Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, I was considering
installing one or two in the cabinet backs to draw hot air out. But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

"Mr. Land" wrote in message
...
Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, I was considering
installing one or two in the cabinet backs to draw hot air out. But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...


Why not just use a thermal switch such as this?
http://uk.farnell.com/732424/industr...questid=516363

Very cheap, very simple, will only switch on the fan when it is needed.
They come in various temperatures.



Gareth.

On Apr 24, 12:47*pm, "Gareth Magennis"
wrote:
"Mr. Land" wrote in message

...



Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). *The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. *One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, *I was considering
installing one or two in the cabinet backs to draw hot air out. *But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. *I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

Why not just use a thermal switch such as this?http://uk.farnell.com/732424/industr...tion/product.u...

Very cheap, very simple, will only switch on the fan when it is needed.
They come in various temperatures.

Gareth.

Now why didn't I think of that? I suppose even an el-cheapo furnace
thermostat might work too.
Thanks for that idea.

"Mr. Land" wrote in message
...
On Apr 24, 12:47 pm, "Gareth Magennis"
wrote:
"Mr. Land" wrote in message

...



Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, I was considering
installing one or two in the cabinet backs to draw hot air out. But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

Why not just use a thermal switch such as this?
http://uk.farnell.com/732424/industr...tion/product.u...

Very cheap, very simple, will only switch on the fan when it is needed.
They come in various temperatures.

Gareth.

Now why didn't I think of that? I suppose even an el-cheapo furnace
thermostat might work too.
Thanks for that idea.



One thing to watch out for is the hysteresis in these devices. The device I
pointed out will turn the fan on at 30 degrees, but it won't go off again
until the temperature drops to 20. If your room is warmer than that it will
never turn off!


Gareth.

One thing to watch out for is the hysteresis in these devices. The device
I pointed out will turn the fan on at 30 degrees, but it won't go off
again until the temperature drops to 20. If your room is warmer than that
it will never turn off!


Gareth.



Could build something. I recall seeing some temperature controller circuits
that used a diode as the sensing element. Should be easy to adjust the
hysteresis by selecting component values.

"James Sweet" wrote in message
news:Kn4Qj.6369$Mm1.4242@trndny07...



One thing to watch out for is the hysteresis in these devices. The
device I pointed out will turn the fan on at 30 degrees, but it won't go
off again until the temperature drops to 20. If your room is warmer than
that it will never turn off!


Gareth.



Could build something. I recall seeing some temperature controller
circuits that used a diode as the sensing element. Should be easy to
adjust the hysteresis by selecting component values.



Well this is the range of those devices:

http://uk.farnell.com/jsp/level5/mod...=en/212166.xml


Note that the opening and closing temperatures on some of them are the wrong
way around, but I reckon that the normally open switch that will switch on
the fan at 55 degrees C and turn it off at 35, part no. 1006853, would be
ideal. 55 degrees is not going to cook any electronics and it is unlikely
that room temperature is ever going to get to 35. Case solved, one
component, no design work required, and extremely reliable.



Gareth.

On Thu, 24 Apr 2008 18:24:30 +0000, Gareth Magennis wrote:


One thing to watch out for is the hysteresis in these devices. The device I
pointed out will turn the fan on at 30 degrees, but it won't go off again
until the temperature drops to 20. If your room is warmer than that it will
never turn off!

Probably why I've seen the sensor directly in front of the fan. when the
fan is operating it is getting cooled faster than the rest of the
cabinent and thus actualy turns off at a higher temperature.

OTOH, unless the fan noise is a problem, does it matter. Fan just
stays on until power to unit is removed, aka it might lert you to the
fact that te entertainment cabinent is still using power when not in
use.

"Mr. Land" wrote in message
...
Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, I was considering
installing one or two in the cabinet backs to draw hot air out. But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

I've sent you a pdf which might do the trick. Let me know if you don't
receive it.

Arfa

"Mr. Land" wrote in message
...
Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, I was considering
installing one or two in the cabinet backs to draw hot air out. But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

Why not just use a USB port to energise a relay or FET or whatever to turn
on the fans. The thermostat idea is better but more complicated, I guess it
comes down to your expertise or lack thereof :-)

--
Cheers ............. Rheilly

On Apr 25, 6:23*am, "Rheilly Phoull" wrote:
"Mr. Land" wrote in message

...



Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). *The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. *One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

Now I have a bunch of very quiet 12V computer fans in a box and, being
a long time victim of chronic tinkering disease, *I was considering
installing one or two in the cabinet backs to draw hot air out. *But I
know that when I am not around, no one in my family is going to take
the extra step to turn on the fans.

So I was thinking of some sort of current sensing switch to energize
the fans when the system was in use, sensing AC current draw over some
adjustable threshold value. *I tried a web search and found current
sensing units, but these seemed to be industrial-quality, overkill for
my application, and well, yes, I'll admit it, it'll be more fun to
build it.

I was wondering if anyone had a pointer to a simple circuit I could
build to accomplish this.

Thanks for any help, best wishes.

Apologies if this post doesn't fall under "repair" in folks' opinions
- I suppose it could be considered "repairing" my entertainment
center...

Why not just use a USB port to energise a relay or FET or whatever to turn
on the fans. The thermostat idea is better but more complicated, I guess it
comes down to your expertise or lack thereof :-)

--
Cheers ............. Rheilly

Excellent idea - however I don't believe any of my components provide
USB ports. Thank you.

On Thu, 24 Apr 2008 09:22:53 -0700 (PDT), "Mr. Land"
wrote:

Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.


I encountered a similar heating problem when putting an LCD TV in a
cabinet. I came up a fix using a $3 PICAXE chip that is programmable
in BASIC and a $5 temperature sensor that gives the actual temperature
(in degrees C). The sensor is mounted above the hottest point of the
TV (nothing inside any component). It's powered by a "wall wart"
supply, so all the wiring is low voltage. The PICAXE programming
software is a free download from http://www.rev-ed.co.uk/picaxe/

http://www.picaxe.us/AV-fan.html

You can set the on and off temperatures (in the program code) to
whatever works best for you. A more sophisticated version would use
the PWM capability of the PICAXE chip to control fan speed, running
the fan(s) only fast enough to maintain an acceptable temperature
rise.

John

On Apr 25, 11:01*am, John wrote:
On Thu, 24 Apr 2008 09:22:53 -0700 (PDT), "Mr. Land"

wrote:
Greetings,

When in use, a few of our home theater components heat up the interior
spaces of our entertainment center to a temperature that I feel is too
hot (yes, that's a very subjective statement). *The entertainment
center uses tall, mostly glass doors, and they are one-piece,
therefore when they are open they protrude pretty far into the room.
When they are closed, there is little-to-no ventilation inside the
cabinets. *One evening, I mustered up some courage and tried simply
leaving the doors open but sure enough, one of my kids came close to
ripping the entire door off of its hinges when she bumped into it.

I encountered a similar heating problem when putting an LCD TV in a
cabinet. *I came up a fix using a $3 PICAXE chip that is programmable
in BASIC and a $5 temperature sensor that gives the actual temperature
(in degrees C). *The sensor is mounted above the hottest point of the
TV (nothing inside any component). *It's powered by a "wall wart"
supply, so all the wiring is low voltage. *The PICAXE programming
software is a free download fromhttp://www.rev-ed.co.uk/picaxe/

http://www.picaxe.us/AV-fan.html

You can set the on and off temperatures (in the program code) to
whatever works best for you. *A more sophisticated version would use
the PWM capability of the PICAXE chip to control fan speed, running
the fan(s) only fast enough to maintain an acceptable temperature
rise.

John

Oh, now this is nice! I've shied away from programmable
microcontrollers in the past, but this looks like something even I
could deal with, and a lot of fun. Thanks a lot for posting this
reply!!