Free electronic circuit design and schematic diagram
When the resistance value of a temperature, light, pressure, or any other resistive sensors Rs drops below a certain point (adjusted by a preset potentiometer), the SCR (silicon controlled switch) will be triggered. The sensor (Rs) and the potentiometer placement can be interchanged to get opposite action, where the SCR need to be triggered at the increase of sensing resistor […]
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This voltage monitor has two threshold, VTH for undervoltage and VTH’ for overvoltage. Using the component values shown in the schematic diagram below, this circuit give 6V for VTH and 15V for VTH1. Above 6V, the LED indicator of this voltage monitor circuit will increase the flash rate until reach 15V. This circuit will stop flashing at voltage below 6V […]
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It will be effective to use simple half wave motor speed control with small universal ac/dc motors. Two amps RMS is the maximum current capability. The control gives excellent torque characteristics to the motor because speed dependent feedback is provided, even at low rotation speeds. By closing switch S1, thus bypassing the SCR, we can achieve normal operation at maximum […]
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A battery level indicator circuit is depicted in the schematic diagram below. This circuit is designed for 9V battery operation, as this circuit will start dimming below 7V and will be completely turned off at 6V. If you want the LED indicator not to dimming but just abruptly turns off at below 6V, then you can remove R3, and change […]
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National LM378 amplifier is used as a basis for economical proportional motor speed controller. This integrated circuit is able to deliver 700 mA continuous current for such DC motor applications such as antenna rotors or motor controlled valves. The basic of proportional control is as simple as amplifying the error signal to produce an action in such direction that minimize […]
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This circuit is two wire light level detector, we don’t separate wires for power this sensor system and for delivering the output signal. With current loop, we do both function in a single pair of cable, just provide the voltage supply and measure the current as the output signal. The core of this circuit is LM10 voltage reference and op-amp […]
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Monitoring battery voltage can be important in some application. Some battery monitor will be simply a continuous LED lamp which is dimming according to the voltage level. Here is presented monitoring circuit that flashing, which is more noticeable than simple dimming the light intensity. At 1.2V, the LED begin flashing, and the flashing rate will increase as the voltage increase. […]
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