cooling fan for entertainment cabinet

[Sixpack98]

Very often when you replace the pretty lame entertainment equipment the coach manufacturer provides or you add other items like a satellite receiver, DVD or other items heat becomes a real problem in the confined compartments they are installed in. I recently upgraded the receiver, added a separate DVD player and DirecTV receiver that really heated up the cabinet they were installed in. So, I set out to find a way to vent the cabinet better than the what the Monaco louvers could provide. I installed a fan at the top of the cabinet and vented it out to an open area beside the cabinet. Since the 12v fan was running at its rated speed it was very loud. It also provided much more cfm than was required to cool the cabinet so I looked for something different.

The following is an example of a very efficient temperature controlled variable speed controller. About $4.00 to build. It uses a thermistor to control a power MOSFET. The thermistor changes resistance relative to heat and controls the output voltage of the MOSFET. At fan shut off the current draw is 3ma so it is not much of a parasitic load on the chassis batteries. The chief advantage is the fan speed changes as the temperature changes and approaches steady speed once it settles in. The trim pot sets the speed controller start temperature.

I found this circuit was found on a power PC web site and I modified it to meet the environment of an RV. Radio Shack has the parts except some don't carry the thermistor but it can be found at any electronic supply or on the web.

If you're not up to grabbing a soldering iron there are several fans available that are temperature controlled. Tate Loon, Thermotake and Cooler Master. The fan does not shut off completely and continues to draw about 50ma. Not much of a draw on the chassis batteries but it still contributes to the parasitic load placed on the chassis 12v batteries.

Every application will be different so I'm not showing where I mounted the fan.




The photo below shows the components mounted on a perf board (available at Radio Shack). The thermistor is at the bottom of the picture, the black wires with blue shrink wrap. It has long lead wires attached so it can be mounted anywhere in the cabinet.

[URL=http://www.irv2.com/photopost/data/500/medium/IMG_1886.JPG]

[Sixpack98]

Very often when you replace the pretty lame entertainment equipment the coach manufacturer provides or you add other items like a satellite receiver, DVD or other items heat becomes a real problem in the confined compartments they are installed in. I recently upgraded the receiver, added a separate DVD player and DirecTV receiver that really heated up the cabinet they were installed in. So, I set out to find a way to vent the cabinet better than the what the Monaco louvers could provide. I installed a fan at the top of the cabinet and vented it out to an open area beside the cabinet. Since the 12v fan was running at its rated speed it was very loud. It also provided much more cfm than was required to cool the cabinet so I looked for something different.

The following is an example of a very efficient temperature controlled variable speed controller. About $4.00 to build. It uses a thermistor to control a power MOSFET. The thermistor changes resistance relative to heat and controls the output voltage of the MOSFET. At fan shut off the current draw is 3ma so it is not much of a parasitic load on the chassis batteries. The chief advantage is the fan speed changes as the temperature changes and approaches steady speed once it settles in. The trim pot sets the speed controller start temperature.

I found this circuit was found on a power PC web site and I modified it to meet the environment of an RV. Radio Shack has the parts except some don't carry the thermistor but it can be found at any electronic supply or on the web.

If you're not up to grabbing a soldering iron there are several fans available that are temperature controlled. Tate Loon, Thermotake and Cooler Master. The fan does not shut off completely and continues to draw about 50ma. Not much of a draw on the chassis batteries but it still contributes to the parasitic load placed on the chassis 12v batteries.

Every application will be different so I'm not showing where I mounted the fan.




The photo below shows the components mounted on a perf board (available at Radio Shack). The thermistor is at the bottom of the picture, the black wires with blue shrink wrap. It has long lead wires attached so it can be mounted anywhere in the cabinet.

[URL=http://www.irv2.com/photopost/data/500/medium/IMG_1886.JPG]

[Bob (WA0MQE)]

Very good Sixpack98. What type of fan did you use? One of the small boxer computer type fans, or was it something else? What about the thermistor, your drawing shows 10K NTC is that all there is to a part number?

[Sixpack98]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bob (WA0MQE):
Very good Sixpack98. What type of fan did you use? One of the small boxer computer type fans, or was it something else? What about the thermistor, your drawing shows 10K NTC is that all there is to a part number? </div></BLOCKQUOTE>

Bob,
Any 12v box fan will work. The MOSFET will handle 20W easily. I had a 2 3/4" fan that, at rated fan speed, puts out about 27 cfm so I can run it at very low speed with very, very little noise. The advantage of the smaller fans is that they are usually 1/2" thick and can fit almost anywhere. It's more efficient to let the fan push the hot air out of the cabinet and the fan mounted either on the top of the cabinet or high up on a side wall. I actually mounted the circuit board on one of the fan holes and glued the thermistor so it was in line with the airflow.
Any Negative Temperature Coafficient (NTC) will work that is in and around 10k to 20k, the trimpot can be adjusted to accommodate a range of thermistors.