lloydi12345
Member
Hi guys, I am having problems with my project Temperature Controller. It is a device that controls gas valves with timer and displays temperature of a cooking fryer. The circuits involved here are microcontroller, piezo speaker, crystal with two 22pf ceramic caps for clock, tack switches, 7 segment displays, switching regulator, transistors and mostly discrete components.
Few months ago, I made this prototype project using locally purchased components and everything worked fine at temperature 360F. The prototype was used for two months without any failures.
The project later on was passed to China to fabricate it. Testing one unit, it fully functioned at first operated at 340F. Several hours later, a problem showed up. Everything slowed down, including the sound, buttons pressed, displays, clock. I checked the switching regulator, touched it and felt no heat at all. It perfectly looked good! So, I suspected that it could be the 4MHz crystal's problem. I am currently testing it again at 340F and currently it still functions as it should be.
Can anyone assume possible problems here too? Thanks.
Few months ago, I made this prototype project using locally purchased components and everything worked fine at temperature 360F. The prototype was used for two months without any failures.
The project later on was passed to China to fabricate it. Testing one unit, it fully functioned at first operated at 340F. Several hours later, a problem showed up. Everything slowed down, including the sound, buttons pressed, displays, clock. I checked the switching regulator, touched it and felt no heat at all. It perfectly looked good! So, I suspected that it could be the 4MHz crystal's problem. I am currently testing it again at 340F and currently it still functions as it should be.
Can anyone assume possible problems here too? Thanks.