søndag den 16. januar 2022 kl. 22.39.02 UTC+1 skrev jla...@highlandsniptechnology.com:> On Sun, 16 Jan 2022 20:50:15 -0000 (UTC), Cydrome Leader > <pres...@MUNGEpanix.com> wrote: > > >jla...@highlandsniptechnology.com wrote: > >> On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader > >> <pres...@MUNGEpanix.com> wrote: > >> > >>>jla...@highlandsniptechnology.com wrote: > >>>> Has anyone run bldc fans in series? I want to run three 12v fans from > >>>> a 48v supply, with a resistor or something in series > >>>> > >>>> I guess I could be cautious and put a cap and a 12v TVS across each > >>>> fan. Hmmm, 3 fans and 4 TVSs might work. > >>>> > >>>> Worst case, I can make a 48 to 12 switcher. > >>>> > >>>> Here's the idea: > >>>> > >>>> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > >>> > >>>Don't do it. They will not share voltage and the losers will burn out on > >>>the first start. Been there, done that. Find 48 volt telecom fans or 24 > >>>volts ones and use individual series resistors. Fans are mechanical so > >>>don't increase your failure rate by using any sort of chain. > >> > >> The 35mm fans I want to use seem to only come in 5v and 12v. And the > >> supply is 48. > >> > >> I suppose I can make a 48-to-12 switcher on this board. Still, a > >> series string with shunt zeners ought to work. > > > >If you can go for a larger diameter fan, even mounted at an angle. They > >run slower, make less noise and can last longer. This also opens up the > >ability to get telecom fans. Fancy options allow for analog or PWM speed > >control as well. > > > >If reliability is key, run two fans in series (air flow wise). There is no > >major performance difference otherwise. You can even get counterrotating > >double thick fan modules as used in servers. The major brand ones like > >Nidec are actually extremely reliable at high temps and speed, even with > >ball bearings. They really figured figured these things out. > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > > I considered all sorts of ways to use one big fan, horizontal or > angled, and couldn't make it work. It would need some sort of ducting, > and the next board is 1.6" away so there's no way to get the air into > and out of a big fan. We do want to shoot the hot air out the rear of > the box, not stir it around inside, another constraint. > > We're building a mockup for thermal testing. I have no analytical or > simulation tools for a thing like this, and my instincts for air flow > are all mediocre guesses.https://www.amazon.com/Cooler-Cooling-LGA1156-LGA1155-Utral-Thin/dp/B07PFH5B69
fans in series
Started by ●January 12, 2022
Reply by ●January 16, 20222022-01-16
Reply by ●January 16, 20222022-01-16
On Sun, 16 Jan 2022 07:30:08 -0800, jlarkin@highlandsniptechnology.com wrote:>On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader ><presence@MUNGEpanix.com> wrote: > >>jlarkin@highlandsniptechnology.com wrote: >>> Has anyone run bldc fans in series? I want to run three 12v fans from >>> a 48v supply, with a resistor or something in series >>> >>> I guess I could be cautious and put a cap and a 12v TVS across each >>> fan. Hmmm, 3 fans and 4 TVSs might work. >>> >>> Worst case, I can make a 48 to 12 switcher. >>> >>> Here's the idea: >>> >>> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >> >>Don't do it. They will not share voltage and the losers will burn out on >>the first start. Been there, done that. Find 48 volt telecom fans or 24 >>volts ones and use individual series resistors. Fans are mechanical so >>don't increase your failure rate by using any sort of chain. > >The 35mm fans I want to use seem to only come in 5v and 12v. And the >supply is 48. > >I suppose I can make a 48-to-12 switcher on this board. Still, a >series string with shunt zeners ought to work.Use a centrifugal impeller rather than a consumer-grade fan. Guaranteed to come in standard system voltages and tango under 35mm thickness. If 24V, you could check for spare fans used on 3D printers, though these are usually 30-40mm, not 35mm and are toy quality. ebay 182623902047, 182623900436, 223792320319, 274774441334 RL
Reply by ●January 17, 20222022-01-17
On Sunday, January 16, 2022 at 8:38:50 PM UTC-5, legg wrote:> On Sun, 16 Jan 2022 07:30:08 -0800, jla...@highlandsniptechnology.com > wrote: > >On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader > ><pres...@MUNGEpanix.com> wrote: > > > >>jla...@highlandsniptechnology.com wrote: > >>> Has anyone run bldc fans in series? I want to run three 12v fans from > >>> a 48v supply, with a resistor or something in series > >>> > >>> I guess I could be cautious and put a cap and a 12v TVS across each > >>> fan. Hmmm, 3 fans and 4 TVSs might work. > >>> > >>> Worst case, I can make a 48 to 12 switcher. > >>> > >>> Here's the idea: > >>> > >>> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > >> > >>Don't do it. They will not share voltage and the losers will burn out on > >>the first start. Been there, done that. Find 48 volt telecom fans or 24 > >>volts ones and use individual series resistors. Fans are mechanical so > >>don't increase your failure rate by using any sort of chain. > > > >The 35mm fans I want to use seem to only come in 5v and 12v. And the > >supply is 48. > > > >I suppose I can make a 48-to-12 switcher on this board. Still, a > >series string with shunt zeners ought to work. > Use a centrifugal impeller rather than a consumer-grade fan. > Guaranteed to come in standard system voltages and tango under > 35mm thickness. > > If 24V, you could check for spare fans used on 3D printers, > though these are usually 30-40mm, not 35mm and are toy quality. > > ebay 182623902047, 182623900436, 223792320319, 274774441334There are fans mounted on GPU boards and inside laptops that would fit in the space. Probably 5 V though. Why not 48V > 5V and make life easy picking the fan? -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Reply by ●January 17, 20222022-01-17
jla...@highlandsniptechnology.com wrote: ================================> > Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in series >** Tested a handful of different 35/40 mm 12VDC 0.6W to 1.3W fans. 1. Load current ( average value ) goes up by 70 to 100% when stalled. 2. Current is drawn in steady pulses of about 90% duty cycle, frequency related to RPM and number of poles. 3. During the "off" time current draw swings briefly negative. 4. All fans are quiet, some damn quiet. IMO all are nice, easy to use items. Go with the 4 x 12V zener idea - using at least 3W types. ...... Phil
Reply by ●January 17, 20222022-01-17
jlarkin@highlandsniptechnology.com wrote:> On Sun, 16 Jan 2022 20:50:15 -0000 (UTC), Cydrome Leader > <presence@MUNGEpanix.com> wrote: > >>jlarkin@highlandsniptechnology.com wrote: >>> On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader >>> <presence@MUNGEpanix.com> wrote: >>> >>>>jlarkin@highlandsniptechnology.com wrote: >>>>> Has anyone run bldc fans in series? I want to run three 12v fans from >>>>> a 48v supply, with a resistor or something in series >>>>> >>>>> I guess I could be cautious and put a cap and a 12v TVS across each >>>>> fan. Hmmm, 3 fans and 4 TVSs might work. >>>>> >>>>> Worst case, I can make a 48 to 12 switcher. >>>>> >>>>> Here's the idea: >>>>> >>>>> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >>>> >>>>Don't do it. They will not share voltage and the losers will burn out on >>>>the first start. Been there, done that. Find 48 volt telecom fans or 24 >>>>volts ones and use individual series resistors. Fans are mechanical so >>>>don't increase your failure rate by using any sort of chain. >>> >>> The 35mm fans I want to use seem to only come in 5v and 12v. And the >>> supply is 48. >>> >>> I suppose I can make a 48-to-12 switcher on this board. Still, a >>> series string with shunt zeners ought to work. >> >>If you can go for a larger diameter fan, even mounted at an angle. They >>run slower, make less noise and can last longer. This also opens up the >>ability to get telecom fans. Fancy options allow for analog or PWM speed >>control as well. >> >>If reliability is key, run two fans in series (air flow wise). There is no >>major performance difference otherwise. You can even get counterrotating >>double thick fan modules as used in servers. The major brand ones like >>Nidec are actually extremely reliable at high temps and speed, even with >>ball bearings. They really figured figured these things out. > > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > > I considered all sorts of ways to use one big fan, horizontal or > angled, and couldn't make it work. It would need some sort of ducting, > and the next board is 1.6" away so there's no way to get the air into > and out of a big fan. We do want to shoot the hot air out the rear of > the box, not stir it around inside, another constraint. > > We're building a mockup for thermal testing. I have no analytical or > simulation tools for a thing like this, and my instincts for air flow > are all mediocre guesses.These beasts are deep (possible design constraint), redundant and last forever. Pretty loud at full blast too. https://www.nidec.com/en/product/search/category/B101/M111/S100/NCJ-R40W-F9/ That's the 40mm version, the make 38 and 35 commie units sized one too, in case you're looking to harmonize with cuba, north korea and russia. 1.6" doesn't quite give enough space for a centrifugal blower, unless your heatsink shrinks into something like an Al square tube. If this is your current sink project, you probably want as much thermal mass as possible though. Not sure what reliability you want, but small thin fans suck, I think some sort of hokey laptop cooler fan in mentioned in the thread. It might help dissipate low tens of watts on a good day. Everone has seen how laptops die. They overheat more and more often and then the thermal stresses finally break connections on system board. That's no accident.
Reply by ●January 17, 20222022-01-17
On Mon, 17 Jan 2022 20:25:57 -0000 (UTC), Cydrome Leader <presence@MUNGEpanix.com> wrote:>jlarkin@highlandsniptechnology.com wrote: >> On Sun, 16 Jan 2022 20:50:15 -0000 (UTC), Cydrome Leader >> <presence@MUNGEpanix.com> wrote: >> >>>jlarkin@highlandsniptechnology.com wrote: >>>> On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader >>>> <presence@MUNGEpanix.com> wrote: >>>> >>>>>jlarkin@highlandsniptechnology.com wrote: >>>>>> Has anyone run bldc fans in series? I want to run three 12v fans from >>>>>> a 48v supply, with a resistor or something in series >>>>>> >>>>>> I guess I could be cautious and put a cap and a 12v TVS across each >>>>>> fan. Hmmm, 3 fans and 4 TVSs might work. >>>>>> >>>>>> Worst case, I can make a 48 to 12 switcher. >>>>>> >>>>>> Here's the idea: >>>>>> >>>>>> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >>>>> >>>>>Don't do it. They will not share voltage and the losers will burn out on >>>>>the first start. Been there, done that. Find 48 volt telecom fans or 24 >>>>>volts ones and use individual series resistors. Fans are mechanical so >>>>>don't increase your failure rate by using any sort of chain. >>>> >>>> The 35mm fans I want to use seem to only come in 5v and 12v. And the >>>> supply is 48. >>>> >>>> I suppose I can make a 48-to-12 switcher on this board. Still, a >>>> series string with shunt zeners ought to work. >>> >>>If you can go for a larger diameter fan, even mounted at an angle. They >>>run slower, make less noise and can last longer. This also opens up the >>>ability to get telecom fans. Fancy options allow for analog or PWM speed >>>control as well. >>> >>>If reliability is key, run two fans in series (air flow wise). There is no >>>major performance difference otherwise. You can even get counterrotating >>>double thick fan modules as used in servers. The major brand ones like >>>Nidec are actually extremely reliable at high temps and speed, even with >>>ball bearings. They really figured figured these things out. >> >> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >> >> I considered all sorts of ways to use one big fan, horizontal or >> angled, and couldn't make it work. It would need some sort of ducting, >> and the next board is 1.6" away so there's no way to get the air into >> and out of a big fan. We do want to shoot the hot air out the rear of >> the box, not stir it around inside, another constraint. >> >> We're building a mockup for thermal testing. I have no analytical or >> simulation tools for a thing like this, and my instincts for air flow >> are all mediocre guesses. > >These beasts are deep (possible design constraint), redundant and last >forever. Pretty loud at full blast too. > >https://www.nidec.com/en/product/search/category/B101/M111/S100/NCJ-R40W-F9/ > >That's the 40mm version, the make 38 and 35 commie units sized one too, in >case you're looking to harmonize with cuba, north korea and russia. > >1.6" doesn't quite give enough space for a centrifugal blower, unless your >heatsink shrinks into something like an Al square tube. If this is your >current sink project, you probably want as much thermal mass as possible >though. > >Not sure what reliability you want, but small thin fans suck, I think some >sort of hokey laptop cooler fan in mentioned in the thread. It might help >dissipate low tens of watts on a good day. Everone has seen how laptops >die. They overheat more and more often and then the thermal stresses >finally break connections on system board. That's no accident.I'd like to dump at least 100 watts on the dummy load board. The little 35 mm fans are good for maybe 7 cfm each unrestricted. Three might manage 15 cfm in real life, maybe less. 100 watts into 15 cfm heats the air roughly 10c, not bad. The heat sink and mosfet temps will of course be higher. So, how hot might we allow the heat sink to get? 100c? With a sticker WARNING HOT SURFACE The giant fets wouldn't get a lot hotter than the sink. -- I yam what I yam - Popeye
Reply by ●January 18, 20222022-01-18
On Wednesday, January 12, 2022 at 10:49:34 PM UTC-5, jla...@highlandsniptechnology.com wrote:> Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in series > > I guess I could be cautious and put a cap and a 12v TVS across each > fan. Hmmm, 3 fans and 4 TVSs might work. > > Worst case, I can make a 48 to 12 switcher. > > Here's the idea: > > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > > > > > -- > > I yam what I yam - PopeyeFrom a reliability standpoint, I wouldn't do it. One fan opens up and the others quit functioning.
Reply by ●January 18, 20222022-01-18
On Wednesday, January 12, 2022 at 10:49:34 PM UTC-5, jla...@highlandsniptechnology.com wrote:> Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in series > > I guess I could be cautious and put a cap and a 12v TVS across each > fan. Hmmm, 3 fans and 4 TVSs might work. > > Worst case, I can make a 48 to 12 switcher. > > Here's the idea: > > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > > > > > -- > > I yam what I yam - PopeyeAre you pushing air over the exchanger fins or pulling air through them? the diagram suggest pushing. I remember reading a paper some time ago that one needs to consider the spacing of the fins...it is a tradeoff: amount fin spacing/surface area, air flow, and channel cross sectional area. Heat transfer optimally occurs with turbulent flow, R =>3500. Also shrouding of the fan and heat exchanger assembly can usually increase the heat transfer rate. If you want to model this, COMSOL Multiphysics with the heat transfer module is a nice tool and would probably give you some useful results. You can get rather detailed and account for all 3 forms of heat transfer (conductive, convective, and radiative ). Then again, you could experiment with some RTDs, fan orientation, channels/shrouds, etc. Would five you some sight as to necessary fan flows, and not make the device sound like a jet engine when running. J
Reply by ●January 18, 20222022-01-18
On Tuesday, January 18, 2022 at 11:50:56 AM UTC-8, three_jeeps wrote:> On Wednesday, January 12, 2022 at 10:49:34 PM UTC-5, jla...@highlandsniptechnology.com wrote: > > Has anyone run bldc fans in series? I want to run three 12v fans from > > a 48v supply, with a resistor or something in series > > > > I guess I could be cautious and put a cap and a 12v TVS across each > > fan. Hmmm, 3 fans and 4 TVSs might work. > > > > Worst case, I can make a 48 to 12 switcher.It might be simpler to use a 120V fan in a big box, with a thermostat fan control. Regulated voltages are unnecessary, dependence on the 48V source is unnecessary, fitting into the thin box is unnecessary, and a thermostat allows complete independence of any logic signals. When the fan needs lube, the guy in the field doesn't need to open a computer at a static-safe station and recalibrate a precision instrument.
Reply by ●January 18, 20222022-01-18
On Tue, 18 Jan 2022 12:21:02 -0800 (PST), three_jeeps <jjhudak@gmail.com> wrote:>On Wednesday, January 12, 2022 at 10:49:34 PM UTC-5, jla...@highlandsniptechnology.com wrote: >> Has anyone run bldc fans in series? I want to run three 12v fans from >> a 48v supply, with a resistor or something in series >> >> I guess I could be cautious and put a cap and a 12v TVS across each >> fan. Hmmm, 3 fans and 4 TVSs might work. >> >> Worst case, I can make a 48 to 12 switcher. >> >> Here's the idea: >> >> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >> >> >> >> >> -- >> >> I yam what I yam - Popeye >Are you pushing air over the exchanger fins or pulling air through them? the diagram suggest pushing. >I remember reading a paper some time ago that one needs to consider the spacing of the fins...it is a tradeoff: amount fin spacing/surface area, air flow, and channel cross sectional area. >Heat transfer optimally occurs with turbulent flow, R =>3500. Also shrouding of the fan and heat exchanger assembly can usually increase the heat transfer rate. >If you want to model this, COMSOL Multiphysics with the heat transfer module is a nice tool and would probably give you some useful results. You can get rather detailed and account for all 3 forms of heat transfer (conductive, convective, and radiative ). > >Then again, you could experiment with some RTDs, fan orientation, channels/shrouds, etc. Would five you some sight as to necessary fan flows, and not make the device sound like a jet engine when running. >J >https://www.dropbox.com/s/o1ikkiolefx9csv/3_fans.jpg?raw=1 The idea is to stuff air into the heat sink. Some sort of channeling might help. If the heat sink has high fin density, there will be a lot of flow restriction - we *want* a lot of flow restriction - so the air will want to sneak around the heat sink and not go through the length of the fins. Think we can dump 100 watts? Maybe we should dump the little fans... they would be a nuisance to install and wire up. With a really big heat sink, the overall box air flow might work as well. We need to try it. "One experiment is worth a thousand expert opinions." I think Werner Von Braun said that. -- I yam what I yam - Popeye
