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Friday, April 12, 2013

LED Volt Meter Circuit

Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four stage LED indicators. The nominal terminal voltage of a Lead Acid battery is thirteen.8 volts and that of a Tubular battery is 14.8 volts when totally costd. The LED voltmeter uses four Zener diodes to light the LEDs at the exact breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed worth to be triumphant in the breakdown threshold degree. When the battery clings 13.6 volts or more, all the Zener breakdown and all LEDs illuminate. When the battery is discharged below 10.6 volts, the entire LEDs stay darkish. So depending on the terminal voltage of the battery, LEDs remove darkness from one after the other or flips off.

Circuit diagram:

$\"LED-Volt-Meter-circuit-diagram12\"$ LED Volt Meter Circuit Diagram

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Wednesday, April 10, 2013

Make an Efficient LED Emergency Light Circuit

The article describes a very simple homemade emergency light circuit that can be used during power failures and outdoors where any other source of power might be unavailable. The circuit uses LEDs instead of incandescent lamp, thus making the unit very power efficient and brighter with its light output. Moreover, the circuit employs a very innovative concept especially devised by me which further enhances the economical feature of the unit.

We know that LEDs require a certain fixed forward voltage drop to become illuminated and it is at this rating when the LED is at it’s best, that is voltages which is around its forward voltage drop facilitates the device to operate in the most efficient way.

As this voltage is increased, the LED starts drawing more current, rather dissipating extra current by getting heated up itself and also through the resistor which also gets heated up in the process of limiting the extra current.

If we could maintain a voltage around an LED near to its rated forward voltage, we could use it more efficiently. That’s exactly what I have tried to fix in the circuit.

Since the battery used here is a 6 volt battery, means this source is a bit higher than the forward voltage of the LEDs used here, which amounts to 3.5 volts. The extra 2.5 volts rise can cause considerable dissipation and loss of power through heat generation.

Therefore I employed a few diodes in series with the supply and made sure that initially when the battery is fully charged; three diodes are effectively switched so as to drop the excess 2.5 volts across the white LEDs (because each diode drop 0.6 volts across itself).

Now as the voltage of the battery drops, the diodes series are reduced to two and subsequently to one making sure only the desired amount of voltage reaches the LED bank.

In this way the proposed emergency lamp circuit is made highly efficient with its current consumption, and it provides backup for a much longer period of time than what it would do with ordinary connections.

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Tuesday, April 9, 2013

LED Bar Off Indicator

The simple indicator presented in this article may be combined, in principle, with any circuit that contains an LED bar display driven by a Type LM3914 IC. It ensures that an LED will light when all LEDs driven by the LM3914 are out. This prevents one drawing the erroneous conclusion that, since all the LEDs are out, the circuit is switched off. The circuit then continues to draw current, which, especially if it is battery powered, costs unnecessary money, apart from other considerations. The LED in the monitor draws a current of only 1 mA. When the LEDs forming the bar, D1–D10 are all out, there is no potential difference across R3, so that T1 is off and T2 is on.

LED Bar Off Indicator

This results in T3, in conjunction with R5 and the internal reference voltage of IC1, to form a current source that causes a constant current to flow through D11 so that the diode lights. When on of diodes D1–D10 lights, a potential difference ensues across R3, which causes T1 to come on. This results in T2 being switched off so that there is no collector current through T3. Consequently, there is no feedback at the emitter of T3, so that the current through R2 rises appreciably. The current through R2 determines the current through the LEDs in the bar. Therefore, when T3 is enabled, the current through R2, and thus the total current in the circuit, is reduced considerably.

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Saturday, April 6, 2013

Running LED with 4017

Running LED with 4017 complete with PCB layout. The series of 8 LED current is the basis for creating an 8-point LED. Slightly different from the running LED with IC 4017 (decade counter), 8 running this led is lit in sequence, but that has been previously flame does not die when the led is lit afterwards. 8 led to death after led to the fire-8. Meanwhile in the running LED (decade counter), the system LED lights like "point", there is only one LED that flashes between the tenth led.

The main component is the IC 74LS164 (SHIFT REGISTER), with its timer is astable multivibrator circuit (using IC NE555).

The series will be more efficient when using a stable power supply (regulator) using IC Regulator 7805. Under this scheme a series of stable power supply 5 volts dc.

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Thursday, April 4, 2013

Simple LED Voltmeter

Four µ741 op-amps are used here to measure the voltage ranging from 3V to 12V DC. The voltage measured is displayed on eight LEDs.

The inverting inputs (pin 2) of IC1 through IC4 are supplied with regulated 12V DC through voltage dividers R1 through R4. So the inverting input of each op-amp forms the reference voltage. The non-inverting inputs (pin 3) of the op-amps are tied together and connected to the input terminals. The voltage to be meaured is fed to these input terminals.

When the input voltage exceeds the reference voltage of any of the op-amps, its output goes high, making the corresponding LEDs to glow.

This circuit is designed to measure 3V, 6V, 9V and 12V DC. For instance, when the input voltage is 3V, LED7 and LED8 glow. When the input voltage is 12V, all the LEDs glow.

Note. You can use a quad device such as LM324 instead of µ741 ICs.

Circuit Diagram:

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