Electronic Door Lock by Danny Howcroft

Door Lock

I have recently finished my A levels (one of which in electronics) and I thought I may share with you my As project. This is an ideal project for students or just for beginners to the world of electronics. Obviously all parts can be bought from Technobots.
I got a grade A with this circuit although I am not promising this will get anybody else the same grade!!! and do not use this to protect your property I am not liable!!!
Digital Door Lock:
This project introduces basic CMOS Logic and even soldering (If your feeling Brave).
Door Lock Circuit
Parts List:
  • Bread Board or strip board ( I suggest you try this first on bread board then transfer to strip board)
  • 4 x Tactile Switches
  • 4 x 1 Kohm Resistors
  • 1 LED or Relay (its up to you)
  • 5 volt battery pack
  • 4017 decade counter
  • 4071 AND
  • 4072 Quad input OR
  • Wire
  • Wire strippers / cutters
  • pliers
  • Soldering iron and solder

Door Lock Kepad

Door Lock Logic Board

Final Notes:
Where I have used the LED feel free to changes this to a relay or even a shoot bolt to suit any purpose. But remember when using a relay always use a protection diode!
Designer: Danny Howcroft

If you need to work out the distance between centres of any two timing pulleys, then this calculator will eliminate the long calculations or trial & error for you.



  Timing Pulley Distance Between Centres Calculator  
  Large Pulley Teeth Number T  
  Small Pulley Teeth Number T  
  Pitch   mm  
  Belt Length   mm  
  Large Pulley PCD   mm  
  Small Pulley PCD   mm  
  Distance Between Centres mm  
  How to use the Pulley Distance Calculator  
  1. Enter the number of teeth on the largest pulley  
  2. Enter the number of teeth on the smallest pulley  
  Note: if 1:1 ratio, enter the same number of teeth in both boxes  
  3. Enter the belt tooth pitch in mm, i.e. T5 is 5mm, T2.5 is 2.5mm  
  4. Enter the belt length in mm  
  The resulting answer is shown in the bottom yellow box. For information, the PCD of the pulleys is also shown in the other yellow boxes.  
  In order to achieve the correct tension, one of the pulleys should be adjustable.  
  Disclaimer: Whilst we have taken evey care to ensure this calculator gives the correct answer, Technobots cannot be held responsible for any errors and their consequencies.