By jawaharlal@excite.com

When activated by pressing a button, this time delay relay will activate a load after a specified amount of time. This time is adjustable to whatever you want simply by changing the value of a resistor and/or capacitor. The current capacity of the circuit is only limited by what kind of relay you decide to use.

 

Schematic

Parts:

Part	Total Qty.	Description	Substitutions
C1	1	See Notes
R1	1	See Notes
D1	1	1N914 Diode
U1	1	4011 CMOS NAND Gate IC
K1	1	6V Relay
S1	1	Normally Open Push Button Switch
MISC	1	Board, Wire, Socket For U1

Notes:

1. Email jawaharlal@excite.com with comments, questions, etc.

2. To calculate the time delay, use the equation R1 * C1 * 0.85=T, where R1 is the value of R1 in Ohms, C1 is the value of C1 in uF, and T is the time delay in seconds.

3. S1 may be replaced with an NPN transistor so the circuit can be triggered by a computer, other circuits, etc.

4. Most any 6V relay will work for K1. If you use a large relay, you my need to add a transistor to the output of the circuit in order to drive the larger load.