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Where To Start In DIY Electronics?
pyrosine writes "I've been thinking about this for a while and have no idea where to start. I have little or no previous experience in electronics — just what is covered in GCSE physics (wiring a plug and resistors — not much, I know). The majority of my interest lies in the wireless communication side of the field — i.e. ham radios and CB — but I am also interested in how many things work, one example being speakers, simply to better understand it. I would preferably like to start with some form of practical guide rather than learning the theory first, but where I would find such a walkthrough eludes me."
Hanging in ##electronics on freenode gave me *a lot* of knowledge. Also, there is a plethora of other channels like #avr, #sparkfun etc for when you get more involved in a specific branch of electronics
It's a nice reference. Once in a while you just have to get right back to the basics and remind yourself how some common BJT circuits such as current mirrors work. Ditto with basic opamp circuits.
Depending what's understood with "electronics" it's big and sprawling subject with many sub-disciplines. You can get into EMI quagmire and never really come out of it, for example.
I was interviewed with one company where "cad heads" and designers are quite separate with layout designers being the less appreciated job.
In any case, there are many, many things to learn and you only become really good when years go by and you accumulate knowledge. You do, however, probably become good only in subset of things you've worked with.
For example. Mosfets are voltage controlled devices and you do not have to worry about power to the gate, right? Wrong. The gate charge, while very small _does_ add up hugely in SMPS circuits and such when you're charging and discharging that small capacitor 100000 times a second or so.
I'd strongly suggest that you do at least a basic level of looking into theory while you're creating "practical circuits" - it's quite helpful when you're debugging to know at least roughly what's meant to happen.
One source I can recommend is the MIT Open Courseware resources - the 6.002 course on Circuits and Electronics is a good place to start; I'm an embedded software engineer who's started to push into the hardware side of things, and that set of lectures helped me turn my vague understanding of electronics (being able to read a circuit and understand what's going on) into something practical (being able to design a circuit).
I have had plenty of times shocking myself when playing with what I thought were safe devices. Here are a couple that caught me off guard:
1: Capacitors. Even though you are unplugged and powered off, a capacitor can be holding a surprise for you. The one that I learned on was built into a camera flash: So even though the device was powered by a couple of AA batteries (removed), sitting in wait was a capacitor with several thousand volts. I recall getting up off the floor wondering WTF just happened.
2: Relays. These devices use an electromagnet to move a metal reed, which closes (or opens) the connection for another circuit. Be aware that when a magnetic field collapses, electricty is 'made'. So even though I was driving the electromagnet with 9v, the shock I got when the field collapsed was likely several hundred volts. This wouldn't have been quite the problem, if I weren't using the relay to drive the relay (the switched circuit was closed in the unpowered position, and open when powered) - which creates an oscillator. This means that I shocked myself quite a few times before I could get the breadboard off of my hand.
Build a crystal set. It's simple and magic. With only a diode, inductor (coil), tuning capacitor and head phones you get real radio. You can build one with just a hammer and nails on a piece of wood (or you can be more sophisticated if you want and use screws or even do soldering, it's up to you).
If you want to build wireless equipment it is a good learing curve about what is important - i.e. capacitance, inductance and the antenna (all them transistors etc are just added extras).
Google and you will turn up loads of free on line designs for crystal sets. Remember if it doesn't work first time, keep trying. Building analogue Radio gear can require much more skill and accuracy than simple digital stuff.
Art is the mathematics of emotion