Very often I, and anyone else that dabbles in access control, get called to troubleshoot problems with an access control system. Whatever the symptoms, the usual checklist of diagnosing the problem(s) includes things like checking for continuity, proper voltage and amperage, integrity of splices, etc. There have been times where everything seems to check out and the only thing that hasn’t been tested is that electrified door hardware itself. This could be an electric strike or an electrified panic device, for example.

Now I know what some of you may be thinking: if it’s getting the proper voltage and amperage it’s obviously the electrified door hardware that’s the problem. Fair point and nearly always true. When diagnosing something like a stuck solenoid or a solenoid plunger that needs adjustment on, say, a Von Duprin panic device with an EL or QEL kit, it can be very problematic to constantly swipe or read a card to send voltage/amperage to the electrified door hardware while diagnosing and/or adjusting it. This is especially true if you’re trying to observe or position a multimeter or pay close attention to something in particular, such as inrush current. Examples abound for the benefit of a makeshift power supply in the field when troubleshooting access control components.

This need doesn’t arise all that often but when it does it’s helpful to know that you can create one of these makeshift power supplies with nothing more than scrap wire and a 9 volt battery, or two.

Note: Keep in mind that this is only for DC powered electrified door hardware.

Basic 9V Circuit(s)

Let’s start by recapping electrified door hardware basics as they relate to our situation. A vast majority operate on either 12 or 24V. Some operate on 16V or 18V and while these are outliers the methods discussed below can still be utilized to diagnose them.

If you are diagnosing electrified door hardware operating on 12V, a 9V battery is enough to test it. I have yet to encounter any 12V electrified door hardware that won’t operate when connected to a fully charged 9V battery. If the electrified door hardware operates on 16, 18, or 24V you will need two 9V batteries connected in series.

If you’re unfamiliar with wiring batteries together, here is brief summary:

  1. Two batteries wired in series combines their voltage.
  2. Two batteries wired in parallel combines their amperage.

By wiring two 9V batteries in series we essentially get a 18V battery (the makeshift power supply). And some of you might be saying, “that’s not enough for 24V!” It’s never not worked for me. If you run across the unicorn I’m still looking for, just add another 9V in series for 27V.

Wiring 9V Batteries

The positive and negative terminals are clearly marked on 9V batteries; the bigger of the two is negative (anode), the smaller positive (cathode).

To wire a battery in series, you connect the positive terminal of one battery to the negative terminal of the other. The remaining positive and negative terminal then become your positive and negative leads, which you connect to the electrified door hardware. It’s that simple.

In a pinch, you can cut wire for the connections and tape them in place. If you diagnose access control systems/components regularly I would highly advise you to grab a pair of snap connectors (they can be salvaged from electronic equipment or purchased at Radio Shack or Frys for less than $2 each) and wire them in series so that you don’t have to cut and splice and tape every time you want to use this makeshift power supply; they’re also much more reliable. I also solder the tips of the leads to keep the wires from fraying or breaking. You could buy clips or probes instead and attach them if you desired. Up to you; no right or wrong answer.