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 is a binder clip connected to a Raspberry Pi. When you select the clip (by an inputted name) from the Pi, the clip begins making a noise allowing you to find it. Or in other words, it beeps. Loudly. And even better, a clip costs about two dollars to make with parts from wholesale electronic vendors, allowing you to flood your house with clips. That beep.
This project is currently under construction.

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.  


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.

  • 1 × ATtiny45 Arduino's smaller, cheaper baby brother, We still love you 328!
  • 1 × Raspberry Pi (and all necessary peripherals) The poster child of the maker movement, and a potential pirate radio.
  • 1 × TEA 5767 Radio Module It's pretty cheap and more importantly, very small.
  • 1 × ISP compatible Arduino (ATmega 328 or higher) The ATtiny doesn't come with a USB programming port; you'll have to use a breadboard and an Arduino to program it.
  • 1 × Speaker or Piezo Small, but powerful so you can actually hear it.

View all 12 components

  • Capitulation

    LordPharaoh08/20/2014 at 18:41 0 comments

    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.

  • Crystal Radio!

    LordPharaoh08/09/2014 at 08:24 0 comments

    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.

  • Software Success

    LordPharaoh08/08/2014 at 02:22 0 comments

    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.

  • Simplification and Irritation

    LordPharaoh07/29/2014 at 05:47 0 comments

    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.

  • The Elusive Tuning Capacitor

    LordPharaoh07/27/2014 at 17:00 0 comments

    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.

  • Radios. Argh.

    LordPharaoh07/27/2014 at 12:04 0 comments

    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.

View all 6 project logs

  • 1
    Step 1

    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.


    Then type 



    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.

  • 2
    Step 2

    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.

  • 3
    Step 3

    Find out the user and Program ID of the Raspberry Pi Radio program.


    sudo ./pifm enterwavhere.wav 89.1


     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.

View all 4 instructions

Enjoy this project?



Benchoff wrote 07/28/2014 at 00:37 point
I know you're actually taking FCC regs into account - and I highly appreciate that - but you might want to bump your frequency up a few hundred kilohertz. You don't want to be transmitting right on the edge of a band...

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.

  Are you sure? yes | no

LordPharaoh wrote 08/06/2014 at 02:52 point
Thank you for your advice! We're all knew to radio, so its greatly appreciated. Luckily, we haven't ordered the hard capacitor yet, so we can up the band easily. We ended up desoldering a tuning capacitor of roughly the right range from RadioShack's pocket FM radio set. It was a pain, but it was worth it. And we're all under 21 over here - Coke cans might work a tad better XD.

  Are you sure? yes | no

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