Using below circuit and LM317 constant current calculator you can design constant current source up to 1.5A, (recommended max output current is 1A). This circuit uses LM317 voltage regulator as current regulator. Because you can get constant current output without affecting input voltage and output load. Also typical load regulation about 0.1% for this. So this constant current regulator can use for led driver, battery charger, current limiter for your dc power supply and more.

You can use below LM317 constant current calculator to calculate R1 resistance and R1 wattage. LM317 IC need good heatsink when the output load is more than 500mA. During this experiment we use 2.5Ω resistor (1.5+1.0) to get 500mA output. As well as max input voltage for above circuit is 37V. Also input voltage should be greater than output load voltage + 4.25 V for good current regulation.

OUTPUT CURRENT = V_REF/R1

V_REF=1.25 for LM317

(Output current units – Ampere, R1 units – Ohms)

e.g. for R1=2.5Ω

Output current=1.25/2.5

=0.5A

LM317 online calculators

LM317 power supply

LM317 REGULATED BATTERY CHARGER CIRCUIT

Ni-MH Ni-Cd Adjustable Constant Current Charger

Simple Ni-Cd Battery Charger

LM317 Calculator App

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This is a simple DIY 5V 3A voltage regulator circuit using LM2576 buck converter IC. So that can use as 5V car charger(12V to 5V), 5V regulated power supply and many more five volts power requirements. Below circuit uses very few components. Because anyone can make it using basic electronic knowledge.

The LM2576 series offers a high-efficiency replacement for popular three-terminal linear regulators. Because it substantially reduces the size of the heat sink, and in some cases no heat sink is required.

The LM2576 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving 3-A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, 15 V, and an adjustable output version. Above circuit uses 5V version.

LM2576 PINOUT

INPUT capacitor (C1) To maintain stability, it should be at least a 100-μF electrolytic capacitor. Also the capacitor leads to be short, and place near the regulator.

The inductor (L1) chosen must be rated for operation at the LM2576 switching frequency (52 kHz) and for a current rating of 1.15 × ILOAD.

OUTPUT capacitor (C2) should be low ESR type. Because low ESR types for low output ripple voltage and good stability. The voltage rating of the capacitor must be at least 1.5 times greater than the output voltage. For a 5V regulator, a rating of at least 8 V is appropriate, and recommends a 10V to 25V rating. In general, low value or low voltage (less than 12 V) electrolytic capacitors usually have higher ESR numbers. Higher voltage electrolytic capacitors generally have lower ESR numbers, and for this reason it can be necessary to select a capacitor rated for a higher voltage than can normally be needed. Because ESR Below 0.20Ω value recommends. But reducing the ESR below 0.03 Ω can cause instability in the regulator.

Catch Diode (D1), fast-recovery diode with soft recovery characteristics is a better choice. Standard 60-Hz diodes (for example, 1N4001 or 1N5400, and so on) are also not suitable. So Schottky diodes provide the best efficiency, especially in low output voltage switching regulators. Because we use 1N5822 Schottky diode for above 5V buck converter circuit.

Also you can go through this 7805 5V 1A Regulated Power Supply with Overvoltage Protection Circuit

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ICL7107 PANEL VOLTMETER CIRCUIT

This is a 3½ digit panel meter circuit using ICL7107 IC. Its voltage  range is 20V. But you can change it to 200mV, 2V, 20V and 200V.

R1 and C1 use for oscillator, R2 integrating resistor, C3 integrating capacitor, C4 reference capacitor and C2 auto zero capacitor.

The oscillator capacitor should be a dipped mica or ceramic type, and the reference and auto-zero capacitors should be either polystyrene or Mylar types. The integrating capacitor should be polypropylene.
Because polystyrene and polycarbonate as second and third choices, respectively. The integrating capacitor must have good dielectric absorption characteristics for the A/D converters to have optimum linearity.

ICL7107 Panel meter IC

ICL7107 is a high performance and low power , 3.5 digit A/D converter. This IC includes seven segment decoders, display drivers, a reference and a clock. Also This circuit can indicate polarity information. This IC is an electrostatic sensitive device (ESD). When you are handling this IC, you need to care about it. So My advice is to use an IC base. If you don’t have ESD safe soldering iron, do not solder IC base with IC.

This IC has internal reference. But this circuit uses an external reference for to get great accuracy. I build this circuit with using internal reference, but it gives many accuracy problems. I don’t now extract the problem. But I think it is depends on the IC and component quality. Because TL431 reference uses for that. In this circuit configuration we need 1V as a reference voltage.

voltage divider

We need a voltage divider for adjusting the voltage range. For that we use R7 and R8. Also VR2 for fine adjustment.  Our circuit use 1V as the reference voltage. Because we can only measure up to 2V without voltage divider. If you need to measure 20 volts you need to divide the input voltage by 10. Because we use a resistor voltage divider for that.

In this circuit

Vin=20, Vout=2V, Rx=R7=1MΩ, R8+VR2=Ry=?

Vout=(Vin X Ry)/(Rx+Ry)

Ry=(Vout X R1)/(Vin-Vout)

=(2 X 1MΩ) / (20-8)

=2MΩ/18

=0.111111MΩ

=111.11KΩ

R8+VR2 need to equal to 111.11kΩ. Because we use R8=100KΩ and VR2=20KΩ. 

Use below chart if you need to change voltage range.

Now we need to calibrate our circuit. First, you need to adjust VR1 for 1.000 volts in the ICL7107 PIN 36 (REF_HI). Then you need to input know voltage to the circuit (Like 5V), after you need to adjust VR2 to read the same voltage in our display.

Also, you need to change the decimal point accordingly voltage range. 0-20V range you need to connect R4 to DS3 pin5 and 0-200V range you need to connect R4 to DS4 Pin5.

D1 and D2 use to adjust the brightness of the seven segment display. If you add another diode in series you can further reduce brightness.

If your power supply is 5V, you can remove IC4 and installed jumper between pin 1 and 2.

IF you need more information about this IC, please refer these documents,

This ICL7107 panel meter circuit needs negative 5V supply. Because we use ICL7660 voltage converter. It is very simple to use. If you difficult to find this IC, you can use NE555 negative 5V generator circuit or any other -5V generator circuit.

This circuit use common anode seven segment display. 

Finally this is our PCB design, please use good quality PCB board. Otherwise, it gives some accuracy problems.

TP1 for test seven segment display, Also TP2 to adjust the reference voltage.

Also you can watch below our Youtube video about ICL7107 panel meter

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This is One Hertz (1Hz) clock generator circuit using 32.768Khz crystal, CD4060 and CD4013 ICs. Our circuit base on crystal oscillator. So we can get very accurate and stable output. That can use for clock, timers and many projects.

XTAL is 32.768KHz crystal. That is a very commonly use in digital clock.

R1 use as bias resistor and R2 use as a current limiting resistor. Also C1 and C2 are load capacitors.

Let’s check how we get 1Hz output.

We need to divide our crystal frequency by 2¹⁵ to get 1Hz. Because CD4060 act as an oscillator and frequency divider. here it is arranged to divide by 16384 which gives 2Hz when you using 32.768KHz crystal.

32.768KHz/2¹⁴=2Hz

Then we use CD4013 dual D-Type Flip-Flop as a frequency divider. But circuit use only one D-type flip-flop. It divides our frequency by 2. Now we can get 1Hz output. Other D-type flip flop is not used and it connects to the ground.

This circuit accuracy slightly depends on crystal quality and ambient temperature. If you have a high accuracy frequency meter you can slightly adjust frequency by changing C2 capacitor valve and you can use 50pF variable capacitor for C2 to do that. You can connect a frequency counter to CD4060 number 9 pin (External C) and adjust C2 to read exactly 32.786KHz. This is not necessary for our normal projects.

Precision 1Hz clock generator circuit PCB design

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This is a toggle switch to momentary (latch to push button)  switch converter. Most of the time we need momentary to toggle switch. But sometime we need to convert some latch signal to momentary signal. Our circuit convert toggle switch constant ON action into a momentary ON action. This circuit base on 555 timer IC and it uses monostable mode.

The Monostable 555 Timer circuit triggers when negative pulse applied to pin 2.This negative pulse need to go down  1/3Vcc.  Once triggered, the 555 Monostable will remain pin 3 output on until the time period (T) set up by the R1 × C2 network has elapsed.

T= 1.1 ×R1 × C2

T in seconds, R in Ω and C in Farads

T=1.1 × (47× 1000) × (10/1000000)

=0.517 ≅ 0.5 seconds

555 timer IC block diagrams and pin information

When the switch is closed C3 capacitor will charge through the SW1 and R2, Because the voltage at pin 2 move below 1/3Vcc. Then 555 triggers and start timing cycle. The output at pin 3 immediately moves up to near the supply voltage and remains at that level until the C2 timing capacitor charges to about 2/3 of the supply voltage.  When the switch is open, the C3 capacitor discharges through the R2 and R3 resistors. The D1 across the R2 prevents the voltage at pin 2 from rising above the supply voltage when the capacitor discharges.

Update1: Toggle to Momentary Switch Youtube Video

Update 2: Toggle to momentary switch PCB design

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Accurate 1 kilohertz (1kHz) square wave frequency generator schematic

This is a simple, accurate 1 kHz (1 kilohertz) square wave crystal oscillator circuit using frequency divider IC and crystal.

Our circuit uses a CD4060 ripple carry binary counter to divide the crystal frequency. CD4060 contains oscillator or astable  stage followed by a 14 stage binary counter/divider. In this circuit pulses at IC1 pin 2 (Q13) divide by 2¹³=8192. When we use 8.192MHz crystal we can get 1 kHz square wave frequency output.

8.192MHz/8192=1kHz

R1 acts as bias resistor. R2 acts as a current limiting resistor.

CD4060 oscillator features – All active components on chip, RC or crystal oscillator configuration, RC oscillator frequency of 690kHZ min. at 15V

CD4060 applications – Control counters, Timers, Frequency dividers, Time-delay circuits

Above circuit works between 5v to 15v.

UPDATE: (09/08/2018)
Please increase supply voltage between 10V to 15V, If circuit fail to oscillate.

1kHz square wave frequency generator circuit testing video

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The post Accurate 1 kHz Square Wave Crystal Oscillator Circuit appeared first on Electronic Circuits.

DIY simple low voltage dual power amplifier circuit TDA2822M

This is a simple low voltage stereo power amplifier circuit using single 8 pins IC. You can easily operate it using two battery cell. TDA2822M IC work within 1.8V to 15V. This can use for many applications like small battery powered radio, alarm, portable cassette player, headphone amplifier and more.

TDA2822M is a monolithic integrated circuit in 8 lead Minidip package.

TDA2822M has Low crossover distortion, Supply voltage down to 1.8V, Low quiescent current and Bridge or Stereo configuration. This IC can deliver a maximum power of 1000 milli-watts per channel, for a total of 2 watts.

R1, C6 and R2, C5 are resistor capacitor branch. They are connect between speaker out and ground to preventing oscillation and improving high frequency stability. C9 capacitor use for power supply filter.

This stereo power amplifier is very simple. because you can easily assemble it using vero board. Also TDA2822M amplifier can made very small and low cost. Additionally I use 3.5mm audio port for connecting portable device.

3V Battery Powered Stereo Amplifier Circuit TDA2822M Video

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7805 5V 1 Amp Regulated Power Supply with Overvoltage Protection Circuit

This is the 7805 5 volts 1 ampere Regulator with Overvoltage Protection Circuit. Most of the COMS, microcontrollers and TTL ICs require a well regulated power supply. these ICs can easily damage when supply voltage is increased. basically this circuit provides overvoltage protection but it has over current, reverse polarity, and the regulator IC protection. So you don’t need to worry about power supply.

Our circuit design using 5V regulator IC, SCR and ZENER diode. Actually this is a crowbar circuit. It is an electrical circuit used to prevent an overvoltage condition of a power supply unit from damaging the circuits attached to the power supply. If the voltage regulator (7805) is faulty, the supply voltage could be applied to the load and it will damage our sensitive circuits. So we need this type of protection circuit. 

When the output voltage exceeds 6.2V, Zener diode conducts. That voltage will switch on SCR, so this provides a short circuit to ground and fuse will be blown. The C1 capacitor is present to ensure that short spikes to not trigger the SCR. Also you can change the protection level by varying the values of D3 and R1. The D1 provides reverse bias protection and D2 provides output polarity reversal protection to the regulator IC.

If you get more than 400mA current, please use this regulator IC with suitable heat sink.

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AC Neon lamp filament or semiconductor blown fuse indicator circuit

This simple circuit tells you have a blown fuse without removing the fuse from its holder or semiconductor fuse status. This neon lamp fuse indicator circuit makes neon lamp flash up if a fuse blows or open.

The fault finding point of view  there is a disadvantage of the semiconductor type fuses. It is they haven’t filaments to indicate fuse state. because we need a this type fuse indicator.

As lone as the fuse is good, the fuse is conductive, so there is no voltage appear between the fuse connection. However if the fuse is open or blown the full supply voltage appears between fuse connections. At this time the neon lamp will start to flash on and off.

C1, R1, R2 and neon lamp act as very low frequency neon oscillator. neon flash rate can be altered by changing the value of C1, R1 and R2.

This blown fuse indicator will work with a wide range of AC supply voltages from 90V to 300V. The neon flash rate also depends on the supply voltage. So you need to change C1, R1 and R2 valves to get desired flash rate.

Above circuit can be used with few milliampere to many ampere fuse.

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Logic Circuit Designing and Simulating Software – Logical Circuits

LogicCircuit – is free, open source educational software for designing and simulating digital logic circuits. Intuitive graphical user interface, allows you to create unrestricted circuit hierarchy with multi bit buses, debug circuits behavior with oscilloscope, and navigate running circuits hierarchy. This windows application requires Microsoft .NET Framework 4.0 or higher.

Download

Source: logiccircuit.org

Now you can download latest version of software using above link.

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