02/04/2021 at 22:18 •
Well, hello there, how nice to see you again. Everything we’ve talked about thus far has laid the foundation for what is to come. In the case of this column, this means we are poised to perform our first hands-on experiments with real electronic components. This is going to be tremendously exciting, so make sure you are sporting appropriate attire (I favor floral Hawaiian shirts myself).
If there’s one thing we tend to use a lot of when we are creating electronic circuits, that thing is resistors. At the end of Part 12, I recommended that you purchase a resistor kit containing a bunch of different 1/4-watt, 5% tolerance components, something like this resistor kit comprising 1,800 pieces spanning 72 values will do nicely (the comments say their leads are a little on the thin and flimsy side, but overall they have a good rating).
As I’ve mentioned before, please note that I have NO connection with and receive NO remuneration from anyone associated with any of the components and tools I may mention in these columns.
Diodes are interesting components in that they conduct electricity only in one direction (we’ll see this in action shortly). The first diodes were created using vacuum tube technology, but we now use semiconducting materials like silicon or germanium. As fate would have it, we won’t be using any regular diodes in this column, but if you really start getting into electronics, you’ll discover that it’s a good idea to have some standard parts close to hand. On this basis, I would suggest something like this diode kit.
Light-Emitting Diodes (LEDs)
There are various types of diodes, each with different characteristics. One type is called a light-emitting diode (LED). As for a regular diode, an LED conducts electricity only in one direction. Unlike a regular diode, however, when the LED is conducting, it also emits electromagnetic radiation (ER). We are typically talking about ER in the form of the visible spectrum -- red, green, yellow, orange, blue, etc. -- but other types of LEDs, like ones that emit infrared (IR), are also available. If you are anything like me, you will end up using a lot of LEDs in your projects -- also, we will be using them in our experiments in this column -- so I think it would be a good idea to splash the cash on something like this LED kit.
9V Battery and Clip
In addition to our resistors and diodes, there are a couple more things we are going to need for the experiments in this column. First, we require something to power our circuit. Just to make things easy, we are going to use a standard 9 V (9-volt) battery. You can, of course, pick one of these up at your local supermarket (but not at a gas/petrol station because they will overcharge you by so much that it will make your eyes water). Note that the smaller connector is the positive (+ve) terminal, while the larger “splayed out” connector is the negative (-ve) terminal.
Now, we could just hold our wires onto the battery terminals with our hands, and you are certainly free to do so, but we can also make our lives a lot easier by using a battery clip. In an earlier column I noted that it’s a good idea to start building up a “treasure chest” of components and other useful items. In this case, on the basis that they will almost certainly come in handy at one time or another, you might consider purchasing something like this 10-pack of 9 V battery clips.
“A LED” or “An LED”?
When you are reading books or articles about electronics, you may see the author write “a LED” or “an LED” -- so, which one is correct? Well, like so many things, the answer is “it depends.” In this case, it typically hinges on how the author sounds things out in his or her head, although it may also be determined by an in-house style guide. If, while chatting, someone says “LED” to rhyme with “bed,” then “...Read more »
12/30/2020 at 23:06 •
Just to make sure we’re all tap-dancing to the same drum beat (and I know whereof I speak, because my dear old dad used to be a dancer on the variety hall stage prior to WWII -- see The Times They Are a-Changin’), let’s remind ourselves that in Part 12 we introduced two multimeters -- a regular digital multimeter that I picked up from RadioShack years ago, and an Auto-Ranging device I purchased from Amazon able to talk about in these columns.
At the end of Part 12, I recommended that you purchase a resistor kit spanning a range of resistance values with a 5% tolerance. So, let’s start by selecting two resistors from our kit: a 1 kΩ (1,000 ohms) with brown-black-red bands and a 10 kΩ (10,000 ohms) with brown-black-orange bands (we described the colored bands in Part 11).Graphical representation of 1 kΩ and 10 kΩ resistors (Image source: Max Maxfield)
For our initial experiments, we’ll use our regular multimeter, which -- in my case -- is my cheap-and-cheerful RadioShack device.My regular RadioShack multimeter (Image source: Max Maxfield)
The reason I call the RadioShack device a “regular” multimeter is that it’s up to the user to use the rotary switch to select the most appropriate voltage, current, or resistance range before making the measurement. In the case of resistance (the “OHM” area of the rotary switch), which is the topic of this column, we have five options: 200, 2K, 20K, 200K, and 2M ohms.
Why do we need these options? Well, selecting the appropriate setting allows us to make the most accurate measurement. This can be confusing if you are a beginner, so let me give you an analogy. Suppose you have two devices you can use to measure the length of something -- let’s say a small ruler with millimeter and centimeter markings and a piece of rope that’s 10 meters long with splashes of paint to mark every meter.
Now, let’s assume you want to measure the diameter of a penny coin. Not surprisingly, you will obtain the best results if you use the small ruler. By comparison, if you wish to determine the distance between your house and the home of a friend who lives at the far end of a long, straight street, then you’ll find the rope better meets your measuring requirements. Remember that analogies are always suspect, and this one doubly so (for all sorts of reasons), but the underlying concept is sound.
Another way of thinking about this is that, at the core of an ohmmeter (the portion of a multimeter used to measure resistance) is a potential divider formed from two resistors we might call R1 and R2 (potential dividers were introduced in Part 7).
Let’s suppose that the value of R1 is known because it’s inside the multimeter, while the value of R2 is unknown because it’s the one we’re trying to measure. For the purposes of what we are trying to do here -- that is, measuring the value of R2 as accurately as possible -- it will make our task easier if the values of R1 and R2 are relatively close together. By comparison, if the value of R1 is say vastly different to that of R2 (say 100 times larger or 100 times smaller), then this will make the task of measuring R2 with any useful level of precision much harder.
Take another look at the previous image. We’ve selected the 20K option, but the probes aren’t connected to anything yet, so the meter displays O.L. As we noted in our previous column, this means “Open Line” (some people may say “Open Loop,” while others may say “Open Circuit”), and it is used to indicate infinite resistance when the probes aren’t connected to anything or if there is no conducting path between whatever the probes are connected to.
Interestingly enough, the actual “OL” presentation depends on the selected range. Even more interesting (at least to me) is that the first time I actually noticed this was when I started to write this column. The various display formats for my meter are shown below (I have no...Read more »
12/04/2020 at 15:40 •
In Part 9 of this mini-mega-series, we mentioned the fact that we can use special tools called voltmeters to measure voltage, ammeters to measure current, and ohmmeters to measure resistance. We also have multimeters, which can measure voltage, current, and resistance, along with a variety of other things, depending on the meter.
It's possible to get all of these meters with either analog or digital displays. For the purposes of these columns, however, we will assume we are working with a multimeter of the digital variety.
A digital multimeter is one of the most useful items in any electronic engineer’s toolbox. You can spend a lot of money on professional, industrial-grade multimeters, but you can also get a very serviceable device for not much money at all. For example, I just had a quick Google (while no one was looking) and found the AstroAI Digital Multimeter (with 4.5 stars from 9,361 ratings) for only $12.99 from Amazon Prime (please note that I have NO connection with, and receive NO remuneration from, anyone associated with any of the components, devices, and tools I may mention in these columns).
Take a look at the photo below. On the left we see a regular cheap-and-cheerful digital multimeter that I picked up from RadioShack years ago and that I use all the time. Observe that this doesn’t have any ports (connectors) per se -- the black and red probe leads just come straight out of the case. On the right we see an ETEKCITY Auto-Ranging Digital Multimeter (with 4.5 stars from 973 ratings) that I purchased for $18.99 from Amazon Prime just to be able to talk about it in these columns.Two low-cost digital multimeters: a regular unit (left) and an auto-ranging unit (right) (Image source: Max Maxfield)
Observe that both of these meters are currently set to measure resistance and are displaying different versions of “OL” meaning “Open Line” (some people may say “Open Loop,” while others may say “Open Circuit”). This is used to indicate infinite resistance when the probes aren’t connected to anything or if there is no conducting path between whatever the probes are connected to.
With regard to the ETEKCITY multimeter, observe that this has three ports (connectors). The black probe is plugged into the COM (“common”) port. This is the probe that is usually connected to the ground (0V) or negative (-ve) part of a circuit. The red probe is plugged into the port marked “VΩmAµA,” which indicates that this port can be used to measure voltage, resistance, and current (in both milliamps and microamps). Different meters will have different annotations on this port, like “VΩmA” or “mAVΩ,” but these are just different ways of indicating the same thing.
Also observe the port with the 10A annotation. This is a special port that is intended to be used only when measuring large currents. As a beginner, you should NEVER be interested in measuring currents larger than a few hundred milliamps, so do your best to forget that the 10A port even exists.
The reason I call the RadioShack device a “regular multimeter" is that it’s up to the user to turn the rotary switch to select the most appropriate voltage, current, or resistance range before making the measurement. In the case of resistance, for example, we have five options indicating 200, 2K, 20K, 200K, and 2M ohms (we’ll discuss this more in my next column).
By comparison, in the case of the ETEKCITY multimeter, the “Auto-Ranging” part of its moniker comes from the fact that all we have to do is set its rotary switch to the Ω (resistance) annotation, and it will automatically work out the most appropriate range when we use the probes to measure the value of a resistor.
Which is best -- a regular multimeter or an auto-ranging device? Well, to a large extent this is a matter of individual preference. One way to think about this...Read more »