Another scenario was a self-service undromat. We tied our system into the ghting circuit through one contactor, nd the boilers into another contactor. verything operates on a schedule — and cess systems are best suited for that! At 30 a.m., the boilers kick on, and the wa- r is heated and ready for their first cus- mer. At 7 a.m., opening time, the lights rn on and the front door unlocks. At 10 m., the boilers turn off for an hour and en back on at 11. You get the picture. t 9 p.m., the front door locks, and at 10 m. the lights go off. It’s total automa- on for the owner. He doesn’t have to ay someone to hang around and watch e place — he does that from his phone ith his CCTV system. One last critical thing when choosing a Figure 3. An electrical contactor typically only needs 24 VDC at half an amp or so to energize — well within the ratings of an access control power supply. track of which employee used them, he convinced himself! At this time, I’d like to introduce the electrical contactor (Figure 3). What is it? Think of it as a high-voltage relay. One of the main differences between a relay and a contactor is load capacity. Relays typically operate with loads less than 10 amps, while a contactor will handle much more electrical current and voltages up to 1,000 volts AC. Also, a contactor’s main terminals are normally open only. These are known as Form A contacts because there is no common. This means that when a contactor is de- energized, there is typically no connec- tion. With a Form C relay, there very well could be. Because contactors are typically carry- ing high loads, they usually have spring- loaded contacts. This helps to ensure the circuit is broken when de-energized. Also, contactors usually have built-in overcur- 24 KEYNOTES FEBRUARY 2019 rent protection (think circuit-breaker). Here’s where we tied in a contactor to an access control system: A contactor only needs (typically) 24 VDC at half an amp or so to energize — well within the ratings of an access control power supply. With the lock output from the panel trig- gering a 24 VDC output from the Altro- nix power supply and using that to trigger a contactor (installed by their electrician), they could power their gas pumps! All I had to do was make sure the lock output relay of the access control sys- tem had the programmability to stay on long enough for the employees to fill up their trucks and equipment. I installed a prox reader by the gas pumps, and they were good to go. They didn’t even have to worry about locking their pumps; with no power, no one gets fuel. With no cre- dential, no one gets power. When they terminate employees, they no longer have access to fuel. ower supply is the current rating. With any options to choose from, please don’t forget the 80/20 rule: Do not exceed 80% of the rated load capacity. If you add up all the requirements of all the devices drawing power, make sure that number is less than 80% of the rated capacity of the power supply. If you connect all electric strikes, chances are slim that there will be an issue. However, if all your locking devices are maglocks, they all need con- stant power and can overload a power supply and cause problems. James K. Ashley, CPS, CPL, CEL, CAI, started in the security industry in 1986 while stationed at Lackland Air Force Base in San Antonio, TX, vol- n apprentice for B&P Lock Shop. James is an educational sponge, and being a musician is the only thing that can eclipse his love for electronics and technol- ogy… and boating. He started Ashley Safe & Security in 2001 in Indianapolis, IN, and is three-term president of the Associated Locksmiths of Indiana. WWW.ALOA.ORG
