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Sunday, May 26, 2013

Three sirens in one Circuit

This is a siren circuit diagram Here I have used UM3561 circuit diagram.This circuit can be operated with 3V.It can generate 3 sirens.Here I have used IC 2SC9013 you can use the same IC or similar IC. Use 8ohm 0.2W speaker.

Note:-

* Dont use more than 3V
* Dont use this for unnecessary things
* Build this circuit on a PCB

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Tuesday, April 9, 2013

IC LM 386 Datasheet Explained in Simple Words

The IC LM386 is a 8-pin tiny power amplifier chip, specially made for operating under relatively low voltage parameters, yet provide considerable amplification. It becomes suitable for applying in small low power audio gadgets like in FM radios, door bells, telephones etc.

Lets begin the IC LM386 datasheet explanation by studying its absolute maximum ratings first, meaning the parameters which should not be exceeded while using this IC in any circuit:

Supply Voltage: Max. 15V (Typical)

Input Voltage: +/- 0.4 volts

Storage Temperature: -65 degrees to +150degrees Celsius

Operating Temperature: 0 to 70 degrees Celsius

Power Output: 1.25 watts

IC manufactured by:

How to Control Gain for the IC LM386

In order to make the IC better with its response, its pin#1 and 8 have been attributed with a gain control facility which may be set externally.

Gain simply means the capacity or the amplifying level of the device up to which it is able to amplify the applied input low signal audio input.

When the above pin outs are kept unconnected to anything, the internal 1.35K resistor sets the gain of the IC to 20.

If a capacitor is joined across the above pin outs, the gain is suddenly lifted to 200.

The gain may be simply made adjustable by connecting a pot in series with the above explained capacitor across the pin 1 and 8.

Practical Amplifier Circuit Diagrams Using the IC LM386

The following figure shows a typical LM386 amplifier circuit having the bare minimum number of components required to make the IC operate at its internally set level of gain 20.
The speaker used is a 2 watt, 8 Ohms type.
The input at Vin may be fed from any audio source such as a cell phone headphone socket, a CD/DVD player RCA L or R socket or any other similar source.

The pin Vs should be connected to +12V DC supply from an AC DC adapter or a home made transformer/bridge power supply unit.

Pin #4 should be connected to ground or the negative of the power supply.

The earth wire or the negative wire from the input audio source should also be connected to the above negative of the power supply.

The input pin#2 goes to a 10K pot which becomes the volume control, one of its end terminals is picked for receiving the input signal while the other end is connected to ground, the center one goes to the hot end of the IC.

The speaker is connected to in #8 via a high value blocking capacitor, the resistor/capacitor arrangement connected across pin #5 and ground has been included for frequency compensation and to provide greater stability to the circuit.

The next circuit shows a similar design as above, except that its pins 1 and 8 have been connected to a capacitor of 10uF, which as explained above helps to pull the gain of the amplifier to 200

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Sunday, April 7, 2013

LCD Module in 4 bit Mode

In many projects use is made of alphanumeric LCDs that are driven internally by Hitachi’s industry-standard HD44780 controller. These displays can be driven either in 4-bit or 8-bit mode. In the first case only the high nibble (D4 to D7) of the display’s data bus is used. The four unused connections still deserve some closer attention. The data lines can be used as either inputs or outputs for the display. It is well known that an unloaded output is ﬁne, but that a ﬂoating high-impedance input can cause problems. So what should you do with the four unused data lines when the display is used in 4-bit mode? This question arose when a circuit was submitted to us where D0-D3 where tied directly to GND (the same applies if it was to +5 V) to stop the problem of ﬂoating inputs.

The LCD module was driven directly by a microcontroller, which was on a development board for testing various programs and I/O functions. There was a switch present for turning off the enable of the display when it wasn’t being used, but this could be forgotten during some experiments. When the R/Wline of the display is permanently tied to GND (data only goes from the microcontroller to the display) then the remaining lines can safely be connected to the supply (+ve or GND). In this application however, the R/Wline was also controlled by the microcontroller. When the display is initialised correctly then nothing much should go wrong. The data sheet for the HD44780 is not very clear as to what happens with the low nibble during initialisation.

Circuit diagram :
LCD module_in_4-bit_Mode_Circuit_Diagramw

LCD Module in 4-bit Mode Circuit Diagram

After the power-on reset the display will always be in 8-bit mode. A simple experiment (see the accompanying circuit) reveals that it is safer to use pull-down resistors to GND for the four low data lines. The data lines of the display are conﬁgured as outputs in this circuit (R/Wis high) and the ‘enable’ is toggled (which can still happen, even though it is not the intention to communicate with the display). Note that in practice the RS line will also be driven by an I/O pin, and in our circuit the R/W line as well. All data lines become high and it’s not certain if (and if so, for how long) the display can survive with four shorted data lines. The moral of the story is: in 4-bit mode you should always tie D0-D3 via resistors to ground or positive.

http://www.ecircuitslab.com

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