Ppl who use fans for cooling planted tanks

[tawauboy]

regulated - output voltage is fixed at rated output voltage until the current being drawn exceeds the current rating. ie. a 12v 1a regulated adapter will output 12v for load current from 0a to 1a. however, above 1a, the output voltage will start to fall below 12v.

unregulated - output voltage varies with the current being drawn from the adapter. the adapter will only output 12v at the rated current. so 12v 1a adapter will output 12v when the load current is 1a. below 1a the voltage will go above 12v. if 0.1a being drawn from 1a adapter, the output voltage can be almost 20v. how high this voltage is depends on the va rating of the adapter.

[vinz]

Thanks, Tawauboy. More questions...

If we use an unregulated 12V, 1A adaptor and use it run say one 0.3A fan, the V will go up. How will this affect the fan and the adaptor?

Can we deduce then that the regulated adaptor is a better choice for running our fans as the V will stay constant, as long as we do not draw more then the rated Amps?

Any other issues that will affect our usage in terms of regulated and unregulated?

[Allen_1971]

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On 12/20/2002 8:07:21 AM
if you use an overrated adapter, you fans will be louder because the voltage supplied is higher causing your fan to run at a higher speed. adapter ratings are given for a particular voltage at a particular load current along the voltage/load curve. for example, an adapter rated at 12v 1a will output close to 20v when there is no load. only when the load is drawing 1a, the output voltage is 12v.
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I haven't done any probing on my DC supplies, but I've always assumed that they were regulated power supplies? Otherwise it doesn't make sense to have that small know which allows you to choose the voltage? In fact I don't think I've seen unregulator DC supplies on the market? It just doesn't make sense. Who would use an unregulated supply? you always have to match your voltage and current requirements to the needs of your equipment.

[vinz]

Allen, yes there is unregulated in the market. The uncle at the shop (at SLT) that I bought my fans and adaptor from gave me the choices.

He also said we can control the fan speed by turning the voltage selector. Don't know if it's safe to do so, but I haven't tried it yet (have not even set up the fans). Anybody can comment on this?

[Allen_1971]

Errr how can there be a voltage selector if the supply is not regulated? The fact that it has voltage selector mean you can choose several fixed voltages. I mean I'm no expert on power supplies, but most of these dc power supplies are just a rectifier + transformer + step down power... following you would probably add a variable resistor or some switches to determine the regulated voltage level. OK so the tolerances may be crap, but you should still have your fixed voltage +/- a % tolerance.

I can understand a voltage regulator losing regulation if too much current is being drawn, but I can't understand where an unregulated DC supply would be used?

[vinz]

Allen, errr... I did not mean for the the 2 topics (voltage selector and unregulated adaptors) in my post, to be directly related.

[Allen_1971]

Ok so just to clarify, you are saying that the uncle gave you 2 choices? One was a dc supply with a voltage selector right? The other was without a voltage selector i assume?

Even if this is the case, the one without the voltage selector should be regulated at a preset level... I doubt it was unregulated....

[tawauboy]

0.3a fan with 12v 1a adaptor
fan will run faster so the fan may fail earlier. by how much the fan's lifespan is shortened, i don't know. normally there are design tolerances built in to allow over voltage operation but i have no idea of the tolerance. i have been running my 12v fans at 18v for almost 1/2yr and so far so good.
no impact on the adapter. adaptor is only affected when you draw more current that the rated current and the ac fluctuation.

regulated adaptor will be a better choice as the fans will be running at the design voltage, maximising the expected operating life.

i don't see any other other issues except the higher output voltage effects of an unregulated adaptor and that a regulated adaptor may be harder to find in the market.

[Allen_1971]

TB,

I still don't get it... how can you possibly say that a DC power supply is an unregulated 12V 1a? I mean making such a claim could be a risk to safety... If I were to stick it into a piece of electronic equipment rated to 12V 0.3A input, the probability of it frying my equipment is pretty high...

Fans I guess are pretty tolerant of higher voltages, but still it probably isn't great to run a lower rated fan at 50% higher voltage (18V as you mentioned).

[tawauboy]

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I haven't done any probing on my DC supplies, but I've always assumed that they were regulated power supplies? Otherwise it doesn't make sense to have that small knob which allows you to choose the voltage? In fact I don't think I've seen unregulator DC supplies on the market? It just doesn't make sense. Who would use an unregulated supply? you always have to match your voltage and current requirements to the needs of your equipment.
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the knob allows you to select the output voltage by switching the secondary windings of the transformer.

most of the adaptor are unregulated. almost all products that need an adaptor comes with one. if you happen to have and adaptor damaged, you will bring it to the shop to find one that meets the voltage and current specification. so there is no problem of matching.

also since almost all electronic products have in-built regulators, there is no need for a regulated adaptor. why pay for 2 regulators when 1 is enough.

[Allen_1971]

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On 12/20/2002 5:41:12 PM

the knob allows you to select the output voltage by switching the secondary windings of the transformer.

<snip>

also since almost all electronic products have in-built regulators, there is no need for a regulated adaptor. why pay for 2 regulators when 1 is enough.
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TB,

I guess for really cheap designs they might do that. If that being the case, you would probably have really poor tolerances in your voltage. Also, I still have difficulty seeing how such a part could be marketed as a 12V 1a part... in order for the part to be useful, it would have to provide an curve of Vout vs Iout... Otherwise, using it would be haphazard at best.

As for electronic devices, its true that they normally have internal regulators, but these regulators also have a maximum DC in after which they will probably fail. If I was expecting a 12V input, its not unreasonable to give a 25% tolerance and cater for a maximum of 15V in. 18V could still wreck my regulator.

I'll go back and check my regulator, but I expect that when it says 12V I'll get my 12V....

[tawauboy]

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As for electronic devices, its true that they normally have internal regulators, but these regulators also have a maximum DC in after which they will probably fail. If I was expecting a 12V input, its not unreasonable to give a 25% tolerance and cater for a maximum of 15V in. 18V could still wreck my regulator.
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most regulators can handle a max dc of 32v. even for those micropower 3.3v regulators.

[tawauboy]

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I still don't get it... how can you possibly say that a DC power supply is an unregulated 12V 1a? I mean making such a claim could be a risk to safety... If I were to stick it into a piece of electronic equipment rated to 12V 0.3A input, the probability of it frying my equipment is pretty high...
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a dc power supply is different from an adaptor. dc power supplies have a lot of curcuits to generate precise voltage.

an adaptor on the other hand consists of a step down transformer(transform 240ac to say 12v), bridge rectifier(to rectify ac into dc) and a capacitor(to reduce ripple voltage). there is not voltage regulating circuit so the output voltage will vary depending on the load current.

[Allen_1971]

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On 12/20/2002 6:04:54 PM

most regulators can handle a max dc of 32v. even for those micropower 3.3v regulators.
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I'm pretty sure thats not true... I work with micropower devices daily... most of the ones I deal with could fry at even 7V input if not lower.

Anyway, I suspect the reason for this differing point of view could be that we are discussing two different classes of devices. I probably have to pop down to SLT to see just what they sell...

One more point of clarification... when I said DC power supply I did not mean those we use in labs where you can set the voltage and current. I meant one of those which you buy in the hardware shops for like 10-20 bucks... I should call it a AC/DC adaptor

Now if I can only find where my wife put the DC adaptor so I can check.

[tawauboy]

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He also said we can control the fan speed by turning the voltage selector. Don't know if it's safe to do so, but I haven't tried it yet (have not even set up the fans). Anybody can comment on this?
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by turning the voltage selector, the output voltage change so you fans speed will change. should not be a problem as long as the adaptor can handle the required current. but fan lifespan may be reduced.

[tawauboy]

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I'm pretty sure thats not true... I work with micropower devices daily... most of the ones I deal with could fry at even 7V input if not lower.

Anyway, I suspect the reason for this differing point of view could be that we are discussing two different classes of devices. I probably have to pop down to SLT to see just what they sell...

One more point of clarification... when I said DC power supply I did not mean those we use in labs where you can set the voltage and current. I meant one of those which you buy in the hardware shops for like 10-20 bucks... I should call it a AC/DC adaptor

Now if I can only find where my wife put the DC adaptor so I can check.
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think we are talking about different classes of devices. the ones i work with are for generic applications(cheaper).

anyway, a regulated adaptor is more expensive and harder to find.

[hosm]

Something on powersupply.
The 2 in question are te regulated and the unregulated.

The regulated supply are design for stable voltage output which means the voltage will stay at the rated voltage, say 12 volts with or without load.
( a load is the device you want to power up in this case is our fan.)

Where as an unregulated supply will output say about 15 or 16 volts before load and maybe drop down to 11 - 13 volts when loaded. Depending on the current drawn.

Nowadays portable electronics equipment ( especially digital type )prefer regulated supply as it provide a stable voltage for theis operation.

If we are using it for our fish fan, an unregulated will do.
All you have to take note is the voltage and current rating.
Of course a regulate one better.

Just somthing to take note of when getting aa supply.

Current.
The supply current must be always larger than the equipment.
ie:
fan = 0.4 amps
supply >0.5 amps or higher.
Under rated current supply will destroy your supply.

Voltage:
Voltage should be the same as rated on the supply and not larger.
ie:
fan = 12v.
supply 12v
Over voltage will on the long run shorten the life of your fan.

hope this helps.

sm