Its a clip. That beeps. The Knowhere is a radio connected device that ensures you will never lose anything again.
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The Knowhere works using an FM transmitter and receiver. A Raspberry Pirate radio is loaded with a program which sends Pulse Modulation radio signals which are decoded using an ATtiny. If the ATtiny identifies that it's 8-bit code is being sent, it beeps and flashes so you can find it easily. It's simple, but incredibly helpful.
**************************************************DISCLAIMER****************************************************
Make this device at your own risk.
According to FCC regulations, Part 15 devices, such as this one, are legal as long as the working range of the device is under 200 feet. If you're in the U.S. like we are, you should be good legally speaking as long as you make sure the radius only covers 200 feet AND is within the AM or FM band (535 to 1075 kHz and 88-108 MHz). Make sure to find an unused channel (you can use the link provided if you are in the US) so you won't have to deal with much interference. We plan to broadcast on FM 89.1 . Your mileage may vary.
If you are in another country, make sure to always follow your local laws, and if they permit, choose the appropriate channels.
The FCC ruling on Unlicensed Low Power Transmitters such as ours is included in the links section. If you're planning to build this device, please look at these regulations, or the ones applicable in your locality, just in case.
Well, I gave up on making my own radio and figured using a module would be only slightly more expensive, much more reliable, and would enable the device to be much smaller than before, which are all good things on the whole I'd say. I still felt like I've given up though, even though my brain says that I just made the rational decision necessary.
We had originally planned on using a power radio because we had researched crystal radios and found that they needed really big coils and even bigger antennas. But recently, we discovered that they actually made pocket-sized crystal radios back in the day, and we plan to build one of those and try it out to see if it will work with our idea. It still has a relatively long antenna, but this can be shortened by adding a trickle of the ATtiny's power into an ampifier. Another problem we went around is the germanium diode. When making a low-power radio, a germanium diode is a necessity. These are both relatively expensive (usually more than one or two dollars) and only available online (RadioShack stopped carrying them a while ago, as well as most electronics vendors). We found many sources that claimed that LED's work nearly as well as germanium diodes, and they're extremely cheap and easy to find. We happened to have a few lying around (who doesn't?) and we plan to build this radio soon. We've left behind trails of radios we built that wouldn't work and the mangled remains of perfectly good commercial radios we took apart to find the secrets inside. Hopefully this will be the solution we were looking for.
Success! We (or rather, Surya I should say), finished the GUI for the Raspberry Pi! The finished screenshots are up on pictures and the code is on GitHub. Additionally, the code for the ATtiny is also finished. The only thing left is the radio receiver, which is still proving slightly problematic although I have hopes of finishing it this weekend.
Well, we've figured out how to remove that extra step of modulation and demodulation that exist in standard AM and FM signals. Our method is called PM, or Pulse Modulation, and it's all binary. Unfortunately, the darn radio doesn't want to work. We'll figure it out. Eventually. Or bribe smarter friends into figuring it out for us. On the bright side, we finished the entire GUI and transmission code for the transmitter (Rasbperry Pi) in one go, and the finished, but untested code will be on GitHub.
Well, we found out a bit too late there is no tuning capacitor in a 50 mile radius of where we are. And unfortunately, today being a Sunday, we can't get it shipped quickly either. So we're going to pillage one out of a radio, along with a few other handy components. Ideally, in the finished product, you would have a fixed, non-variable capacitor. We're finding what exact capacitance we need to make the radio receive 88.1 (or your channel of choice) properly, then ordering that capacitor from an electronics warehouse.
All of us have reasonable experience in programming and hardware, but didn't know anything about radios until we started this project. We're aware that FM radios go through a step of modulation and demodulation and this isn't necessary if you are sending raw digital data, like we are, but we're not entirely sure how to bypass it. If it works with the extra step, great, but in a perfect world, we'd eliminate the extra complication.
Type this into your RasPi Terminal to download the transmission code. This isn't ours, I must credit the original makers of the RasPi radio, Icrobotics.
wget www.icrobotics.co.uk/wiki/images/c/c3/Pifm.tar.gz
Then type
Is
then
tar -xvf Pifm.tar.gz
Also, put the Python code from Github on the RasPi. You can copy and paste it into your IDE if you want, you will need to be editing it a little bit anyway.
Download a wav file of a solid BEEEEEP sound that lasts at least 2.5 seconds. You should have no problem finding one online for free. The pitch doesn't matter at all. Edit the variables at the top of the code, enter the name of your wav file as well as the frequency you would like to transmit on. Don't include any spaces before or after the words and numbers or it will mess the terminal command up.
Find out the user and Program ID of the Raspberry Pi Radio program.
Type
sudo ./pifm enterwavhere.wav 89.1
then
ps -elf | grep python
into the Linux terminal.
You should then see a bunch of results. Find the program, the name should contain the word Pifm.
Write down the programs PID in the Github code afte rits on the RasPi. There should be a variable called "enterPID". Same goes here, please dont include any spaces before or after the PID.
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Nice project, and if you're having trouble sourcing tuning capacitors, you can make some out of beer cans. Be sure to drink the beer first.