Do-it-yourself thermostat for a heating boiler, diagram

It is difficult to imagine a modern heating boiler without the use of a thermostat. This device turns the device on and off when certain temperatures are reached. Currently, thermostats have a complex structure with control buttons or touch screens. They can set temperature conditions depending on the date and time. Devices with remote control and Internet connection are also available for sale. However, a simple thermostat for a heating boiler with your own hands, the circuit can be assembled by any home craftsman who knows how to hold a soldering iron in his hands.

Simple thermostat device

Most often, a simple thermostat consists of the following elements:

• temperature sensor;
• actuator;
• threshold scheme.

Resistance thermometers, thermistors, thermal relays and other semiconductor devices can be used as temperature sensors.

The simplest circuit of this device is a device based on bipolar transistors. The temperature sensor here is a thermistor that changes the resistance depending on the temperature conditions.

Potentiometer R1 sets the bias of thermistor R2 and potentiometer R3. Based on the adjustment, relay K1 is activated when the resistance of the thermistor changes. The diode protects the output transistor from voltage surges.

ATTENTION! Before making a thermostat, it is recommended to study all the information in more detail. Since you can often see on the Internet a discrepancy between the description and the diagram.

Thermostat diagram for heating boilers

Correct calibration is important for the device to function properly. For self-production, it is most convenient to use the following diagram.

In this device, the zener diode is the K561LA7 microcircuit. The temperature is set by variable resistor R2. The voltage is supplied to the 2I-NOT converter, then transferred to capacitor C1.

In this scheme, the operating principle is quite simple:

• when the temperature drops, the voltage in the relay increases;
• When the temperature reaches a certain value, the relay is activated.
• The power supply can be any power supply operating in the range from three to fifteen volts.

ATTENTION! Before installing homemade devices, you should make sure they are working correctly. Otherwise, this may lead to equipment failure.

As you have seen, making a thermostat for heating boilers can be done at home. To do this, it is enough to be able to read simple diagrams and use a soldering iron. This way you can assemble the device yourself without extra costs.