>><jlarkin@highlandtechnology.com> Gave us: >>> >>>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>>><DLU1@DecadentLinuxUser.org> wrote: >>>> >>>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>>> >>>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>>that? >>>>>> >>>>> >>>>> Absolutely presents a problem... >>>>> >>>>> This will let the smoke out. No question. >>>> >>>>That's only 8 volts above the Vceo spec. No problem. >>> >>> >>> Pretty fucking unprofessional statement, Larkin. >> >>I pointed out to him that he should not leave the base open, which is >>what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >>application, but if he already has them, the risk of using them is >>nil. >> >>Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >>don't have any in stock. >> >>> >>> I ran two to drive the front end of my HV switcher drives into >>>transformer. >>> >>> One designs within the spec, not over it, dipshit. >> >>One designs things that work and can be sold. >> >> >>> >>> A 1N4001 can do 1000V, but there is no way I would use them in a >>>multiplier. >> >>Too slow, mostly. And thru-hole axial! >> >>> >>> Folks spec EL and even solid state caps at just over half their rated >>>voltage. You seem to not even know, much less understand why. >> >>Sometimes I derate caps, and sometimes I use them at over their rated >>voltages. Low voltage ceramic caps can stand 10x or 20x their rated >>voltages; you just lose capacitance. Tantalums can run at rated >>voltage in some cases, or should be derated 3:1 in others. >> >>We were just yesterday discussing how much power we can dissipate into >>standard surface-mount resistors. It's safe to go way over their >>ratings if you put decent power pours on the end caps. >> >>Datasheet specs are sort of arbitrary anyhow. > >Speaking of which, I have 15 volts available. Should I use a 12 volt >fan, or a 24 volt fan?Depends >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●May 8, 20152015-05-08
On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Fri, 08 May 2015 12:52:17 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > >>On Fri, 08 May 2015 12:19:38 -0700, John Larkin >><jlarkin@highlandtechnology.com> wrote: >> >>>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno >>><DLU1@DecadentLinuxUser.org> wrote: >>> >>>>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >>>><jlarkin@highlandtechnology.com> Gave us: >>>> >>>>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>> >>>>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>>>> >>>>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>>>that? >>>>>>> >>>>>> >>>>>> Absolutely presents a problem... >>>>>> >>>>>> This will let the smoke out. No question. >>>>> >>>>>That's only 8 volts above the Vceo spec. No problem. >>>> >>>> >>>> Pretty fucking unprofessional statement, Larkin. >>> >>>I pointed out to him that he should not leave the base open, which is >>>what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >>>application, but if he already has them, the risk of using them is >>>nil. >>> >>>Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >>>don't have any in stock. >>> >>>> >>>> I ran two to drive the front end of my HV switcher drives into >>>>transformer. >>>> >>>> One designs within the spec, not over it, dipshit. >>> >>>One designs things that work and can be sold. >>> >>> >>>> >>>> A 1N4001 can do 1000V, but there is no way I would use them in a >>>>multiplier. >>> >>>Too slow, mostly. And thru-hole axial! >>> >>>> >>>> Folks spec EL and even solid state caps at just over half their rated >>>>voltage. You seem to not even know, much less understand why. >>> >>>Sometimes I derate caps, and sometimes I use them at over their rated >>>voltages. Low voltage ceramic caps can stand 10x or 20x their rated >>>voltages; you just lose capacitance. Tantalums can run at rated >>>voltage in some cases, or should be derated 3:1 in others. >>> >>>We were just yesterday discussing how much power we can dissipate into >>>standard surface-mount resistors. It's safe to go way over their >>>ratings if you put decent power pours on the end caps. >>> >>>Datasheet specs are sort of arbitrary anyhow. >> >>Speaking of which, I have 15 volts available. Should I use a 12 volt >>fan, or a 24 volt fan? > >Depends >:-} > > ...Jim ThompsonThanks for that input. We stock a really cute 30mm 12-volt Sunon fan. It starts spinning around 3 volts and works fine at 20, as far as I dared to go. What's weird is that, at 15 volts, if you stall it, usually it won't start. If I then drop the supply a couple of volts, it starts spinning again. It's probably OK at 15, since I don't expect anybody to stall it, but it's weird. We'll get some 24 volt versions to test. Possibly the FPGA guy did something silly, like using a zillion registers instead of a RAM. The FPGA seems to be awfully hot, given that we're not doing all that much and the main clock is only 64 MHz. It would sure be easier to change some VHDL instead of adding a fan. Seems like half my hassles lately are thermal. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 8, 20152015-05-08
On Fri, 08 May 2015 13:29:55 -0700, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Fri, 08 May 2015 12:52:17 -0700, John Larkin >><jlarkin@highlandtechnology.com> wrote: >> >>>On Fri, 08 May 2015 12:19:38 -0700, John Larkin >>><jlarkin@highlandtechnology.com> wrote: >>> >>>>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno >>>><DLU1@DecadentLinuxUser.org> wrote: >>>> >>>>>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >>>>><jlarkin@highlandtechnology.com> Gave us: >>>>> >>>>>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>>> >>>>>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>>>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>>>>> >>>>>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>>>>that? >>>>>>>> >>>>>>> >>>>>>> Absolutely presents a problem... >>>>>>> >>>>>>> This will let the smoke out. No question. >>>>>> >>>>>>That's only 8 volts above the Vceo spec. No problem. >>>>> >>>>> >>>>> Pretty fucking unprofessional statement, Larkin. >>>> >>>>I pointed out to him that he should not leave the base open, which is >>>>what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >>>>application, but if he already has them, the risk of using them is >>>>nil. >>>> >>>>Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >>>>don't have any in stock. >>>> >>>>> >>>>> I ran two to drive the front end of my HV switcher drives into >>>>>transformer. >>>>> >>>>> One designs within the spec, not over it, dipshit. >>>> >>>>One designs things that work and can be sold. >>>> >>>> >>>>> >>>>> A 1N4001 can do 1000V, but there is no way I would use them in a >>>>>multiplier. >>>> >>>>Too slow, mostly. And thru-hole axial! >>>> >>>>> >>>>> Folks spec EL and even solid state caps at just over half their rated >>>>>voltage. You seem to not even know, much less understand why. >>>> >>>>Sometimes I derate caps, and sometimes I use them at over their rated >>>>voltages. Low voltage ceramic caps can stand 10x or 20x their rated >>>>voltages; you just lose capacitance. Tantalums can run at rated >>>>voltage in some cases, or should be derated 3:1 in others. >>>> >>>>We were just yesterday discussing how much power we can dissipate into >>>>standard surface-mount resistors. It's safe to go way over their >>>>ratings if you put decent power pours on the end caps. >>>> >>>>Datasheet specs are sort of arbitrary anyhow. >>> >>>Speaking of which, I have 15 volts available. Should I use a 12 volt >>>fan, or a 24 volt fan? >> >>Depends >:-} >> >> ...Jim Thompson > >Thanks for that input. > >We stock a really cute 30mm 12-volt Sunon fan. It starts spinning >around 3 volts and works fine at 20, as far as I dared to go. > >What's weird is that, at 15 volts, if you stall it, usually it won't >start. If I then drop the supply a couple of volts, it starts spinning >again. > >It's probably OK at 15, since I don't expect anybody to stall it, but >it's weird. We'll get some 24 volt versions to test. > >Possibly the FPGA guy did something silly, like using a zillion >registers instead of a RAM. The FPGA seems to be awfully hot, given >that we're not doing all that much and the main clock is only 64 MHz. >It would sure be easier to change some VHDL instead of adding a fan. > >Seems like half my hassles lately are thermal.Fan motor's voltage range is pretty much dependent on how they do the commutation. Here's the beasty... <http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg> that I designed a controller for... Bosch Motor (B�hlertal), ultimately into a Mercedes A/C blower... nasty speed control specifications plus it had to pass a noise test... chief engineer put head into the ductwork and commutation noise couldn't be audible ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●May 8, 20152015-05-08
On Fri, 08 May 2015 15:42:59 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Fri, 08 May 2015 13:29:55 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > >>On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Fri, 08 May 2015 12:52:17 -0700, John Larkin >>><jlarkin@highlandtechnology.com> wrote: >>> >>>>On Fri, 08 May 2015 12:19:38 -0700, John Larkin >>>><jlarkin@highlandtechnology.com> wrote: >>>> >>>>>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno >>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>> >>>>>>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >>>>>><jlarkin@highlandtechnology.com> Gave us: >>>>>> >>>>>>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>>>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>>>> >>>>>>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>>>>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>>>>>> >>>>>>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>>>>>that? >>>>>>>>> >>>>>>>> >>>>>>>> Absolutely presents a problem... >>>>>>>> >>>>>>>> This will let the smoke out. No question. >>>>>>> >>>>>>>That's only 8 volts above the Vceo spec. No problem. >>>>>> >>>>>> >>>>>> Pretty fucking unprofessional statement, Larkin. >>>>> >>>>>I pointed out to him that he should not leave the base open, which is >>>>>what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >>>>>application, but if he already has them, the risk of using them is >>>>>nil. >>>>> >>>>>Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >>>>>don't have any in stock. >>>>> >>>>>> >>>>>> I ran two to drive the front end of my HV switcher drives into >>>>>>transformer. >>>>>> >>>>>> One designs within the spec, not over it, dipshit. >>>>> >>>>>One designs things that work and can be sold. >>>>> >>>>> >>>>>> >>>>>> A 1N4001 can do 1000V, but there is no way I would use them in a >>>>>>multiplier. >>>>> >>>>>Too slow, mostly. And thru-hole axial! >>>>> >>>>>> >>>>>> Folks spec EL and even solid state caps at just over half their rated >>>>>>voltage. You seem to not even know, much less understand why. >>>>> >>>>>Sometimes I derate caps, and sometimes I use them at over their rated >>>>>voltages. Low voltage ceramic caps can stand 10x or 20x their rated >>>>>voltages; you just lose capacitance. Tantalums can run at rated >>>>>voltage in some cases, or should be derated 3:1 in others. >>>>> >>>>>We were just yesterday discussing how much power we can dissipate into >>>>>standard surface-mount resistors. It's safe to go way over their >>>>>ratings if you put decent power pours on the end caps. >>>>> >>>>>Datasheet specs are sort of arbitrary anyhow. >>>> >>>>Speaking of which, I have 15 volts available. Should I use a 12 volt >>>>fan, or a 24 volt fan? >>> >>>Depends >:-} >>> >>> ...Jim Thompson >> >>Thanks for that input. >> >>We stock a really cute 30mm 12-volt Sunon fan. It starts spinning >>around 3 volts and works fine at 20, as far as I dared to go. >> >>What's weird is that, at 15 volts, if you stall it, usually it won't >>start. If I then drop the supply a couple of volts, it starts spinning >>again. >> >>It's probably OK at 15, since I don't expect anybody to stall it, but >>it's weird. We'll get some 24 volt versions to test. >> >>Possibly the FPGA guy did something silly, like using a zillion >>registers instead of a RAM. The FPGA seems to be awfully hot, given >>that we're not doing all that much and the main clock is only 64 MHz. >>It would sure be easier to change some VHDL instead of adding a fan. >> >>Seems like half my hassles lately are thermal. > >Fan motor's voltage range is pretty much dependent on how they do the >commutation. Here's the beasty... > ><http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg>Our fan is tiny, 30x30x10 mm. Awfully cute.> >that I designed a controller for... Bosch Motor (B�hlertal), >ultimately into a Mercedes A/C blower... nasty speed control >specifications plus it had to pass a noise test... chief engineer put >head into the ductwork and commutation noise couldn't be audible ;-) > > ...Jim ThompsonCorrection: the fan appears to be smarter than I am. If the fan is stalled, at any voltage, it pulls current for about a second and then shuts down. It starts up if the voltage changes significantly, or after a roughly 10 second delay. It quits spinning at about 23 volts but recovers if the voltage is reduced. Sunon calls it a 12 volt fan but has no min/max specs. There must be a lot of logic inside that tiny fan. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 8, 20152015-05-08
On Fri, 08 May 2015 16:03:20 -0700, John Larkin <jlarkin@highlandtechnology.com> wrote:>On Fri, 08 May 2015 15:42:59 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Fri, 08 May 2015 13:29:55 -0700, John Larkin >><jlarkin@highlandtechnology.com> wrote: >> >>>On Fri, 08 May 2015 13:06:01 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Fri, 08 May 2015 12:52:17 -0700, John Larkin >>>><jlarkin@highlandtechnology.com> wrote: >>>> >>>>>On Fri, 08 May 2015 12:19:38 -0700, John Larkin >>>>><jlarkin@highlandtechnology.com> wrote: >>>>> >>>>>>On Fri, 08 May 2015 02:54:45 -0400, DecadentLinuxUserNumeroUno >>>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>>> >>>>>>>On Thu, 07 May 2015 13:51:28 -0700, John Larkin >>>>>>><jlarkin@highlandtechnology.com> Gave us: >>>>>>> >>>>>>>>On Thu, 07 May 2015 16:36:08 -0400, DecadentLinuxUserNumeroUno >>>>>>>><DLU1@DecadentLinuxUser.org> wrote: >>>>>>>> >>>>>>>>>On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >>>>>>>>><bperryb@bowdenshobbycircuits.info> Gave us: >>>>>>>>> >>>>>>>>>>Is it safe to operate a 2N3904 in a switching application with a supply >>>>>>>>>>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>>>>>>>>>When the transistor switches off, the collector to emitter voltage will be >>>>>>>>>>48 and the base voltage will be near 0 through a resistor. Any problems with >>>>>>>>>>that? >>>>>>>>>> >>>>>>>>> >>>>>>>>> Absolutely presents a problem... >>>>>>>>> >>>>>>>>> This will let the smoke out. No question. >>>>>>>> >>>>>>>>That's only 8 volts above the Vceo spec. No problem. >>>>>>> >>>>>>> >>>>>>> Pretty fucking unprofessional statement, Larkin. >>>>>> >>>>>>I pointed out to him that he should not leave the base open, which is >>>>>>what Vceo measures. I wouldn't pick a 2N3904 for a 48 volt >>>>>>application, but if he already has them, the risk of using them is >>>>>>nil. >>>>>> >>>>>>Actually, I wouldn't use a 2N3904 for anything. Klunky old beast. We >>>>>>don't have any in stock. >>>>>> >>>>>>> >>>>>>> I ran two to drive the front end of my HV switcher drives into >>>>>>>transformer. >>>>>>> >>>>>>> One designs within the spec, not over it, dipshit. >>>>>> >>>>>>One designs things that work and can be sold. >>>>>> >>>>>> >>>>>>> >>>>>>> A 1N4001 can do 1000V, but there is no way I would use them in a >>>>>>>multiplier. >>>>>> >>>>>>Too slow, mostly. And thru-hole axial! >>>>>> >>>>>>> >>>>>>> Folks spec EL and even solid state caps at just over half their rated >>>>>>>voltage. You seem to not even know, much less understand why. >>>>>> >>>>>>Sometimes I derate caps, and sometimes I use them at over their rated >>>>>>voltages. Low voltage ceramic caps can stand 10x or 20x their rated >>>>>>voltages; you just lose capacitance. Tantalums can run at rated >>>>>>voltage in some cases, or should be derated 3:1 in others. >>>>>> >>>>>>We were just yesterday discussing how much power we can dissipate into >>>>>>standard surface-mount resistors. It's safe to go way over their >>>>>>ratings if you put decent power pours on the end caps. >>>>>> >>>>>>Datasheet specs are sort of arbitrary anyhow. >>>>> >>>>>Speaking of which, I have 15 volts available. Should I use a 12 volt >>>>>fan, or a 24 volt fan? >>>> >>>>Depends >:-} >>>> >>>> ...Jim Thompson >>> >>>Thanks for that input. >>> >>>We stock a really cute 30mm 12-volt Sunon fan. It starts spinning >>>around 3 volts and works fine at 20, as far as I dared to go. >>> >>>What's weird is that, at 15 volts, if you stall it, usually it won't >>>start. If I then drop the supply a couple of volts, it starts spinning >>>again. >>> >>>It's probably OK at 15, since I don't expect anybody to stall it, but >>>it's weird. We'll get some 24 volt versions to test. >>> >>>Possibly the FPGA guy did something silly, like using a zillion >>>registers instead of a RAM. The FPGA seems to be awfully hot, given >>>that we're not doing all that much and the main clock is only 64 MHz. >>>It would sure be easier to change some VHDL instead of adding a fan. >>> >>>Seems like half my hassles lately are thermal. >> >>Fan motor's voltage range is pretty much dependent on how they do the >>commutation. Here's the beasty... >> >><http://www.analog-innovations.com/SED/DC_Motor_Electronically_Commutated.jpg> > >Our fan is tiny, 30x30x10 mm. Awfully cute. > >> >>that I designed a controller for... Bosch Motor (B�hlertal), >>ultimately into a Mercedes A/C blower... nasty speed control >>specifications plus it had to pass a noise test... chief engineer put >>head into the ductwork and commutation noise couldn't be audible ;-) >> >> ...Jim Thompson > >Correction: the fan appears to be smarter than I am. > >If the fan is stalled, at any voltage, it pulls current for about a >second and then shuts down. It starts up if the voltage changes >significantly, or after a roughly 10 second delay. > >It quits spinning at about 23 volts but recovers if the voltage is >reduced. Sunon calls it a 12 volt fan but has no min/max specs. > >There must be a lot of logic inside that tiny fan.You can put an awfully large amount of smarts into a small chip. The size only goes up with the current handling. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●May 8, 20152015-05-08
"DecadentLinuxUserNumeroUno" <DLU1@DecadentLinuxUser.org> wrote in message news:14jnkal3sg1hncthrdmnn9q8kvqonfpf42@4ax.com...> On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" > <bperryb@bowdenshobbycircuits.info> Gave us: > >>Is it safe to operate a 2N3904 in a switching application with a supply >>voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>When the transistor switches off, the collector to emitter voltage will be >>48 and the base voltage will be near 0 through a resistor. Any problems >>with >>that? >> > > Absolutely presents a problem... > > This will let the smoke out. No question.I thought the specs indicated "guaranteed" performance? Vceo of 40 would imply every device would meet that spec plus a little more? It's a resistive load, so there aren't any inductive considerations. And the base will be grounded to the emitter through a 3K resistor when the collector voltage is 48. --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Reply by ●May 9, 20152015-05-09
On Friday, May 8, 2015 at 4:45:53 PM UTC-7, Bill Bowden wrote:> I thought the specs indicated "guaranteed" performance? Vceo > of 40 would imply every device would meet that spec plus a > little more?I would expect the answer to this question would depend on the date code. A part from the 1980s made by diffusion would probably have a very wide range of propeerties, both within a lot and lot-to-lot. Something made in the 21st century by ion implantation might have a very tight range, and could be manufactured with very little "safety margin". Why do you raise the question? Is it academic curiosity, or do you havee a specific application and lots of 2N3904s in the warehouse? The 2N3904 is cheap (about 10 cents is smalll hobbyist quantities), so a part with a sufficiently higher BV is probably less than 20 cents in large manufacturing quantities. You would have to sell a lot of widgets to recover the additional engineering cost of using an underspec'd part.
Reply by ●May 9, 20152015-05-09
On 5/8/2015 7:45 PM, Bill Bowden wrote:> "DecadentLinuxUserNumeroUno" <DLU1@DecadentLinuxUser.org> wrote in message > news:14jnkal3sg1hncthrdmnn9q8kvqonfpf42@4ax.com... >> On Sat, 2 May 2015 19:45:51 -0700, "Bill Bowden" >> <bperryb@bowdenshobbycircuits.info> Gave us: >> >>> Is it safe to operate a 2N3904 in a switching application with a supply >>> voltage of 48 volts? The data sheet says Vceo is 40 and Vcbo is 60 volts. >>> When the transistor switches off, the collector to emitter voltage will be >>> 48 and the base voltage will be near 0 through a resistor. Any problems >>> with >>> that? >>> >> >> Absolutely presents a problem... >> >> This will let the smoke out. No question. > > I thought the specs indicated "guaranteed" performance? Vceo of 40 would > imply every device would meet that spec plus a little more? It's a resistive > load, so there aren't any inductive considerations. And the base will be > grounded to the emitter through a 3K resistor when the collector voltage is > 48.The collector-base leakage rises steeply with V_CB. With the base left open, it gets multiplied by beta, so I_C goes through the roof at a lower voltage. If you prevent the B-E junction from getting forward-biased, e.g. by shorting B-E, it holds up out to V_CES, which is higher. A resistor isn't quite as good, and reverse bias is a bit better, so you have a family of breakdown voltages rather than just one. V_CEO < V_CER < V_CES < V_CEX . Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 10, 20152015-05-10
John Larkin <jlarkin@highlandtechnology.com> wrote:> It's probably OK at 15, since I don't expect anybody to stall it, but > it's weird. We'll get some 24 volt versions to test.Toss in a couple of 1N4001s (or surface-mount equal) in series with the fan connector and get on down the road. Yes, I usually write software for a living... why are you looking at me funny?> Seems like half my hassles lately are thermal.Pic somewhat related: https://xkcd.com/451/ , especially the first panel. Matt Roberds
