Design and Technology
My Own Personal Yellow Brick Road
transistor circuit to fix

My logic circuit is a nice, simple NAND gate to start this off:   The transistor circuit is one that I’ve not tried out before, I’ve simulated it using Circuit Wizard in my previous post so now time to bring it into the real world:  Next is the monostable: And lastly the beast… The binary to decimal […]

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binary counter wave form

I wanted to create a couple of circuits using 555 timers and 4017 decade counters but I seem to have hit a brick wall in trying to obtain any 4017s! Rapid look through equivalent chips with Dean and it looks like I can use a 4028 chip instead. A 4028 is officially known as a BCD […]

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resistor colours

Now we get to have a little fun… I’m going to take a look at the 3 types of circuit you can make with a 555 timer, astable, monostable and bistable. Monostable – one stable state This is my monostable circuit and I’ve calculated that I need a 100K resistor with my 100µf capacitor to […]

Setting up the Light Box

Right, Ok then, Eeeep… This originally sounded like Dean was asking me to something on par with “just run along to the nearest dragons lair and bring me back some rubies would you , oh and careful you don’t get scorched along the way”. Me? Make a PCB? From scratch? Right. First step, what is a […]

Almost complete

Right, now I have decided on my product I need to purchase the keypad kit, put it together and make my alterations. The kit comes from a company called Tech Supplies ( and contains the basics I need for making my safe. Before I received my kit I had assumed that the keypad would work by […]

circuit diagram

Aahhhhhh! it’s stopped working! After painstakingly putting the kit together and testing it, my contrary PIC chip has decided to stop working. Today I plugged it in to find that only some of the keypad keys are working, the LED won’t flash and the buzzer is making a constant low level bzzzzzzzzzzzzzzzzzzzzzzzzzz (very annoying when […]


Now that I have all my pieces cut and temporarily fixed together (thank you masking tape) I need to return my attention to my wiring. The flying leads I used when first putting the keypad together are far too long and are made from single core wire making them very stiff and prone to breaking […]