Showing posts with label controller. Show all posts
Showing posts with label controller. Show all posts
Wednesday, November 12, 2014
Maximum Temperature Detector For Fan Controller
The fan controller circuit for the Titan 2000 and other AF heavy-duty power amplifiers, has an output that sets a voltage if the fan controller reaches the end of its range. Since the controller responds to temperature, this signal is seen by the amplifier protection circuitry as an over temperature indication. The disadvantage of this output is that the maximum voltage for the fans is not constant, but depends on the load (number of fans, defective fans) and the mains voltage. This variation is caused by the fact that the supply voltage for the output stage is taken directly from the filtered transformer voltage.![Maximum]()
If the fans should fail, for example, the maximum temperature limit would lie at a considerably higher level than the desired value. The accompanying circuit, which compares the magnitude of the fan voltage to a fixed reference value, has been developed to allow the maximum temperature to be reliably detected. This circuit is tailored for 12-V fans. The reference voltage is generated by the ‘micro power voltage reference’ D1 and the FET T1, which is wired as a current source. These components are powered directly from the applied fan voltage. The current source is set up to deliver approximately 50µA.
D1 can work with as little as 10µA. The supply voltage for the IC is decoupled by R10, C3 and C4, with D4 providing over voltage protection. A maximum supply voltage of 16 V is specified for the TLC271. This opamp works with a supply voltage as low as 3 V and can handle a common-mode voltage up to approximately 1.5 V less than the positive supply voltage. Accordingly, 1.2 V has been chosen for the reference voltage. The fan voltage is reduced to the level of the reference voltage by the voltage divider R2–R3–P1. The limits now lie at 11.2 V and 16.7V.
If you find these values too high, you can reduce R2 to 100 kΩ, which will shift the limits to 9.5 V and 14.2 V. The output of the voltage divider is well decoupled by C2. A relatively large time constant was selected here to prevent the circuit from reacting too quickly, and to hold the output active for a bit longer after the comparator switches states. A small amount of hysteresis (around 1 mV) is added by R4 and R5, to prevent instability when the comparator switches. D2 ensures that the magnitude of the hysteresis is independent of the supply voltage. Two outputs have been provided to make the circuit more versatile.
Output ‘R’ is intended to directly drive the LED of an optocoupler. In addition, transistor T2 is switched on by the output of the opamp via R7 and R8, so that a relay can be actuated or a protection circuit triggered using the ‘T’ output. The high-efficiency LED D3 indicates that IC1 has switched. It can be used as a new ‘maximum’ temperature’ indicator when this circuit is added to the fan controller. The circuit draws only 0.25 mA when the LED is out, and the measured no-load current consumption (with a 12.5V supply voltage) is 2.7 mA when the LED is on.Resistors:
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D1 can work with as little as 10µA. The supply voltage for the IC is decoupled by R10, C3 and C4, with D4 providing over voltage protection. A maximum supply voltage of 16 V is specified for the TLC271. This opamp works with a supply voltage as low as 3 V and can handle a common-mode voltage up to approximately 1.5 V less than the positive supply voltage. Accordingly, 1.2 V has been chosen for the reference voltage. The fan voltage is reduced to the level of the reference voltage by the voltage divider R2–R3–P1. The limits now lie at 11.2 V and 16.7V.
If you find these values too high, you can reduce R2 to 100 kΩ, which will shift the limits to 9.5 V and 14.2 V. The output of the voltage divider is well decoupled by C2. A relatively large time constant was selected here to prevent the circuit from reacting too quickly, and to hold the output active for a bit longer after the comparator switches states. A small amount of hysteresis (around 1 mV) is added by R4 and R5, to prevent instability when the comparator switches. D2 ensures that the magnitude of the hysteresis is independent of the supply voltage. Two outputs have been provided to make the circuit more versatile.
Output ‘R’ is intended to directly drive the LED of an optocoupler. In addition, transistor T2 is switched on by the output of the opamp via R7 and R8, so that a relay can be actuated or a protection circuit triggered using the ‘T’ output. The high-efficiency LED D3 indicates that IC1 has switched. It can be used as a new ‘maximum’ temperature’ indicator when this circuit is added to the fan controller. The circuit draws only 0.25 mA when the LED is out, and the measured no-load current consumption (with a 12.5V supply voltage) is 2.7 mA when the LED is on.Resistors:- R1 = 22kΩ
- R2 = 120kΩ
- R3 = 10kΩ
- R4,R6 = 1kΩ
- R5 = 1MΩ
- R7,R8 = 47kΩ
- R9 = 3kΩ9
- R10 = 100Ω
- P1 = 5kΩ preset
- C1,C3 = 100nF
- C2 = 100µF 25V radial
- C4 = 47µF 25V radial
- D1 = LM385-1.2
- D2 = BAT85
- D3 = high-efficiency-LED
- D4 = zener diode 16V/1W3
- T1 = BF245A
- T2 = BC547B
- IC1 = TLC271CP
- K1 = 2-way PCB terminal block, raster 5mm
- K2 = 3- way PCB terminal block, raster 5mm
Saturday, October 4, 2014
12V Fan Temperature Controller
this simple design allows|permits an correct speed control of 12V dc fan motors, proportional to temperature. A n.t.c. Thermistor (R1) is employed as temperature sensor, driving two directly coupled complementary transistors wired during a dc feedback circuit. An optional circuitry was added to remotely monitor fan operation and to permit some type of rough speed indication by means that of the increasing brightness of a LED.
Notes:
- R5 must be set to allow motor just starting at the desired temperature.
- Any n.t.c. Thermistor in the 6K8 - 22K range value might work, provided R2 value is one/tenth of Thermistors value.
- R6, R7 and D1 are optional: R7 must be adjusted until the LED glows faintly when the motor is just running.
Thursday, September 25, 2014
Central Heat Controller Circuit
This circuit is used for optimum regulation of the flow of hot water in a central heating system.
It measures the water temperature, and arranges for a particular valve or pump in the system to be switched on to achieve a user-defined temperature distribution in the home. Residual heat in the central heating system can thus be used to lower the cost of fuel. Fig. 1 shows that water in temperature range I can be used for the central heating and the storage vessel, while that in range II is also suitable for directing to the boiler. In most cases, it is not recommended to re-use water with a temperature below 30 °C. The circuit arranges for an alarm to be activated when the water temperature falls below 5°C, or exceeds 95 °C. The circuit diagram of the central heating control appears in Fig. 2. Relays Re1 and Res are activated upon measuring the maximum and minimum permissible temperature, respect- ively.
The temperature sensor is a Type LM35, which has a scale factor of +10 mV/°C. Its output voltage is amplified in At and fed to the non-inverting inputs of comparators A2-A6. The presets at the inverting input of each of these is used to set the toggle voltage, i.e., the temperature at which the relevant relay is switched on or off. The relay drivers are open-collector power buffers with built-in freewheeling diodes to afford protection against inductive surges.
The use of the Type ULN2003 makes it possible to use relays with a coil voltage of upto 50 V without the need for additional interfacing. Each temperature setting has a hysteresis of about 2 °C. Transistors T1-Ta serve to disable the previously energized pump or valve upon detecting a water temperature that falls within another, predefined, range. In this manner, only one relay is activated at a time. It stand to reason that the temperature sensor, IC1, must be mounted such that it is in thermal contact with the water in the heating system. Make sure that the device is well-insulated, and that it does not cause leakage. The temperature range settings for the presets are shown opposite.
It measures the water temperature, and arranges for a particular valve or pump in the system to be switched on to achieve a user-defined temperature distribution in the home. Residual heat in the central heating system can thus be used to lower the cost of fuel. Fig. 1 shows that water in temperature range I can be used for the central heating and the storage vessel, while that in range II is also suitable for directing to the boiler. In most cases, it is not recommended to re-use water with a temperature below 30 °C. The circuit arranges for an alarm to be activated when the water temperature falls below 5°C, or exceeds 95 °C. The circuit diagram of the central heating control appears in Fig. 2. Relays Re1 and Res are activated upon measuring the maximum and minimum permissible temperature, respect- ively.
The temperature sensor is a Type LM35, which has a scale factor of +10 mV/°C. Its output voltage is amplified in At and fed to the non-inverting inputs of comparators A2-A6. The presets at the inverting input of each of these is used to set the toggle voltage, i.e., the temperature at which the relevant relay is switched on or off. The relay drivers are open-collector power buffers with built-in freewheeling diodes to afford protection against inductive surges.
The use of the Type ULN2003 makes it possible to use relays with a coil voltage of upto 50 V without the need for additional interfacing. Each temperature setting has a hysteresis of about 2 °C. Transistors T1-Ta serve to disable the previously energized pump or valve upon detecting a water temperature that falls within another, predefined, range. In this manner, only one relay is activated at a time. It stand to reason that the temperature sensor, IC1, must be mounted such that it is in thermal contact with the water in the heating system. Make sure that the device is well-insulated, and that it does not cause leakage. The temperature range settings for the presets are shown opposite.
Monday, September 8, 2014
Simple Tactful Triac Controller Wiring diagram Schematic
Simple Tactful Triac Controller Circuit Diagram. This is the sensitive triac schema in this schema the single transistor connected between the capacitor and the common side of the ac line allows a logic-level signal to control this triac power schema. Resistor R2 prevents false triggering of the triac by the trickle current through the diac.
Simple Tactful Triac Controller Circuit Diagram
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