Home |
Search |
Today's Posts |
#1
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
I've got a plain 12V DC cooling fan that I took out of an old computer
that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If I have the female plug that accepts the adapter's male part, it's a straight connection is that right? If let's say I don't have the female plug, I can cut off the male part of the adapter and solder the adapter wires directly to the fan? Lastly, if I want to hook up two fans together, can I use a 12V adapter and hook up the fans in parallel as described above? |
#2
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
|
#4
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On 24 Jul 2006 12:39:58 -0700, wrote:
I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If it is rated for 12 volts DC (not AC) it should work. The wall wart - supplies pulsating DC with an average RMS value of 12 volts when under load - your fan may not like the pulsating DC or may try to synchronize to it - speed will fluctuate - in that case you'd need to put a capacitor in there to smooth it out. Wall warts, as a rule, don't contain filter caps. A few do. If I have the female plug that accepts the adapter's male part, it's a straight connection is that right? DC fans are polarity sensitive and have to have the correct polarity to work. If let's say I don't have the female plug, I can cut off the male part of the adapter and solder the adapter wires directly to the fan? Lastly, if I want to hook up two fans together, can I use a 12V adapter and hook up the fans in parallel as described above? Should work. You may notice speed fluctuations as result of one fan trying to sync to the other - usually only with two identical fans - and if the slight noise doesn't bother you it won't hurt anything. Fan speed and noise can be controlled, over some range, by lowering the voltage too. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#5
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Tue, 25 Jul 2006 07:57:13 -0400, default wrote:
On 24 Jul 2006 12:39:58 -0700, wrote: I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If it is rated for 12 volts DC (not AC) it should work. The wall wart - supplies pulsating DC with an average RMS value of 12 volts when under load --- That's not true. If it were, the DC peaks would be at around 17V. --- - your fan may not like the pulsating DC or may try to synchronize to it - speed will fluctuate - in that case you'd need to put a capacitor in there to smooth it out. Wall warts, as a rule, don't contain filter caps. A few do. --- That's also not true. Unregulated AC to DC wall-warts, almost without exception, contain the filter cap and put out their rated DC voltage (plus ripple) when properly loaded. -- John Fields Professional Circuit Designer |
#6
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Tue, 25 Jul 2006 11:38:03 -0500, John Fields
wrote: On Tue, 25 Jul 2006 07:57:13 -0400, default wrote: On 24 Jul 2006 12:39:58 -0700, wrote: I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If it is rated for 12 volts DC (not AC) it should work. The wall wart - supplies pulsating DC with an average RMS value of 12 volts when under load --- That's not true. If it were, the DC peaks would be at around 17V. Well got one here and measured DC out with a scope and has 18.6 VDC zero to peak - unloaded - rated 12VDC 200 ma. --- - your fan may not like the pulsating DC or may try to synchronize to it - speed will fluctuate - in that case you'd need to put a capacitor in there to smooth it out. Wall warts, as a rule, don't contain filter caps. A few do. --- That's also not true. Unregulated AC to DC wall-warts, almost without exception, contain the filter cap and put out their rated DC voltage (plus ripple) when properly loaded. Damn I must be the exception then - three out of three had 100% ripple - but I have seen caps in some of the ones I took apart. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#7
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Tue, 25 Jul 2006 13:18:57 -0400, default wrote:
On Tue, 25 Jul 2006 11:38:03 -0500, John Fields wrote: On Tue, 25 Jul 2006 07:57:13 -0400, default wrote: On 24 Jul 2006 12:39:58 -0700, wrote: I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If it is rated for 12 volts DC (not AC) it should work. The wall wart - supplies pulsating DC with an average RMS value of 12 volts when under load --- That's not true. If it were, the DC peaks would be at around 17V. Well got one here and measured DC out with a scope and has 18.6 VDC zero to peak - unloaded - rated 12VDC 200 ma. --- What does it measure loaded to 200mA average DC out? --- - your fan may not like the pulsating DC or may try to synchronize to it - speed will fluctuate - in that case you'd need to put a capacitor in there to smooth it out. Wall warts, as a rule, don't contain filter caps. A few do. --- That's also not true. Unregulated AC to DC wall-warts, almost without exception, contain the filter cap and put out their rated DC voltage (plus ripple) when properly loaded. Damn I must be the exception then - three out of three had 100% ripple - but I have seen caps in some of the ones I took apart. --- Maybe they were purpose built to be used with a specific piece of equipment which had the filter external to the wall wart? -- John Fields Professional Circuit Designer |
#8
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Tue, 25 Jul 2006 15:11:14 -0500, John Fields
wrote: What does it measure loaded to 200mA average DC out? Fuse on my ammeter is dead but with a 75 ohm 5 watt resistor I see 16.4 zero to peak. May be a poor choice, I think this particular wall wart was to float charge a battery. --- Maybe they were purpose built to be used with a specific piece of equipment which had the filter external to the wall wart? No telling where some these came from, just acquired them in my junk box (room). Nothing on the label suggests a product manufacturer. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#9
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Tue, 25 Jul 2006 16:23:04 -0400, default wrote:
On Tue, 25 Jul 2006 15:11:14 -0500, John Fields wrote: What does it measure loaded to 200mA average DC out? Fuse on my ammeter is dead but with a 75 ohm 5 watt resistor I see 16.4 zero to peak. May be a poor choice, I think this particular wall wart was to float charge a battery. --- That makes sense, since what's required to charge a battery is to pump current into it until its voltage rises to where it's supposed to be to be charged. No filter is required because it wouldn't do anything helpful. Good call. I hadn't thought about that application, so I guess there _are_ quite a few wall-warts out there without filters. Thanks. :-) --- --- Maybe they were purpose built to be used with a specific piece of equipment which had the filter external to the wall wart? No telling where some these came from, just acquired them in my junk box (room). Nothing on the label suggests a product manufacturer. --- OK... -- John Fields Professional Circuit Designer |
#10
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
In ,
default mentions: On Tue, 25 Jul 2006 11:38:03 -0500, John Fields wrote: On Tue, 25 Jul 2006 07:57:13 -0400, default wrote: On 24 Jul 2006 12:39:58 -0700, wrote: I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? If it is rated for 12 volts DC (not AC) it should work. The wall wart - supplies pulsating DC with an average RMS value of 12 volts when under load --- That's not true. If it were, the DC peaks would be at around 17V. Well got one here and measured DC out with a scope and has 18.6 VDC zero to peak - unloaded - rated 12VDC 200 ma. My own experiments with walwarts concur with yours, they seem to have very strange voltages. (particularly new ones w/out a load) I've suspected it was the newer switched minimal-transformer transformers. (I hate those..) For whatever reasons, (suspect each one is different) it's always a good idea to make sure there is a small load on them if you want the voltage right. --- That's also not true. Unregulated AC to DC wall-warts, almost without exception, contain the filter cap and put out their rated DC voltage (plus ripple) when properly loaded. Damn I must be the exception then - three out of three had 100% ripple - but I have seen caps in some of the ones I took apart. I've seen it too, (the ripple) I usually put a capacitor on them when I power something sensitive with them, though, I doubt it matters much with a motor. (I have a walwart that makes a mess of a radio if I don't) Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
#11
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
I've got a plain 12V DC cooling fan that I took out of an old computer
that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? AC != DC. If the fan runs on 12 volts DC then you can't connect AC to it or you will destroy it. You will have to feed it through a rectifier first. If the 12VAC is actually an RMS value, the real value (RMS * SQRT(2)) is about 17V peak. So you will need to drop the extra 5V somewhere (a 5.1 Zener could do the job). But I would say if you can find an adapter that outputs 12 volts DC, that would be the best way to go. If I have the female plug that accepts the adapter's male part, it's a straight connection is that right? It doesn't matter how you connect it physically, as long as the voltage is correct. If let's say I don't have the female plug, I can cut off the male part of the adapter and solder the adapter wires directly to the fan? Please see above. Lastly, if I want to hook up two fans together, can I use a 12V adapter and hook up the fans in parallel as described above? Parallel can work so long as the voltage is the same. Remember DC != AC (not equal). Just make sure that the adapter can put out enough current (amperage) to drive all of the fans. You add up the currents of all the fans in parallel. Your power adapter has to be able to put out at least this much current. |
#12
Posted to alt.electronics
|
|||
|
|||
Cooling fan question
On Thu, 27 Jul 2006 23:20:00 GMT, "Ernie Werbel"
wrote: I've got a plain 12V DC cooling fan that I took out of an old computer that I'd like to reuse in another place. If i got an ordinary AC adapter that's rated at 12V, I can wire the adapter to the fan without any problems correct? AC != DC. If the fan runs on 12 volts DC then you can't connect AC to it or you will destroy it. You will have to feed it through a rectifier first. If the 12VAC is actually an RMS value, the real value (RMS * SQRT(2)) is about 17V peak. So you will need to drop the extra 5V somewhere (a 5.1 Zener could do the job). --- No. If the adapter puts out 12V RMS, and the motor runs on 12VDC, then as long as the output of the rectifer isn't filtered everything will be just as it should be, neglecting the timing/syncing effects that rectified AC may have on the fan. --- But I would say if you can find an adapter that outputs 12 volts DC, that would be the best way to go. --- Unless it's regulated, it needs to put out 12V at the fan's rated current, since the lightly loaded output voltage may be more than the fan was designed to handle. --- If I have the female plug that accepts the adapter's male part, it's a straight connection is that right? It doesn't matter how you connect it physically, as long as the voltage is correct. --- If you go back and read the thread, particularly: ups.com You'll find that she's using an AC -DC adapter, so the polarity of the connection becomes important. --- If let's say I don't have the female plug, I can cut off the male part of the adapter and solder the adapter wires directly to the fan? Please see above. --- Please see above. -- John Fields Professional Circuit Designer |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Generator cooling tower tank? | Metalworking | |||
condensation on ductwork and cooling efficiency | Home Repair | |||
Question about cooling loss due to hot attic | Home Repair | |||
Simple question regarding Ceiling tiles and sound? | UK diy | |||
Simple question regarding Ceiling tiles and sound? | Home Ownership |