I recently got a call from a facility management company who is a good customer. Someone had damaged the electric door entry on a residence which had been converted over to multiple-dwelling student housing. I got there and the manager handed me a body bag containing the old door strike which was in pieces. The door had a cylindrical lock and the door and lock were fine, but the door frame was damaged in the area where the forced entry had dislodged the electric release. I noticed that the old strike had a label on it indicating the operating voltage was 16-24V. I told the manager I would see what we had in stock, but perhaps it would be necessary to order something. He said the sooner the better!
Where I messed up was that I didn’t bother to put my meter on the wires in the frame to determine the voltage or function of the strike.
Although the old strike was labeled, it did not indicate if the voltage was AC or DC. And without measuring, I was unsure precisely what the actual voltage was. Additionally, because I was in too big a hurry, I didn’t know if the strike was failsafe or fail secure.
A quick call to HES resolved all my concerns. The #5200 is field configurable for 12 or 24 Volts, and operates well in its 12 volt setting with a 16 V (AC or DC) voltage applied. Of course, the #5200 is also field-configurable for failsafe or failsecure.
We work with a variety of voltages in security. The Graphic Display of Voltage chart depicts several. When using a DC Power Supply, you hopefully are getting the nice straight line variety shown in the graph. Depending on the equipment, the voltage level and purity of the voltage will be critical for proper operation.
If you are using an AC Transformer, then you are hopefully getting the nice line wave shown in our graph.
When you are overloading your power source, you may be getting a lot of ripple on your supply, which is a mixture of DC voltage with an AC component referred to as ripple. A certain amount of ripple may be acceptable when operating locking devices, but if the ripple is the result of an overload condition on your power source, it is not allowable since you are stressing your power supply and a failure is inevitable.
If your voltage is fluctuating, all bets are off, since you’ve got issues somewhere in the circuit which needs to be addressed immediately. A loose wiring connection or a component beginning to six means there’s trouble ahead.
I have spent a lot of hours staring into an oscilloscope, the type of test equipment required to see these wave forms. However in an installation setting, it is not typically necessary to analyze voltage to this extent. But it doesn’t hurt to know what’s going on. For example, if you have a suspicion that there are problems with your circuits, you can diagnose pretty well with a professional quality digital multimeter. You can determine the voltage levels, whether you are dealing with AC or DC.
Many DVMs have an analog bar display along the bottom of the display so you can see fluctuations in real time. Those of us who remember the era where a voltmeter was a needle which swept across a dial probably based our troubleshooting techniques on the ability to track voltage fluctuations in this manner. The bar graph display is a carry forward of this feature.
You can also switch your DVM from AC to DC to gain a little insight. For example if you are metering a DC voltage and you switch your meter to AV and get a reading that amount to more than a minute level, you are looking at ripple or noise component on your power supply which might be an indication of the problem mentioned above.
The other important issue is voltage drop. This is when the voltage present at the device (lock, card reader, etc) is lower than the operating specification for the particular device. Cameras, door locks and readers are sensitive to the voltage level they receive, and presenting too high or too low a voltage is not advisable. Voltage drop calculators are available at many web sites (Altronix and Securitron as two examples). If you are troubleshooting a system, keep voltage drop in mind as the use of too low a gauge wire, as well the weakening of power sources, and the increased loads caused by defective components are all common occurrences in real world adventures.