Electronic Timer Switch - TIMER PROJECTS

Electronic Timer Switch

This electronic timer switch project is a good project to build to simulate the presence of occupants in a house. In these days when security is becoming more of a concern when no one is at home, having this device will deter the thief from breaking in. When power up, after 60 minutes, the relay will turn ON for 100 secs, OFF for the next 100 secs, and ON again for 100 secs before OFF again for the next 60 mins. This sequence will be repeated. A device such as a lamp that is connected to the relay will turn ON and OFF according to this timing.

Schematic Diagram

The schematic of the project is as shown below.

The core of this electronic timer switch project uses a CD4060B binary counter. The binary counter has 10 outputs and the counter are counted by configuring the oscillator. Every negative clock will trigger the counter of the IC internally.

The timing of the circuit is affected by resistor R3(1M ohm) and capacitor C2(0.1uF). By connecting the four outputs in an AND configuration, the transistor Q1 will only turn ON if all the 4 outputs are in logic "1". If any of the logic is "0", the transistor will remain OFF.

For a complete cycle, the transistor will be ON twice when the output at pin 15, QJ goes to logic "1" and "0" twice when the other outputs QL, QM and QN remain at "1". When this happen, the relay K1 will switch status accordingly. The timing of the switching can be changed by changing the resistor values R2, R3 and C2. Download the data sheet of CD4060B from Texas Instrument website for more details.

Note that since the oscillator is not using crystal, the timing may not be as accurate compared to the ideal calculation. In most cases, fine tuning the resistor and capacitor are good enough to make this project a success. To check whether the circuit is working, connect a LED in series with a 390 ohm resistor at output QD. It will flash ON and OFF as the oscillator oscillates.

Parts List

REMOTE SPEAKER SETUP

Even if your hi-fi amplifier does not have output terminals for remote speakers, it is easy enough to add them without complex switching equipment. With few exceptions, modern solid-state amplifiers have no output transformers and automatically match any speaker impedance between 4 and 16 ohms. The only important consideration is that the total impedance connected to the left and/or right speaker output is never less than 4 ohms, or the amplifier will attempt to deliver so much power output, the output transistors will self-destruct. If your main speakers have an impedance of 8 or 16 ohms, simply add remote speakers as shown :

Switch S1 turns the remote speaker on and off. Since transistor amplifiers usually put out more power at 4 ohms than at 8 or 16 ohms, adding the extra speakers does not substantially reduce the volume at the main speakers because the amplifier sees a lower impedance load and attempts to drive more power output into the combined speaker load. If your speakers are 4 ohms, and you plan to use 4 ohm remote speakers use the circuit modification shown. Switching in the remote speaker will result in the main and remote speakers being series connected for a total load of 8 ohms.

IMPROVED VERSION OF MUSCULAR BIO STIMULATOR-BIOMEDICAL PROJECTS

This circuit is a big improvement of the small Muscular Bio-Stimulator design

DOWNLOAD THE CIRCUIT DIAGRAM

COMPONENTS REQUIRED

P1_____________100K  Linear Potentiometer
P2,P3___________10K  Linear Potentiometers

R1_____________560K  1/4W Resistor
R2______________68K  1/4W Resistor
R3,R4___________10K  1/4W Resistors
R5______________22K  1/4W Resistor
R6,R7____________4K7 1/4W Resistors
R8_____________330R  1/4W Resistor
R9_______________2K2 1/4W Resistor
R10____________470R  1/4W Resistor
R11_____________47R  1/4W Resistor

C1_______________1µF  63V Polyester Capacitor
C2,C3__________100nF  63V Polyester or Ceramic Capacitors
C4_____________220nF  63V Polyester Capacitor
C5_____________220µF  25V Electrolytic Capacitor

D1______________LED  (Any dimension, shape and color)
D2,D3________1N4148   75V 150mA Diodes

Q1____________BC547   45V 100mA NPN Transistor
Q2,Q3_________BC327   45V 800mA PNP Transistors

IC1,IC2________7555 or TS555CN CMos Timer ICs

T1_____________230V Primary, 12V Secondary 1.2VA Mains transformer (see Notes)

SW1,SW2________SPST  Toggle or Slide Switches

Notes:

• T1 is a small mains transformer 230 to 12V @ 100 or 150mA. It must be reverse connected, i.e. the 12V secondary winding across Q3 Collector and negative ground, and the 230V primary winding to P3 and output Electrodes.


• The circuit has been thoroughly tested, and it works nicely when supplied in the 3V - 9V range. Running on 3V supply with a 12V 1.2VA transformer it would be no more dangerous than the circuit already published. But please note that using 9V battery supply it can output 120V signals and could be very dangerous.


• Electrodes can be obtained by small metal plates connected to the output of the circuit via usual electric wire and can be taped to the skin. In some cases, moistening them with little water has proven useful.


• Commercial sets have frequently a built-in 30 minutes timer. For this purpose you can use the Timed Beeper the Bedside Lamp Timer or the Jogging Timer circuits available on this Website, adjusting the timing components to suit your needs.