In having a nosy at what my fellow students have been doing I’ve come across another digital logic device called a flip flop. The ever helpful Steve has aslo been building a binary counter but he has done it in a very different way to mine, he has used a chain of 4 linked D […]

In my explorings I have come across the terms ‘pull up’ and ‘pull down’ resistors in conjunction with digital circuits. So… what are they? How do they work? And why do we need them? CMOS gates are sensitive to static electricity and can be damaged by high voltages, they may also assume any logic level […]

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 […]

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 […]

Brilliant session with Dean today, loads to add… First, the Darlington driver or Darlington pair. You basically feed the emitter of one NPN transistor to the base of another, this multiplies their individual current gains so massively boosting the signal. Darlington pairs can be used like this to convert analogue signals to digital ones. If you had […]

I’ve moved on a bit since the last time I looked at logic gates so I think it’s about time to revisit… I’ve found out a bit more on NOT gates, they are actually called inverters, not surprisingly as they ‘invert’ the input into the output. When you connect up two inverters in series you […]

Digital ICs are classified into logic families depending on how they’re constructed on the inside. Some construction methods make the circuits run faster or work using lower currents or just by being able to fit more gates in. There are loads of logic families but the two most famous (and the ones I’ll likely be using) are […]

One thing that has kept coming up in my research has been the term Boolean algebra or Boolean logic, this apparently is a system of logic that was developed in the 1840′s by a chap called George Boole. It basically laid out several rules of relationships between mathematical quantities that were limited to being true […]

If I’m going to teach electronics (or even develop my interest as a hobby) there are three ICs that I will have to look at. They are the op amp (operational amplifier), the 555 timer and the 4017 decade counter. Op Amp – this IC takes a weak signal and gives it a boost, it’s made up […]

Right, as I’ve stated before, logic gates are made up of lots of components arranged in just the right way to produce a desired logical outcome. If you had to build one of these circuits each time you needed a gate you’d probably throw your hands up in disgust as it would not only take huge […]