powered up until the input power is interrupted, at
which point the delay period becomes active again. Load
rating for the relay is 1/3HP @115V (seven amps) so it
should be able to handle a number of devices such as a
power head and a filter or air pump.
S-S Electric Repair Shop
#4 I had the same problem with my fishtank forgetting
to reconnect the filter pump after feeding my fish. There
are many solutions to remedy the problem, but the simplest I found is a delay on release timer from Amperite
P/N 120ACR600C. Newark Electronics (800-4-Newark)
can supply this timer. Only additional component
needed is a momentary NO pushbutton switch.
■Frank Kretkowski, Jersey City, NJ
#5 May I suggest a universal start/stop timer kit made
by Velleman Kits. It is available at MCM Electronics for
$15.95. www.mcminone.com/ part #80-2855. You can
put the timer/relay in line of an inexpensive extension
cord. The kit requires 12VDC which can be from
batteries or a small wall transformer.
■Bob Lindstrom, Broomfield, CO
#6 A very simple solution would use a low cost
mechanical appliance timer. These are available at
hardware stores for under $10. Just set the "Off" time to
midnight and the "On" time 15 minutes later. Whenever
you feed the fish, spin the timer wheel around until the
pump turns off. Fifteen minutes later, it will turn back on.
If the fish are fed at least once a day, then the pump will
never turn off by itself. But, if it should, it will not be a
big deal since it will only be off for a few minutes.
■Thomas B., Folsom, CA
#7 This circuit will interrupt the power
to your aquarium pump for approximately
10 minutes. When you press S1, C1
charges very rapidly to + 12 volts. The charge on C1
biases Q1 (an NPN Darlington) on and the relay is energized, interrupting power to the pump. The specified
relay requires only 220 m W, well within the Q1 rating of
625 m W, and its contacts can handle up to eight amps.
The relay will
remain energized (
keeping the pump
off) until C1
volts, and the
depends primarily on the
size of C1 and
R2. You could
use a one
meg pot in
place of R2 if
you want the timing to be adjustable. Any 12 volt DC
wall wart will power the circuit.
C1 - 1000 uF 25V
D1 - 1N4001
K1 - Omron G6RN-1-DC12 (Mouser P/N 653-G6RN-1-
Q1 - 2N6427 NPN Darlington (Mouser P/N 512-2N6427)
R1 - 3. 3 K
R2 - 680 K
S1 - Push button momentary switch
■Ed Schick, Harrison, NY