Free electronic circuit design and schematic diagram
A battery threshold indicator circuit shown in the schematic diagram below has current regulation mechanism in driving the LED. A sufficient current should be satisfied at the minimum voltage but no excessive current when the voltage is at the highest level. Balance pin (5) is used as the reference voltage for regulating the current. This pin generate 23 mV, which […]
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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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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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We can make a very simple battery monitor using a dual-colour LED and a few additional components. When the red and green LEDs are illuminated, the LED produces orange. The following battery monitor circuit turns on the red LED below 10.5v. The green LED illuminates above 11.6v. The orange LED illuminates between 10.5v and 11.6v. This simple battery monitor circuit […]
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Three separated LEDs is used on this battery monitor circuit. For red LED, it’s turn on from 6v to below 11v and turns off above 11v. For the orange LED, its illuminate between 11v and 13v and turns off above 13v. The green LED illuminates above 13v. This battery indication is suitable for monitoring your car battery condition. Green indicate […]
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Current handling capability of a power supply system often needed to be checked. Finding high power rated variable resistor to provide variable load testing might be difficult. There is wire wound type but it’s not always available at your local store, and the price and performance might be disappointing. This variable high power “resistor” uses 2N3055 power transistor to provide […]
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