Free electronic circuit design and schematic diagram
Using optocoupler to directly transfer a linear (analog) voltage would produce a large unpredictable linearity error, which is also sensitive to temperature changes. By using frequency modulation, the total system’s linearity will depend only on the linearity of the V/F and F/V converter, which is fortunately cancel each other if we use similar devices with similar non-linearity error characteristic. A […]
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This is a one direction motion sensor circuit. This motion sensor circuit is used to detects an object passing in one direction, ignoring an object that going to opposite way. This circuit uses two sensors to identify the movement only in one direction. The basic principle of this circuit is simple, where one sensor is used to generate a short […]
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In the relay’s point of view, dark activated means the relay will be activated when the light intensity fall below a certain threshold. Without hysteresis, the relay will be activated and deactivated if the sensed brightness fall under or rise above a single point of darkness level. With hysteresis, the darkness level for activating and deactivating the relay will be […]
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Using LM10 amplifier and voltage reference, a light intensity meter featured with five decades dynamic range (which is suitable for photographic application) can be built. Please note that the linear to log conversion is not temperature compensated, and can make 40% error (a half stop in photography) at the worst point of conversion slope at ±18°C temperature drift. It should […]
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This is a simple 220V power interface circuit. This circuit used as interface for monitoring electric devices and equipments using a computer. The circuit only senses whether the device being monitored is turned off or on. The galvanic isolation between the AC main line being monitored and the interface to the computer is an important aspect of the circuit. We […]
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A laser diode driver can be implemented using voltage-controlled current source. This simple linear laser diode driver gives cleaner drive current than a switched (PWM) drivers. Here is the schematic diagram of the circuit: A Howland current pump with a current booster is used as the basic of this laser diode driver. Q1 is used as the current booster on […]
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