In our previous post, we designed a Refrigerator Door Open Alarm Circuit with IC 555 but however, in this post, we design a Simple LDR Based Refrigerator Door Warning Circuit without using any IC. Moreover, this circuit helps to alert the user when the fridge door stays open for a long time, as this simple […]
Dual Threshold Voltage Comparator Circuit using IC LM741
A dual limit comparator is an important electronic circuit which compares one input voltage with two fixed voltage levels. In simple words, this Dual Threshold Voltage Comparator Circuit using IC LM741 checks whether the input voltage stays within a fixed range and it also checks whether the voltage crosses the upper limit or the lower […]
Simple AC Mains Presence Indicator Circuit
An Simple AC Mains Presence Indicator Circuit helps us check whether AC mains supply is present at the input and whether power reaches the load side. This circuit is easy, low-cost and very useful for home appliances, control panels, extension boards and industrial systems. In this circuit, two LEDs show two different conditions, first LED1 […]
Three LED Blinking Circuit with NPN Transistors
This article is for Three LED Blinking Circuit with NPN Transistors that uses 3 NPN transistors, resistors, capacitors and a 9V battery, which works as an astable multivibrator, so it does not need any external clock signal. Instead, the circuit creates its own oscillation, because of this, the LEDs alternately flash ON and OFF at […]
Current to Voltage Converter Circuit using Op-Amp
This simple Current to Voltage Converter Circuit using Op-Amp helps convert small input current into easy measurable voltage output. This circuit is very useful to measure current from sensors like photodiodes, LDR modules and other low current devices, the main work of this circuit is to change input current into proportional voltage, so we can […]
Mini Light Intensity Meter Circuit using LDR
Here, is very simple and useful mini light intensity meter circuit using LDR which uses one LM334 IC, one LDR, small analog milliamp meter and 1.5V battery or power supply. The circuit checks light level by changing meter current as per LDR resistance. When light increases, LDR resistance changes so meter needle moves, because of […]