The KeyTek MZ-15 ESD Simulator
that I have used in many of the experiments on this website and in
countless seminars is powered from internal Ni-Cd AA batteries of about
700 mAh capacity. The machine is not in daily use and the result is
that the batteries go bad in a few years and will no longer hold a
charge, necessitating a trip back to the factory. Also, in the case of
many ESD simulators, if the battery is dead and the charger is not
available immediately or there is no mains power available, an ESD test
may have to be postponed.
To solve the problem of the bad Ni-Cd battery pack in my case, I
carefully removed the (leaking) Ni-Cd batteries from the small plug-in
circuit board they were soldered to. I used vinyl gloves and a covered
work area as the chemicals in Ni-Cd batteries (especially the cadmium)
are toxic to humans. Next, I mounted a high quality four AA battery
holder on the bottom of the Mini-Zap as shown in Figure 1 using double
stick tape such as used to mount pictures or secure a carpet to the
floor underneath. Very small "V" grooves on opposite sides of the
Mini-Zap housing were made to feed the battery wires into the unit and
the battery wires were soldered to the small plug-in board that
originally held the Ni-Cd batteries. I was careful to connect the "+"
wire in such a way as to preserve the function of the small fuse on the
original battery board.
A side view of the completed
modification is shown in Figure2 with a close-up of the positive
battery wire entering the side of the Mini-Zap housing shown in Figure
Figure 2. Side View of External Battery Modification
Figure 3. Close-up View of Battery Connection
The capacity of a good set of Ni-MH batteries or AA alkaline batteries
is on the order of 2.5 to 3.0 Ah (Ampere-hours) when discharged over
several hours so a set of alkaline AA batteries should last for many
hours of use. In my case, the Mini-Zap will go weeks between uses so I
just put in a set of AA alkaline batteries when I am ready to test.
If you are using a Mini-Zap for calibrated EMC compliance testing, the
calibration of the Mini-Zap should be checked after modification. The
modified unit works perfectly off of the AA batteries for my purposes
though. Also, do not make this modification
if your simulator is still under factory or other warrantee.
Summary: A simple modification of a KeyTek ESD simulator is described that will power the unit from four AA alkaline or Ni-MH batteries.