NE555 Monostable

This is a monostable mode circuit of NE555 IC timer. Feature : timing period is 1.1msec, precision, Simple circuitry, independent output duration, 12V supply. Component : Resistor, capacitor, NE555 timer IC. [zen22142.zen.co.uk]

Basic 555 Squarewave Oscillator

The following circuit is a Basic 555 squarewave oscillator. Feature : 1 Khz tone, Simple circuitry, limit = 200 mA, inductive voltage reduced, 4.5-9 Supply voltage. Component : 555 timer IC, resistor, capacitor, Speaker, 2N3053 transistor, push button. [qsl.net]

Bicycle back Safety Light

This is a circuit of bicycle back safety light. Feature : 13 LEDs flashing, 3V supply voltage, Simple circuitry, low voltage, high efficiency, battery powered. Component : Resistor, capacitor, LED, switch, battery, 7555 timer IC. [redcircuits.com]

Four-Hour Timer

The following schematic diagram is four hour timer circuit. Feature : easy to build, 3 hours 53 minutes total time,9V supply voltage. Component : 555 timer IC, Resistor, capacitor, switch, transformer, LED, CD4040B, Relay, BC547 transistor, 1N418 diode, variable resistor. [wiredworld.tripod.com]

DS1621 PC Thermometer Circuit

The following circuit is PC thermometer using DS1621. Feature : plug in any free PC com port, range of -20 to 125°C, Centigrade (°C) of Farenheit (°F) scale, basic accuracy and resolution 0.5°C, readable data log, sampling rate 1, 5, 30 or 60 seconds, basic accuracy and resolution 0.5°C, no external power supply required, easy to build, no calibration required. Component : 1N418 diode, Capacitor, LM2936Z, regulator, DB9 female, Zener diode, DS1621. [riccibitti.com]

CPU Clock Display Circuit

This is a CPU clock display circuit. This circuit shows the CPU speed. Feature : Simple circuitry, easy to build, 5V supply, can display CPU clock. Component : 7 Segment display, Resistor, 1N4001 diode, jumper. [turbokeu.com]

Isolated Full Duplex RS232C Interface Circuit

This is a Isolated Full Duplex RS232C Interface circuit. This circuit is used to protect PC from direct connection to hazardous voltages. Feature : isolate TxD and RxD lines from the PC serial port , baud rate of 19.2k baud, 5V supply. Component : capacitor, 1N4148 diode, LED, DB9, terminal block resistor, 6N137, CNY17-3, 74HC14. [chaokhun.kmitl.ac.th]

Simple Temperature Regulated FAN Speed Controller Using MOSFET

The following circit is Simple temperature regulated FAN speed controller using MOSFET. Feature : + 12 V input voltage, 0-12 V output voltage, nice smooth regulation, noise removed, 47C max load, fan speed was about 3000 as usual.Component : capacitor, resistor, MOSFET P.[www.webx.dk]

Smart Battery Charger Using A Single-Transistor Circuit

The following circit is a smart battery charger using a single transistor. Featre : Simple circuitry, 13.3 VDC supply voltage, single transistor. Component : Battery, resistor, C1061 transistor, 1N4001 diode, relay, capacitor, potentiometer. [electronicdesign.com]

Single Transistor Nicad Battery Charger

This is a nicad battery charger circuit. Feature : Simple circuitry, charge nicad battery, changeable rate, single transistor, charging current 15mA or 45mA,for 1.5V and 9V battery, 12VAC supply voltage. Component : 1N4001 diode, Capacitor, 1N4148 diode, BD140 transistor, switch, resistor,transforme, Fuse.[zen22142.zen.co.uk]

NiCad Discharger for Rx & Tx Packs

This is a NiCad discharger circuit for Rx and Tx Packs. Feature : Simple circuitry, for NiCad battery, Tx battery 8 cell pack,Rx battery 4 cell pack. Component : LM3900 op amp, BD681, LED, resistorm capacitor,7805 voltage regulator, push button, BC548 transistor, Buzzer. [sentex.ca]

Lithium Chargers

This is a lithium charger circuit. Feature : variable current 100mA-2A, simple circuitry, easy to build, inexpensive circuitry, +12V supply voltage. Component : LM741, variable resistor, resistor, zener diode, capacitor, L200. [flyelectric.ukgateway.net]

Motorcycle Battery Charger

The following schematic diagram is a motorcycle battery charger. Feature : 115 or 220V Ac supply voltage, current of 3A, full indicator, simple circuitry, 14.1 volt output. Component : LM350, Transformer, bridge rectifier, capacitor, resistor, potentiometer, 1N4148 diode, BC558 transistor, 1N4001 diode, LED, LM1458. [sentex.ca]

14 Watts Audio Amplifier

The following circuit is a Audio amplifier which can give 14 watts of power. Feature : provide 14 watts of power, a discrete power op-amp, gain of approximately 150, preamp has voltage gain of 10, has extremely low distortion, relatively insensitive to the choice of components. Component : Capacitor, Resistor, potentiometer, CA3140, LM301, 1N751 Zener diodes, Speaker, 2N3904 transistor, 2N3906 transistor, TIP2955,1N4001 diode, Inductor,TIP3055.[michaelgellis.tripod.com]

100W Guitar Amplifier Using TL072

This is a guitar amplifier using TL072. This amplifier can amplify up to 100W. Feature : 100W amplification, Simple Circutry, Elegant design, provides excellent tonal range, suit any style of playing, provide a huge amount of gain. Component : Resistor, TL072, Capacitor, Potentiometer, BC549 transistor, Switch, Diode, Zener diodes.[sound.westhost.com]

2.5 W Stereo Class D Audio Power Amplifier Using LM4663

This circuit is a 2.5 W stereo class D audio power amplifier using LM4663. Feature : Two stereo input selector, Micropower shutdown mode, Stereo headphone amplifier, no heatsink needed, “Click and pop” suppression circuitry, Delta-sigma modulator, high efficiency, single supply. Component : resistor, capacitor, LM4663, speaker, headphone.[national.com]

Bench Amplifier

The following circuit is a bench amplifier. Feature : voltage gain of 200, 325mW of power, simple circuitry, work on 4 to 12Volts DC. Component : capacitor, resistor LM386, switch, variable resistor.[zen22142.zen.co.uk]

Balanced microphone preamp

The following circuit is a balanced microphone preamp. Feature : Simple circuitry, inexpensive, 60dB amplification, 12V supply voltage. Component : Resistor, transformer, potentiometer, ne5532, rectifier, 7812, 7912, fuse, capacitor, 7805, zener diode. [nomad.ee]

MPX4115 Barometric Pressures Circuit Diagram

Barometric Pressures Circuit Diagram

Description: The following circuit shows about MPX4115 Barometric Pressures Circuit Diagram. This circuit based on the MPX4115 IC. Features: bring the voltage down to the active range of 5 volt opamps, output is fed to the 1-Wire DS2438 A/D, available overall gain is about 12.6 (i.e. 0.68 * 2.16 * 8.58), opamp stage with a gain of U1A, capable of a gain range of 1/1 to about 8.58/1, 4.25 to 3.79 volts at sea level, 2.77 to 2.45 volts at 10,000 feet. Component: Resistor, IC, Capacitor, Variable Resistor.[davidbray.org]

Electrical Circuit Diagram Of 1-Wire Master/Slave Configuration

The following circuit shows about Electrical Circuit Diagram Of 1-Wire Master/Slave Configuration. This circuit uses a single data line plus ground reference. Features: Each 1-Wire slave device has a unique, controls the communication with one or more 1-Wire slave devices on the 1-Wire bus, 64-bit ID (identification number), unalterable, a serial protocol using a single data line plus ground reference for communication, factory-programmed. Component: 1 Wire Device, Interface Control, Device Function, Port Control, 1 Wire Host, Power Supply.[maxim-ic.com]

1 wire Barometer Using MPX4115

This is a 1 wire barometer using MPX4115 circuit. Feature : Simple circuitry, more reliable, output voltage ranges from about 4.17 to 3.72 volts at sea level, about 3.5 to 3.04 volts at 5000 feet, gain of 4.4. Component : MPX4115, 7805 regulator, DS2438, 1N4001 diode, resistor, capacitor, 2N4403 transistor, LM358 op amp, variable resistor. [davidbray.org]

Opto isolated 1-Wire bus

The following schematic diagram is a opto isolated 1 wire bus circuit.
Feature : 1 wire in, 1 wire out, Input is fully 1-Wire compatible, slow rate limited active output, DC/DC converter.
Component : Resistor, transistor, Capacitor, Optocoupler. [home.kpn.nl]

Light Pollution Meter

This is a light pollution meter circuit. Feature : control range of about 2 to 30 microamps, Simple circuitry, easy to build, battery powered, 9V supply voltage. Component : LED, NPN transistor, Digital multimeter, Resistor, potentiometer, toggle switch, battery. [avery.home.mindspring.com]

Water-level Alert

The following circuit is a water level alert. Feature: Simple circuitry, low voltage, 1.5V supply voltage, portable unit, battery powered, low current consumption. Component : Resistor, capacitor, LED, 1N5819 diode, 7555 timer IC, piezo sounder, Battery. (redcircuits.com)

Water Level and TDS Sensor

This is a water level and TDS sensor circuit. Feature : Simple circuitry, Battery powered, 9V supply voltage, very low power consumption. Component : Resistor, capacitor, probe, battery, speaker, TLC555 timer IC, switch. [pbv.thunder-bay.on.ca]

Ultra-Sonic Ranging Circuit

This is an ultrasonic ranging circuit. Feature : The current consumption, at 2.5 Amps during the sonic burst, The 150mA quiescent current, The maximum range of 10.7 metre, The minimum range of 26cm. Component : Capacitor, resistor, PIC12C508, ST232CD, N1076, LM6032, LP301, transistor, diode. [robot-electronics.co.uk]

Ultrasonic Range & Imager Circuit

Description : The following circuit is ultrasonic range and imager circuit. Feature : one piezoelectric tranducer for tramsmit & receive, range of 2.5m, high gain. Component : crystal, resistor, capacitor, 1N4149 diode, 1N4148 diode, BC557 transistor, BC549 transistor, BF245, 4016, PIC12C509. [ele.uva.es]

12 V to 100V DC/AC inverter

 The following circuit is a 12V to 100V DC/AC inverter using SN7400. Feature : input voltage is 12 VDC, output voltage is 100VAC, the oscillator’s frequency is 60Hz. Component : SN7400 nand gate, resistor, 1S1588 diode, capacitor, 2SD880 transistor, 78L05 regulator IC, 2N3055 transistor, Transformer.[piclist.com]

Mobile Phone Battery Charger Circuit

Mobile phone chargers available in the market are quite expensive. The circuit presented here comes as a low-cost alternative to charge mobile telephones/battery packs with a rating of 7.2 volts, such as Nokia 6110/6150.

Circuit diagram:

 

Mobile Phone Battery Charger Circuit Diagram 

Parts

R1 = 1K
R2 = 47R
R3 = 10R
R4 = 47R
C1 = 1000uF-25V
D1 = LEDs any color
D2 = LEDs any color
D3 = LEDs any color
D4 = 1N4007
D5 = 1N4007
IC1 = LM7806
T1 = 9VAC Xformer 250mA
BR1 = Diode bridge 1A


Circuit Operation:

The 220-240V AC mains supply is down-converted to 9V AC by transformer T1. The transformer output is rectified by BR1 and the positive DC supply is directly connected to the charger’s output contact, while the negative terminal is connected through current limiting resistor R2. D2 works as a power indicator with R1 serving as the current limiter and D3 indicates the charging status. During the charging period, about 3 volts drop occurs across R2, which turns on D3 through R3.

An external DC supply source (for instance, from a vehicle battery) can also be used to energies the charger, where R4, after polarity protection diode D5, limits the input current to a safe value. The 3-terminal positive voltage regulator LM7806 (IC1) provides a constant voltage output of 7.8V DC since D1 connected between the common terminal (pin 2) and ground rail of IC1 raises the output voltage to 7.8V DC. D1 also serves as a power indicator for the external DC supply. After constructing the circuit on a veroboard, enclose it in a suitable cabinet. A small heat sink is recommended for IC1.

A 12V Car Charger For ASUS Eee Notebook

The ASUS Eee is a fantastic ultra portable notebook with almost everything required for geeks. Plus it features fantastic build quality & is very well priced. If u live in New Zealand you can get them from DSE, at the time of writing they are the exclusive supplier. I worked out it’s the same cost as importing one once you include all the duties & tax, plus you get the advantage of a proper NZ-style mains charger. Anyway, being so small I thought it would be nice to be able to carry this around in the car. Unfortunately I couldn’t find a car charger available anywhere at the time so I decided to tackle the problem myself. As a bonus this provides an opportunity for an external high-capacity battery.

 

Commercial Equivalent:
I thought at this stage it would be worth noting that a commercial car charger is now available for less than it cost me to build this from Expansys & is available in most countries . It outputs 9.5v from 10-18v in at up to 2.5A. I’d actually recommend it over the design here is it seems to perform better at lower voltages. However I have kept this page up as a reference for those who enjoy tinkering
.

Design:
The charger included with the Eee is rated at 9.5v, 2.315A. There isn’t a fixed voltage regulator available for this exact voltage, so the circuit needed to be designed around an adjustable regulator. I decided to design the charger around the LM2576 “Simple Switcher” IC from National Semiconductor. There are tons of ICs like this available, many of which are a bit more efficient, however I selected this one because it is readily available relatively cheap. It also has a lower drop-out voltage (~2V) than many other chips I looked at which is important when powering the device from a car or 12v SLA battery.

This circuit could have used a standard three pin regulator IC such as the LM317, however most types require an external transistor when handling so much current and not to mention the fact that they are very inefficient; they draw the same amount of current from the input as the load & the difference in power is dissipated as heat. The main problem with using the LM2576 is the fact it needs quite a large inductor due to its somewhat low switching frequency. The inductor I used is made by Pulse Engineering, part number PE92108KNL. I’d prefer a smaller one, however I couldn’t find one capable of supplying the required current that I could purchase in single units. Besides the PE92108KNL is apparently designed specifically to work with the LM257x series.

The circuit also includes a low voltage cut-out based on a 9.1v Zener diode BC337 transistor that will shut down the regulator if the input voltage is below 11.5V. This prevents unstable operation of the regulator at lower input voltages, & also helps prevent accidental flattening of the supply battery. Substituting this transistor for similar type may affect the cut-out voltage; the Vbe of the transistor should be 1.2v.All of the components used should be pretty readily available in most areas. I got everything from Farnell. Jaycar also sells everything except the inductor. Make sure you specify high temperature, low ESR capacitors as these help result in more stable operation & better efficiency of the charger

Unfortunately the end result is a charger that is slightly bulkier than I would really like. I attempted to fit this inside an old mobile phone charger case so the whole thing could hang out of the cigarette lighter, however I ran into trouble making the circuit stable enough and dissipating all the heat. Due to the high current involved compared to a mobile phone charger the components are much bulkier so it’s pretty tricky to get all to fit! If I do get it finished I’ll add an update.

Parts List:
2x 10k resistor (R1 & R4)
2x 22k resistor (R2 & R3)
1x 1.5k resistor (R5)
1x 120μF 25v electrolytic capacitor (C1)
1x 2200μF 16v electrolytic capacitor (C2)
1x 1N5822 Schottky diode (or equivalent)
1x 9.1v 0.5W Zener diode
1x BC337 NPN transistor
1x LM2576T-ADJ IC
1x 100uH, 3A inductor (e.g. Pulse PE92108KNL)
25°C/W or better minature heatsink (e.g. Thermalloy 6073)
Cigarette lighter plug with 3A fuse and 2.1mm DC plug (e.g. DSE P1692)
2.1mm DC chassis mount socket
1.7mm x 4.75mm (ID x OD) DC plug and cable
Small plastic enclosure
Building It:
Make yourself a PCB using the template below (600dpi). I simply laser print (or photocopy) the design onto OHP transparency sheet and then transfer the toner onto a blank PCB using a standard clothes iron. Any missing spots can be touched up with a permanent marker before etching. This is quick, usually results in pretty tidy boards and hardly costs a thing. There is a tutorial on a variation of this method at http://max8888.orcon.net.nz/pcbs.htm.

Install the components on the PCB and triple check the layout before soldering. It is much easier to start with the low profile components such as resistors and diodes, then install the larger components after-wards. Don’t forget the wire link; this is shows as a red line on the layout guide above. Remember to smear a small amount of heatsink compound on the regulator tab before mounting the heatsink.

For a case I used a small plastic enclosure from DSE, part H2840, as it was all the local store had in stock that was remotely suitable. The PCB is designed to fit into this particular case, however any small box should be suitable. If you have a dead laptop charger lying about it might be worth ripping the guts out of that and salvaging the case. If your enclosure is different you may need to modify the design to suit, so I have provided the schematic & PCB design files for download. They were created using Eagle. The Eee uses a standard 1.7mm DC power connector with a positive tip.

Testing:
Connect the circuit to a 12v supply. If you use a car or lead acid battery ensure you have a 3A fuse fitted in line with the circuit before connecting it, just in case. Use your multimeter to check that the circuit outputs about 9.45v with no load. Connect a 12V, 21W lamp or similar load across the output & check that the voltage doesn’t vary much. You should now be able to connect your Eee. The circuit design should be good for up to 2.5A, so there is plenty of margin for the Eee to fully function & charge its own battery off this supply.

SLA Battery Carry-bag:
Jaycar have a really cool carry bag with a shoulder strap designed to perfectly fit a 12v 7AH sealed lead acid battery. The bag features a fused cigarette lighter socket and is the perfect compliment to this charger. It works well with the Eee and provides hours of extra use. The shoulder strap means it’s not too bothersome to carry about and the charger circuit itself zips up neatly inside the bag. The under-voltage cut-off means the battery will never run completely flat, and the Eee will simply cut over to its internal battery once the SLA runs out. I got my SLA battery from Rexel as they are much cheaper (approx NZ$18 including GST last time I bought one) and they don’t sit as long on the shelf as many other suppliers.

Disclaimer:
This circuit is intended for people who have had experience in constructing electronic projects before. The circuit design and build process are provided simply as a reference for other people to use and I take no responsibility for how they are used. If you proceed with building or using this design you do so entirely at your own risk. You are free to use the content on this page as you wish, however I do ask that you include a link or reference back to this page if you distribute or publish any of the content to others