GSK-4 - GLOBAL SPECIALTIES - Datasheet.Directory

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GSK-4 Basic Power

Supply Kit

The GSK-4 power supply can be connected to the

mains electrical supply of your house and which can

provide the range of DC voltages that are required

for basic electronic projects.

The circuit is basic but it will satisfy the requirements

of most electronic kit users especially when starting

out. Two DC voltage outputs are available; one is a

fixed regulated 5V for TTL use. The other output is

variable from 5V upwards. The maximum output

voltage depends on the input voltage. The specified

maximum input DC voltage to the regulator is 35V.

The minimum input voltage must be 2 volts higher

than the regulated output voltage.

The kit is constructed on a single-sided printed

circuit board (PCB).

ASSEMBLY INSTRUCTIONS

It is best to add the lowest height components to the

board first: the resistors & monoblok capacitors.

Care must be taken when bending the terminal leads

of the 7805 regulators. Hold the leads in needle nose

pliers when you bend the leads. Do not bend them

against the case by pushing them over with your

fingers as this can easily break the case (really it can

- we know from experience.) Make sure to get the

1000uF (1mF) ecap and the bridge rectifier around

the correct way.

CIRCUIT DESCRIPTION

The circuit is based around the 7805 voltage

regulator. It has only 3 connections (input, output

and ground) and it provides a fixed output. The last

two digits of the part number specify the output

voltage, for example 05, 06, 08, 10, 12, 15, 18, or

24. The 7800 series provides up to 1 amp load

current and has on-chip circuitry to shut down the

regulator (rather than blowing out) if any attempt is

made to operate it outside its safe operating area. (If

this happens to you, let the chip cool down & attach

the heatsink.)

It can be seen that there are in fact two separate

circuits in this power supply. One 7805 is directly

connected as a fixed 5V regulator. The second 7805

has a resistor divider network on the output. A

variable 500R potentiometer is used to vary the

output voltage from a minimum of 5V up to the

maximum DC voltage depending on the input

Instruction Manual

voltage. It will be about 2V below the input DC

voltage.)

The capacitor across the output improves transient

response. The large capacitor across the input is a

filter capacitor to help smooth out ripple in the

rectified AC voltage. The larger the filter capacitor,

the lower the ripple.

For small applications the heat sinks will not be

needed. The tab on the regulator will dissipate 2W

at 25° C just in air. (This is equivalent, for example,

to an input voltage of 9V, an output of 5V and

drawing 500 mA.) However, as your projects get

bigger they will draw more current from the power

supply and the regulators will operate at a higher

temperature. We have supplied the heat sinks with

the kit to cover this. You may easily experiment with

this Kit to add voltage & current meters to it and to

put it into a suitable plastic case connected to a

transformer.

WHAT TO DO IF IT DOES NOT WORK

An LED has been put into the output of the fixed 5V

regulator to indicate that the circuit is working. (It

may be left out of the circuit if you do not want it.)

Poor soldering is the most likely reason that the

circuit does not work. Check all solder joints carefully

under a good light. Next, check that all components

are in their correct position on the PCB. Thirdly,

follow the track with a voltmeter to check the

potential differences at various parts of the circuit.

Other items to check: are the regulators in the

correct way & are the electrolytic capacitor & bridge

rectifier in correctly. Look at the + & - signs on the

component and the overlay and make sure they

correspond.

WHAT TO LEARN FROM THIS KIT

These types of regulators are inexpensive and easy

to use. They have made it practical to bring

unregulated DC voltages to individual PCB's and do

the regulation locally on each circuit card.

OTHER POWER SUPPLY KITS BY GLOBAL

SPECIALTIES

 Kit 60. Regulated Power Supply. PCB &

components to take one positive 3-pin

regulator.

The internet is the place to find out all about 3-pin

positive voltage regulators. Go to the website of

national Semiconductor national.com and search