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RE: [Homebrew_PCBs] Re: Temp upgrades of lam's HOW high is high heat conditions

2017-01-02 by Mark Lerman

Yes, a thermocouple is the proper sensor to use here, but a thermistor will work just fine. In fact, all of the laser printers I have taken apart in my successful quest to print directly on copper have used thermistors as the temperature sensor in the fuser. Invariably just a voltage divider with the voltage proportional to the temperature and read by an adc. Very easy to implement and very accurate.

Mark

At 02:37 AM 1/2/2017, you wrote:


The transistor is being used as a diode. I’ve seen this on amplifiers to monitor the power transistors and adjust the bias so it don’t go into thermal runaway. In all heater circuits I have dealt with we always used a temperature control with a thermocouple. These withstood the higher temperatures . they also had some form of high limit protection in case of a shorted thermocouple or controller failure.if the thermocouple failed open the controller simply shut the heat off altogether.


From: Homebrew_PCBs@yahoogroups.com [ mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, January 01, 2017 2:12 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: RE: [Homebrew_PCBs] Re: Temp upgrades of lam's HOW high is high heat conditions


A transistor with two of three legs soldered together makes a temperature probe. Is
the temperature inside of lam too hot? Google for temperature probe circuits like I
do for other projects.


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