Keypad Operated Switch No.2 - testing your circuit

The prototype of Keypad Switch No. 2 was built using only the Stripboard Layout as a guide. So - if you have faithfully reproduced that layout - you will have a working circuit. Once you`re satisfied that your layout is correct - and you have made a careful and thorough check of the underside of the board - it`s time to power-up the circuit and tes
Keypad Operated Switch No.2 - testing your circuit - schematic

t its operation. This is always an anxious moment. If you construct a lot of circuits - you might consider building the Current Limiting Power Supply - or alternatively - you could add the Simple Current Limiter to your existing PSU. Both will let you set an upper limit on the amount of current supplied to your circuit - and so protect it from any serious damage. A resistor and a couple of LEDs are all that`s needed to demonstrate that the relay contacts are switching properly - and you can simulate the keypad-switches using short lengths of wire. Connect five short lengths of wire to the "A B C D & E " terminals. Connect a longer piece of wire to the "Com" terminal. You`re going to touch the short wires with it - so it needs to be long enough to reach as far as "E". Strip a little of the insulation from the ends of all six wires. = Connect a 2k2 resistor between the "+" terminal and the "Pole" Terminal. Connect an LED from the "N/C" terminal to the negative line. Connect another LED from the "N/O" terminal to the negative line. I used two different colour LEDs in the diagram because - in what follows - I wanted to be able to distinguish between them. You can use whatever colours you have available. = Finally, connect the 12-volts DC to the input terminals. Pay particular attention to the polarity of the supply. Note that the positive connection goes to the top terminal. = Turn On The Power The relay should energize - the...

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