I’ve had this idea in the back of my head for quite a while now, a small clock, placed under the skin and shows the time by shining light through it. To avoid draining the battery and causing excess heat the time should only be displayed when you tell it to.
I decided to approach the trans-dermal input with a very simple but functional idea, magnetic activation using a reed relay…….Anyone willing to put a clock inside their body, has probably already inserted a magnet into a finger


My original idea was very simple, take an Arduino Nano, Neopixel ring, QI receiver and a Li-Po, arrange it nicely and bioproof* it.
But the more I thought about it, it started sounding worse and worse, having a huge development board that is barely used, a large PCB with nothing but LED’s, a separate QI receiver and so on.

*(That I do not know how to do, something I have to educate myself on if I wish to create this device)


(Most ideas begin with crude whiteboard drawings)



I did however thing the basic electronics behind it was logical, so I spent some time deconstructing every single piece of it and start designing it as a single PCB


(Block image of the design)

After having the basic concept down, I went and read up on the necessary IC’s to make this both function.

This design uses the

LM7805 for power regulation (WIP component, it’s too big for real usage)
MCP73831 for charging the Li-Po
bq51013B as a QI receiver
ATmega328P as micro-controller
WS2812 for the leds
RTC module has not been picked

(the basic circuit design)

How it would look


In conclusion, I think this is an interesting concept to play with, far far away from being a realistic idea today but, we could make this a reality within a few years


  1. Brian McEvoy says:

    Hey, this is McSTUFF from the biohack.me forum.
    Since this project is still young I thought I’d pipe in with my thoughts.
    First of all, cool.
    You have a reed relay listed as the part for receiving a signal of when to light up but I think you mean a reed switch. A reed relay is basically a reed switch inside a solenoid but you don’t need the wire wrapping. That will shrink your design a bit, so that’s cool.
    Red light shines through skin without too much trouble but different wavelengths don’t do as well so it might be better to devise a way to use only red LEDs such as first displaying the hour and then the minutes. That also shrinks the components because you don’t need the individually addressable WS2812B chips just a dozen red SMD LEDs.
    To make the clock easier to read what about having a tattoo done beforehand with clock numerals in a circle the same diameter as the implant? Maybe you want all twelve numbers tattooed but I only want four dots at the cardinal directions. Now it’s easy to personalize as well. It would be extremely important to get the implant positioned correctly.
    Data could be passed through Bluetooth but you could also program some tricks into the reed switch. Maybe if you hold a magnet there for more than ten seconds it sets the clock to exactly noon when the magnet is released. It forces you to set the watch at noon but it shouldn’t have to be done often so that’s a minor in my opinion.
    It might be possible to attach the reed switch to a serial data pin and actually receive data but don’t quote me on that, it might be too fast for the reed switch to keep up. Or wear out your switch prematurely.
    If the sky is the limit add a compass. But that’s definitely scope creep.
    Send me an email and we can chat on the phone if you want to have a live brainstorming session.

    • admin says:

      Thanks fpr the input

      I meant reed switch not reed relay, just got the terms switched in my brain

      The idea about the red leds is very interesting, would simplify the construction a lot and if RGB LED’s don’t shine well through the skin, that complexity is being wasted.

      I had considered using the reed switch as a time-reset switch as well, it seems a bit dirty but then again, how often do I have to reset my clock

      The first thing I need to do to research this concept is to do some testing with implantable magnets, reed switches and an arduino to see how it behaves, that entire idea might be a dead end

      • Brian McEvoy says:

        Look at what you can do with just a bare chip and components soldered to it. Arduinos, as I’m sure you know, have a lot of supporting components which aren’t necessary once the chip has been programmed. A prototype, non-implantable, could be a tangle of wires, processor, inductive charging coil, battery, 12 LEDs, reed switch, two caps and a crystal all suspended in a disc of silicone.
        At that point you can legitimately test if you can read the LEDs through some chicken skin and activate the reed switch with a finger magnet. It will give you a baseline of how big you can expect it to be. Flexible PCBs are probably a necessity here. Soldering can probably be done by you.
        By then hopefully you’ve gleaned enough information about coatings. Revise your design as necessary and see how you feel about the whole thing. Maybe you’ll abandon it as a bad idea or maybe you’ll be so psyched you’ll order the parts that night.
        Hopefully none of those steps seem impossible, but there were a lot of them. And undoubtedly some I’ve missed.
        Check out the Misfit “Shine” and Misfit “Flash.” They were discussed as a possible candidate for implantation and look similar to what you’re thinking of building.

        • Brian McEvoy says:

          After recommending the Misfit devices I went and bought a Misfit Flash. It has 12 lights and tells the time when the button is pressed. I haven’t opened it up but it feels like a simple tactile switch so that could easily be replaced by a reed switch. The battery life is supposed to be 6months on a CR2032 battery. Replacing the coin cell with a 3V rechargeable lithium and inductive charger *shouldn’t* be too much trouble. If you use the guts from one of these devices you already have communication. And it gives you a selfie button so E’RYONE will want one.
          I worry that the lights in the Misfit Flash might not shine through flesh but I haven’t put it under chicken skin to check. The other problem is that it is 8mm thick with the current case.

  2. Trybal Wolf says:

    trybalwolf from biohack.me

    I personally wouldn’t want numerals tattooed. Perhaps simple dots with a concave diamond at 12. Also, no reason to do the tattooing first. I have been tattooed over implants and have had no issue, just an odd feeling of the vibration of the tattoo machine being transferred over a larger area.

    This is definitely a project I would be interested in. While I currently lack technical expertise to be of any help here, I would definitely be up for beta testing. ^^

    This idea could possibly be combined with the Northstar device. Providing both clock and compass functions.

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