Secret Electronic Lock Without Visible Interface

I always wanted to use touch and magnetic switches for some secret locking mechanism and now I finally find some time to make it happen

in this instructable you can follow my steps and make something similar

as I mention I using magnetic switches which could be switched through 5mm walls with strong magnets and touch switch which can be switched by your finger, all invisible from the outside

you can also use some till switches, hall sensors accelerometers..... for activating hidden mechanisms

I will use just simplest methods using electronics which could be easily replicated

Step 1: Servo Driver With LM555

there are a few ways how to make this lock mechanism I recommend to make servo driver first and then start building locking mechanism

I tried this first it works fine but I didn't have right components so I used NE555 instead of LM555 and a different diode so it could be a reason why was my circuit behave a little bit weirdly (output signal was different as servo standard) but only when it was open so it wasn't a big problem

I don't know if this was caused by the wrong diagram which I found here or my chose of components replacement so if you decide to make this and it will work without little mowing in one of the positions please let me know in the comment section

I created two circuit diagrams one just with magnetic switches and one with additional touch switch for the more complicated opening sequence it's up to you which one you prefer

components:

magnetic switch link
LM555 timer link
100K potentiometer link
1N4007 rectifying diode link
22nF capacitor link just select 22nF and order
resistors link just select 3.3M and 65K or 68K, 1K (when you use touch switch) and click to order or buy some resistor kit which contains needed values
servo motor link
touch switch TTP223 link
BC547 transistor link
battery holder link
neodymium magnet link I used 10x5x3mm

Step 2: Servo Driwer With Arduino

if you prefer arduino I used this code link just change value 180 to whatever position you want (i used 45)

add a magnetic switch between the power input and arduino, connect I/0 pin from touch switch to arduino pin 9 you don't need 1K ohm resistor because it is built in inside of TTP223 touch switch

for more details watch little notes in pictures or ask me in the comment section

components:

magnetic switch link
servo motor link
touch switch TTP223 link
battery holder link
neodymium magnet link I used 10x5x3mm
arduino pro mini link you can also use Arduino nano or UNO with the same code
FTDI programmer for arduino pro mini link (if you don't have one)
pins link
code

servo_button.ino
Download

Step 3: Door Lock Mechanism

here I have little demonstration made out of cardboard but you can use wood, plastic or even metal to make a strong lock

so if you made one of servo controller circuits from previous steps connect servomotor to it and set one position

mark center of your door and make sure your latch have correct dimensions for the closed and opened position

place servo in center and test if servo arm is in correct positions when you switching between open and closed position then you can glue servo arm to your latch and mark both positions with a marker. This will help you later to pick up spots for holding the servo in position without risk of collision with latch

when you have all positions marked you can pick places for servo stands and attach the servo to it

if you have your servo attached and it works well you can make little holders for latch when it is in the closed position to add strength because if someone tries to open it with force servo is the only think what holds latch on the place remember to leave some space between latch and holder

if is needed add holders also to the door site

Step 4: Implementation in Flower Pot

when I had my circuits working I implemented it into a flower pot with a secret compartment

if you want to make it I recommend to use some plywood or plastic instead of cardboard (i didn't had plywood) you can glue stones or wood substrate to the visible top to make it look like a common flower pot

chose flower which had large volume but needs only small space for roots to hide small pot or you can put some very good imitation of a plant to save inside space