Instant hot water heater automatic constant temperature experiment circuit diagram
The hot water heater at home has been used for many years, but every time the bath is bothering, the water temperature control of the water heater is divided into 9 files. From 1 to 9. The higher the number the greater the temperature, normally it should be a good use. However, water flow can also dominate the temperature of the water and often cause temperature to go out of control. E.g. reduced pressure results in water becomes small, the heat is not taken away instantly by water, the temperature inside the heater (protection) will switch from the control. You will be hot very hot for a while, after the torture suffered another cold water, very hard to accept.
In order to change this situation, I added a simple temperature control circuit to control the heating time of the original circuit, that is, duty cycle. The effect is satisfactory, especially the temperature (protection) switch inside the water heater has never been operated again and is very comfortable.
The temperature sensor in the circuit is an old-fashioned thermistor. Because the resistance value is a little small, a germanium diode is added to it.
The main components used in the water heater circuit are: ULN2003AN, 7805/7812, BTA41600B, JQX-15F, HMS87C1202A, MOC3021