Free electronic circuit design and schematic diagram
The temperature of a quartz crystal for oscillator should to be kept constant to operate at very stable frequency. This oven temperature controller is suitable for such purpose. Here is the schematic diagram of the temperature control circuit: Although this circuit is small and simple, the design use a PWM output to preserve the efficiency. The circuit uses LM335 temperature […]
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LM56 is a monolithic thermostat designed for simple temperature control. The chip has two programmable threshold that can be used to drive a fan and or alarm. Here is the schematic diagram of the fan control circuit: The circuit will turn on the fan when the temperature rise above 50 Celsius degree, and this threshold is set by the voltage […]
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Thermocouples give many benefits compared to thermistor/RTD (Resistance Temperature Devices). Some advantages of thermocouple are their wider temperature range, their reliability, and their consistency over long period of time. In some cases, thermocouple calibration is even unnecessary. Thermocouple temperature sensors are widely used in temperature controllers for boilers, oven, pressurized reactor, even in high temperature furnace. A general purpose temperature […]
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Current loop interface has been widely used in industrial environment because it’s robustness. Noise resistance and fail detection capability made it suitable for long distant transmission in harsh environment. This circuit provide current loop transmitter for temperature sensor. Here is the circuit’s schematic diagram: The temperature measurement is done by LM35 temperature sensor chip. You can use general silicone diode […]
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If you send a DC voltage signal to carry the information for a long distance, then the signal will suffer attenuation with unpredictable characteristic introduced by the medium, for example the cable resistance that vary with temperature changes. If you carry the information with frequency, not a DC voltage level, then the frequency will be stable even though it’s amplitude […]
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If you have a digital voltmeter, or any voltmeter with millivolt resolution and high input impedance, then you can use this temperature-to-voltage adapter circuit to measure room temperature. Here is the circuit’s schematic diagram: Note that the voltage output of this circuit is floating, not referenced to ground. You have to use separate supply if your voltmeter has single ended […]
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