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# I want to learn about electronics, not plumbing.October 9, 2013 7:12 PM   Subscribe

What are some books (or other resources) that would help me understand electricity and hobbyist electronics without a hydraulic metaphor?

I want to learn more about how electronics and electricity work, but the books I've read recently haven't been particularly helpful. My main problem is that the beginner books I've picked up (like, my most recent attempt, Make: Electronics) all use a nonsensical (at least to me) hydraulic/plumbing metaphor, involving water in pipes. It's confusing me. I want to understand electricity, not water, after all.

For an example of my difficulties, check out the capacitor example on this Wikipedia page. Why would a rubber diaphragm be inside a pipe and why would that do anything even vaguely useful?

I'm coming from a pretty basic level. I can safely handle a soldering iron and have no trouble at all programming my Arduino. But I have a hard time solving problems in circuits or making new ones without instructions. Please recommend something that might help me remedy this.
posted by ddbeck to technology (10 answers total) 14 users marked this as a favorite

posted by raildr at 7:40 PM on October 9 [2 favorites]

I suggest http://www.allaboutcircuits.com for a good introduction to electronics. Their free online book is really good. That coupled with YouTube videos and some tinkering should give you a good base.

That said it really depends on how in depth you want to go. Ohms law, which is what the water pipe analogy is describing, is a simplification of the laws of electromagnetism which provides a very good description of what's going on in most situations. Ohms law with some circuit analysis techniques(thevenin/norton and superposition) which are covered in the link above will allow you to solve for voltages in most DC circuits which will help you develop some intuition as well.

The water pipe analogy is used because it's easyish to understand and provides an intuitive way of thinking about voltage, current, and resistance.

Voltage ~ pressure. If you increase the pressure across a piece of pipe you get more water flow. Likewise if you increase the voltage across a resistor you get more current flow. Where current is just the number of electrons being driven through the resistor.

You can also increase the current by lowering the resistance, ie just make the pipe bigger. It makes most sense to me if I think about the pipe being very small and really limiting the amount of water through the pipe.

The key to the analogy is that voltage, current, and resistance are all interdependent, which is exactly what ohms law describes. You increase the voltage current goes up. Take out a resistor and put in a lower value, current goes up.

V = I *R.

If you really want to know what's going on in the devices and conductors then learning some E&M is the way to go. I can recommend the 8.002 course from MIT which is available online if you want to head down this road, but be wary it does involve some heavy math(calculus, etc). I'm sure other sources are available and not as heavy but I haven't done the work to find a good one.
posted by Quack at 8:14 PM on October 9 [1 favorite]

Part of this is figuring out exactly what you are trying to understand (which can be hard to do if you don't understand it much...). What applications are you trying to figure out?

But Quack gives the basics, and allaboutcircuits is a pretty good resource, although sometimes it assumes that you may know more than you really do.

But, basically, electrons are trying to go from high potential energy to low potential energy. That difference is the voltage.

Various devices provide paths for that, that once the electrons start flowing, it creates current. How the amount of current is related to the voltage is the crux of the matter. For a resister, there's ohm's law. For other devices, (PV cells, diodes, capacitors, inductors, zener diodes, etc) there are more complicated equations for this... but you can learn these after you learn the basics of DC circuits with resisters.

(And, as someone with a fluid mechanics background, the electricity-hydraulics analogy always bothers me as well, since electrical analogies are a terrible way to describe hydraulics. ;) )
posted by kaszeta at 8:36 PM on October 9

The hydraulic analogy is used because it is a really good analogy, the problem is that you don't know about hydraulics. To take your example, the capacitor as rubber diaphragm, these are all over - hydraulic accumulators, household water tanks (for people that have wells), and hot water expansion tanks. It's a great analogy for a capacitor: the diaphragm in a pipes blocks continuous flow but transmits pressure pulses, just like a capacitor blocks DC and passes AC.
posted by 445supermag at 9:07 PM on October 9 [2 favorites]

You could take a look at the Art of Electronics. It might be a little too advanced, and parts of it will be dated, but if you're interested in more advanced circuits, both digital and analog, it is very good. According to the wikipedia page on it, a new version is supposed to be out next year.
posted by pombe at 9:20 PM on October 9 [1 favorite]

I had tremendous luck with Electronics for Inventors. They tip their hat at the various water analogies, but they don't stay there for long.
posted by Kid Charlemagne at 10:18 PM on October 9

Prepare to stay confused. Most stuff happening in electronics is invisible and the units are defined in relationship to one another. Once you 'get it', you'll appreciate the water metaphor more. Immersion helps. One day, you suddenly speak French, as it were and it all kind of comes together. I was bewildered for a decade and still have enormous swaths of ignorance. Comes with the territory. If you ever feel like you know it all, you're most certainly wrong.

Good to find a mentor. Any cousins, uncles, friends, sisters ham radio operators? They were 'makers' 100 years before the term got its new, common meaning. Easy to find, too, and usually happy to help noobs.
posted by FauxScot at 12:24 AM on October 10

I'd like to at least try and explain the metaphor to you. The hydraulic analog is used in electronics because fluid systems are analogous to electronics. Mechanical systems, fluid systems, and electronic systems are all conceptually the same because they are all governed by virtually the same second order differential equations.

In mechanics you have springs, masses, and dash pots (i.e. shock absorbers, viscous dampers). In electronics you have resistors, inductors, and capacitors. In the fluid system you have constrictions in the pipe, paddle wheels, and hydraulic accumulators. The reason that rubber diaphragm is in the pipe is to offer an analogy to a capacitor. A capacitor is a device that stores electric charge at one rate and then discharges it at a different rate.

The suggestion to read a Forest Mims book was an excellent one IMO. I think you would learn more from a practical approach versus learning the underlying math. Build RLC circuits and vary the components to see the effect versus doing the math, for example.
posted by Rob Rockets at 9:58 AM on October 10

The only thing I loathe about the hydraulic analogy is that when a switch is "closed", electrical current can flow, but when a fluid valve is "closed", it blocks the flow. Other than that it's really quite good.

I think you're gonna just have to suffer the annoyance because most folks who know anything will explain it with the best analogy they know, and that's the best analogy anyone's come up with.

(Oh, and the diaphragm in the pipe? Go look at how a water-hammer arrester works; it's used in almost the same way as a bypass capacitor.)
posted by Myself at 12:32 PM on October 10 [1 favorite]

Thank you, everyone. Based on your responses, I think I just haven't been patient enough, because some of your explanations of the metaphor were quite helpful. I think 445supermag was on to something with, "the problem is that you don't know about hydraulics." I will give your suggestions a try, and maybe revisit some of the materials that have confused me before. Again, thanks!
posted by ddbeck at 6:21 PM on October 10

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