January 24th, 2010 by Ian
This experiment was the longest yet. The goal here is to build up a circuit that makes a pulsating style noise, like a burglar alarm. In the process I learned about programmable unijunction transistors (PUTs), and how to use bipolar transistors (in this case the 2N2222) to amplify a signal.
Making some notes to myself here about PUTs, as this is the major new component introduced in this experiment. The most common PUT is model 2N6027.
Like a bipolar transistor, a PUT has three leads. However, they are called the anode (input), gate, and cathode (output). The lead orientation of a PUT is opposite of a 2N2222. So if you have the flat side facing left and the round side facing right, this will put the anode at the top and cathode at the bottom.
There are two main differences between a PUT and a bipolar transistor. Read the rest of this entry »
January 21st, 2010 by Ian
My startegy for learning stuff by lonesome is triangulation. When you are book learnin, often times there will be gaps in one author’s explanation. By getting two or three books that cover the same material, you can can use your secondary books to backup your ‘main’ book.
Make: Electronics is still my main book. But now I got the classic Getting Started in Electronics too. Also picked up Electronics for Dummies. I’ve already run into a few things I was spotty on. For instance, with a unijunction transistor, I get that you program it’s voltage tipping point via a resistor. But what I don’t get is how you know what that point is. Hoping that when I run into these kinds of situations, the other books will help me out.
January 20th, 2010 by Ian
Resistors have a color code that tells you how many ohms of resistance they offer. This site quizzes your memorization of the codes.
January 10th, 2010 by Ian
Iâ€™ve wired up Experiment 10 from the book Make: Electronics by Charles Platt.
I show a couple of things in this video. First off, I’m using an NPN style transistor to switch complete the circuit to an LED. A NPN transistor has three leads: a collector, a base, and an emitter. When the base receives current it enters a switched state, which connects the collector and and emitter leads. The collector is positive and the emitter is negative (this is reversed for a PNP transistor).
Read the rest of this entry »
January 10th, 2010 by Ian
I’ve wired up Experiment 9 from the book Make: Electronics by Charles Platt.
This experiment shows you can use use a resistor and a capacitor to create a timer. The multimeter on the left measures voltage. As I swap in a 100K resistor, a 47K resistor, and a 10K resistor, the charge up time gets faster and faster. In other words, the less resistance in the circuit, the “quicker” the flow of current to the capacitor, and the faster it charges up.
I’m using the push button in this experiment to complete the circuit, that way it’s not always going while I swap out resistors.
January 3rd, 2010 by Ian
The same circuit as this one, but breadboardified. Finally (nearly) free of alligator clips.
January 2nd, 2010 by Ian
I’ve wired up Experiment 8 from the book Make: Electronics by Charles Platt. Iâ€™m 90% Iâ€™ve got it right.
By adding a 100uF capacitor to experiment 7, the relay stays in the non-relaxed switch position for a little under a second, then very briefly relaxes, and then re-engages. This is why the green LED (relaxed state) blinks on every second, but the amber LED appears to be almost solid. The amber LED actually is blinking for a split second, but itâ€™s imperceptible in this video.
January 1st, 2010 by Ian
I’ve wired up experiment #7 from the book Make: Electronics by Charles Platt.
This purpose of this circuit is to demonstrate how to use a relay to switch between two LEDs. Using a DPDT non-latching 12v relay + SPST push-button switch, two LEDs, and a 680 ohm resistor. Power is off of a spliced radio shack 1000ma DC power supply set at 12v.
God I hate alligator clips. The circuit is a tad wobbly due to my crummy wiring.