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Workshop Power Supply
 
Workshop Power Supply


 

Workshop Power Supply

 


With a maximum capacity of 20 volts and 1 amp, it will supply most of your projects, it's greatest quality is the protection all your projects, it is capable of limiting the maximum current to as low as 1mA, saving your ICs and transistors in case of an accidental short circuit during the experimenting period of your projects. It is also an excellent battery charger.


Workshop Power Supply

It all started following a need for my workshop, I began this project in 1973, I had found an outline of circuit in the Circuit Cellar magazine. It took me several years to get it going nicely.

The cost can vary between $0 and $50 according to the size of your junk box.

Using an old LM723 (30 years) can seem antiquated, but it's still the most precise of the variable regulators. The precision is due to the internal reference voltage of 7 volts. By applying this reference to the one of the input of the error amplifier and the other input to a voltage coming from the output of the supply, the smallest deviation will make the output of the amplifier go + or - to control the output voltage of the supply.

Let's replace the old current transistor 2N3055 by a Darlington transistor TIP142. This transistor as a gain of 1000, so it requires only 1 mA to supply 1 Amp. The original 2N3055 which was used had a gain of 10. The TIP142 is protected by a diode witch prevents its destruction in case of an inverted voltage applied at the output, it's internal resistors R1 and R2 allows him to reduce the output current rapidly to 0, by dissipating the excess loads at his base.

The power supply can be a laptop power supply or a transformer with a
diode bridge and a electrolytic capacitor. I used an old Apple laptop power supply (24VDC @ 1.87A). The source must have at least 3 volts more than the voltage required at the output.

Description of the circuit:
The 7 volts reference at pin 6 of the 723 voltage controller is divided by two (3V) and applied to pin 4 witch is an inverting input, we can see that resistances R11 and R8 pass a current of 1 mA (I=E/R or 1mA=7V/7K), this voltage (pin4) is compared to the non-inverting pin 5. We must also maintain 1mA in the circuit at the non-inverting pin, this is done by resistance R 10, R 9, and VR02, if we maintains 1mA, VR02 will gives 1V drop for each 1000 Ohms, therefore 20K = 20 Volts.

The current limiter 723 function in the same way, but it measures 1V max,
the resistor which measures the current R02 is selected to give 1V at the maximum current. Notice that R01 has a value of 1K. The output pin 9 of the current limiting device controls the input CL of the 723 to close it if necessary and to limit the current to the selected value.

Building the supply
The layout of the circuits is not critical, using a PC Board will facilitate construction. The TIP142 can dissipate 24W at his maximum and we must use a heat sink. I used a heat sink that I took from an old PC.

Conclusion:
Using a variable supply with a limiting current capacity facilitates the experimentation of electronic circuits. It can also charge batteries of all kinds: Lead, NiMH, NiCd, Li-ion.


Workshop Power Supply




Workshop Power Supply

Workshop Power Supply





Accurate LC Meter Capacitance Inductance Meter with 16F628 and LCD
Volt Ampere Meter with 16F876 Microcontroller and LCD display
 
Accurate LC Meter

Build your own Accurate LC Meter (Capacitance Inductance Meter) and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings.
PIC Volt Ampere Meter

Volt Ampere Meter measures voltage of 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with 16x2 backlighted LCD.

50MHz 60MHz Frequency Meter / Counter with 16F628 & LCD
1Hz - 2MHz XR2206 Function Generator
60MHz Frequency Meter / Counter

Frequency Meter / Counter measures frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
1Hz - 2MHz XR2206 Function Generator

1Hz - 2MHz XR2206 Function Generator produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Output of 1Hz - 2MHz XR2206 Function Generator can be connected directly to 60MHz Counter for setting precise frequency output.

BA1404 HI-FI Stereo FM Transmitter
USB IO Board PIC18F2455 / PIC18F2550
BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
USB IO Board

USB IO Board is a tiny spectacular little development board / parallel port replacement featuring PIC18F2455/PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB IO Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible.

ESR Meter / Transistor Tester Kit
Audiophile Headphone Amplifier Kit
 
ESR Meter / Capacitance / Inductance / Transistor Tester Kit

ESR Meter kit is an amazing multimeter that measures ESR values, capacitance (100pF - 20,000uF), inductance, resistance (0.1 Ohm - 20 MOhm), tests many different types of transistors such as NPN, PNP, FETs, MOSFETs, Thyristors, SCRs, Triacs and many types of diodes. It also analyzes transistor's characteristics such as voltage and gain. It is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time.
Audiophile Headphone Amplifier Kit

Audiophile headphone amplifier kit includes high quality audio grade components such as Burr Brown OPA2134 opamp, ALPS volume control potentiometer, Ti TLE2426 rail splitter, Ultra-Low ESR 220uF/25V Panasonic FM filtering capacitors, High quality WIMA input and decoupling capacitors and Vishay Dale resistors. 8-DIP machined IC socket allows to swap OPA2134 with many other dual opamp chips such as OPA2132, OPA2227, OPA2228, dual OPA132, OPA627, etc. Headphone amplifier is small enough to fit in Altoids tin box, and thanks to low power consumption may be supplied from a single 9V battery.
 

Arduino Prototype Kit
RF Remote Control 433MHz Four Channel
 
Arduino Prototype Kit

Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB. It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.
200m 4-Channel 433MHz Wireless RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and can find many uses for controlling different devices, and it works even through the walls. You can control lights, fans, AC system, computer, printer, amplifier, robots, garage door, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of.
 

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