The regulator, the description of which is given in this article, was developed and manufactured at the request of a fellow owner of a ZIL 5301 (“Bull”) truck. The need to rework the heater fan speed control is due to the fact that the standard heating system of this car has only 2 interior heating modes - medium and maximum. The regulator developed by the author has 5 stages of heating regulation, and the set level is saved in the memory of the regulator microcontroller when the ignition is turned off. This regulator can also be used to replace mechanical heater fan speed switches with ballast resistors in other cars with an on-board 12 V power supply.
To heat the interior in modern cars, coolant is used as a coolant, which heats up, taking away thermal energy from the running engine.
Behind the front panel of the cabin there is a separate radiator connected to the engine cooling system, to which two pipes are connected for circulating coolant (antifreeze, antifreeze, or water) in this radiator. To control the temperature, a tap is installed on the inlet pipe of the stove. A fan located behind the heater radiator drives air from the engine compartment through the radiator into the cabin, where warm air enters. When the heater switch is set in the red zone, the tap opens and the heated coolant (coolant) flows from the engine cooling system into the heater radiator, depending on the position in which this switch is set (from “Off” to “Hot”). Car enthusiasts know that the heater tap is short-lived and does not always work reliably. Therefore, it was decided to regulate the temperature in the car interior by changing the speed of rotation of the fan screw using an electronic controller.
The electrical circuit diagram of a car heater fan speed controller is shown in Fig. 1.
The regulator is assembled on a microcontroller IC2 type from Microchip in a DIP-8 package. The pin assignments of microcontroller IC2, taking into account the software, are shown in the table.
The microcontroller is clocked by an internal clock generator (INTOSC) of 4 MHz. The speed controller is powered from the ignition switch through a 5 V voltage regulator on an IC1 type chip.
The device provides five levels of speed control with indication on 5 LEDs, which are controlled by a signal from pin 5 of IC2 through an IC3 type shift register in a DIP-14 package. Clock pulses are sent from pin 6 of IC2 to pin 8 of IC3.
When switched off, all device LEDs are off. When the 1st level of stove speed is turned on, LED1 is on, when the 2nd level is on, LEDs LED1 and LED2 are on, etc., and when the 5th level is on, the line of all 5 LEDs is on. Speed adjustment is made using the UP and DOWN buttons. These buttons discretely change the duration of the pulses on pin 7 of the microcontroller IC2 (PWM method), to which the Q2 heater motor control key is connected. Since the PIC12F629 microcontroller does not have a hardware PWM module CCP (Capture/Compare/PWM), PWM is organized in software. To avoid the characteristic “sound” of the electric motor of the stove, the PWM frequency is raised to 22 kHz.
When the ignition is turned off, the previously set level of rotation speed of this engine is stored in the non-volatile memory of MK IC2. The stove engine turns on 3 seconds after turning on the ignition and runs at the speed the level of which was saved in the MK memory. Since the cabin of the ZIL 5301 car is quite noisy, a five-volt electromagnetic buzzer (Magnetic Buzzer) SP1 type KX-1205 is used to sound the button presses, which is turned on by a key on the field-effect transistor Q1 type BS170 by command from pin 2 of IC2.
The device is assembled on a printed circuit board made of single-sided foil fiberglass laminate measuring 50x46 mm (see photo at the beginning of the article). The drawing of the printed circuit board is shown in Fig. 2, and the location of the parts is shown on this board in Fig. 3.
The program for the microcontroller is written in assembly language. The program source file, firmware file, files for the Proteus program, as well as printed circuit board drawings in the Eagle program format are available for download via the link.
For self-assembly, we offer a proven heater motor speed controller circuit for almost any car.
1 . When power is turned on, the last selected power is set. LED_0 indicates the device is ready for operation. LEDs LED_1 - LED_10 display the set fan power.
2 . Change power using the PLUS/MINUS buttons.
3
. Setting the speed of power change.
3.1. Press the PLUS and MINUS buttons simultaneously.
3.2. LED_0 will start flashing. The number of power LEDs turned on corresponds to the selected speed.
3.3. Use the PLUS/MINUS buttons to change the speed.
3.4. To exit the mode, press the PLUS and MINUS buttons simultaneously again. LED_0 will stop flashing.
Note: the indication is reversed. The more LEDs turned on, the lower the rate of change in power. The rate of change of power can be recorded when flashing the MK into the EEPROM cell with address 0x00. The number must be no more than 10 (or 0x0A in hex format). If the number is greater, then the default value of 5 is taken.
4 . After ~3 seconds from the last button press, the new settings will be written to non-volatile memory.
“On my car, the heater engine speed controller burned out. The original costs about $300, so I decided to make it myself. I made several PWM controllers. I think the most successful was the controller, the circuit of which was developed by V.N. Kravtsov, for which I thank him very much. I I previously posted a regulator circuit from BMW, but there is a problem - the transistor heats up at high currents. The fact is that MOSFET transistors are completely open, while at the drain-source junction there is minimal resistance, when a voltage of about 30 volts is applied to the gate. This option is implemented Kravtsov V.N. The circuit practically does not need adjustment. There is another interesting circuit, where a DS0026 microcircuit is used to increase the gate voltage, which I could not purchase. If anyone has an MS, I will send the circuit."
Regulator board for commutator motor. The scheme was developed by V.N. Kravtsov. www.kravitnik.narod.ru
Mirror seal
The board is designed for the heater fan control unit of a Mercedes C240 car body W203 Dimensions 46 by 76 mm.
Another diagram of the engine speed controller for the heater fan MB W140, W240
Regulator circuit
