When looking up electronics shields the only useful information I could find pertained to Electromagnetic shielding. But when inspecting Arduino shield schematics most offer no protection to the Arduino.

So it begs the question, why are Arduino peripherals called shields?



  • \$\begingroup\$ I don't really know why they came up with that term, but they did coin/reappropriate it... by all accounts [here] electronics.stackexchange.com/questions/158201/… \$\endgroup\$ – SX welcomes ageist gossip Oct 19 '15 at 16:04
  • \$\begingroup\$ You can do this question at Arduino SE. \$\endgroup\$ – Butzke Oct 19 '15 at 16:04
  • \$\begingroup\$ This reminds me. Could someone please set the EE.SE tag wiki for shield straight? \$\endgroup\$ – Nick Alexeev Oct 19 '15 at 16:09
  • \$\begingroup\$ @NickAlexeev: it seems to me it should be discussed in meta how to deal with overloading (of the term) in terms of tagging. \$\endgroup\$ – SX welcomes ageist gossip Oct 19 '15 at 16:23
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    \$\begingroup\$ @KyranF At least, the word "cape" is not used in the standard EE terminology. So "cape" seems like a somewhat better choice than "shield". \$\endgroup\$ – Nick Alexeev Oct 19 '15 at 16:41

I doesn't look like they've registered a trademark for it ("shield").

The mostly obvious explanation is the mechanical position of the daughterboard. One book says:

These boards are called “shields,” because they usually fit over the top of Arduino like a protecting shield.

The setup is by no means new. I had an ancient (1990-era) video card that had a 2MB addon-VRAM card (for a total of 4MB); it looked like the image below

enter image description here

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  • \$\begingroup\$ stacking PCB is an ancient technique, and follows good design reasoning - if you run out of space in 2D, stack into 3D! \$\endgroup\$ – KyranF Oct 19 '15 at 16:38
  • \$\begingroup\$ Yes. There are other things I can remember using that e.g. SPARC boards, but the above is the closest to an Arduino in looks. \$\endgroup\$ – SX welcomes ageist gossip Oct 19 '15 at 16:45
  • \$\begingroup\$ Thank you for your answer. Shields provide physical protection, like sword and shield rather than interference protection. \$\endgroup\$ – Westly Oct 19 '15 at 16:50
  • \$\begingroup\$ @Westly - it's true that shields provide physical protection, but that's not the purpose of an Arduino "shield". An Arduino "shield" provides additional board space for easy-to-add accessories. \$\endgroup\$ – Pete Becker Oct 19 '15 at 17:18

It's hard to answer questions "why somebody did something non-technical in a certain way". I can think of 2 possibilities, though.

  • Primordial ardweenies haven't thought it through.
  • More likely, they knew better, but decided to go with a fun terminology like "sketch" and "shield" and sacrificed technical accuracy to marketing.

Recently, I was reading an application note written by a large company. When they had to mention Arduino extension board, they wrote "Arduino extension board". [I can't seem to find that app note again. It was by Texas Instruments, iirc.]

Finally, the question has been already answered here.

(trivia: Arduinos are named after Bar di Re Arduino pub, where the primordial ardweenies were meeting up. Source.)

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Daughterboard, shield, hat, cape, ...

The standard name for a subsidiary printed circuit board (PCB) that plugs into a main PCB is "daughterboard"

However, the somewhat artsy communities that produce these small experimental microcontroller boards each tend to invent their own name for daughterboards that have the required dimensions and connector to mate with the primary form of main PCB in that community

Arduino:       shield.
Raspberry pi:  hat.
Beaglebone:    cape.

So they tend to borrow the name of some type of accoutrement that a human might loosely attach to themselves. There is a vaguely protective theme here but I think that is largely irrelevant.

I'm not sure what the first Arduino shield was but it was probably something that mediated between the Arduino and the outside world. Also from its shape it isn't too dissimilar to a rectangular shield, I suppose it also (uselessly) shields the Arduino from light (and fingers). Most Arduinos have no (or little) electrical protection on their inputs and outputs, at least some shields provide a modicum of additional protection - although that is usually not their main purpose.

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  • \$\begingroup\$ Thanks for your answer. I never knew about the terms hats or capes being used. So it each community has their own term for an add-on board. Is daughterboard the official name? Or is it another made up name like shield and cape? \$\endgroup\$ – Westly Oct 21 '15 at 14:51
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    \$\begingroup\$ @Westly: Daughterboard is just a general term that has been used for a long time. You'll also see "expansion board" used sometimes. Both these terms date back to the previous millennium and are long-established well-understood terms in the electronics world. \$\endgroup\$ – RedGrittyBrick Oct 21 '15 at 15:26

It's a brand name. Compare it to the names that other manufacturers of other systems give to their plug-on, stackable, add-ons.

Why did they choose that brand name? It had to be different from the others. And easy to say. And it helps if it conjures up something small and single-layer. And has good rather than bad connotations.

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