The first time I heard the term "shield" in connection with arduino [some years back], I had to google it. So, I'm curious if this term—which seem to me to translate roughly as "daughterboard" in pre-arduino terminology—was in use [roughly with this or a similar meaning] in some other EE context before arduino became popular.

(This question actually came to me while I was reading our meta-thread about the arduino tag, in which someone noticed that arduinistas seem to use at least some terminology that's not common in EE at large.)


2 Answers 2



The whole "shield" thing came about at about the exact time as the arduino became popular.

"Shield"s were, are, and will still be daughterboards or modules in pretty much any serious context for the foreseeable future.

<< snark>>
Speaking loosely, "shield" means "extension module I don't really understand (because electronics are just like lego, right?)"
<< /snark>>

I do make judgments about the knowledge of people who refer to plug-in modules as a "shield", though.

  • 6
    \$\begingroup\$ I would love to meet the guy that thought up the term shield and slap him silly. \$\endgroup\$
    – Matt Young
    Mar 5, 2015 at 4:24
  • 3
    \$\begingroup\$ What's worse, the BeagleBone and Raspberry Pi camps call the same thing "capes". \$\endgroup\$
    – tcrosley
    Mar 5, 2015 at 4:54
  • 1
    \$\begingroup\$ @tcrosley I'm surprised how angry learning this has made me just now. \$\endgroup\$ Mar 5, 2015 at 5:01
  • 6
    \$\begingroup\$ The term "Shield" is ill conceived beyond reasonable belief. BUT I do make value judgements about people who make value judgements about the knowledge of people who refer top Shields as Shield. If the system name for a plug in module is "A Shield" then calling it a Quark or an Octarine-Due is liable to confuse many. And calling it a plug in module is going to confuse almost as many. \$\endgroup\$
    – Russell McMahon
    Mar 5, 2015 at 5:01
  • 1
    \$\begingroup\$ @tcrosley When you find him/her come back and tell me, and give them a notional slap along the way from me. You can add the promulgator of the title "Maker" to that list. They have both (if not the same person) done the world a grave disservice. Many people of inflexible mental bent, of which excellent examples may be found on this list cannot see past these inane titles and it blinds them to the value of the underlying tools. While the aforesaid inflexibles need a bit of slapping as well, the originators deserve a double share for their sins. \$\endgroup\$
    – Russell McMahon
    Mar 5, 2015 at 5:06


A shield has always meant some sort of barrier for protection. Think 2000 years ago of something large and flat you hold so that the other guy can't clobber you with his sword.

In electronics, the term shield means a conductive layer that prevents capacitive coupling to whatever you are trying to protect with the shield. A common example is found in typical audio cables. These are coaxial meaning both conductors are symmetric about the same axis. The signal-carrying conductor is a ordinary wire in the center, and the ground conductor is a hollow cylinder around it, with insulation between the inside of this cylinder and the center wire. External (noise) signals to the cable can capacitively couple to the outer ground wire. The little bit of current picked up there thru the capacitance to the noise source is harmlessly shunted to ground. The inside conductor only sees the 0 V of the ground shield all around it and doesn't pick up the noise.

In electronics, shields also work in reverse. We sometimes put a conducting shield layer around something with lots of noise voltage. This heads off the touble it might cause at the source.

The Arduino Confusion

Arduinos are just microcontroller development boards with software and documentation that strive to let people get simple things done simply without having to know much about microcontrollers, firmware, or electronics. So far so good.

The problem was caused by arduino marketing taking this a step further. I guess they felt the artists who were their target customers at the time might run away screaming when confronted with a "daughter board" or "plug-in board". Their solution was to call such things a "shield". The fact that this word already had a established meaning, and even a more specific meaning in electronics was of no consequence to them. "Screw you, it's not our problem."

In addition to appropriating the word "shield" for their own personal gain at the expense of everyone else, they also did this with the word "sketch". Again, they apparantly felt the few neurons devoted to technobabble in their artist customers' brains would overload at thinking they were writing software, or (gasp!) actually programming. Ewe! The solution? "You're just creating a sketch. Nope, no programming here. Never mind that what you write looks a lot like something those silly knurds call C.".

As you can imagine, this arrogant attempt to repurpose existing words for the personal gain of the arduino sellers at the expense of everyone else pisses off a lot of people. This is particularly true of electrical engineers, for whom "shield" already has a special meaning specific to the discipline. As a result, those using "shield" in the arduino context will be met with much hostility here. I personally am likely to downvote any such question, and look for a handy excuse to close it too. And, I'm not the only one.

Arduino Questions Don't Belong Here

This section is really a meta discussion, but it needs to be said within the context of the above.

This site (EE.SE) is for electrical engineering. That means we are all about understanding circuits, components, and how they work. We are happy to help others who are trying to learn this too, or have particular problems in the course of doing electrical engineering.

Note that arduinos were specifically created for the opposite, which is getting results without having to understand the underlying technology. Again, that's all fine by itself, but this site is about the underlying technology and helping people who want to learn it. It is absolutely NOT for "i dunno, jus plug dis inta dat and it work".

Therefore, asking about something related to a arduino here is basically saying you just want to get results and don't want to be bothered with all those silly 'tronics thingies. Just gimme da codz! Naturally that will result in the digital equivalent of getting tarred and feathered while run out of town.

How to Ask Arduino Questions Here

This may seem odd since I just got done saying that arduino questions don't belong here. However, electronics questions that happen to come up while doing something with a arduino can be fine. The point is these questions must

  1. not be about the arduinoness,

  2. be about a real electronics problem,

  3. and exhibit a desire to learn about the underlying technology, not just to get a particular result now.

Since "arduino" in a question will be read as "I don't wanna know how this stuff works, just gimme da answer so I can go back to laughing at all you silly techno-weenies behind your backs. Hey, if I actually respected you lot, I wouldn't barge in here flagrantly misusing your specialized words, and maybe I'd bother with one of those skmatic thingies instead of this wires diagram some software I found on the internet made for me. So fork over the answer already, you insufferable knurds.", it would be wise to leave it out. Put another way, by mentioning "arduino" at all, you have shifted the presumption of what you are here for. The burden of proof is now on you, and the bar will be set higher. Such things happen when you piss people off.

So what to do? Don't mention "arduino". Not only won't that immediately label use a one of those annoying ardweenies, but it's a good test for you whether your problem is appropriate here. If you could just as well say "microcontroller" or "microcontroller development board", then you probably do have a general electronics questions. Of course then there is no need to actually mention "arduino", so don't. If the fact that the problem is related to a arduino is important, then it's a strong clue that it's a arduino user-level issue and doesn't belong here.

So in summary, first get rid of all mention of "arduino" and related usages of "shield" and sketch", then

  • If the question still makes sense, you have a general electronics question. Ask it here.

  • If the question no longer makes sense, then it doesn't belong here. Go away. We don't give a crap where to (although there is now a Arduino.SE site where your question may be a fit).

  • 2
    \$\begingroup\$ This might have been one of the worse examples of friendly help, which is what stackexchange is suppose to be about, I've seen. Adults and children in an effort to learn electronics start with platforms, like Arduino, which make it easy to learn without having to be an expert. Your comment could easily sour their appetite which is a shame. In my opinion this is exactly the place to pose Arduino questions. Even if you don't like their terminology it is still a very useful and amazing project, especially for educators. \$\endgroup\$ Jan 6, 2017 at 0:15
  • 1
    \$\begingroup\$ @LanceCaraccioli: there is arduino.stackexchange.com for Arduino questions. I don't think they belong here as long as they are not very hardware related, e.g. referring to the internals of the micro controller. \$\endgroup\$ Sep 5, 2017 at 12:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.