Very Simple Power Failure Light Circuit

This simple circuit has many uses, from lighting up rooms and walkways in the case of a power failure, to monitoring and security uses. This circuit is a very basic power failure lighting circuit based around a relay. Here’s the figure of the circuit;

 

There are many different power failure circuits out there based on 555 timers or transistors but they all have different problems including limited input voltage, price and complexity, and poor backup power. This unit has been designed to work with mains power all the way down to 5 volts, and power 3 LEDs to provide light for a hallway or a child's room in the event of power failure. The PCB includes many simple add-ons and modifications too. This circuit is connected to ac power through J1 then rectified to dc through D1-D4. D5 is a 12 volt zener diode being used along with the resistor R1 and the coil resistance of relay RL1 to regulate the input voltage to 12 volts and C1 is used to help smooth this power. Alternatively a dc voltage of 5 volts or more can be connected directly to J2 and J3, positive to J2 and negative to J3; in this setup the circuit would not need J1, D1-D5, and R1. The relay RL1 is a SPDT 5vDc relay and when power is applied to it, it opens the circuit with the LEDs so they are off as long as power is on if the power goes off, the relay closes the circuit and the battery BAT1 powers the LEDs D6, D7, and D8. In this circuit BAT1 is a 9 volt battery that powers the 3 LEDs through R3; however BAT1 can be many different batteries depending on your needs. J4 is also available in parallel with the LEDs to connect a buzzer or etc.

Simple 300W Lamp Dimmer Circuit

Here’s the figure of the circuit simple lamp dimmer uses only a Triac, a Diac and some other passive components to achieve power control on lamp . It is suitable for 230V incandescent lamps with a total power of up to 300 Watts.

At first triac TR1 is not conducting; C1 is charged through R1/P1 until the trigger level of diac D1 is reached. When the diac trigger level is reached (about 30 V), D1 fires and Triac TR1 is switched on. The triac will remain in conductive mode until the mains current is lower than the triac hold current at the end of the half mains period. This works for both the negative and positive mains period because both the triac and the diac are bi-directional. R1 is added to protect the potentiometer in the case of a short circuit. The fuse is absolutely mandatory as the discharge arc in a failing incandescent lamp is virtually a short circuit.

FM Radio Using TDA7000

Here’s a design simple circuit using TDA7000 that can build an FM radio with a minimum of components; most of them so easy to manage, like the ceramic capacitors that do not require polarization and only two resistors. Here’s the figure of the circuit;

The components you will employ will be of small dimensions and low cost. Even the integrated circuit itself, the TDA 7000, is not of great cost.

Dual Relay Driver Circuit

Here’s a design circuit for a simple and convenient way to interface 2 relays for switching in dual relay driver circuit. This is the figure of the circuit;

This circuit has input - 12 VDC @ 84 mA, Output - two SPDT relay. Power Battery Terminal (PBT) for easy relay output connection is a one part in there. The circuit has four mounting holes of 3.2 mm each.

DIY Water Usage Meter Circuit

Here’s a design circuit for measure water usage. This is a simple circuit. Here’s the figure of the circuit;

 

Working with the interaction design team, a bunch of us at Teague have been tinkering with measuring water, analyzing usage data in real time to affect behaviors, and storing it to see patterns over time. At the heart of the exploration was a need to cheaply measure water from the tap. Water meters vary quite drastically in price (from $250+ for industrial grade sensors to $6 for garden hose attachments that limit total usage based on rough estimates). We settled on a $20 water meter used for PC cooling systems (the INS-FM17N by Koolance) due to its accuracy, low price, small size, and electronic sensing method that could be easily measured by a microcontroller.

Simple Touch Switch Using 4050 CMOS Buffer

Many efforts has been made to make simpler circuit, and here is one result, a very simple touch switch.  You can build up to 6 similar circuit using only one 4050 chip. If you touch the “on” pad, the output will be on remains on until you or some one the “off” pad. This is the figure of the circuit;

 

When the power supply is first applied, the output will be high because C1 capacitor trigger the buffer gate, after the output get high then the input will not depend on the C1 charging anymore because it maintained by the R1 that connect the output to supply voltage level. When the output is high, although the input is connected to the output via R1, if you touch the “off” pad, then the voltage of the input pin will be low because your skin resistance (below 1Mega Ohm) is much lower than R1 resistance (10 Mega Ohm). Because now the input is low, then the output will we low. Releasing your finger doesn’t switch back the output because now the input is connected to ground by the output via R1. If you touch the “on” pad when the output is low, the input pin will be high because your skin resistance is much lower than its output grounding via R1. After the input goes high then the output will switch to high and now the output will maintain the input remain high after the touching gone, via R1.

Simple Digital Ammeter Circuit Diagram Using DMS-30PC-0-RS

This is a design circuit for a simple Digital Ammeter Circuit Diagram using DMS-30PC-0-RS from Murata Power Solutions. This digital ammeter is basically a very sensitive voltmeter with a typical input range of ±200mV. The circuit below depicts that the voltage across the shunt is only 0.1Vdc above pin 3 (5V RETURN). This is the figure of the circuit;

This is well below the ±2V common mode voltage limitation of the meter. The 0.1Ohm shunt, with 1.0 Amperes through it, will develop 0.100Vdc or 100mV across it.