Hi there,
I want to make a low power, tiny radio transceiver setup to send morse code messages back and forth. Ideally one that works with an ATtiny85 and 3V 2032 watch battery. I'm really trying to make this as small as possible, and don't need much range (10-20m would be plenty).
I've been looking at different transceivers, like the HC-12 and others, but the problem is that they all seem to need at least 3.3V which would require a much larger battery setup than the watch battery I'm aiming for. I haven't found much instructional content online about making these transceiver setups as small as possible so I wanted to ask for advice here. Are there any transceivers on the market that fit the bill?
Thank you for your help!
Cool project idea. One thing to consider from the beginning, somewhat obvious but easy to gloss over - radiated power can never be more than the battery can supply. So ditch any special optimism about that and live with what is actually possible according to physics.
1 Like
Many of the 3.3V radio modules will run on a CR2032 battery, but only for very short transmissions, and battery life will be very short.
A capacitor across the battery terminals (470 to 1000 uF) will help with the power draw during the short transmissions.
You can make a tiny transmitter that will run on a single 1.5V watch battery, by following this idea, from a 1968 article in Scientific American: Goof-Proof Biotelemetry Transmitter Construction | The American Biology Teacher | University of California Press
The original article is https://www.scientificamerican.com/article/the-amateur-scientist-1968-03/
1 Like
Because that is advanced engineering, not entry level hobby stuff. What transceiver setups? Did you actually find some projects online? Can you provide links?
Always, it's easier to work with something than with nothing. If you can make a larger transceiver, you are in a much better position to miniaturize it, than if you don't have anything at all built and tested.
The only miniature devices you will find will ONLY be able to send digital messages, not Morse code or "CW" messages. The actual problem is not a low powered transmitter, but the receiver being able to receive a signal with no antenna.
Right, you will be forced to implement some kind of "Morse conveyed over some digital protocol".
The higher the frequency, the smaller you can make a basic antenna. So think in GHz.
@Jackstapes Will transmission be "line of sight" or will there be obstacles?
Thank you for finding this! It goes to show how simple these setups can be. Do you know if a receiver could be added that's simple as well? I'd like to get the Morse code to be vibrated out with a small vibration motor, and im not sure if that level of complexity would then require a microcontroller. Thank you!
Yes, I've read the OP's optimistic requirements.
Consider using drone technology for data transmission.
1 Like
Carrier pigeon emulation? Ok, nah... you mean the RF transport stuff, yeah...
It's time to ask, what is your RF engineering experience?
I built one of those and swallowed it. It's not suitable for Morse Code since it sends only a periodic click. The thermal properties of the transistor allow you to use the click rate to measure temperature.
1 Like
That's a very good point. I found one that sent morse code with a built-in transceiver on a BBC Micro-bit.
https://longislandcwclub.org/wp-content/uploads/2021/08/p56_57_microbit_radcom_aug212.pdf
It's pretty similar to what I'd like to do, but I would ideally like to put together just the components I need so I could make it smaller / in whatever form factor I need
Zero 
but I'm wanting to get into it! So I'm open to trying simpler projects as a way of learning first if this one is too complicated
I'm planning to use this to communicate indoors with some level of obstacles
Not to be mean, but I'm out. You have what you need and can get here at this stage. Any more discussion is just a waste of time. Go research some more and come back with questions on specific parts and designs.
Again, not meanness but practicality.
My opinion, yes this is too complicated for someone at your level. Unless, you are willing to lower your expectations and spend a year or so developing a few different and gradually improving systems...
Just a suggestion, but you might consider an infrared transceiver. Over the range you mentioned, it might work, as IR will reflect nicely off walls and get around most obstructions.
2 Likes
How can I go about getting the experience I need in RF engineering? I have found projects with an arduino starter kit pretty simple to follow until this project. Should I start with a certain transceiver that's easy to learn with?
