I haven’t posted much lately as I’ve been very focused on updating textbooks (I just did a major overhaul of the Digital Systems book, consider it a legit 2nd edition), lab manuals (big changes to my online physics labs as well as updates to Microcontrollers and Circuit Analysis, and I’m helping my fellow physics faculty publish open source lab manuals for our E&M classes), ancillaries (developing lots of practice problems for Digital and Microcontrollers), and class content in general. It’s exciting work but not very flashy. Meanwhile, I still have a bunch of fun projects on hold waiting for me to get more focused time to work on them.
So why not talk about something simple that you might not know about? Different types of resistors!
I went onto Digikey’s website on September 24, 2025 to do a price comparison of each type of resistor. I tried to be as consistent as possible for each resistor to compare apples to apples as much as I could. For each type of resistor, I calculated the price per resistor when ordering 10 resistors with the specs of 1k ohm, 1/4 W power dissipation, and +/- 2% tolerance. (Prices get cheaper if your tolerance doesn’t need to be so exact or if you want to order 100s or 1000s of them.)
Axial Carbon Film Resistors (Through-Hole)
If you’re a hobbyist, this is likely the first kind of resistor you picture in your head. These are typically made of carbon film shaped into a helix with a cross-sectional area and length tailored to a particular resistance value. Colored stripes are placed on the packaging around the carbon fiber. These stripes can be read to determine the value of the resistance as well as the tolerance. (Red-red-brown is 220 ohms, a gold stripe means +/- 5%. Refer to chapter 2 in Circuit Analysis or my infographic for more info on reading colored resistor bands.)
These resistors are very easy to use, extremely cheap, and work great in any type of prototype circuit. Honestly, many of my printed circuit boards that don’t have footprint constraints contain axial carbon film resistors. Shown below is a photograph of some of the many carbon film resistors used on my simultaneous equation solver circuit. (Sadly, this circuit isn’t working at the moment, and I haven’t had time to debug or fix it yet. Thankfully I have video evidence that it did, at one time, indeed, function!)
Using the search parameters I described above, an axial carbon film resistor will set you back about 2.5 cents per resistor. So if you need a cheap resistor and space isn’t an issue, this is likely a good option.
DIP Resistors (Through-Hole)
Did you know you can buy packages of resistors? There are through-hole (and, I imagine, surface mount, but I haven’t looked into it) DIP resistors. The ones I use are DIP-16, which means there are 8 resistors inside. Essentially, the left side of the DIP chip contains one of each axial lead, and the right side of the DIP chip contains the other of each axial lead. A diagram of this is shown below.
I would say the biggest benefit of using a DIP resistor over axial through-hole resistors is that you can use a socket, which means replacing burnt out resistors (or even changing the resistor values entirely) is not as much of a hassle. Otherwise, it doesn’t save any space and it’s certainly not cheaper.
The figure below shows a photo of my ones counter circuit from a few years ago that features a DIP resistor. The one in the project is bright yellow, which makes it hard to miss. The resistance is printed onto the top of the package, although it’s illegible in the photo. These are 102 = 1k ohm.)
The price per resistor for a package of 8 resistors in a DIP format is 24 cents. (The entire DIP resistor chip is $1.94.) This is the most expensive of the resistors I looked up prices for in this circuit.
Honestly, if you don’t need the socket or the aesthetics of using a DIP chip… I’d recommend just using the axial through-hole resistors.
Bussed Resistors (Through-Hole)
Bussed resistors are also sometimes referred to as SIP (single in-line package) resistors. Inside the package, each resistor shares a common connection. The pin containing the common connection is usually depicted with a dot of some sort on the package. A diagram of this is shown below.
This resistor type is perfect for pull-down resistors. It could also be useful for current-limiting resistors only if all the resistors connect to ground. (So it would be a bad option for segmented display decoders.)
Below is a photo of bussed resistors used in one of my current projects in the prototype phase on a breadboard. (I’ve also used them in PCB projects as well.) Note the square depicting the common pin, and the value of the resistor printed onto the package (331 = 330 ohms).
This is perfect for eliminating how axial through-hole resistors will inevitably short together if the resistors aren’t trimmed flush to the breadboard. It also frees up a lot of space for the rats nest of wires.
The bussed resistors I looked up online had a per resistor cost of 6 cents. (The entire package of 8 resistors was $0.509.)
Surface Mount Resistors
Surface mount… the final frontier. I’ve been doing more surface mount stuff now that my skills have improved. I feel like any discussion of resistors would be incomplete without a discussion of at least one surface mount device. A project I’ve been slowly soldering over the past several years (you read that correctly… years) containing individual discrete surface mount resistors is shown below. Note the value of the resistor is printed onto the top of the package. (A magnifying glass helps.)
As an aside about surface mount devices. One of the reasons it’s taken me years of working on the board shown above (I bought it, I didn’t design it myself) was because I had to learn how to surface mount solder. Then once I finally had some skills (which are not that great, as evidenced by the huge globs of solder you can see in the photo. I should probably be too embarrassed to show this off online) and started soldering, I think I sneezed and lost one of the capacitors. So I had to buy a set of SMD capacitors to continue working on the project. Then I got distracted. But I have learned a lot about SMD soldering, am currently working on my own project including lots of SMD components, and do intend to post about that once I finish it (so, who knows, maybe another few years).
At any rate, this is THE option for modern devices that need small footprints. These bad boys are also pretty cheap, at about 5.4 cents each. Just don’t sneeze while you’re soldering unless you have a bunch of spares.
Size Comparison
I took a photo of one of each type of resistor with a quarter for scale. Each is 1k ohm. The photo is shown below. (No, I didn’t forget the surface mount resistor. Look near George Washington’s nose.)
