Introduction
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That’s really complicated
I once had a boss ask me jokingly why I needed so many different components. Couldn’t I just use resistors and capacitors to do everything I need? It was a joke of course, but I have often thought about what could be done with only resistors and capacitors. Sometimes these kinds of questions are good to get your mind working. They get you thinking about the kinds of things we do every day, but take for granted.
Recently I heard that someone asked my son, a very mechanically inclined and practical individual, what the back side of a hammer was used for. You know, the little curved V-shaped part of a claw hammer. The question was 100% serious. This person had used a hammer his whole life for banging on things. It occurred to him that the back of the hammer must have some practical use but he had no idea what it was.
When we get in the habit of doing things in the same way all the time, we lose some of the creative part of ourselves. While the “use it or lose it” idea cannot be applied to every situation, it does apply to our talents. When we stop being creative we start to cobble things together rather than come up with truly unique was of doing things. As an engineer, I find that terrifying. We make our living by coming up with new and novel ways of doing things.
100 things you can do with just resistors and capacitors – Go!
I don’t think we could come up with 100 things to do with R’s and C’s if we actually used them as electrical devices. I have seen some really cool art projects made with electrical parts, but that is not really what I had in mind.
• Just one resistor – With just a single resistor I think we could make a little heater or possibly a fire. I remember the smell of burned components from my first year in electronics lab. It seemed someone was always testing the limits of ohms law. Or at least probing the non-linear extremes of it. You might laugh, but some day you are going to have a cold chip and you will use a resistor to warm it up a little and think about this newsletter and laugh.
• A pair of resistors – The world opens up when you have a pair of resistors. Now you can scale down a voltage using a voltage divider; 100 percent in and 0 to 100 percent out.
• A pair of capacitors – The same holds true for a pair of capacitors, just not at DC. With the proper pair of capacitors, you can make an AC voltage divider to scale the amplitude of your AC signal.
• A single capacitor – you would not think a single capacitor would be of much use, but you would be wrong. A single capacitor can be used to block DC signals and allow AC signals to pass.
• Just recently we had an embedded processor that worked perfectly until it turned on the radio circuit and then it reset. There was a very short, very sharp drop in the voltage input to the MCU when the radio turned on. We fixed the problem with a single ceramic capacitor, 10uF 10V. A single capacitor maintains the voltage in an area of your circuit. It can do this by supplying current where it is needed or absorbing it when necessary.
• It can provide a low impedance path to ground for a high frequency noise signal.
• A single capacitor can be your energy supply if you have a large enough capacitor or a small enough need.
• A resistor and a capacitor – Now we are getting fancy. With both, we can really smooth things out. We can use them as a low pass filter or a high pass filter.
• If all you have is an R and a C you are in much better shape if you want to use an analog to digital converter. An R-C circuit will help you prevent aliasing.
• A whole bunch of resistors can be used to create a resistor ladder (an R-2R ladder). The arrangement of resistors can be used to convert a digital signal (VCC and Ground) to an analog signal (D/A converter). While tedious, this is a practical use for a handful of resistors.
• You can also use a bunch of resistors connected between two voltages to produce an analog to digital (A/D converter).
• Marx Generator – I don’t know if this is of much practical use, but with a bunch of R’s and C’s and a KV power supply you can make some great sparks.
Now that the hard part is done…
So those are the hard ideas to come up with. The rest must be easy. What would you do? Can you think of other things that can be made with only resistors and capacitors?
Final thoughts
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