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thermistor_troubleshooting [2016/04/16 15:17] – created Traumflug | thermistor_troubleshooting [2018/05/27 16:10] (current) – external edit (unknown user) | ||
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* //CT1// means to smooth out noise, it's not directly involved in the measurement circuitry. | * //CT1// means to smooth out noise, it's not directly involved in the measurement circuitry. | ||
* // | * // | ||
- | * //RT1// makes up a [[https:// | + | * //RT1// makes up a [[https:// |
- | Connecting components this way gives a voltage on the signal line which depends on the thermistor' | + | Connecting components this way gives a voltage on the signal line which depends on the thermistor' |
+ | ===== Hardware Measurements ===== | ||
+ | Before searching for firmware misconfigurations, | ||
+ | |||
+ | ==== Thermistor Type ==== | ||
+ | |||
+ | Actually, thermistor type doesn' | ||
+ | |||
+ | 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 ==== | ||
+ | |||
+ | 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 ==== | ||
+ | |||
+ | 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. | ||
+ | |||
+ | If resistance is always zero, there' | ||
+ | |||
+ | ==== Check Voltage on the Processor Pin ==== | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | This is what the firmware actually " | ||
+ | |||
+ | This measurement can be done without the processor installed. If one is installed, the firmware shouldn' | ||
+ | |||
+ | 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 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.1460812666.txt.gz · Last modified: 2018/05/27 16:10 (external edit)