inglewoodpete
Senior Member
I am in the process of designing a fan controller for my Topfield 4400 PVR.
As background, I upgraded the hard drive from 80GB to 320GB. The specs said there was very little change in power consumption for that particular HD model. However, there must be additional heat that is tipping the Toppy over its limits. When cooped up in the video cabinet, the picture colour starts to lose its blues. When I open the doors on the video cabinet and hang the PVR partly off the shelf, the colours all restore indicating an overheating problem. The wife is not too impressed with my current cooling solution
My proposed solution involves a 14M using PWM to control a computer cooling fan (the Toppy does not come with a fan). There will be a couple of DS18B20s and an audio integrator to detect when the PVR is not in standby mode. The idea being, the fan only revs up when it is really needed, to keep fan noise at a minimum.
My question is about PWM using a 2N7000. The fan is a 12v 1.2w (Ie 100mA continuous). Reading the data sheet, the 2N7000 is rated at 200mA continuous (500mA pulsed). Is this suitable for PWM control of a DC motor? Does the reactive load affect the power rating of the FET? I'm trying to avoid using a larger FET with all the driver issues that raises.
-Peter
As background, I upgraded the hard drive from 80GB to 320GB. The specs said there was very little change in power consumption for that particular HD model. However, there must be additional heat that is tipping the Toppy over its limits. When cooped up in the video cabinet, the picture colour starts to lose its blues. When I open the doors on the video cabinet and hang the PVR partly off the shelf, the colours all restore indicating an overheating problem. The wife is not too impressed with my current cooling solution
My proposed solution involves a 14M using PWM to control a computer cooling fan (the Toppy does not come with a fan). There will be a couple of DS18B20s and an audio integrator to detect when the PVR is not in standby mode. The idea being, the fan only revs up when it is really needed, to keep fan noise at a minimum.
My question is about PWM using a 2N7000. The fan is a 12v 1.2w (Ie 100mA continuous). Reading the data sheet, the 2N7000 is rated at 200mA continuous (500mA pulsed). Is this suitable for PWM control of a DC motor? Does the reactive load affect the power rating of the FET? I'm trying to avoid using a larger FET with all the driver issues that raises.
-Peter