December 2015 13
device starts up, whereas CPLDs store their configurations
and are thus ready for action upon start-up. FPGAs contain
complex functions such as adders, multipliers, memory,
and SerDes (Serializer/Deserializer), whereas CPLDs do
not. FPGAs are more capable than CPLDs, but are slower
in their operation.
This is an extremely oversimplified discussion of CPLDs
and FPGAs but I hope it will help you further understand
these very useful devices.
Breaker Tripped/Sump Pump Alarm
QSince my septic tank is higher than the drain line from my house, I have a holding tank with a pump to push the wastewater up to the septic tank. I found out this weekend that the pump,
sump pump, and crawl space lights are all on the same
breaker when the lights would not work. Fortunately, it
was my sump pump that had caused the overload. I need
something to alert me if this breaker is off due to the septic
backup possibility. I guess an indicator light would be
easiest. However, I was thinking I would like to have a small
alarm that would sound when this breaker is tripped. Can
you give me some suggestions? Love your column.
AIn Figure 11, I have shown a simple way to alarm when a breaker is tripped. Be sure to have an alarm device that is
compatible with the voltage between the
hot and neutral lines; be sure the alarm
device has the proper circuit interrupter
(fuse, etc.) to avoid fires or damage in the
event of a failure; and be sure that there is
no switch between the alarm device and
the neutral line.
The alarm device could be a lamp or
buzzer that is compatible with the line
voltage (I assume 120 VAC for a sump
pump circuit). If you want to use an electronic (i.e., low
voltage) device, a relay could be hooked up as my alarm
device and its contacts used to trigger the low voltage
device. REMEMBER: Be careful when working around line
voltages to avoid electrocution and/or DEATH. If in doubt,
call a licensed electrician.
If you want a simple plug-in alarm solution, I found a
couple of devices on Amazon.com for reasonable prices
(see Q&A SIDELINES). NV
n FIGURE 10.
n FIGURE 11.