More Complex Chasing Light Controller Using Relays

Producing More Perceptible Light Movement And Lowering The Power Consumption Chasing light controller presented in our previous light controller circuit has very simple design. It control three lamp power lines to make moving light effect by turning on two lamps and turning off one lamp in sequences. Now I have designed new moving light controller circuit which turning on only […]

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Small Audio Power Amplifier Using Op-Amp and Two Transistors

Sometimes we need small power amplifier circuit while we have unused op-amp section in one of our applied chip. Instead of adding more IC (such as LM386 or similar devices), adding  two small transistor and several passive components can be cheaper solution if we can employ the unused op-amp section. Using two small transistors (2N3904 and 2N3906), we can build […]

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Small Audio Power Amplifier Using 3 Transistors

Amplifier Circuit

For some simple applications such as toys, intercom, or small gadgets, there is sometimes a need for small, simple, low cost, or low voltage solution of power amplifier circuit. For this requirement, high fidelity is rarely needed. A modification of amplifier circuit from Bowden’s circuit collection is presented in our article, completed with the guidance on how to modify for […]

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Chasing Lights Controller Circuit Using Relays

Chasing Light Controller Using Relays

Introduction to Chasing Light Running lights or chasing light is very attractive for advertisement display. A sequence of on-off at minimum three lamps gives an effect of moving lights. These three lamps then can be extended by paralleling the wire to give long bulbs chain. Modern lighting control system might have micro controller  inside for complex lighting pattern, but here […]

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Continuous Frequency Sweeping Alarm Circuit for Ambulance or Police Siren

Assembled Alarm Circuit

Sweeping out the frequency of an alarm that produce continuous spectrum has some benefits. First, it improve the alertness of the signal since people normally get alerted on the perception of “change”, and it works for almost any signal (audio, visual, thermal, etc.). Second, sweeping the frequency makes sure that  all people will get their sensitive spectrum covered. With these […]

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Simple Running LED / LED Chaser Circuit Using 3 Transistors

Running LED CIrcuit Diagram

Running/Chasing LED Circuits on The Web Running LED circuit, or sometimes called LED Chaser circuit, has very popular implementation using 4017 integrated circuit (IC). Almost all electronic websites has the circuit in their list of schematic diagram collection, you can check this dancing light circuit for example. The circuit based on that IC, is very flexible since its speed can […]

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Classic Flip-Flop Lamps Circuit and How It Works

Flip-Flop Circuit Diagram

Introduction When I learned about electronics in the past, trying to understand how circuit works by reading theories and practicing by building the circuit, the first one excited me was the  flip-flop lamp circuit. The invention of this circuit might be rooted back to 1918, when William Eccles and F. W. Jordan build the first flip-flop circuit using vacuum  tube, […]

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Flasher Circuit with DPDT Relay Works for Any-Wattage Load

Simple DPDT Relay Flasher Circuit

Introduction Classic series relay flasher circuit usually need minimum wattage for the connected load to work. Beyond the specified minimum wattage, then the flasher will not work or become unstable. Here I designed a simple solution using DPDT relay, that works for loads with any wattage. The Circuit and How It Works The circuit need one DPDT relay, two resistors […]

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Classic Alarm Circuit Employs Class-C Aamplifier for More Power

Picture of Assembled Alarm Circuit

Basic alarm with small transistors presented in our previous alarm circuit article is usually enough for toys, but we might need more power if we wanna use it for automotive or industrial application. If you usually see class-c amplifier application in radio frequency circuit, then we will show you how it can be applied in audio circuit as well. From […]

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Classic Two Transistor Alarm

Assemble Alarm Circuit

A very simple alarm circuit can be built using two transistors and several passive components. We don’t know who is the inventor of this circuit, but it usually presented in many old electronics books, so let’s call it “classic”. This simple circuit implement complete function of an alarm, which is nothing more than an oscillator  with high enough power to […]

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Simplest Relay Flasher Circuit with Better Stability

A flasher circuit with only three components (relay, capacitor, and resistor) is very popular design, which is advertised as the simplest design for relay flasher. I don’t know who is the designer of this circuit but the schematic diagram is spread on many websites. Here is one example, using 12V relay, 220Ω, and 2200uF capacitor for building 12V flasher circuit. […]

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Lamp Flasher Circuit Using Two Relays

Lamp Flasher Circuit Lamp flasher circuit is an electronic device that control a lamp to flash in periodic manner. Lamp flasher can be designed using semiconductor or other active components. Here we use two relays as the active components, plus some other passive components. Relay can be considered as an active component since it receives small power input to control […]

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