500-in-1 Electronics Kits? 125
Oneamp asks: "I'm interested in a '500-in-one' type electronics kit. Amazon lists a few, but I've seen some user reviews that maybe they are not all they're cracked up to be. Most of the complaints seem to be of the 'Manual sucks' variety. Nevertheless, I'm sold on the idea. Can any of you, who have had actual experience with any of these kits, recommend a good one?"
I just bought... (Score:4, Informative)
It comes with a 76 page illustrated book that takes you through building circuits of greater and greater complexity. I'm only up to page 22 or so (capacitors). The illustrated book is fairly clear, uses a water/pipe analogy to explain what's happening..
This, along with this free book [ibiblio.org], has provided hours of fun and an interesting intro to how these electric devices we see all the time actually work...
I haven't used a 500-in-1 kit yet, but considering how cheap this was, I feel like I've already gotten my moneys worth in watching a capacitor charge at different rates depending on the resistance I throw in front/behind it.
I know, I know. I'm easily entertained. Can't wait to make the transistor radio. That'll be cool. I mean, when it's done... I'll know how a radio works!
For anyone who's ever been interested in electronic machines and how they operate, I highly recommend the book ("Lessons In Electronic Circuits"), which is easy to read, and getting one of these little kits. Good times.
Buy kit + good electronics book (Score:2, Informative)
200-in-1 kit, link and review (Score:5, Informative)
I see that the same company makes a 500-in-1 kit. Assuming this is of the same quality, it would be worth considering.
The problem with the 200-in-1 kit is probably common to all such kits. The transistors, ICs and LEDs are real - they are easy to damage by incorrect connection. You can replace the transistors with a bit of effort, but some components are soldered directly to a board. It's a real pain if you damage anything. I also don't like the use of batteries as a power source. I suppose that's a safety thing, but I'd prefer a good quality low-voltage PSU with an electronic fuse.
I think the next step after a kit like this is making your own circuits from 74-series logic ICs, which provide basic logic functions and some more complex devices like flip-flops, registers and counters. You can make all sorts of fun stuff with this, and you really only need a data book that covers the 74 series, a breadboard and a 5 volt PSU. This is great fun. Especially when you add a microcontroller!
Op-amps (Score:5, Informative)
When a voltage is presented at the inverting input, a current flows into it; the transistor on that side tries to let a larger current through its collector (and thus its emitter). The voltage at its emitter -- the output -- goes down. When a voltage is presented at the non-inverting input, a current flows into the base of the transistor on that side and it tries to let a larger current through. But the shared emitter resistor means that the other transistor can't let so much current through anymore, so the voltage at its collector goes up.
The reason for using a constant-current sink in the emitter path is that the changing collector-emitter resistances of the transistors can be significant, making the transfer function horribly non-linear unless the device is only working over a very narrow voltage range (much less than the supply voltage). This was never a problem with valves, when the circuit was called a "long-tailed pair" in reference to the large resistance between the two common cathodes and ground. Fortunately, constant-current sources and sinks are not hard to build using transistors, as long as you can find a pair which have similar electrical properties (obviously) and are in good thermal contact (so temperature variations affect both equally). Such conditions are easily met in an IC.
Get Radio Shack's "Electronics Learning Lab" (Score:3, Informative)
Re:They need to have a sit-down with their marketi (Score:2, Informative)
You can start with one of those kits, but once you get to the point where you'll really learn what you're doing, go look for books and kits separately. Look for books by Forrest Mims III [forrestmims.org] and Don Lancaster [tinaja.com] (TTL Cookbook and CMOS Cookbook are classics). Check their sites out as well.
As for parts sources, for online shopping, I'd recommend Digi-Key [digikey.com]. Jameco [jameco.com] is a little pricey, but they have some really interesting parts, including a lot of older stuff. All Electronics [allelectronics.com] is a place I used to buy from a lot; they have a lot of manufacturer surplus parts, so it's kind of like shopping in a flea market or surplus auction. Another surplus shop is MPJA. [mpja.com] Newark [newark.com] and Mouser [mouser.com] are good places to look when you want some specific part that Digi-Key doesn't have.
For starters, you'll want to buy a modular breadboard [jameco.com], and one of the pre-cut wire kits for them. Or, if you want to blow some more dough, you might want to get one of the Analog Design Lab [jameco.com] or Digital Design Lab [jameco.com] things that has a bunch of things like power supplies, LEDs, and switches integrated into it already. Also look for parts assortments, like resistor and capacitor assortments (e.g. Digi-Key items RS125-ND and PHD1-KIT-ND). If you're going to be doing digital work, you'll probably want to get lots (20 or so) of 10K resistors (for pullups) and 0.1 uF capacitors (for decoupling).
Radio Shack is where you go as a last resort. Their selection is lousy and prices are worse.
Re:Op-amps (Score:3, Informative)
Now, what good is this? One example is to decode an FM stereo signal. When stereo capabilities was added to FM radio, it had to remain compatible with mono radios. So the idea of broadcasting the left channel on one frequency and the right channel on another flys out the window. So, the solution was to broadcast the left + right (L + R) on the main channel, then send the difference (L - R) on a sub channel. So you end up with two channels, M (main) and S (sub channel), with M = (L + R) and S = (L - R). Using a bit of algebra, we can get L = (M + S) / 2, and R = (M - S) / 2. Op amps are therefore a good fit to do the addition and subtraction on the two channels (the "/2" can be dropped -- without it, you only end up with double the volume, which ain't a problem with audio).
Of course, it's been a while since I studied any of this, and I know that it isn't a complete acurate description of stereo broadcasting, but it should suffice for a discussion on op amp usage.
Re:Op-amps (Score:3, Informative)
It was in response to somebody saying they knew what it did, but not how it did it...
But anyway, operational amplifiers amplify the difference in voltage between their two (inverting and on-inverting) inputs. They're largely useless used open-loop, as they have voltage gains of tens of thousands to millions, so even slght noise sends the ouptut swinging about wildly. They are virtually always used with negative feedback (some connection between the output and inverting input). An op-amp with negative feedback drives the output till the two inputs are at the same voltage. With various simple circuits around them they can be made to amplify, add or subtract voltages, form the heart of filters (high-, low- or band-pass), buffer signals, integrate or differentiae signals, drive high-power loads or many other things I can't remember just now. Check out National Semicondustor Application Note AN-31 for a whole bunch of circuits you can build around an op-amp or two with a few other basic components. AN-4 and AN-20 give a written introduction to the theory and applications of op-amps.
Re:Here is a real desc. of op-amps, not a crap one (Score:4, Informative)
The reason why the input voltage difference is nearly zero when negative feedback is applied, is because the amplifier is operating linearly. So actually, the difference between the two input voltages is the output voltage, divided by the open-loop gain. But the open-loop gain is huge, so the input voltage difference will be tiny.
Now, there's a thought. If you applied the same inputs to a second op-amp on the same chip (so, hopefully, having the same open-loop gain), would you get a sane voltage at the output, even with no negative feedback?