Posted on July 26, 2020
Samsung A50 Temperature Too High or Too Low Repair Solution
Here we have ultra high resolution solution ways for the Samsung A505F A505GT A505G A505GN A505FN and A505FM.
These thermistors are NTC devices meaning the higher the temperature the higher resistance, you can’t jumper them, best to replace okay!
Enjoy the diagram without the stupid watermarks!
Negative Temperature Coefficient Thermistor
Negative temperature coefficient of resistance thermistors, or NTC thermistors for short, reduce or decrease their resistive value as the operating temperature around them increases. Generally, NTC thermistors are the most commonly used type of temperature sensors as they can be used in virtually any type of equipment where temperature plays a role.
NTC temperature thermistors have a negative electrical resistance versus temperature (R/T) relationship. The relatively large negative response of an NTC thermistor means that even small changes in temperature can cause significant changes in their electrical resistance. This makes them ideal for accurate temperature measurement and control.
We said previously that a thermistor is an electronic component whose resistance is highly dependent on temperature so if we send a constant current through the thermistor and then measure the voltage drop across it, we can thus determine its resistance at a particular temperature.
An NTC thermistors reduces its resistance with an increase in temperature and are available in a variety of base resistances and temperature curves. NTC thermistors are usually characterised by their base resistance at room temperature, that is 25oC, (77oF) as this provides a convenient reference point. So for example, 2k2Ω at 25oC, 10kΩ at 25oC or 47kΩ at 25oC, etc.
Another important characteristic of a thermistor is its “B” value. The B value is a material constant which is determined by the ceramic material from which it is made. it describes the gradient of the resistive (R/T) curve over a particular temperature range between two temperature points. Each thermistor material will have a different material constant and therefore a different resistance versus temperature curve.
Then the B value will define the thermistors resistive value at a first temperature or base point, (which is usually 25oC), called T1, and the thermistors resistive value at a second temperature point, for example 100oC, called T2. Therefore the B value will define the thermistors material constant between the range of T1 and T2. That is BT1/T2 or B25/100 with typical NTC thermistor B values given anywhere between about 3000 and about 5000.
Note however, that both the temperature points of T1 and T2 are calculated in the temperature units of Kelvin where 00C = 273.15 Kelvin. Thus a value of 25oC is equal to 25o + 273.15 = 298.15K, and 100oC is equal to 100o + 273.15 = 373.15K, etc.
So by knowing the B value of a particular thermistor (obtained from manufacturers datasheet), it is possible to produce a table of temperature versus resistance to construct a suitable graph using the following normalised equation: