LED lighting display detection circuit with overload protection

This article introduces a detection circuit for LED light-emitting display that can play a major role in solving problems in some physical demonstration experiments . As shown in the figure below, A and B in the circuit are the current input terminals to be measured. Transistors VQ1, VQ3 and VQ2, VQ4 respectively form common-emitter direct-coupled DC amplifiers on both sides, and light-emitting diodes VD1~VD5 and VD6~VD10 serve as display components for current in both directions. When the measured current flows from input terminal A to B, the base potential of transistor VQ2 decreases, the operating current decreases, and then VQ4 is cut off, and the light-emitting diodes VD6~VD10 do not emit light without operating current. At this time, the base potential of VQ1 increases, causing VQ1 and VQ3 to be in an amplified state. Sufficient current flows through the collector of VQ3, and the light-emitting diodes VD1~VD5 conduct and emit light for display. The brightness and number of light-emitting diodes are approximately proportional to the current flowing through the input end. That is, when the input current is small, the number of LEDs emitting light is small and the brightness is small; when the input current is large, the number of LEDs emitting light is large and the brightness is high. When the input current changes from small to large, the light-emitting order is VD1, VD2~VD5, and the brightness increases from small to large accordingly; when the input current changes from large to small, the brightness of the light-emitting diode correspondingly dims until it goes out, and the order is VD5, VD4 ~VD1, more vivid and intuitive. When the input current B flows to A, the operating current of the transistors VQ1 and VQ3 decreases, the light-emitting diodes VD1~VD5 do not emit light, while VQ3 and VQ4 are in the amplified state, and the light-emitting diodes VD6~VD10 light up and display. The process is the same as the aforementioned process. By working correspondingly on both sides of VQ1, VQ3, VD1~VD6 and VQ2, VQ4, VD6~VD10, the magnitude and direction of the measured current are clearly displayed. In order to meet the needs of demonstration experiments, 3 range gears are available for selection, and there is diode overload protection.