Electronic Switch with Delay Time For Lambs


elect_timer_switch_for_lamb1.gif (21827 bytes)


A circuit that will find enough applications. Basically the designing became in order to exist delay in quench one or more lamps in a stairwell or in any other space exists this need. It can become use, for the control various motor or other appliances, what is connected in the contacts of J3. The activation command is given by exterior pressing switches connected parallel [Fig2]. Does not exist restriction in the number of these switches. The switches lead with a simple cable of three cables with small diameter, to the J1. Each switch is constituted by the pressing switch and Led that works constantly, facilitating to find the place of switch in dark spaces. If the switches are placed in exterior spaces, it will be supposed they are waterproof. Parallel to the J2 terminate the switch S2, Led D9, which can be placed above in the box of circuit or near this or can be used if it does not need. If pressing anyone of switch excited the Led of optocoupler IC1 the transistor closes and grounding the entries of gate IC2A, his exit becomes High. Capacitor C3 charges via the D2 roughly in the supply voltage. The exit of IC2B becomes Low the exit of IC2C becomes High. Transistor Q1 excites it and the RL1. His contacts close and it turns on the lamb that we have connected in his contacts, and it remains thus until discharge the C2. As soon as we stop pressing some switch the exit of IC2A goes Low, the C2 it begins discharge through the R5 and the TR1. Proportionally the resistance of TR1 changes also the time of C2 discharge, hence also the time that the RL1 remains excited. This time depends from the prices of C2, R5 and TR1. The use optocoupler facilitates in order to we avoid problems of accidental excitation from parasitic signals in the entry of IC2A.

The circuit supplied by one relatively simple power supply with stabilization in +12V dc. With switch S1 we cut the supply of circuit if it needs.

The D15 shows the circuit supplies with power and the D12 turns on when the RL1 is on. If him you do not need you can him suppress? The power of load that will supply the RL1 depends from his contacts. Can place relay with one or more contacts.

Attention, in the entire region where it exists the high voltage of network, exists always the danger of electrocution.

Part List

R1=See Text and Table1-2 C3=10uF 25V D4=1N4148
R2-3-7-8=1K 1/4W 5% C6=1000uF 35V J1-2=3pin 3.96mm pin step Connector
R4=10K 1/4W 5% IC1=4N35 or Similar Optocoupler J3=8pin Connector with Screws
R5=470K 1/4W 5% IC2=4093 CMos RL1=12V Relay with 2, 3 or 6 contacts
R6=33K 1/4W 5% IC3=7812 Regulator 1A S1=On/Off MicroSwitch 1A
TR1=1M Trimmer Q1=BD679 Darlington S2.......6=Push Button [See Text]
C1-4-5=100nF 63V MKT 5% D1-2-3-6....9=1N4002 T1=110-230Vac @12V 2A Transformer
C2=4.7uF 25V D4-10-11-12-13-14-15=Red Led 3mm or 5mm
Table 1   [Leds in Parallel] Table 2  [Leds in Series]

Calculate the value of R1 resistor

R1.gif (1388 bytes)

R1B.gif (1408 bytes)

For Exable: 5 Switches with 5 Red Leds 3mm in Parallel.

For Exable: 5 Switches with 5 Red Leds 3mm in Series.

R1A.gif (2632 bytes) R1C.gif (2689 bytes)
P=V.I=10.2V x 0.05A=0.5W P=V.I=3V x 0.01A=0.03W
Idt= Id X (Number of Leds) Vdt=Vd X (Number of Leds)
Red Led 3mm Id=10mA Vp=12V Vd=1.8V
Red Led 5mm Id=20mA Vp=12V Vd=1.8V

Led connection of external switches.

In Fig.2-3 appear two ways of connection of clue Led that are found on each external switch. In the Fig.2 the Led of all switches, are connected parallel the one with the other. In this case the calculation of resistance R1 becomes as it appears in the Table1. The connection Led in series appear in the Fig.3 and the calculation of R1 value exist in the Table2. If you do not need Leds then you can abolition.

elect_timer_switch_for_lamb2.gif (7327 bytes)

Various connection modes, of external loads.

Various connection modes exist in the Fig.3,4,5. In the Fig.3 exist one of typical house connection, where the Sw is the existing switch of wall house. When the Sw is closed lamb it turns on independent from the operation of circuit. If the switch Sw is open then the circuit takes on her operation.

elect_timer_switch_for_lamb3.gif (6150 bytes)   elect_timer_switch_for_lamb4.gif (4898 bytes)      elect_timer_switch_for_lamb5.gif (4486 bytes)


elect_timer_switch_for_lamb6.gif (2206 bytes)

Example of placement of Led in exterior switch.


Sam Electronic Circuits 8/04