Wednesday, December 10, 2008

Whats The Difference Between A Thermal Fuse And A Thermal Switch

Writen by Mark Boehm

Over the past 25 years I have had the unique opportunity to talk directly with many of the professionals and instructors who use Overhead Projectors as an integral part of their profession. Through these interactions I have accumulated notes and information that has inspired me to write these articles that pertain to some of the most common problems experienced by owners of today's and yesterday's Overhead Projectors. This is the sixth article in a series of articles that will be written from a professional Electronics Technicians point of view in regards to some of today's most common Overhead Projector problems. This article will cover the difference between a thermal fuse and a thermal switch.

Let's start with the thermal fuse. In many cases the manufacturer will place a thermal fuse in the electrical circuit of your Overhead Projector to protect the projector from damage due to excessive heat.

How the thermal fuses works is rather simple in nature. The fuse is rated a particular temperature rating pre determined by the manufacturer. If for some reason the cooling system in your overhead projector fails the thermal fuse will open once it has reached the pre-determined temperature, shutting the power off to the projection lamp. Once the thermal fuse has done its job, it will need to be replaced, as it can not be reset.

I am often asked if this thermal fuse can be bypassed instead of being replaced. Yes it can, but our advice is not to by-pass this important safety feature of your Overhead Projector. Saving a few dollars now could cost you a lot more in the future without this important safety device.

Thermal switches perform a different function in your Overhead Projector. The thermal switch we refer to here is used to control the cooling system of the Overhead Projector. The thermal switch remains in an open state (no current flow) until it reaches a pre determined temperature, at which time the thermal switch closes and makes an electrical circuit allowing the cooling fan to operate. When the Overhead Projector is turned off the fan will continue to run until the unit cools off enough to let the thermal switch open back up turning the fan off.

Both of these electronic components are an integral part of your Overhead Projector and should be replaced by a professional Electronic Technician.

Mark Boehm is the president of M-B Electronics He has over 25 years of experience in the Audio Visual and Electronics Industry. You can contact M-B Electronics at 800-872-9456 or

Furhter Info:

No comments: