ffd

Simple and cheap, the circuit built based on well-known IC regulator LM317 with current booster of power transistor 2N3782. Don’t forget to add heatsink especially for power transistor 2N3782.

This is the project of Digital Fan Regulator Circuit diagram. The circuit presented here can be used to control the speed of  fans using induction motor. The speed control is nonlinear, i.e. in steps. The current step number is displayed on a 7-segment display. Speed can be varied over a wide range because the circuit can alter the voltage applied to the fan motor from 130V to 230V RMS in a maximum of seven steps.  The triac used in the final stage is fired at different angles to get different voltage outputs by applying short-dura-tion current pulses at its gate. For this pur-pose a UJT relax-ation oscillator is used that outputs sawtooth waveform. This waveform is coupled to the gate of the triac through an optocoupler (MOC3011) that has a triac driver output stage.  Pedestal voltage control is used for varying the firing angle of the triac. The power supply for the relaxation oscillator is derived from the rectified mains via 10-kilo-ohm, 10W series dropping/limit-ing...

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...

Working of Regulator with 2 Photocoupler that is : Photocoupler N901 - used as a coupling-off control on the regulator by mikrokontrol. Which is set high and low voltage B + (st-by at the B + voltage is low). Control of the pin-37 POWER mikrokontrol → V610 → VD913 V908 → N901. Photocoupler N903 - used to control on-off the regulator of X-ray circuit protector. X-ray protector circuit of flyback → VD451 → VD452 → SCR VS472. If the flyback voltage regulator over the job will automatically be turned off by N903 To disable the X-ray circuit protector, it can be temporarily removed photocoupler N903 first. In normal conditions the voltage at the transistor V474 should be zero. Regulator Schematics Trobelshuting there is no voltage for 5v st-by on the secondary : Disable by removing the first circuit protectors N903 Check the voltage of 300V Check all transistors Check the start voltage of 300V by R909 >> R906 to the base of transistor power regulator Check the feedbac...

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....

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...

The switching regulator power supply used LM2575-5.0 on this schematic. You can make the stable voltage by using the 3 terminal regulator like LM317. However, because the output electric current and the inputted electric current are the same approximately, the difference between the input electric power (The input voltage x The input electric current) and the output power (The output voltage x The output current) is consumed as the heat with the regulator. Because it is, the efficiency isn�t good. Data sheet for LM2575 SIMPLE SWITCHER 1A Step-Down Voltage Regulator http://www.national.com/pf/LM/LM2575.htm

Recently the author had to adapt  a standard circuit configuration  (which often uses an npn bipolar) so as to operate as a low-dropout (LDO) regulator. The circuit shown here uses that rarity,  a depletion-mode MOSFET to implement the LDO function. What to do when you have to derive an analogue supply voltage  (close to +5 V) from an existing ‘digital’ 5-volt rail, ensuring sufficient decoupling between the two? One answer is  to step up and then use a linear regulator to step back down. However, if around 4.5 volts will suffice then an alternative is a home-made LDO regulator. The circuit is usually a fairly  standard shape typically a npn transistor (with base-current limiting resistor) is used. Circuit diagram :   LDO Regulator Circuit Diagram Initially, it would appear that this design suffices after all, the text books say the saturation voltage  is around 0.2 V. Unfortunately,  this is no longer true when the collector is tied directl...

Most off-the-shelf car battery chargers cannot not be left connected to the battery for long periods of time as over-charging and consequent battery damage will occur. This add-on circuit is placed in series with the battery being charged and is powered by the battery itself. In effect, the circuit uses a high-current Mosfet to control the charging current and it turns off when the battery voltage reaches a preset threshold. Power for the circuit is fed from the battery to 3-terminal regulator REG1 which provides 8V. LED1 indicates that the battery is connected and that power is available. The 555 timer IC is configured as an astable oscillator running at approximately 100kHz. It feeds a diode pump (D1 & D2) to generate adequate gate voltage for Mosfet Q3, enabling it to turn on with very little on resistance (typically 14 milliohms). With the Mosfet turned on, current flows from the charger's positive terminal so that charging can proceed. The battery voltage is monitored by...

This circuit was designed to ensure that an amplifier circuit containing a TDA1516Q would not exceed its maximum supply voltage when the load is small. This amplifier is used in a PC to increase the audio power somewhat. The PC power supply, however, created so much interference that an additional power supply was required. Discrete Low-Drop Regulator Circuit Diagram The power supply has its own power trans-former with a secondary voltage of 12 V AC. After rectification and filtering this results in a DC voltage of about 16 V. The regulator consists of a P-channel MOSFET SJ117, the gate of which is driven via a voltage divider connected to T2. The base of T2 is held at a constant voltage by LED D2, so that the volt-age across emitter resistor R2 is also constant and therefore carries a constant cur-rent. When the output voltage is higher than about 13.5 V, zener diode D1 will start to con-duct and supply part of the current through R2 — as a result the MOSFET will be turned on a li...

The schematic diagram below shows a simple trivial low-cost 12 volt DC 50W off-line SMPS switching power supply circuit. It can be used for DIY home projects or to learn operation of flyback converters. This PSU can work over a universal input AC line range 90-264 VAC. It provides a nominal 12V DC output at more than 4A load. Line and load regulation is better then 0.5%. The unit has over current, over temperature and over voltage protections, as well as passive inrush current limiting. Output ripple are approximately 0.2 V peak to peak in the range 0 to 20 MHz. If you need to get lower ripple, you may put an additional output capacitor or an LC filter outside of the feedback loop. This project is a modification of a 24V circuit that I've designed many years ago as a consultant for a small company. That company wanted a plug-in replacement to a cheap off-the-shelf AC to DC power supply, which had a long lead time. By the time I've completed the design and built a proto, they ...

ADJUSTABLE 1.5A STEP DOWN 1.5MHz SWITCHING REGULATOR ELECTRONIC DIAGRAM However, an Adjustable 1.5A Step Down 1.5 MHz switching regulator circuit can also be used to overcome such problem. It uses ST1S03 step down DC-DC converter. The ST1S03 can also be used to power low-voltage digital core in HDD application . With input voltage range 3V to 16V, the ST1S03 can gives current up to 1.5A. The circuit can use tiny surface-mount components due to an high switching frequency (1.5 MHz). Resistor divider is used to set the output voltage value. Components needed to build the divided are capacitors (2 pieces), schottky diode (1 piece), and inductor (1 piece).

Here is simple Electronic circuit project of 5 volt micropower regulator circuit. This micro power 5 volts DC regulator can be designed using few operational amplifiers and some other electronic parts. 5 Volt Micro-Power Regulator Circuit Diagram:   This 5 volt regulator is ideal for instrumentation requiring good power efficiency . Maximum load current is 10 mA , and can be increased by changing Q1 to a power transistor and proportionally increasing the set current of A2. This circuit accepts a wide input voltage range between 6.5 volt and 30 volts. Low power 3 terminal IC regulators typically draw 2mA to 5mA quiescent current compared to only 50uA with this discrete implementation. 

One way to provide good negative-voltage regulation is with a low-drop-out positive-voltage regulator operating from a well-isolated secondary winding of a switch-mode circuit transformer. The technique works with low-dropout types. Under all loading conditions , the minimum voltage difference between the regulator Vin and Vout pins must be at least 1.5V , IC LT1086 low-dropout voltage. If this requirement isn't met, the output falls out of regulation. Two programming resistors, R1 and R2, set the output voltage 12V, and the IC LT1086 servo the voltage between the output and its adjusting terminals to 1.25V. Capacitor C1 improves ripple rejection, and protection diode D1 eliminates common-load problems. Since a secondary winding is galvanically isolated , a regulator 12V output  can be referenced to ground. Therefore , in the case of a negative-voltage output , the positive-voltage terminal of the regulator connects to ground , and the 12V output comes off the anode of D1. The Vin ...