通过互连单个晶体管，二极管和少数其他无源部件，可以构建非常简单的温度指示器电路。
Using Transistor as a Heat Sensor
As we know that all semiconductors have this "bad habit” of changing its basic characteristics in response to ambient temperature changes.
特别是晶体管和二极管等基本的电子元件容易发生它们的壳体温度变化。
The change with their characteristics with these devices is typically in terms of the passage of voltage through them, which is directly proportional with the magnitude of the temperature difference surrounding them.
使用晶体管（BJT）作为温度传感器
In the present design a diode and a transistor are configured in the form of a bridge network.
As both these active parts have identical properties as far as ambient temperature changes are concerned, they both complement each other.
使用二极管进行参考电压
二极管是地方的reference device while the transistor is connected to perform the function of a temperature sensor.
显然，由于二极管被放置为参考，因此必须放置在具有相对一致的温度条件的环境中，否则二极管还将开始改变其参考电平导致误差在指示过程中的误差。
这里在晶体管的集电极处使用LED，其直接解释晶体管条件，从而有助于显示晶体管周围发生的温差。
LED表示温度变化
LED用于获得晶体管感测的温度水平的直接指示。在该设计中，二极管放置在环境温度或室温下，晶体管放置或附接到需要测量的热源。
晶体管的基本发射极电压与D1和R1的结二极管产生的二极管产生的参考电压电平有效。
This voltage level is taken as the reference and the transistor remains switched OF as long as its base emitter voltage remains below this level. Alternatively this level may be varied by the preset P1.
现在当晶体管上的热量开始上升时，它基础发射器由于晶体管的特性改变而开始上升。
If the temperature crosses the preset value, the base emitter voltage of the transistor exceeds the limit and the transistor starts conducting.
LED逐渐开始亮起，并且其强度与晶体管传感器上的温度成比例。
Caution
Caution must be maintained, not to exceed the temperature over the transistor above 120 degree Celsius, other wise the device may get burnt and damaged permanently.
可以进一步修改所提出的简单温度指示器电路以使其在响应于感测的温度水平开启或关闭外部设备。
如何计算温度阈值
我会在我的第四篇文章中讨论它。使用以下公式计算配置的电阻值：
R1 = (Ub - 0.6)/0.005
R2 =（UB - 1.5）/ 0.015
这里UB是输入电源电压，0.6是BJT的正向电压降，0.005是BJT的标准工作电流。
Similarly, 1.5 is the forward voltage drop for the selected RED LED, 0.015 is the standard current for illuminating the LED optimally.
计算结果将是欧姆。
P1的值可以是150至300欧姆之间的任何位置
录像片段
嗨主席先生，我想检查你如何使用温度电路来检测水温，如果水温高，继电器将打开风扇以进行冷却目的。谢谢！
I have a simple circuit from my school textbook and i have made it out. i have a problem now is that i don't know how to set the 2 variable resistor to make the circuit work. i may need to send you the circuit diagram, can i send it thru email to you?
是的，您可以通过电子邮件发送或上传任何免费图片托管站点，并提供给我的链接。
给我发了一封电子邮件styleang@gmail.com如果可能的话。谢谢先生！
sir, can i use diode NI5408 for this circuit?
是的，你可以使用它。
我可以连接蜂鸣器@ 100c
buzzer will not work properly
预设的评级是什么？
Can this be used to indicate water temperature? Can a sl100b transistor be used?
yes it can be used for indicating water temp
Please tell me how can I get heat in the range of 45 deg. to 50 deg.
Please sir, how to make it to automatically on/off an appliances and how to calculate the temperature value. Thanks
你可以尝试这个
https://www.homemade-circuars.com/how-to-build-simple -electronic/
sir I get 2280 for R1 ,and 700 for R2 respectively.
are the values in kilo ohms or just ohms ,
and can I use _TIP41 For the transistor and IN4007 For the diode? ,am thinking of placing the transistor as close as possible to the heatsink of my amplifier bolting it beside the chip.
Shedies,
The results will be in Ohms.
Tip41是功率晶体管，并且可能不适合于该应用，同样适用于1N4007二极管。
You can use BC547, 2N2222, 8050 for the transistor, etc. For diode only 1N4148 is recommended for a perfect response.