A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use.
| Part | Total Qty. | Description | Substitutions | | R1 | 1 | 1 Meg Pot | | | R2 | 1 | 10 K 1/4 Watt Resistor | | | C1 | 1 | 10uf 25V Electrolytic Capacitor | | | C2 | 1 | 0.01uf Ceramic Disc Capacitor | | | D1,D2 | 2 | 1N914 Diodes | | | U1 | 1 | 555 Timer IC | | | RELAY | 1 | 9V Relay | | | S1 | 1 | 1A 120V SPST Switch | | | MISC | 1 | Board, Wire, Socket For U1 | |
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- R1 adjusts the on time.
- You can use a different capacitor for C1 to change the maximum on time.
- S1 is used to activate the timing cycle. S1 can be replaced by a NPN transistor so that the circuit may be triggered by a computer, other circuit, etc.
