Various diagram: voltage

Showing posts with label voltage. Show all posts

Friday, November 14, 2014

VOLTAGE COMPARATOR SWITCH

This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The limits are adjustable and the circuit made to trigger from the adjustable "window". The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. V1 could be set to 14V and V2 to 11V thus giving an indication of over charge or a weak battery.

Circuit Diagram

Fig. 1

Important Points

Only pins 7 and 4 (power supply), pin 6 (output) and pins 2 and 3 (inverting and non-inverting inputs) are used. All other pins are not connected. The pinout for the CA3140 is shown below.

Fig. 2

The op-amps used here are MOSFET CA3140. They are used to advantage as they have very little output offset voltage and can switch down to near 0 volts. If any other op-amp is used such as LF351 or CA741 then it will be necessary to have an offset null control. This is just a 10k preset contacted between pins 1 and 5, the wiper connected to the negative supply rail or op-amp pin 4. With this circuit either op-amp will light the LED if the input voltage goes out of limits, the two 1N4148 diodes forming an "AND"-gate at the output. The input voltage to be monitored is fed via a series 10k resistor to inputs of both op-amps. If the input voltage is greater than the limit set by V1 then the CA3140 will swing its output to almost the full supply voltage and light the LED. Similarly, if the input voltage is less than the limit defined by V2 then this op-amp will swing towards Vcc and light the LED.

Saturday, November 8, 2014

SP Network Voltage Indicator

Using this schematic is created a network voltage indicator electronic circuit. If the input voltage is gift across the network, the optocoupler transistor is open, T1 is blocked and controlled rectifier, Th1, is in a very state of conduction. Since each terminals of the piezoelectric buzzer is at identical potential, buzzer is off. If voltage disappears, the transistor T1 enters the conduction and therefore makes the terminal of buzzer to be placed on the bottom (maintains thyristor conduction state).

during this state of affairs, theres a sufficiently giant potential distinction across the buzzer and D5s to see that these 2 components to point AC power loss, each audible and visual. By pressing the reset button current is interrupted by Th1, therefore thyristor enter in blocking state and therefore the different terminal of the buzzer is connected to ground.

Friday, October 31, 2014

Universal Battery Charger Battery charger for general purpose usage Universal Battery Charger circuit diagram The chargers output voltage is adjust

Universal Battery Charger

Battery charger for general purpose usage.

The chargers output voltage is adjustable and regulated, and has an adjustable constant-current charging circuit that makes it easy to use with most NiCad batteries. The charger can charge a single cell or a number of series-connected cells up to a maximum of 18V.

Power transistors Q1 and Q2 are connected as series regulators to control the battery chargers output voltage and charge-current rate. An LM-317 adjustable voltage regulator supplies the drive signal to the bases of power transistor Q1 and Q2. Potensiometer R9 sets the output-voltage level. A current sampling resistor, R8 (a 0.1 ohm/5W unit), is connected between the negative output lead and circuit ground. For each amp of charging current that flows through R8, a 100mV output is developed across it. The voltage developed across R8 is fed to one input of comparator U3. The other input of the comparator is connected to variable resistor R10.

As the charging voltage across the battery begins to drop, the current through R8 decrease. Then the voltage feeding pin 5 of U3 decreases, and the comparator output follows, turning Q3 back off, which completes the signals circular path to regulate the batterys charging current.

The charging current can be set by adjusting R10 for the desired current. The circuits output voltage is set by R9

Wednesday, October 22, 2014

Build a Car Voltage Regulator Circuit Using LM317

The car cigarette lighter socket does not only light cigarettes, but can be utilized as an electrical channel for powering tools to work on the car such as laptops and other electronic devices. The following circuit diagram shows a way of powering a two-way mobile radio using the LM317T voltage regulator.

The LM317T is an adjustable 3-terminal positive voltage regulator that efficiently provides a load current of 1.5 Amps over an output range of 1.2 V and 37 V. With reference to the circuit, it can accept 14 volts without any hassle and the voltage can be controlled easily with the use of a potentiometer, a 3-terminal resister with sliding contact. The whole circuit will contain the following components:

Printed Circuit Board (PCB)
Resistor 1 (R1): 270 ohms
Resistor 2 (R2): 2K carbon potentiometer
Capacitor 1 (C1): 100nF
Capacitor 2 (C2): 1uF tantalum
LM317T Voltage Regulator
Heat Sink
DC Power Jacks
Green LED: Power
Red LED: Over Voltage
Zener Diode: over voltage LED switch

The zener diode switches on the over voltage LED if the voltage passing through is larger than the breakdown or preset voltage. The use of zener diode permits a constant amount of voltage and can be very beneficial for devices that inputs the same amount of voltage.

LM317T is cheaply available in the market and is very simple to integrate into several energy system to supply a maximum current or voltage.

Monday, October 20, 2014

Simple Dual Voltage Power Supply 12 Volt

This is the simple circuit diagram of Dual Voltage Power Supply. It is used for Misc… application. This circuit is called regulated power supply. For this reason the main component of this circuit is Regulator IC. It also needs few components to built. The regulator 7812 is the positive voltage regulator and 7912 is the negative voltage regulator.

You can also use 7809 for 9 volt positive power supply and 7909 for negative voltage power supply. It regulates voltage from 24Volt to 12 Volt (DC). The transformer input is 110Volt to 220Volt (AC) and the output must be between 12Volt to 24Volt (AC) and current must be 500mA. In this circuit some capacitors are used as a filter for removing repole.

Thursday, October 2, 2014

Voltage and Frequency Calibrator Circuit Using IC 555

This circuit of a voltage and frequency calibrator provides simultaneous voltage and frequency calibrations by generation of a precision squarewave.
The 555 timer IC is used in a slightly unusual configuration, having the advantage that an exact 50:50 mark/space ratio may be attained by trimming R1. The frequency of oscillation may be set between l0 kHz and 1 kHz by switching timing capacitors C14. C5 decouples the internal ref- erence potential-divider of the 555 from supply·transients. The squarewave output from pin 3 of the IC, while stable in frequency, is not stable in peak-to-peak voltage as this depends on the supply voltage. This is used to switch on and off a temperature compensated constant- current source O1. R2 ensures that the current·source turns off completely when pin 3 goes high. The current- source output, trimmed by R3 to be exactly 1 mA, drives a resistor ladder network so that a series of precise squarewave voltages are generated. The advantage of current drive rather than voltage drive for this sort of net- work is that calibration is much easier. A simple ladder network is shown by way of example, and more complex ones may simply be constructed to give a wider variety of output voltages. The non-standard component values used were obtained by paralleling standard values. For the timing capacitors several in parallel had to be used, and only the resultant value is shown on the diagram.

Friday, September 26, 2014

Inverter Voltage Wave Circuit Diagram

This circuit voltage inverter was designed using common electronic components, it produces a negative voltage from a positive. It is very simple, its operation is reasonable and can be used in different utilities in electronics where one has to inverts tensions of a wave.

Inverter Voltage Wave Circuit Diagram

Wednesday, September 24, 2014

Maximum Minimum Voltage Indicator

This circuit indicates which of three voltages in the range from about about -4V to about +4V - at A, B and C - is the highest by lighting one of three indicator LEDs. Alternatively, it can be wired to indicate the lowest of three voltages or to indicate both the highest and lowest voltages. Op amps IC1a, IC1b & IC1c are wired as comparators, while the three indicator LEDs and their series 1kO current limiting resistors are strung across the op amp outputs to implement the appropriate logic functions.

Circuit diagram:

Maximum Minimum Voltage Indicator Circuit Diagram

For example, LED A will light only when pin 8 of IC1c is low (ie, A greater B) and pin 7 of IC1b is high (ie, A greater C). Similarly, LED B will light only when pin 8 of IC1c is high (ie, B greater A) and pin 1 of IC1a is low (ie, B greater C). LED C works in similar fashion if the voltage at C is the highest. Note that if all the LEDs and their parallel 1N4148 diodes are reversed, the circuit will indicate the lowest of the three input voltages. And if each 1N4148 diode is replaced by a LED, the circuit will indicate both the highest and lowest inputs.

Author: Andrew Partridge - Copyright: Silicon Chip

Saturday, September 20, 2014

High Low Voltage Cutout Without Timer

This inexpensive circuit can be connected to an air-conditioner/fridge or to any other sophisticated electrical appliance for its protection. Generally, costly voltage stabilizers are used with such appliances for maintaining constant AC voltage. However, due to fluctuations in AC mains supply, a regular ‘click’ sound in the relays is heard. The frequent energisation/de-energisation of the relays leads to electrical noise and shortening of the life of electrical appliances and the relay/stabilizer itself. The costly yet fault-prone stabiliser may be replaced by this inexpensive high-low cutout circuit with timer.

The circuit is so designed that relay RL1 gets energised when the mains voltage is above 270V. This causes resistor R8 to be inserted in series with the load and thereby dropping most of the voltage across it and limiting the current through the appliance to a very low value. If the input AC mains is less than 180 volts or so, the low-voltage cut-off circuit interrupts the supply to the electrical appliance due to energisation of relay RL2. After a preset time delay of one minute (adjustable), it automatically tries again. If the input AC mains supply is still low, the power to the appliance is again interrupted for another one minute, and so on, until the mains supply comes within limits (>180V AC).

Circuit diagram: High

The AC mains supply is resumed to appliance only when it is above the lower limit. When the input AC mains increases beyond 270 volts, preset VR1 is adjusted such that transistor T1 conducts and relay RL1 energises and resistance R8 gets connected in series with the electrical appliance. This 10-kilo-ohm, 20W resistor produces a voltage drop of approximately 200V, with the fridge as load. The value and wattage of resistor R8 may be suitably chosen according to the electrical appliance to be used. It is practically observed that after continuous use, the value of resistor R8 changes with time, due to heating. So adjustment of preset VR1 is needed two to three times in the beginning.

But once it attains a constant value, no further adjustment is required. This is the only adjustment required in the beginning, which is done using a variac. Further, the base voltage of transistor T2 is adjusted with the help of preset VR2 so that it conducts up to the lower limit of the input supply and cuts off when the input supply is less than this limit (say, 180V). As a result, transistor T3 remains cut off (with its collector remaining high) until the mains supply falls below the lower limit, causing its collector voltage to fall. The collector of transistor T3 is connected to the trigger point (pin 2) of IC1. When the input is more than the lower limit, pin 2 of IC1 is nearly at +Vcc.

In this condition the output of IC1 is low, relay RL2 is de-energised and power is supplied to the appliance through the N/C terminals of relay RL2. If the mains supply is less than the lower limit, pin 2 of IC1 becomes momentarily low (nearly ground potential) and thus the output of IC1 changes state from ‘low’ to ‘high’, resulting in energisation of relay RL2. As a result, power to the load/appliance is cut off. Now, capacitor C2 starts charging through resistor R6 and preset VR3. When the capacitor charges to (2/3)Vcc, IC1 changes state from ‘high’ to ‘low’. The value of preset VR3 may be so adjusted that it takes about one minute (or as desired) to charge capacitor C1 to (2/3)Vcc.

Relay is now de-energised and the power is supplied to the appliance if the mains supply voltage has risen above the lower cut-off limit, otherwise the next cycle repeats automatically. One additional advantage of this circuit is that both relays are de-energised when the input AC mains voltage lies within the specified limit and the normal supply is extended to the appliance via the N/C contacts of both relays.

Tuesday, September 16, 2014

Voltage Booster Wiring diagram Schematics

This is voltage booster schema diagram.you can get 24V from 12V DC.Q1 and Q2 are D1616.If you are unable to find D1616 You can use 2N 3055,C2236,SL 100.

Note

# For high current (around 5A) games use 2N 3055 transistor or more powerful Darlington pairs for Q1 and Q2.

– Voltage On Bargraph Display

The LM3914 is a truly versatile component. Besides LEDs, only a few other components are needed to make the ‘bidirectional’ bargraph voltmeter shown here. The circuit is similar to a conventional bar display, but it offers a possibility to change the direction in which the LEDs are switched on. This may be useful, for example, when positive and negative voltages are measured. For a positive input voltage, the LEDs are switched on in the usual manner, that is, from D3 to D12, while for negative voltages, the LEDs are switched on in the opposite direction, from D12 to D3. Obviously, the negative voltage must be ‘rectified’, i.e. inverted, before the measurement.

A suitable circuit for this purpose is presented in the article ‘Absolute-value meter with polarity detector’ elsewhere in this website. A set of transistor switches (MOSFETs) controls the direction in which the LEDs light. When the control voltage is high (+6V, according to the schematics, but any voltage that is at least 3V higher than reference voltage will do), T1 and T4 are switched on, while the other two MOSFETs are off. In this way, the LM3194 is configured in the usual manner with the top end of the resistor network connected to the internal voltage reference and the low end connected to ground.

+/–

As the input voltage rises, the comparators inside the LM3914 will cause the indicator LEDs to be switched on one by one, starting with D3. When the control voltage is lower than about –3V, T2 and T3 are switched on while T1 and T4 are off. Consequently, the ends of the resistor network are connected the other way around: the top end goes to ground and the low end, to the reference voltage. The first LED to be switched on will then be D12; i.e., the LEDs that forms the bargraph display light in the opposite direction. Although not documented by the manufacturer of the LM3914, this option works well, but only in bar mode (in dot mode, internal logic disables any lower-numbered LEDs when a higher-numbered LED s on, which obviously conflicts with our purposes).

To achieve good symmetry, an adjustable resistor is added to the voltage divider in the LM3914. Using a DVM, adjust the preset until the voltage across P1+R4 equals 1/11th part of Urefout. Sensitivity is determined with the ratio of resistors R5 and P2. If, for example, the reference voltage is set to 2.2 V by means of P2, there will be a voltage drop of 200 mV per resistor in the ladder network (including R4-P1). So, the first LED will switch on when the input voltage exceeds 200 mV, the second, at 400 mV, and so on, and the whole display will be on at 2 V. The circuit draws about 100 mA when all LEDs are switched on.

Monday, September 1, 2014

Using 555 Timer Voltage Controlled Switch

In this schema the 555 timer is used in a novel way, as a voltage controlled switch.The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example schema: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage.

If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage. It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors cant compete with. (This high impedance input must not be left open.) A large hysteresis makes the schema immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenously, regardless of the input signal shape.

Voltage Controlled Switch Circuit Diagram

The voltage drop across the NE555s output stage (at 35-100 mA) is 0.3-2.0 V, depending on the way the relay is connected and the exact current it draws. D1 is absolutely vital to the safety of the integrated schema.