ffd

Useful for power lines control, Simple, transformer less circuitry. This circuit, designed on request, has proven to be useful to indicate when the voltage in a power supply line is changing from 120V to 240Vac. It can be used in different circumstances and circuits, mainly when an increase in ac or dc supply voltage needs to be detected. D3 illuminates when the line voltage is approaching 120V and will remain in the on state also at 240V supply. On the other hand, D6 will illuminate only when the line voltage is about 240V and will stay on because the latching action of Q1, Q2 and related components. C1, D1 and D2 provide a low dc voltage in the 4.5V - 6V range in order to allow proper operation of latch circuit and LEDs. 110 and 220V AC LED Voltage Indicator Circuit diagram: 110 and 220V AC LED Voltage Indicator Circuit Diagram Parts: R1__________470R 1/2W Resistor R2__________220K 1/4W Resistor R3,R7_______470R 1/4W Resistors R4__________1K 1/4W Resistor R5__________2K2 1/4W Resis...

Here is a simple Fixed voltage regulator circuit using 7805 and 7905 voltage regulator ICs Components Required: 1) Breadboard 2) 1Amps Fuse 3) 9 - 0 - 9 center tapped Transformer 4) 1N4007 diode = 4 5) 2200uf capacitor = 2 6) 100nf capacitor = 2 7) LM7805 Positive Voltage Regulator IC 8) LM7905 Negative Voltage Regulator IC Explanation for Dual Voltage Regulator: Connect the circuit as shown in the circuit diagram below. The output of the center tapped transformer is AC voltage. Voltage between the center and anyone of the other terminal gives +9Volt AC, Voltage between the two outer terminals gives +18Volt AC. Connecting in center tapped pattern gives +9Volt AC across terminals 1 & 2 and gives -9Volt AC across terminals 3 & 2. Four 1N4007 diode connected as shown below forms a bridge circuit which converts bidirectional AC into unidirectional DC. The converted signal is not pure DC, it still consists of some AC signals. The 2200uf capacitor is used as a filter, which allow...

This Mini Voltage Source with Adjustable Current Limit variable is very simple and efficient, ideal for small shippers or circuits that require a current limiter with adjustable voltage that this circuit can vary from a few mA up to 2 A and voltage 1.225v up to 12V or more, depending on the power supply. Adjustable Voltage and Variable Current Limiter Circuit Diagram Once the current reaches the limit set by the 100R resistor, transistor BC547 begins to act on the voltage regulator in the Adj pin and the output voltage starts to decrease. If the output is shorted, the output voltage will reduce to almost zero, as a kind of protection.

Battery Charger > In this my circuit , which is one of a series of simple battery charger , but this circuit to charger the Nicad battery . This circuit included with current and voltage limting . Why use it ?? because with current voltage you can choose voltage to charge a battery , and the limiting voltage use limit voltage if the battery is fully, because if battery fully that damaged quickly. See this schematic below : Click to view Enlarge Lamp 1 will glow brightly and the LED will be out when the battery is low or run out and the circuit is processing being to charged , but the LED will bright and the light dim when the battery is almost ready. Output voltage between 12 to 14 volt with current 100 mA.

This is the Simple Ac line Voltage Announcer Circuit Diagram. The range of this simple ac-voltage monitor is 100 to 140 Vac, with a resolution of 1 V. The speech processor interprets an 8-bit binary input code from an analog-to-digital converter. The processor`s pulse-code-mod ulated output then passes through a filter and an amplifier before driving tbe circuit`s speaker to vocalize the corresponding number. Each time switch S1 is _pressed, the speech-processor program enun ciates tbe monitored voltage readings from 100 to 140 V, depending on the code at the input of a 27C64 EPROM.   Simple Ac line Voltage Announcer Circuit Diagram The voltage-monitoring circuit consists of a bridge rectifier, filter capacitors, and a 10-Kilload resis tor. A divider, RA and RB, limits the input voltage to a maximum 2.55 V. The aid converter, IC4, then sends the voltage reading to tbe 27C64 EPROM, ICS. Pressing Sl sends a negative transient pulse to the write, WR, input of the aid converter, I...

This Digital Mains Voltage Indicator Circuit diagram project designed by  Pratap Chandra Sahu . Continuous monitoring of the mains voltage is required in many ap-plications such as manual volt-age stabilisers and motor pumps. An ana-logue voltmeter, though cheap, has many disadvantages as it has moving parts and is sensitive to vibrations. The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-pur-pose analogue voltmeter. The status of the mains voltage is available in the form of an LED bar graph. Presets VR1 through VR16 are used to set the DC voltages corresponding to the 16 voltage levels over the 50-250V range as marked on LED1 through LED16, respectively, in the figure. The LED bar graph is multiplexed from the bottom to the top with the help of ICs CD4067B (16-channel multiplexer) and CD4029B (counter). The counter clocked by NE555 timer-based astable multivibrator generates 4-bit binary ad-dress...

This circuit was developed to power an AVR microcontroller from a 12 V lead-acid battery. The regulator itself draws only 14 µA. Of course, there are dedicated ICs, for example from Linear Technology or Maxim, which can be used, but these can be very hard to get hold of and are frequently only available in SMD packages these days. These difficulties are simply and quickly avoided using this discrete circuit. Circuit diagram : The series regulator component is the widely-available type BS170 FET. When power is applied it is driven on via R1. When the output voltage reaches 5.1 V, T2 starts to conduct and limits any further rise in the output voltage by pulling down the voltage on the gate of T1. The output voltage can be calculated as follows: UOUT = (ULED + UBE) × (R4 + R2) / R4 where we can set ULED at 1.6 V and UBE at 0.5 V. The temperature coefficients of ULED and UBE can also be incorporated into the formula. The circuit is so simple that of course someone has thought of it before...

It will be easier to understand the operation of the circuit if we separate the under and over-voltage protection circuitry comprising transistors T1, T2 and associated components from the rest of the regulator circuit. Diode Dl arid. capacitor C2 provide 24V DC supply required to operate the relays.  Diode D2 and capacitor Cl provide the sample DC voltage for generating reference voltages for the cutout. For initial setting of cutout, collector of Tl is not connected to the base of T2. Also the time delay capacitor C4 is only connected after both under- and over- voltage points have been preset independently. Initially, due to the potential divider action of resistors R4, R6 and preset VR2, a voltage would appear at the base of T2. · lf this voltage is 0.6 ·V or more above the zener diode voltage of D4, transistor T2 would conduct, energising the relay and connecting the hot tap of the auto-transformer to the universal socket’s hot terminal through N/O contacts of the relay RLl....

A voltage regulator is used to produce a constant linear output voltage. It’s generally used with AC to DC power supply. And also it can be used as well as a DC to DC voltage converter . To regulating low voltage, most used device is one single IC. 7805, 7812, 7905 etc. 78xx series are design for positive and 79xx series are for Negative voltage regulator. 7805 is a three terminal +5v voltage regulator IC from 78XX chips family. See 7805 pinout below. LM78XX series are from National Semiconductor. They are linear positive voltage regulator IC; used to produce a fixed linear stable output voltage.  National Semiconductor has also negative voltage regulator chips family, they indicate with LM 79XX. 78xx is used more than 79xx because negative voltage has a few usability purposes as we see. I was previously posted a 5v regulated power supply circuit using 7805 IC , that circuit and this 7805 voltage regulator circuit is almost the same. Its output voltage is +5V DC that we need....

Here is a simple variable voltage regulator circuit using LM317 and LM337 ICs Components Required: 1) Breadboard 2) 1Amps Fuse 3) 15 - 0 - 15 center tapped Transformer 4) 1N4007 diode = 4 5) 2200uf capacitor = 2 6) 100nf capacitor = 2 7) 150 ohm resistor = 2 8) 3.9 kilo ohm Potentiometer (POT) = 2 9) LM317 Positive Voltage Regulator IC 10) LM337 Negative Voltage Regulator IC Explanation for Dual Voltage Regulator: Connect the circuit as shown in the circuit diagram below. The output of the center tapped transformer is AC voltage. Voltage between the center and anyone of the other terminal gives +15Volt AC, Voltage between the two outer terminals gives +30Volt AC. Connecting in center tapped pattern gives +15Volt AC across terminals 1 & 2 and gives -15Volt AC across terminals 3 & 2. Four 1N4007 diode connected as shown below forms a bridge circuit which converts bidirectional AC into unidirectional DC. The converted signal is not pure DC, it still consists of some AC signals...

With a suitable load, the terminal voltage of a NiCd or lithium-ion battery is proportional to the amount of stored energy. This relationship, which is linear over a wide range, can be used to build a simple battery capacity meter.    Voltage Tester for Model Batteries Circuit Image  This model battery tester has two functions: it provides a load for the battery, and at the same time it measures the terminal voltage. In addition, both functions can be switched on or off via a model remote-control receiver, to avoid draining the battery when it is not necessary to make a measurement. The load network, which consists of a BC517 Darlington transistor (T2) and load resistor R11 (15 Ω /5 W), is readily evident. When the load is active, the base of T1 lies practically at ground level. Consequently, T1 conducts and allows one of the LEDs to be illuminated.  Circuit Diagram : Voltage Tester for Model Batteries Circuit Diagram The thoroughly familiar voltmeter circuit, which ...

Continuous monitoring of the mains voltage is required in many applications such as manual voltage stabilisers and motor pumps. An analogue voltmeter, though cheap, has many disadvantages as it has moving parts and is sensitive to vibrations. The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-purpose analogue voltmeter. The status of the mains voltage is available in the form of an LED bar graph. Presets VR1 through VR16 are used to set the DC voltages corresponding to the 16 voltage levels over the 50-250V range as marked on LED1 through LED16, respectively, in the figure. The LED bar graph is multiplexed from the bottom to the top with the help of ICs CD4067B (16-channel multiplexer) and CD4029B (counter). The counter clocked by NE555 timer-based astable multivibrator generates 4-bit binary address for multiplexer-demultiplexer pair of CD4067B and CD4514B. The voltage from the wipers of presets are mul...

Zener Diode Voltage Regulator When the input of a Zener diode is greater than the Zener voltage the Zener diode works in the breakdown region, provided it is connected in the reverse bias. This principle is used in the regulator along with its equivalent circuit is shown in fig. in this circuit the Zener diode is reversely connected across the load R L across which constant output is desired. The series resistance R S absorbs the output voltage fluctuations so as to maintain constant voltage across the load. It may be noted that the Zener will maintain a constant voltage V Z across the load so long as the input voltage does not fall below V Z . When the circuit is properly designed, the load voltage V O remains essentially constant equal to V Z even though the input voltage V i and load resistance R L may vary over a wide range. Suppose the input voltage increases, since the Zener is in the breakdown region, the Zener diode is equivalent to a battery V Z as shown in the fig. it is c...

Circuit diagram   Parts D1 LED R1 1.2k Resistor R2 10k Var. Resistor U1 UA741 OP AMP Description When the input voltage is 0 the LED glows. The LED stops glowing when the voltage rises to the level determined by R2. Reverse + and - pins to reverse operating mode. To set voltage at which LED goes off, (1) Set 0V at input. (2) Set input voltage at desired level. (3) Adjust R2 to point right after LED goes out.

The Pocket Voltage Supply is a USB powered variable voltage supply. It can be powered with any 5V USB hub and can supply up to 1.5A. 5V USB hubs can be found almost anywhere; desktop computers, laptops, cell phone chargers, even portable USB battery banks. Pairing the Pocket Voltage Supply with a portable USB battery bank allows the user to test circuits and prototypes outside of a lab setting and even bring testing to the field! [ ]

In this circuit 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 circuit: 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 can't compete with. (This high impedance input must not be left open.) A large hysteresis makes the circuit immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenou...

The circuit described here is mostly aimed at development engineers who are looking for an economical step-down converter which offers a wide input voltage range. As a rule this type of circuit employs a step-down converter with integrated switching element. However, by using a more discrete solution it is possible to reduce the total cost of the step-down converter, especially when manufacturing in quantity. The TL5001A is a low-cost PWM controller which is ideal for this project. The input voltage range for the step-down converter described here is from 8 V to 30 V, with an output voltage of 5 V and a maximum output current of 1.5 A. Low-Cost Step-Down Converter With Wide Input Voltage Range Circuit Diagram When the input voltage is applied the PWM output of IC1 is enabled, taking one end of the voltage divider formed by R1 and R2 to ground potential. The current through the voltage divider will then be at most 25 mA: this value is obtained by dividing the maximum input voltage (30 V...

Occasionally you come across some unusual  situations when setting up measurement  systems. The author once had to set up a system to register the vibrations and strain supposed to be  present in a contactor that operated at a voltage of 25 kVAC. One of the biggest problems with this project turned out to be the power supply for  the measurement system. Since it required  a power of about 30 W it wasn’t possible to  use batteries since the system had to operate  for many hours at a time. A logical solution  would seem to be to use an isolating trans-former, but still.25 kVAC means a peak volt-age approaching 40 kV, and on top of that  you would have to include a safety margin. In  addition, everything that is connected to high  voltage lines should also be able to withstand  lighting strikes! Circuit diagram :   Power Supply with High Voltage Isolation Circuit Diagram Consequently the isolation should be able to  co...