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thermistor_troubleshooting [2016/04/16 17:12]
Traumflug [Thermistor Type]
thermistor_troubleshooting [2018/05/27 16:10] (current)
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 ==== Thermistor Type ==== ==== Thermistor Type ====
  
-Actually, thermistor type doesn'​t matter much for troubleshooting. They all work by the same principle, so the circuitry shown above always works (unless it'​s ​faulty). Most RepRap printers use thermistors with 100\_kOhms nominal resistance. This means they have 100\_kOhms at 25\_°C ("room temperature"​).+Actually, thermistor type doesn'​t matter much for troubleshooting. They all work by the same principle, so the circuitry shown above always works (unless it'​s ​broken). Most RepRap printers use thermistors with 100\_kOhms nominal resistance. This means they have 100\_kOhms at 25\_°C ("room temperature"​).
  
 During firmware configuration types matter a lot more, because there we want not only a working principle, but also reasonably accurate readings. During firmware configuration types matter a lot more, because there we want not only a working principle, but also reasonably accurate readings.
 ==== Check Supply Voltage ==== ==== Check Supply Voltage ====
  
-Easiest way to do this is to disconnect the thermistor and measure voltage between both pins. With no thermistor connected, it should be full supply voltage, 3.3\_or 5\_volts depending on the controller.+Easiest way to do this is to disconnect the thermistor and measure voltage between both pins on the board. With no thermistor connected, it should be full supply voltage, 3.3\_or 5\_volts depending on the controller.
  
 ==== Check Thermistor Wiring ==== ==== Check Thermistor Wiring ====
  
-This measurement is simple, too. Disconnect ​the thermistor and measure resistance between both pins. At room temperature this should be around the nominal value of the thermistor, typically 10\_kOhms or 100\_kOhms. Warming the thermistor by hand should reduce this resistance.+This measurement is simple, too. Unplug ​the thermistor ​connector ​and measure resistance between both pins there. At room temperature this should be around the nominal value of the thermistor, typically 10\_kOhms or 100\_kOhms. Warming the thermistor by hand should reduce this resistance ​by a few kOhms.
  
 Measuring the thermistor while it's plugged in gives false results. Measuring the thermistor while it's plugged in gives false results.
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 This measurement can be done without the processor installed. If one is installed, the firmware shouldn'​t make these pins an output, but keep the default, input. This measurement can be done without the processor installed. If one is installed, the firmware shouldn'​t make these pins an output, but keep the default, input.
  
-Without a thermistor connected, both pins should read full 3.3\_volts (5\_volts on 5\_V controllers). Connecting a thermistor at room temperature should drop this not much, but a bit. Typically to 3.2\_... 3.3\_volts.+Without a thermistor connected, both pins should read full 3.3\_volts (5\_volts on 5\_V controllers). Connecting a thermistor at room temperature ​(not to these processor pins, but to the thermistor header on the board) ​should drop this not much, but a bit. Typically to 3.1\_... 3.2\_volts.
  
-Warming the thermistor by hand might change that slightly, perhaps by another 0.05\_V drop. Warming the thermistor with a lighter (be careful to not overheat it!), should drop that voltage further, down to very low readings, like 0.5\_V.+Warming the thermistor by hand might change that slightly, perhaps by another 0.05\_V drop. Warming the thermistor with a lighter ​or soldering iron (be careful to not overheat it!), should drop that voltage further, down to very low readings, like 0.5\_V.
thermistor_troubleshooting.1460819571.txt.gz · Last modified: 2018/05/27 16:10 (external edit)