I would like some guidance from people who know a bit more about the subject than I do. I would like to create a device that sends temperature data from one Arduino to another on the 433 MHz band. (I have purchased the MKR wan 1300 and have some Nanos with HC-12 modules that I am considering using.)
Before I get too far into this I want to make sure I am not going to break any rules or ruin anyone else's space in the radio wave world. (After reading quite a few threads it seems they are a passionate group who want some decency and rightly deserve it.)
The project is to be mounted with the antenna (came with the MKR wan 1300) on a camper roof and will send the temperature data from the camper to the receiver. The longer the range the better but if it's only 100 meters that would be okay too as the beach is not too far off. The device's sole purpose is to make sure the AC in the camper works properly so that my dog does not overheat while the family is on the beach.
I know we could just get up and check the camper periodically or purchase a device that uses cellular data ($200 for the unit plus a monthly subscription) but I like to build things and have been using Arduino for a couple of years now so thought it would be an interesting project.
Okay, enough monologuing... In your opinions;
Are there any legal implications of making a device this small (I think I fit into FCC part 15?)
Is there any personal reason I should not attempt to make this?
Am I in the wrong thread because if so I completely apologize and will take my questions elsewhere.
Thanks ahead of time and I hope you all have a great day. (Any other views or questions are welcome! Let me know what you're thinking)
You assume that two Arduino boards with a wireless connection over 100 meters is more reliable than your AC ?
Can you add a very loud alarm on the camper if the temperature gets too high or if the AC stops ?
Yes, it has a thermostat. The Flordia sun can warm a camper pretty quickly in the summer though. So if the AC for whatever reason did fail it would allow me to know quickly. (it's a newer unit so I don't think there would be a problem... famous last words). I will probably lean towards making a device that has an alarm as Koepel suggests.
In any case, is there any suggestion on how to within the legal/courtesy zone for transmitting data with my MKR wan 1300?
I may be overthinking this and nothing of what I accomplish with this little board and 3.3v but I feel it my responsibility to know...
Hi,
If your AC is a newer unit, check that it might have a set of terminals with open/close contacts when a fault condition occurs.
I would consult with the AC installer/manual and ask what the AC does when it is overloaded, over heats or just plane "cannot cut the mustard"?
That's great to know! Thanks, Geek Emeritus! It will do 915 so that is where I will stay. I thought the FCC website had 433 as "amateur" but maybe I would need the Ham license or something like that? Thanks for the information!
TomGeorge:
Hi,
If your AC is a newer unit, check that it might have a set of terminals with open/close contacts when a fault condition occurs.
I would consult with the AC installer/manual and ask what the AC does when it is overloaded, over heats or just plane "cannot cut the mustard"?
Tom...
I will do that Tom! That is something I haven't even considered. There may be something that can be added to the current system that can trigger an alarm. Unless there is something from the dealer I wouldn't want to add anything myself and possibly void a warranty. Thanks for the input though I will look into the manual!
Even though there are millions of 433 MHz devices in the U.S., this is generally correct.
§ 15.240 Operation in the band 433.5–434.5 MHz.
(a) Operation under the provisions of this section is restricted to devices that use radio frequency energy to identify the contents of commercial shipping containers. Operations must be limited to commercial and industrial areas such as ports, rail terminals and warehouses. Two-way operation is permitted to interrogate and to load data into devices. Devices operated pursuant to the provisions of this section shall not be used for voice communications.
As with most regulations there is a loophole: § 15.23 Home-built devices.
(a) Equipment authorization is not required for devices that are not marketed, are not constructed from a kit, and are built in quantities of five or less for personal use.
(b) It is recognized that the individual builder of home-built equipment may not possess the means to perform the measurements for determining compliance with the regulations. In this case, the builder is expected to employ good engineering practices to meet the specified technical standards to the greatest extent practicable.
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.
These can be used between 410-470MHz with emissions limits, however, testing is not required as per Part 15.23 but good engineering practices should be employed,with the all encompassing caveat that it may not create interference and must accept interference.
So to summarize. In the USA you can use up to 5 unlicensed non-type accepted transmitters for your own personal use as long as you aren't selling them. And if you're that concerned about emissions limits (that anyone still curious is welcome to google for themselves) then feel free to spend the thousands of dollars required to comply with something you're not expected to test for anyway.
Also, if you cause interference to a licensed user of the 433-434 MHz frequency band, you must cease operations. Since Amateur Radio operators who are licensed to use 433-434 MHz are aware of the huge number of 433 MHz devices, they just don't use 433-434 MHz.
if you use RF, you need some sort of receiver.
if you want to use your cell phone, then you need to send a signal it can receive.
my first thoughts of distance go to LoRa
and, if you can park near an open wifi, you can just txt your phone
if you have a spare phone, you can set it for wifi as an access point.
long distance wireless devices for things like driveway monitors are available. but you would need to trip the alarm based on temperature.
if you buy a wireless weather station that has a range of 1,000 feet, you can have the outdoor sensor indoors and the indoor display outdoors. and you get temperature and humidity
you can extend distance if you have the unit in a plastic window and not hidden behind metal siding.
SteveMann:
So to summarize. In the USA you can use up to 5 unlicensed non-type accepted transmitters for your own personal use as long as you aren't selling them. And if you're that concerned about emissions limits (that anyone still curious is welcome to google for themselves) then feel free to spend the thousands of dollars required to comply with something you're not expected to test for anyway.
Also, if you cause interference to a licensed user of the 433-434 MHz frequency band, you must cease operations. Since Amateur Radio operators who are licensed to use 433-434 MHz are aware of the huge number of 433 MHz devices, they just don't use 433-434 MHz.
Thanks for the info, Steve! I think I will poke around the emission limits but as you said, I don't have thousands to spend on compliance and I will not be testing if I can avoid it. Thanks again your response is really helpful! I think if I have learned correctly the lower Hz coincides with a smaller message but increases distance right?
dave-in-nj:
if you buy a wireless weather station that has a range of 1,000 feet, you can have the outdoor sensor indoors and the indoor display outdoors. and you get temperature and humidity
you can extend distance if you have the unit in a plastic window and not hidden behind metal siding.
The wireless weather station is a really interesting concept. I will do some research on that!
Since Amateur Radio operators who are licensed to use 433-434 MHz are aware of the huge number of 433 MHz devices, they just don't use 433-434 MHz.
Lots of use in the 434 range. The DOD recently ordered all amateur activity in 434 MHz in the White Sands NM area to cease operation by June 1. There are lots of repeater linking and control uses there and the DOD has a new control system they are putting in place.
Paul
One might consider adding a SIM card to a device that does the environmental in the camper. The device can then transmit the environmentals to your web sites database. Sitting on the beach, you can use the cell phone to go to the web site and view the campers environmental.
If cell phone is an issue and the project is important. I'd go with a satellite phone. I own one and carry it when backpacking, I only subscribe during backpacking season.
One could use a SPOT type device that can be triggered by the MCU sensing environmentals to send messages to a cell phone. Only subscribing to the SPoT type device in during the camper use season.
§ 15.240 Operation in the band 433.5-434.5 MHz.
(a) Operation under the provisions of this section is restricted to devices that use radio frequency energy to identify the contents of commercial shipping containers. Operations must be limited to commercial and industrial areas such as ports, rail terminals and warehouses. Two-way operation is permitted to interrogate and to load data into devices. Devices operated pursuant to the provisions of this section shall not be used for voice communications.
this does not say 433 mhz devices are kosher. it says take them off in the first port where the container enters the country.
this is why asian tracking numbers stop tracking when the package enters the country.
Paul_KD7HB:
Lots of use in the 434 range. The DOD recently ordered all amateur activity in 434 MHz in the White Sands NM area to cease operation by June 1.
Is there a specific page I should be looking to find this information in my area? I can do the normal google searches but if you have a recommendation on where to look I would love to hear it, Paul.
Idahowalker:
One might consider adding a SIM card to a device that does the environmental in the camper. The device can then transmit the environmentals to your web sites database. Sitting on the beach, you can use the cell phone to go to the web site and view the campers environmental.
I have started to read your linked information on the radio waves. Thanks for that information Idahowalker! I did think about using a sim card with cellular data but wanted to avoid monthly fees. For the most part, I haven't had trouble with cell service so it might be the way to go in the end.
Just want to say thanks again everyone for all the help.
I guess from the readings I have done on part 15 the last question I really don't know anything about is, and I quote, "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."
I heard that the device must check to see if there is a signal being transmitted before it can send its own (we will see how my coding works in that aspect). But how do I know my device will accept interference and not cause it?
"it will accept interference" is a poor choice of words. the true meaning is, the owner will accept he fact that it accepts the interference. if you complain, you're just talking to the sky.
"not allowed to cause interference" is a poor choice of words. if they did the testing required to verify that the device causes no interference in any other band, you could not buy the device off ebay for a couple of bucks. the true meaning is, if a licensed user complains of interference, shut it down. if another Part 15 user complains, tough luck, Chuck. not our circus, not our monkeys.
I have a similar system running where I monitor temps all around my house, garage and backyard. Each sensor measure a temp and sends it to a base where a 2.8" TFT displays temps. The base is connected to my wifi so I can see the temps from my phone. I use nanos and thermistors for the sensors and send wirelessly to an ESP-32. I use an ESP as it *was" easy to connect it to my wifi. The ESP32 generates web page posting the temps so i can monitor from my home. I use AJAX with XML to update just the temps but you could simply rebuild and send the web page. The base pings each sensor every few minutes to request a temp reading. Your setup could simply keep sending data to the base--either way its not a real simple project, but not over the top.
I'll not disclose my radio frequencies but since I bought the wireless units on the internet, the frequencies must be legal
