I just learned about the Moteino platform a week or so ago and I'm trying to see if it will work for my project needs. I like the idea of using a microcontroller with wireless capabilities built-in. For my project, I will have a "receiver" module which is only for receiving signals in order to operate a couple of servos. Then the other unit will be only for transmitting signals. Basically it will act as a remote for activating the servos from a distance. There will be no need for two-way communication, at least at this point. As I said I am new to this platform and new to the whole DIY electronics world, so I'm not really sure what direction to go or which platforms and components would be most useful or relevant.
Basically, what I need to find out now is can or should I use Moteino for this type of project? I have researched other RF receivers, but there seems to be some reliability and signal strength issues with the most common receivers. So Moteino seems like a better solution and should require less power. Another question is, if I am using another Moteino to act simply as a remote, and without any need to receive signals itself, would it need an antenna as well? I would definitely put a small dipole antenna on the receiver unit. I was thinking that since RF remotes do not require the use of an external antenna for transmission, a Moteino based transmitter would not need an external antenna either. Is that a mistaken assumption?
Quote from: dmehling on February 14, 2015, 08:04:56 PM
I just learned about the Moteino platform a week or so ago and I'm trying to see if it will work for my project needs. I like the idea of using a microcontroller with wireless capabilities built-in. For my project, I will have a "receiver" module which is only for receiving signals in order to operate a couple of servos. Then the other unit will be only for transmitting signals. Basically it will act as a remote for activating the servos from a distance. There will be no need for two-way communication, at least at this point. As I said I am new to this platform and new to the whole DIY electronics world, so I'm not really sure what direction to go or which platforms and components would be most useful or relevant.
Basically, what I need to find out now is can or should I use Moteino for this type of project? I have researched other RF receivers, but there seems to be some reliability and signal strength issues with the most common receivers. So Moteino seems like a better solution and should require less power. Another question is, if I am using another Moteino to act simply as a remote, and without any need to receive signals itself, would it need an antenna as well? I would definitely put a small dipole antenna on the receiver unit. I was thinking that since RF remotes do not require the use of an external antenna for transmission, a Moteino based transmitter would not need an external antenna either. Is that a mistaken assumption?
Given what you've described, Moteino, with the RFM69 radio, should suit your needs. Answering your last question first, yes, you need an antenna on both ends. The antenna is required to get the RF energy radiated/received to/from devices. However, please note that an 'antenna' could be nothing more than a piece of wire that is 1/4 wavelength long (see the "All about Moteino" page to see what lengths are needed).
Moteinos have a fairly simple, but reliable communications protocol, with the bulk of the 'effort' performed in the radio module so, from an implementer's perspective, they are easy to use and reliable. There is a pretty good set of example functions included in the download so you can start with these and 'adjust' the code to meet your needs.
Hope this helps. ASK questions if you have more. You'll find plenty of support on this forum.
Tom
Does Moteino actually use RF? I gather that it is a type of RF specific to this platform. The reason I ask is I thought perhaps it could pick up the signal from any kind of RF remote if the frequency is the same. Or is that something that is just too complicated?
If I indeed need to use an antenna on the transmitter part, I would like to go with the smallest one possible, like this one in the sample photos:
https://www.flickr.com/photos/15304611@N03/8435723130/in/set-72157636923824146
What kind of range would this style of antenna be capable of? I really don't need much range, no more than 30 m at the most. What would be the smallest type antennae I could get that would still work at that range?
To answer your Q we'd spend the next 2 months on this thread, so I'll give you the tldr;
Yes it uses FSK type RF signals.
For shorter antennas use 868/915mhz frequencies. Best scenarios is with antenna straight up perpendicular to the GND plane. The moment you start to coil and mash it, you lose signal. That's just the way it is.
I sort of asked this already, but what would be the range when using the coil shaped wire antenna (still don't know the actual term for this one)? A follow-up question is, will the range be impacted significantly if the antenna is inside of a small plastic enclosure?
Hard to put a number on that. Signal will be affected even if you wave your hand to block the TX path (not by a lot but to give you an idea).
Plastic usually does not affect signal that much, at least in my experience. I have a bunch of sensors with the wire monopole wrapped around in the case, or Moteino inside the case and antenna going out of the case, all those nodes work fine from within a 120ft range of the receiver (some outside the house, receiver is in basement below grade). The more distance and obstacles (dirt/walls/concrete/trees) there are in the path the more affected the signal is.
It's best to just experiment on your own in your own environment to really get a feel for how affected the signal is.
Quote from: dmehling on February 17, 2015, 02:51:12 PM
I sort of asked this already, but what would be the range when using the coil shaped wire antenna (still don't know the actual term for this one)? A follow-up question is, will the range be impacted significantly if the antenna is inside of a small plastic enclosure?
As Felix pointed out, there are LONG answers to this question, medium answers to this question, and REALLY short answers to your question.
The LONG answers are probably not going to be addressed here.
The medium answers are, in fact, answered here, see the very excellent tutorial on antennna and this post: https://lowpowerlab.com/forum/index.php/topic,904.msg5784.html#msg5784 for the how the Helical antenna (spiral wound wire like you've shown, affects performance - in both positive and negative ways).
The REALLY short answer is: Try it! It's easy to do! Only you will know if the result meets your needs.
Tom
PS: assuming the plastic is not impregnated with some conductive material it won't have a measurable effect on performance.