Hi! This will be my fifth update for this challenge, this will be a short update where we will take a look at some of the things that will provide feedback to the user of the skeleton key device. There are three different types of signals that I would like to incorporate into this build and that would be light, sound and tactile signals. Since this project is primarily aimed towards visually impaired people, sound and tactile feedback are of great importance, but having the light signals as well can only improve the device. So first off, let's start with the simplest of the bunch, the light signals.



Light signals

For the light signals of course I will rely on LED-s, 4 of them to be precise, 1 green, 1 yellow, 1 red and a white one to be used as a light to help with finding the key hole when it's dark outside. I will use them to give me a lot of different information. Some of the things that I want to cover with the light signals are:


  1. Battery level
    1. Would be activated by a long press on the button, or signaling on its own when the battery is running low
    2. All three colored LED-s lit if the battery is above 66%
    3. Red and yellow lit if it's 33%-66%
    4. Red if it's 10%-33%
    5. Blinking red if it's <10%
  2. Fingerprint recognized
    1. Flashing green LED
    2. If there are multiple users it can blink corresponding to the ID of the fingerprint
  3. Fingerprint not recognized
    1. Flashing red LED
  4. Tag recognized
    1. Flashing green LED
    2. Can flash a certain number of times depending on the number of the tag/key
  5. Tag not recognized
    1. Flashing red LED
  6. Done selecting the key
    1. Blinking green LED
  7. Beacon (triggered when looking for a device)
    1. All of the lights blinking
  8. Flashlight
    1. Turn on/off the white LED


This is the plan for the light signals for now, can't test this part at the moment since it all requires to work with the RFID and fingerprint module, so these will all be integrated in the first prototype.


Sound signals

This is the second type of signals, here I have a choice between 2 different things, a standard buzzer and a mechanical buzzer. To see what is better I tested them to see how loud they are, their size and their current draw. So here is the comparison between them:


Doing these tests it made the choice easy, and it is the standard buzzer. It has a much higher pitch than the mechanical buzzer, draws less current, it's smaller and the mechanical buzzer has another big issue and that is to achieve the 70 dB it has to be firmly attached to a solid surface. One thing that did cross my mind, which I will try out, is using only the mechanical buzzer instead of a buzzer + vibration motor combo. Now we have to do something similar like with the LED-s. For "positive" actions (fingerprint recognized, key chosen,...) I will do short double beep, while for the most of the "negative" actions (fingerprint not recognized, tag not recognized, battery level low,...) a longer single beep. One more sensor I will be adding, as soon as it arrives, is a vibration sensor (for detecting falls), so in this case, the buzzer will go instantly and beep until the device is picked up. Another thing I would like to do is, like with the LED-s, do a certain number of beeps depending on the number of the tag, and of course when the mode for looking for the device is activated the buzzer will just go on and off.


Tactile signals

The general idea is using a vibration motor from a gamepad, they are designed for 5V anyway, but there are a few things about it. Draws a lot of current, and it's pretty powerful. I have few of them laying around, and this is the one that spins up the fastest of them all:



This was a short update where I just wanted to address all of the feedback that the device will be giving to the user. For the light signals it is pretty straight forward, but when it comes to the other 2, I am still going through all of the options. I would like to keep the small buzzer because it's so audible, but on the other hand, the mechanical buzzer can pretty much do 2 things at once. Maybe both buzzers? I will do some further testing and playing around with this when I have the device assembled to an extent, to see how effective the mechanical buzzer is compared to the vibration motor. Thanks for reading the blog, hope you liked it!