Good afternoon everyone. I am looking at making a custom nrf24l01 board. I had a question on the crystal being used.
Here is the crystal:
Even though its 20pF, do I still use 22pF capacitor's to GND? Could I use a 10pF Crystal? What is the difference? What caps should I be using?
Thanks for the help!
The capacitors have two effects:-
Look at the capacitance of the crystal input in the data sheet and subtract that from your crystal's capacitor requirement to get the value of the external capacitor you need to add.
I am looking at making a custom nrf24l01 board.
Did you know that making your own transmitter without a license is illegal? You are only permitted to use "type approved" transmitters in the license free bands, not home made stuff.
Did you know that all the nrf24l01 premade chips are not FCC certified and fall under the same classification you are mentioning yet we are able to purchase them for prototyping? I am using a chip antenna and staying within the legal spectrum.
Did you know that all the nrf24l01 premade chips are not FCC certified and fall under the same classification you are mentioning yet we are able to purchase them for prototyping?
Yes I did know that.
It is not the chip vendors job to enforce the law. There are all sorts of things you can buy legally but not use legally. You can buy a ham band transmitter but you can not legally use it unless you have a license.
It is the same with the chips, you can buy them but unless you have a license to build prototype transmitters then you can not use them.
I am using a chip antenna and staying within the legal spectrum.
You might be, but that does not affect the legality of what you are doing, which, as I said before, is illegal.
So if I have what you are saying correct, everyone who is using any wireless transceiver that is not UL/FCC certified, and EVEN if it is, "technically" the entire device would need to be re-certified as a non intrusive wireless device is doing so illegally and should be reprimanded by law.
You do realize that goes against the "maker" community moto and hindering creativity because of an FCC certification which I have researched will not be enforced unless an external source "complains" about it.
In my mind if I am doing this for personal, no cash value, there is no harm in what I am doing as this device is not used for nefarious purpose like a radio jammer. By your logic, everyone on the forums should stop what they are doing, stop tinkering, don't open up your switches, plugs, or even change a lightbulb (Requires a licensed electrician by law in NY).... and everyone get an electrical engineering degree, open up an LLC, create a special laboratory that follows all code rules, after said prototyping is done, submit to FCC and spend between 10-20k and countless revisions until said device is working to code, just so we can build a simple device.
You do realize that prototyping has no merits on code violations as FCC is required for selling correct? Think of it this way, do you not need to prototype first before submitting for FCC testing? Or should you not turn on your circuit because you could violate air waves? lol
And if you need proof of you... well being wrong, here you are:
"Hobbyists, inventors and other parties that design and build Part 15 transmitters with
no intention of ever marketing them may construct and operate up to five such
transmitters for their own personal use without having to obtain FCC equipment
authorization. If possible, these transmitters should be tested for compliance with the
Commission's rules. If such testing is not practicable, their designers and builders are
required to employ good engineering practices in order to ensure compliance with the
Part 15 standards."
You do realize that goes against the "maker" community moto
Hay - I must have missed the bit where a maker community motto overrides the law.
So you are in the U.S. are you? No indication before those last two posts where in the world you are.
Thanks for pointing me towards those bizarre rules. What an odd place you live in. Don't try that in most of the rest of the world.
You noticed that I did not withhold any information from the post, but you got angry didn't you.
By the way it goes on to say:-
Home-built transmitters, like all Part 15 transmitters, are not allowed to cause interference to licensed radio communications and must accept any interference that they receive. If a home-built Part 15 transmitter does cause interference to licensed radio communications, the Commission will require its operator to cease operation until the interference problem is corrected. Furthermore, if the Commission determines that the operator of such a transmitter has not attempted to ensure compliance with the Part 15 technical standards by employing good engineering practices then that operator may be fined up to $10,000 for each violation and $75,000 for a repeat or continuing violation.
Think of it this way, do you not need to prototype first before submitting for FCC testing?
Well no, the next paragraph specifically states:-
Operating a prototype of a product that is ultimately intended for market is not considered "personal use." Thus, a party that designs and builds a transmitter with plans to mass produce and market a future version of it must obtain an experimental license from the FCC in order to operate the transmitter for any purpose other than testing for compliance with the Part 15 technical standards.
brolly759:
Even though its 20pF, do I still use 22pF capacitor's to GND?
From the crystal's point of view, the two 22pf caps are in series.
So 11pf across the crystal.
Then there is the board/track capacitance.
And the input pin capacitance.
Leo..
Hi,
Why make a custom version of the nrf?
It is more then just a tx/rx, it is basically a packet comms system on one PCB.
And all for the cost of less than half the parts if you bought them separately, probably even less when you factor the r&d time, assembly cost, debugging.
Tom... 
TomGeorge:
Hi,Why make a custom version of the nrf?
It is more then just a tx/rx, it is basically a packet comms system on one PCB.
And all for the cost of less than half the parts if you bought them separately, probably even less when you factor the r&d time, assembly cost, debugging.Tom...
Size/packaging/learning. I want to continue learning on building prototype hardware and even venture into wireless. Learning traces, components, manufacturing will all help in any entrepreneur ventures I may lead down the way. Yes the current nRF chips are completely fine but I would like to package something as small as possible with Arduino + nrf and sensors on 1 board with a coin cell.
@Grumpy_Mike. You must keep misreading what I say huh. I showed this post and our conversation back and forth with a coworker and we laughed agreeing you sound like an electrical engineer who lost work due to outsourcing. Anyways, for starters the reason why I get "angry" is when you post and accuse an individual of doing something illegal and base it off NO facts what so ever.
Now back to your last comment about the link I sent.
"Operating a prototype of a product that is ultimately intended for market is not considered "personal use.""
The keyword there is INTENDED FOR MARKET. This product will NEVER reach market so I do NOT need to certify it for FCC. As I said and will continue to say, if you are prototyping for yourself without selling, there is no reason to accuse or feel guilty that you are doing something illegal. The fact of the matter is, no profit now or future = OK
I asked an engineer who I worked with in the past and to answer my own question, the crystal has internal capacitors that don't need any external ones to connect to GND.
brolly759:
I asked an engineer who I worked with in the past and to answer my own question, the crystal has internal capacitors that don't need any external ones to connect to GND.
Engineer is wrong.
Some crystal modules have all the parts inside, including oscillator.
The crystal you linked to in post#0 has no internal capacitors or other parts.
If the combined capacitance of external, tracks, case, chip, etc. add up to the recommended capacitance for the crystal, then the crystal resonates on the given frequency.
When the capacitance is off, the frequency will be off. The oscillator might also have trouble starting up.
Leo..
Grumpy_Mike:
By the way it goes on to say:-Home-built transmitters, like all Part 15 transmitters, are not allowed to cause interference to licensed radio communications and must accept any interference that they receive. If a home-built Part 15 transmitter does cause interference to licensed radio communications, the Commission will require its operator to cease operation until the interference problem is corrected. Furthermore, if the Commission determines that the operator of such a transmitter has not attempted to ensure compliance with the Part 15 technical standards by employing good engineering practices then that operator may be fined up to $10,000 for each violation and $75,000 for a repeat or continuing violation.
Which is in fact common to all operations of most transmitters, notably Amateur Radio stations, so nothing special here.
Note in respect of crystal capacitance, the load capacitance to the crystal is made up of the series equivalent of the combination of the pin capacitance and the trim capacitance on each of the "oscillator in" and "oscillator out" pins. If both pin capacitances and trim capacitances are equal (as they commonly are), then you simply add the pin capacitance and trim capacitance and halve the sum.
Which is in fact common to all operations of most transmitters,
No it is not.
Yes it is the sort of thing you get for Amateur Radio stations but you have the responsibility to make it work. The operation of most transmitters is done by non competent personnel.
so nothing special here.
Yes it is special. If a transmitter screws up then the nurse operating the pager is not liable, the ambulance driver is not liable if his transmitter makes a mess all over the spectrum. It is possibly the liability is in the manufacturer of the transmitter.
However my point is that if the OP is asking such a simplistic question it is highly unlikely that he will be able to construct anything "employing good engineering practices" that would mollify an FCC technical assessor.
He says:-
Size/packaging/learning. I want to continue learning on building prototype hardware and even venture into wireless. Learning traces, components, manufacturing will all help in any entrepreneur ventures I may lead down the way.
My advice to him would be to get a ham license and learn what to do with transmitters. That way he would stay the right side of the law. I doubt that he understands the power limits in that PDF he posted a link to.
I showed this post and our conversation back and forth with a coworker and we laughed agreeing you sound like an electrical engineer who lost work due to outsourcing.
So you both are as wrong about this as you are in reading the FCC regulations. I have been a Radio Ham since the mid 70s, I have made and operated transmitters, including TV transmitters. I was responsible at one place of work for ensuring that designs were compliant with both UL and FCC, for intentional emitters.
The keyword there is INTENDED FOR MARKET. This product will NEVER reach market so I do NOT need to certify it for FCC.
That is nether here nor there. I was answering your so called conundrum.
You have to construct your transmitter withing the power limits, "employing good engineering practices". Can you do that? If you think so then you are probably experiencing the Dunning–Kruger effect .
Dunning–Kruger
You really think that after I make my circuit and board I wouldn't pass the info along to someone more accredited to verify my work? Regardless of the possible wireless issues, it would be a waste of money and time to create and build if at the end it doesn't work properly.
Brolly, Mike is mostly right in his points, 'possibly' incorrect in his presentation.
Anyone can , within the laws governing the United States' build a device which causes radio frequency emissions. The laws in place restrict the frequency and RF power levels appropriate for licensed and unlicensed 'operators'. If an individual, licensed or unlicensed, knowingly operates an RF emitter outside the limits of the law, in particular (but not limited to causing operational interference to other users), that person is an operator in violation and is subject to civil AND criminal liability, for repeated use. It doesn't matter if you are doing it for profit or amusement, or learning, or prototype vs. production. if you operate it beyond the grants of the law, you are liable.
There are experimental and hobby bands which allow unlicensed operation at restricted power levels (as long as no operational interference is caused). There are also provisions for unlicensed radiation in the broadcast bands. Again, with restricted power levels and NO INTERFERENCE to others.
You and Mike can go on with your pissing contest if you want. but don't be stupid. read and understand the rules from the FCC. if you continue without doing so, you are likely to get a visit from two guys in a black SUV, inviting you to a vacation in a federal facility and wanting to take your 'equipment' home with them.... Here in the States, 'Charlie' gets really upset with violators in digital emissions, more so than audio/video. Must be a 911 thing.
bottom line is that you keep your RF power low and don't mess up anybody's reception, you can probably get away with most anything in the experimental or hobby bands. Let your freq creep out of band, at any power, and you're asking for trouble. Goes for harmonics too.
One place I worked had a walk-in sized Faraday cage for RF testing in the cellular band. That's how it's done by the big stake players.
I didn't see there was a page 2 to this thread. I know a few people who work for the FCC. This is there procedure. If someone complains they will send you a cease and desist letter, if you do not stop they will send you 1 more. Then they will fine you. I was also told by the co worker that they rarely ever enforce such rules/laws.
Again these are all assuming you are sending dirty transmissions and causing interference for someone else. In that worst case scenario then yes, you are going against that law, but to be called out as doing a criminal act is uncalled for when there are so many unknowns and I asked a simple question on PROPER schematics so I do NOT cause any issues... Again, FCC does NOT need to be involved if you are creating a wireless device that does not interfere with other and is limited to 5 prototypes that has not intended for Market. I really don't care where or what his experience is, if you assume legality over someone's actions you better know what you are talking about and know for SURE what the other individual is doing is illegal.
If I started this thread and said " I need a proper schematic for an EMP disrupter", that would be a completely different story!
Big coil, a bunch of caps, and a whole lot of AAA's....... again, as we seem to agree, no problem building it, its just that the problem start when you fire it...
As far as your war of words with Mike, you are a fool if you don't listen (which you don't) and he has much more credibility here than you. With a "I already know more than than the people I am asking for advice" attitude, maybe you would be better served by trying some other forums, like some ham sites, or maybe the ARRL? ... just sayin'
When someone says:
"Did you know that making your own transmitter without a license is illegal? You are only permitted to use "type approved" transmitters in the license free bands, not home made stuff."
But FCC regulations goes on to state:
"Home-Built Transmitters that are Not for Sale
Hobbyists, inventors and other parties that design and build Part 15 transmitters with
no intention of ever marketing them may construct and operate up to five such
transmitters for their own personal use without having to obtain FCC equipment
authorization. If possible, these transmitters should be tested for compliance with the
Commission's rules. If such testing is not practicable, their designers and builders are
required to employ good engineering practices in order to ensure compliance with the
Part 15 standards.
Section 15.23
Home-built transmitters, like all Part 15 transmitters, are not allowed to cause
interference to licensed radio communications and must accept any interference that
they receive. If a home-built Part 15 transmitter does cause interference to licensed
radio communications, the Commission will require its operator to cease operation
until the interference problem is corrected. Furthermore, if the Commission determines
that the operator of such a transmitter has not attempted to ensure compliance with the
Part 15 technical standards by employing good engineering practices then that operator
may be fined up to $10,000 for each violation and $75,000 for a repeat or continuing
violation.
Section 15.5
47 U.S.C. 503
Operating a prototype of a product that is ultimately intended for market is not
considered "personal use." Thus, a party that designs and builds a transmitter with
plans to mass produce and market a future version of it must obtain an experimental
license from the FCC in order to operate the transmitter for any purpose other than
testing for compliance with the Part 15 technical standards. Information on
experimental licenses may be obtained from the contact point listed in the Additional
Information section of this bulletin. FCC authorization is not required in order to test
a transmitter for compliance with the Part 15 technical standards."
If Mike would of said instead:
"Did you know that making your own transmitter that can cause external wireless interference is illegal? You are only permitted to use a home-built transmitter that follows with FCC compliance and is not going to be a marketable product."
Then we wouldn't of had any issues and this thread could of stuck to the original question. Mike may have much credibility but you start to lose that once you accuse someone of an illegal act. This is not a " I know more than you" because trust me, I know a drop in the bucket compared to many of the forum people on here... I am simple defending myself that what I am doing is not ILLEGAL as Mike has stated and that "home made stuff" is actually ALLOWED not the other way around.