I've built a small consumer device that contains an Arduino Nano. It's coupled to a custom daughter board that allows it to pulse a 12V electromagnet at about 1 hertz as well as inteface to some sensors. It does not intentionally produce any RF emissions like wifi or bluetooth.

I'd like to sell my device in the US, and I'm trying to determine what certification I need to legally sell it. From what I've read about FCC certification, including similar questions here, it's needed by nearly all electronic devices that oscillate above 9 kHz.

So, if I understand this correctly, my custom daughter board wouldn't require FCC certification? The Arduino Nano contains a clock that oscillates at 16 MHz, but I believe it already has FCC certification. Does my composite device constitute something that needs to be re-certified by an FCC approved testing lab? I'm not sure how much I'll be able to sell the device for, and don't expect to make much money, so if I can avoid wasting $10,000 on worthless certification for an unintentional emitter, I'd like to do so.

I'm not sure if this is an appropriate question for this site. If it's not, where could I find an answer to this? I've checked the FCC's website, but aside from vague FAQs, I can't find any way to contact anyone with a clue. I've seen some test labs offering to give me a quote to answer this question, but since they have nothing to gain by telling me "no don't bother paying us thousands to test your device", I'm hesitant to trust a response from them.

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    \$\begingroup\$ I think this is and apt. question, and I also think it is quite interesting. +1. \$\endgroup\$ Oct 1, 2017 at 18:50
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    \$\begingroup\$ One way to learn the ropes is to engage the services of a consultation engineer who has taken a product through the certification process before. A few hours of consultation can layout the groundwork ahead of you help you to adjust your product design if needed before you ever show up at a test lab. That alone can save you 1000's in not misstepping on the first trip to a lab. Find someone experienced in the same product category field. \$\endgroup\$ Oct 1, 2017 at 21:18
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    \$\begingroup\$ Agree with @MichaelKaras. There's a similar device sitting on my desk right now, and I'm happy that a professional consultant checked the design. If the FCC ever knocks on our door, we have the paperwork. \$\endgroup\$
    – MSalters
    Oct 2, 2017 at 15:06
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    \$\begingroup\$ 1. Ensure solenoid is well clamped on release (reverse diode at least and maybe some RC to slow the edges). 2. Cheap & easy DIY tests that work surprisingly well. Not 100% certain that these will not miss something but usually very useful: Take a portable am band radio and tune across AM broadcast band looking for "spuries". At very low range (a few inches) there WILL be some or even many. At a few feet there may be a few. At ten feet there will hopefully be little. See what range each has and see if you can find how to reduce the largest ones. ... \$\endgroup\$
    – Russell McMahon
    Oct 4, 2017 at 2:40
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    \$\begingroup\$ ... (2) Doing that same with an FM radio works but is less useful. (3) The probably now rather rare lowish cost portable manually tuneable, (usually) black & white (typically 12 volt) TVs are excellent for finding signals in the VHF/UHF bands. They do not cover all frequencies but you can SEE signals and also heard them. If you pass the AM radio test well the TV is usually reasonably clean as well. The manual tuning is MUCH more useful than station switched TVs which can easily miss signals. \$\endgroup\$
    – Russell McMahon
    Oct 4, 2017 at 2:41

6 Answers 6


You are confusing certification and emissions requirements. Only intentional radiators need to be certified. From your description, your device is not a intentional radiator.

However, you are still obligated to ensure it does not radiate excessively. The limits are defined in part 15 of the FCC rules.

How you determine for yourself and ensure that the device does not radiate more than allowed is up to you. The FCC doesn't go looking at the millions of devices that are unintentional radiators and test them for compliance. However, your competitors might. If they find your device radiates illegally, they can file a complaint with the FCC.

The worst case is if some communication got interfered with, the FCC investigates, and finds one of your devices causing the problem. Then it gets serious fast.

Large resellers may require a recognized lab to certify that your device radiates legally, or they won't carry it.

All that said, for a little guy selling a few 100 gizmos a year off some web site, there is very little chance anyone is going to check whether the device radiates within the limits. If you follow best practices, like a good overall grounding strategy, filtering of external wires, etc, chances are very low your device will radiate enough past the limits for anyone to notice or to care.

As Dirty Harry would say: "you've got to ask yourself one question: 'Do I feel lucky?' Well, do ya, punk?"

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    \$\begingroup\$ Purportedly common practice with cheap imported devices these days: Forge the certification mark, hope that it will make investigators consider the problematic device found faulty instead of non compliant by design, and let the importing company catch any remaining fallout. Morally, that depends whether you have more respect or contempt for your regulatory agency; legally it can obviously open a catastrophic can of worms. \$\endgroup\$ Oct 1, 2017 at 22:19
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    \$\begingroup\$ Doesn't that add a very big barrier to small companies and hobbyists who want to sell a product to a very small consumer base? For ex - if I make a shield for arduino which has some sensors, a wifi/bluetooth module and I am expecting to sell around 1000 pieces, saving 10 USD on each, I can't even think about going forward with the idea. Whatever I save will be lost in certification and most importantly, I will need the certification money up front, even before I sell a single piece. Is there a way out of this? \$\endgroup\$ Oct 2, 2017 at 4:22
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    \$\begingroup\$ @Whiskeyjack I think FCC certification/verification mainly concerns consumer appliances or devices meant to be used in homes of businesses. I don't think bare circuit boards that are meant to be part of a larger device normally go through the same testing, since the final device will be tested. For example, you'll find a ton of custom boards on Tindie, and none of them have any FCC certification. \$\endgroup\$
    – Cerin
    Oct 2, 2017 at 4:37
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    \$\begingroup\$ @Whiskeyjack Be aware that your shield WITH Bluetooth/WIFI is now an intentional radiator because it has those radios on it, so depending on exactly what module you use and the details of the aerials may now be subject to the MUCH more serious set of tests that apply to radio transmitters! You can find modules that are effectively pre-approved (They have built in aerials and have been thru the process) which cuts down the work required because the radio part is no longer in need of heavy testing, and this is something well worth checking on. \$\endgroup\$
    – Dan Mills
    Oct 2, 2017 at 10:08
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    \$\begingroup\$ @Whiskeyjack Actually, many of the ESP8266 modules are certified, even including cheap chinese ones. esp8266.com/wiki/doku.php?id=esp8266-module-family has a list. \$\endgroup\$
    – Jules
    Oct 2, 2017 at 12:06

Code of Federal Regulations, Title 47, Part 15 (47 CFR 15) of Federal Communications Commission (FCC) rules and regulations regarding unlicensed transmissions. Nearly every electronics devices sold inside the United States radiates unintentional emissions, and must be reviewed to comply with Part 15 before it can be advertised or sold in the US market.

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The verification procedure requires that tests be performed on the device to be authorized. These tests measure the levels of radio frequency energy that are radiated by the device into the open air or conducted by the device onto the power lines. After these tests are performed, a report must be produced showing the test procedure, the test results, and some additional information about the device including design drawings. The specific information that must be included in a verification report is detailed in Part 2 of the FCC Rules. Sections 2.951 through 2.957 Once the report is completed, the manufacturer (or importer for an imported device) is required to keep a copy of it on file as evidence that the device meets the technical standards in Part 15. The manufacturer (importer) must be able to produce this report on short notice should the FCC ever request it.

There is no filing with the FCC required for verified equipment.

There are a number of exemptions outlined but not limited to the following:

EXEMPT "Test equipment" includes devices used for maintenance, research, evaluation, simulation and other analytical or scientific applications in areas such as industrial plants, public utilities, hospitals, universities, laboratories, automotive service centers and electronic repair shops.


Something that pulses once a second could easily go under the radar of scanning Sweep tests. So you ought to minimize the unintended radiation with twisted pairs, CM chokes and or snubbers so that it cannot be hear on an AM radio 30m away on a weak channel.


You will require an emissions certification for your product. The certification process would include your complete product in it's enclosure and would have to be tested with any normal accessories like an AC adapter attached. It is also typical that representative cables must be plugged into all interface connectors that would normally be used during operation of the device.

If your device is operated off the mains power line you have to undergo additional certifications for conducted emissions and immunity to certain applied disturbances like electrical spikes and surges.

There also requirements for your product to be tested for immunity to static discharge. Safety testing may also be required depending on the product category and customer /user location.

The fines and potential liability claims can be considerable if you do not follow the rules and would most certainly be far in excess the cost of having certification done.


You'll want to look at this answer that talks about when testing is compulsory: https://electronics.stackexchange.com/a/16938/39344

You have an "unintentional radiator" regulated under Part 15, Subpart B. Your 12V electromagnet can be a much bigger source of problems that you might imagine, depending on how sharp the signal leading to it is.

Your testing need not be expensive: get multiple quotes, educate yourself before calling, make it clear you're an easy quick pass.

You can "get away with it" for a while, if your volume and ambitions are low. But it's not all that hard to do it right.


If it makes any sense for your device, perhaps you can consider your daughterboard a 'subassembly'. In other words, if it makes any sense for you to market the daughterboard apart from the Arduino itself, that daughterboard could be considered a 'subassembly' and thus exempt from FCC authorization:

You may be asking yourself how companies such as Sparkfun, a business based on selling electronics kits and wireless development kit companies continue to sell large numbers of non FCC authorized kits, with seeming impunity. For Sparkfun, the rules that apply in most cases relate to “subassemblies”. This just means that Sparkfun’s customers will most likely use the products to build larger products containing a number of subassemblies. For example, that may include an Arduino™ processor board along with several sensors or peripherals and an LCD. The user may even put all of these parts into an enclosure. If the user sells this product containing multiple subassembly parts in an enclosure, for all intents and purposes they are now a “manufacturer” and their equipment is subject to the normal FCC authorization procedures.

EMC FastPass

There is also an "Exempted" product list, that perhaps your product might fall under:

  • A digital device utilized exclusively in any transportation vehicle including motor vehicles and aircraft.
  • A digital device used exclusively as an electronic control or power system utilized by a public utility or in an industrial plant. The term public utility includes equipment only to the extent that it is in a dedicated building or large room owned or leased by the utility and does not extend to equipment installed in a subscriber’s facility.
  • A digital device used exclusively as industrial, commercial, or medical test equipment.
  • A digital device utilized exclusively in an appliance, e.g., microwave oven, dishwasher, clothes dryer, air conditioner (central or window), etc.
  • Specialized medical digital devices (generally used at the direction of or under the supervision of a licensed health care practitioner) whether used in a patient’s home or a health care facility. Non-specialized medical devices, i.e., devices marketed through retail channels for use by the general public, are not exempted. This exemption also does not apply to digital devices used for record keeping or any purpose not directly connected with medical treatment.
  • Digital devices that have a power consumption not exceeding 6 nW. Joystick controllers or similar devices, such as a mouse, used with digital devices but which contain only non-digital circuitry or a simple circuit to convert the signal to the format required (e.g., an integrated circuit for analog to digital conversion) are viewed as passive add-on devices, not themselves directly subject to the technical standards or the equipment authorization requirements.
  • Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines.
  • Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption.

The FCC And Open Source Hardware


Define it as OEM device instead of Consumer device. In such case, it's the end user that should put it in an adequate shielded case and perform the FCC tests if he intends to sell the device. If it's just for his personal use, it's considered evaluation. It's surely worth checking if such backdoors exist in the law.


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