Nuts and Volts - December 2015

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.

Les Manis via e-mail

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.