Running fans off a 12v trigger? - AVS Forum
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post #1 of 24 Old 02-14-2011, 09:48 AM - Thread Starter
 
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I'm no expert on electrics, so I am hoping that I can get some help with an idea I have. I did a quick search, but couldn't find anything definite on the subject. It seems that most people in this situation use a power adapter and an intelligent power strip, but that's not an option for me.

If possible I would like to run 2x 120mm fans off the 12v trigger outputs of my Receiver. It has 2 of them and the manual states that they go up to a maximum of 150mA.

I have found some very quiet 12v fans that are 50mA. I presume it is safe for me to use these?

I'm also guessing that I would have to use a seperate trigger for each fan, rather than try to run them off the same output?
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post #2 of 24 Old 02-14-2011, 10:41 AM
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I take it that the triggers are always powered up when the receiver is powered up? That makes sense, but I never tested it.

Seems using one per fan is safer as the total draw is 100ma, and they are not really designed for driving loads.

"But this one goes up to 11"
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post #3 of 24 Old 02-14-2011, 12:04 PM - Thread Starter
 
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Originally Posted by MichaelJHuman View Post

I take it that the triggers are always powered up when the receiver is powered up? That makes sense, but I never tested it.

Well the triggers are for Zones 2 and 3, but I can program them to switch on when I power up the Receiver. It also gives me the option not to use them unless I need to.
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post #4 of 24 Old 02-14-2011, 12:33 PM
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I doubt the current in the 12v trigger will be enough to power the fans.
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post #5 of 24 Old 02-14-2011, 12:48 PM
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Fans are a nasty inductive motor load. That means big turn-on and turn-off spikes that your AVR's trigger outputs might not like even if the steady-state draw is low enough that your trigger circuit would power them. While you can design a little circuitry to protect the AVR, I personally would not hang a fan on the trigger circuit. It's just not the thing the trigger circuits are designed to drive. You couild get one of the power strips that take a trigger input instead if that's an option, then powre the fans off a cheap 12 V (or whatever) supply plugged into that. For that matter, I used an X10 transmitter that has a voltage input driven off my trigger circuit, then a pair of X10 receiver modules to switch on my subwoofers when the AVR comes on.

http://www.thehomeautomationstore.com/psc01.html
http://www.thehomeautomationstore.com/pam02.html

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post #6 of 24 Old 02-14-2011, 03:29 PM - Thread Starter
 
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Originally Posted by Chicagorep View Post
I doubt the current in the 12v trigger will be enough to power the fans.
What do you mean by "current" please? Sorry if that sounds like a basic question, but I just want to understand.
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post #7 of 24 Old 02-14-2011, 03:40 PM
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Quote:
Originally Posted by mjf_uk View Post
What do you mean by "current" please? Sorry if that sounds like a basic question, but I just want to understand.
Because it is what it says it is. A trigger only, not a form of a continuous power supply. There are many options to do what you want and do it safely without the chance of damaging your current equipment. Go over to coolerguys.com and click on their section for HT cooling options. They have any configuration you want as far as fans and other cooling options go. Way less expensive than what may happen to your gear if you try what you want to do. Good luck and hope you find your answer.
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post #8 of 24 Old 02-14-2011, 03:41 PM - Thread Starter
 
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Originally Posted by DonH50 View Post
Fans are a nasty inductive motor load. That means big turn-on and turn-off spikes that your AVR's trigger outputs might not like even if the steady-state draw is low enough that your trigger circuit would power them. While you can design a little circuitry to protect the AVR, I personally would not hang a fan on the trigger circuit. It's just not the thing the trigger circuits are designed to drive. You couild get one of the power strips that take a trigger input instead if that's an option, then powre the fans off a cheap 12 V (or whatever) supply plugged into that.
Yes, that makes sense, I didn't think about initial power spikes when first switching things on. I just hoped that it might okay with a low RPM fan. I suppose it probably is better to look at proper power supply for them.

I just really need to understand more about what I need to get so that I can run 2 cooling fans. To work this out I need to know the answers to some really basic and probably seemingly stupid questions.
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post #9 of 24 Old 02-14-2011, 03:45 PM
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Quote:
Originally Posted by mjf_uk View Post
Yes, that makes sense, I didn't think about initial power spikes when first switching things on. I just hoped that it might okay with a low RPM fan. I suppose it probably is better to look at proper power supply for them.

I just really need to understand more about what I need to get so that I can run 2 cooling fans. To work this out I need to know the answers to some really basic and probably seemingly stupid questions.
No questions are here are stupid. Just need to be led down the right path. Not anyone here knows everything. Coolerguys does have the 1 or 2 fan solution for you. 120mm computer case fans draw the most heat from your equipment and are the quietest in doing it. Again good luck.
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post #10 of 24 Old 02-14-2011, 03:51 PM - Thread Starter
 
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Quote:
Originally Posted by phantom52 View Post
Because it is what it says it is. A trigger only, not a form of a continuous power supply. There are many options to do what you want and do it safely without the chance of damaging your current equipment. Go over to coolerguys.com and click on their section for HT cooling options. They have any configuration you want as far as fans and other cooling options go. Way less expensive than what may happen to your gear if you try what you want to do. Good luck and hope you find your answer.
Thanks, I had seen someone mention doing it (on another forum) which is what gave me the idea to begin with. But the last thing I want to do is damage the Receiver, so I do need to understand more and look into the options.

I am in the UK, so will be looking more at what is available here. I just need to power 2 fans that I won't hear, nothing fancy. Coolerguys seem to be adding quite a premium on what they offer. Surely it is less than half the price to do it yourself in the US?
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post #11 of 24 Old 02-14-2011, 03:55 PM
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This is just an idea for you to look into where your are located. Also all you need to get in order to do it.



http://www.coolerguys.com/comcool.html
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post #12 of 24 Old 02-14-2011, 04:12 PM - Thread Starter
 
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Originally Posted by phantom52 View Post
This is just an idea for you to look into where your are located. Also all you need to get in order to do it.
Thanks. I've been looking at my options for 120mm fans to use, the only thing I am not sure of is how to power them.

I think I know what to get to run a single fan, but I would like to run 2 or possibly 4 from the same power supply. That is where I'm not sure what power supply would be required.
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post #13 of 24 Old 02-14-2011, 06:58 PM
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Quote:
Originally Posted by MichaelJHuman View Post

I take it that the triggers are always powered up when the receiver is powered up? That makes sense, but I never tested it.

Over some years I've found different types of 12v triggers in assorted equipment I've owned.
More recent gear, if it's well thought out, should probably give you some kind of programming options, other then just setting them to on/off.

For example:

You may be givin the option to select a steady DC signal or pulse type.

If pulse is an option, a setting for the duration of the pulse is handy.

If more then one trigger is supplied or in use, you might be able to select whether or not they will all turn on/off at the same time or allow to be set sequentially.

If a sequential option is provided, a setting for how many seconds in-between before the next trigger is activated might also be available.

My old SSP had 4 - 12v triggers that were not programmable and set at the factory to be a continuous 12v signal, they were mostly useless to me as that type of signal would turn my 3 power amps right off, instead of taking them in or out of stand-by.

My power center (Monster type device) on the other hand requires a steady 12v signal to stay on.

TURN IT UP!
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post #14 of 24 Old 02-14-2011, 08:18 PM
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Quote:
Originally Posted by mjf_uk View Post

Thanks. I've been looking at my options for 120mm fans to use, the only thing I am not sure of is how to power them.

I think I know what to get to run a single fan, but I would like to run 2 or possibly 4 from the same power supply. That is where I'm not sure what power supply would be required.

Almost any power supply would work that is 12V and rated for the combined current draw of the fans (assuming you connect the fans in parallel and leave yourself some margin on the current rating). Virtually any power supply can handle the turn on spike current from such fans, worst case the voltage drops a bit which will still spin up the fan just more slowly but still within a couple seconds. This isn't infinitely expandable, i mean you may run into trouble with 10 fans but 4 should be fine.

Get fans that have a 'PWM input' rated for 12V. Feeding this with a constant 12V from the receiver output will cause them to run at full speed and draw very little current from the receiver.

This is exactly what the 'coolerguys' package mentioned above does.
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post #15 of 24 Old 02-15-2011, 01:13 AM
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a few thoughts:

1. Does your receiver have a switched power outlet? If so, you should be able to run a small power supply on it to power some fans. I have certainly read about people doing just this.

2. What receiver (make/model)? Maybe someone can lookup the specs of the trigger circuit, or has tried running fans off the trigger circuit of the same receiver.

3. How many fans do you really need? The true answer might be zero, in which case you can save yourself the hassle of buying anything and adding noise and system complexity. Consider measuring temps, with your own measurement equipment, or using a button code to show the internal temp sensor readings from the receiver's sensor(s). That way you can use real data to judge if you need fan and/or optimize the size / type / speed / placement of any that you do decide to purchase and install. It is easy to talk yourself into an apparent overkill solution, and then later realize that you can hear the fans after all, or that you just don't want the mess and complexity of extra fans after you've had the system for a while. Personally, I don't want any fans -- I prefer passive solutions such as a more open cabinet, or just accepting that some gear runs warm/hot -- it will probably be obsolete before it cooks itself anyway (if it ever really does cook itself).

-Max
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post #16 of 24 Old 02-15-2011, 02:56 AM
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There are dedicated 12 VDC power supplies, which are being used for powering HDs (computer hard discs). Even some 120 mm fans come already equipped with the corresponding Molex connectors. That's what i used.

Quote:
Originally Posted by mjf_uk View Post

Thanks. I've been looking at my options for 120mm fans to use, the only thing I am not sure of is how to power them.

I think I know what to get to run a single fan, but I would like to run 2 or possibly 4 from the same power supply. That is where I'm not sure what power supply would be required.

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post #17 of 24 Old 02-15-2011, 04:37 AM - Thread Starter
 
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Originally Posted by maxcooper View Post

a few thoughts:

1. Unfortunately there is no power outlet on the Receiver.

2. It's the Onkyo 3008. The manual states 12v/150mA.

3. I've been monitoring the temperature over the past few days or so and I do want to add a couple of fans to draw the heat out of the Receiver. I may then use 2 more fans which would be used to help to prevent that hot air going straight back in. The main reason for doing this is that I am triggering the fans in the Receiver quite easily, even though the ambient temperature is relatively cool at the moment. So I am concerned about what will happen in the summer. I know I could probably just leave the onboard fans to deal with it, but I would prefer some quieter fans that run constantly, to prevent the Receiver from getting up to 50°C to begin with. I am unable to increase the space around the Receiver, which has always been enough for every other Receiver I have owned, so it seems that fans are the only way.
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post #18 of 24 Old 02-15-2011, 04:44 AM - Thread Starter
 
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Originally Posted by gurkey View Post

There are dedicated 12 VDC power supplies, which are being used for powering HDs (computer hard discs). Even some 120 mm fans come already equipped with the corresponding Molex connectors. That's what i used.

Thanks. I found a couple of those online last night while looking around. But a 12v power adapter can be bought for half the price. I'm still looking though.
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post #19 of 24 Old 03-02-2011, 10:15 AM - Thread Starter
 
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After successfully running 4 fans of an old 12v/1A power supply with no problems, I decided to buy one with with a molex connector. It is rated at 12v/2A, but I've tried 2 of them so far and both of them have blown about 10 minutes after powering up.

I don't really understand what is going on. It would have been nice to use the molex type, as I intended to use a molex socket as a power connector.
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post #20 of 24 Old 04-20-2011, 03:19 PM
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I have the trigger option on my pioneer THX receiver. Does coolerguys have a fan or controller I can use as a relay? I have plenty of power 12v supplys laying around.

http://www.coolerguys.com/
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post #21 of 24 Old 04-20-2011, 04:31 PM
 
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The trigger output is capable of supplying 150mA at 12V...that's all the information required. You could run 3, 12v 50mA fans.
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post #22 of 24 Old 04-20-2011, 05:12 PM
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Quote:
Originally Posted by SAM64 View Post

The trigger output is capable of supplying 150mA at 12V...that's all the information required. You could run 3, 12v 50mA fans.

except for pioneer

Quote:
The trigger maximum power is DC OUT 12 V/50 mA
(50 mA total for terminals 1 and 2).

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post #23 of 24 Old 04-20-2011, 05:21 PM
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would something like this work with a small 80mm fan with a 12v 500ma power supply? does it get wired like a regular automotive type relay?


http://www.radioshack.com/product/in...ductId=2062479
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post #24 of 24 Old 04-20-2011, 06:17 PM
 
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I don't think the OPis using a Pioneer, he gave the specs in th first post:

Quote:


12v trigger outputs of my Receiver. It has 2 of them and the manual states that they go up to a maximum of 150mA.



Quote:


would something like this work with a small 80mm fan with a 12v 500ma power supply?

Maximum switching current is 500mA, coil voltage appears to be 5V.
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