DoorBell circuit using UM 66 IC

DoorBell circuit using UM 66 IC

Doorbell Circuit

Description

Here is a simple and easy to build doorbell circuit using IC UM 66.The  details of UM 66  is given in the older post “Melody Generator using UM 66″. This is a slight modification of that circuit.In the previous circuit you have to keep the switch pressed for making the IC play the full music.Here if once the push button is pressed C1 is charged and the transistor Q2 will keep the IC playing the music till it ends.The time for the IC to play depends on discharging time of C1  which can be set by R1.Set R1 to select your time ,whether full tone or a part in one press.Transistor Q2 drives the speaker.

Doorbell Circuit Diagram with Parts List

Notes

• Do not give more than 4.5 V to UM 66.
• POT R2 is not necessary and can be bye passed .But if included you can set the loudness.

We have many other Tone Generator circuits that you may like take a look:
1. Tone Generator
2. High Power Siren Circuit
3. Melody Generator
4. Doorbell Circuit using 555 Timer
5. UJT Organ Circuit

Low cost / Automatic Emergency Light

Low cost / Automatic Emergency Light
author: Izhar Fareed - izhargmx.us - extremecircuits.net

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Description

Here is a white-LED-based emergency light that offers the following advantages:

1. It is highly bright due to the use of white LEDs.
2. The light turns on automatically when mains supply fails, and turns off when mains power resumes.
3. It has its own battery charger. When the battery is fully charged, charging stops automatically.

The circuit comprises two sections: charger power supply and LED driver.The charger power supply section is
built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver section is built around transistor BD140(T2). In the charger power supply section, input AC mains is stepped down by transformer to deliver 9V, 500mA to the bridge rectifier, which comprises diodes (IN4007x4). Filter capacitor (25v/1000uf)eliminates ripples. Unregulated DC voltage is fed to input pin 3 of IC1 and provides charging current through diode IN4007(D5) and limiting resistor (16ohm)R16. By adjusting preset 2.2K(VR1), the output voltage can be adjusted to deliver the required charging current. When the battery gets charged to 6.8V, zener diode conducts and charging current from regulator (IC1) finds a path through transistor BC547(T1) to ground and it stops charging of the battery. The LED driver section uses a total of twelve 10mm white LEDs. All the LEDs are connected in parallel with a 100-ohm resistor in series with each. The common-anode junction of all the twelve LEDs is connected to the collector of pnp transistor T2 and the emitter of transistor T2 is directly connected to the positive terminal of 6V battery. The unregulated DC voltage, produced at the cathode junction of Bridge(Diodes), is fed to the base of transistor T2 through a 1k resistor. When mains power is available, the base of transistor T2 remains high and T2 does not conduct. Thus LEDs are off. On the other hand, when mains fails, the base of transistor T2 becomes low and it conducts. This makes all the LEDs (LED1 through LED12) glow. The mains power supply, when available, charges the battery and keeps the LEDs off as transistor T2 remains cut-off. During mains failure, the charging section stops working and the battery supply makes the LEDs glow. Assemble the circuit on a general-purpose PCB and enclose in a cabinet with enough space for battery and switches. Mount the LEDs on the cabinet such that they light up the room. A hole in the cabinet should be drilled to connect 230V AC input for the primary of the transformer. I have tested the circuit with twelve 10mm white LEDs.You can use more LEDs provided the total current consumption does not exceed 1.5A. Driver transistor T2 can deliver up to 1.5A with proper heat-sink arrangement.

 

Download

Download this circuit in PDF

low-cost-water-pump-controller-circuit.

Here the circuit diagram of low cost water pump controller. The automatic pump controller minimizes the need for any manual switching of water pumps installed for the functionality of pumping water from a reservoir to an overhead tank . It instantly switches on the pump once the water level within the tank falls below a specific low level (L), provided the water level in the reservoir is above a specific level (R). Subsequently, because the water level in the tank increases to an upper level (M), the pump is turned off instantly. The pump is turned on again only if the water level once again falls beneath level L in the tank, provided the level inside the reservoir is above R. This automated action
continues.

The circuit is intended to ‘overlook’ the transient oscillations of the water level that would otherwise trigger the logic to modify its state rapidly and unnecessarily. The circuit works by using a single CMOS chip (CD4001) for logic processing.

No utilization of any moving electromechanical elements within the water-level sensor has been made. This assures fast reaction, no wear and tear, and no mechanical problems. The circuit diagram can be seen on above image. The unit performed satisfactorily on a test run in conjunction with a 0.5 HP motor and pump.

The sensors applied to the circuit could be any two conducting probes, preferably resistant to electrolytic corrosion. For example, in the easiest case, a appropriately sealed audio jack could be utilized to operate as the sensor.

The circuit may also be utilized like a constant fluid level maintainer. For this objective, the probes M and L are brought pretty near to one another to make sure that the fluid level is maintained within the M and L levels.

The benefit of this system is that it could be applied to tanks/reservoirs of any volume whatsoever. Even so, the circuit can’t be applied for purely non-conducting fluids. For non-conducting fluids, some modifications have to be prepared in the fluidlevel sensors. The circuit can on the other hand be kept intact.

Read more @ Low Cost Water Pump Controller circuit ~ Todays Circuits ~ Engineering Projects | Final Year Projects | Electronics News http://todayscircuits.blogspot.com/2012/01/low-cost-water-pump-controller-circuit.html#ixzz2GcYANVsN
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Low cost Mic Mixer

Low cost Mic Mixer

admin

April - 20 - 2010

3 Comments

Description

This is the schematics of a low cost mic mixer that can be assembled from the components in your junk box.This two channel mike mixer is designed for handling high impedance dynamic microphones.Transistor Q1 can be any general purpose pnp transistor like BC177 or BC157B. Resistor R5 biases the transistor while R3 and R4 provides channel isolation. How ever better the transistor quality better the performance.  C1 and C2 performs the job of input coupling and DC isolation while C4 is the output DC decoupling capacitor.Resistors R1 and R2 can be used for the level control of input signals.

Circuit Diagram With Parts List.

Notes

• All capacitors are of ceramic type.
• Always use a battery two reduce noise .
• Avoid using power transistors for Q1. This is because power transistors have high leakage current and it adds to the noise which is not suitable for our purpose here

Low cost AM radio

Low cost AM radio

john

September - 17 - 2009

11 Comments

Description.
Here is the circuit diagram of a simple and low cost AM radio. The working of this radio circuit is straight forward. Inductor L1 and capacitor C1 forms the necessary tank circuit. Diode D1 performs the job of de-modulation. Transistor T1 is wired as a preamplifier whose output is further amplified by the IC LM386 to drive the head phone Z1. The 10K POT R3 can be used as a volume controller.
Circuit diagram.

Notes.

• The circuit can be powered from a 9V PP3 battery.
• Use a 100cm long metal wire as antenna.
• Experiment with the value of L1 for catching other bands.
• The circuit can be assembled on a Vero board.

Emergency light mini project

This is an LDR based Emergency Lamp that turns on a High watt White LED when there is darkness in the room. It can be used as a simple emergency lamp in the child’s room to avoid the panic situation in the event a sudden power failure.It gives ample light in the room.

The circuit is too simple so that it can be enclosed in a small box. A 12 volt miniature battery is used to power the circuit. Two transistors T1 and T2

 are used as electronic switches to turn on / off the white LED. When there is sufficient light in the room, LDR conducts so that the base of the PNP transistor T1becomes high and it remains off. T2 also remains off since its base is grounded. In this state, White LED remains off. When the light falling on the LDR decreases, it cease to conduct and T1 forward bias providing base current to T2. It then turns on and White LED switches on.White LED used in the circuit is 1 watt High bright Luxeon LED . Since 1 watt White LED consumes around 300 milli ampere current, it is better to switch off the lamp after few minutes to conserve battery power

Electronics For u free download

http://www.ziddu.com/download/14018038/deekshith_efy_ckts_bundle.zip.html