An acquaintance of mine was a salesman for a HVAC controls
company in the mid-to-late eighties, and he had an idea for a tester
that furnace service technicians could use to determine if the
electronic igniter was faulty. He was able to arrange a contract for
me to design and build one prototype.
My design used a microcontroller to control the test sequence,
the activation of relays and other circuits, and the collection of
results. The igniter board was connected to the tester as if it were
connected to a furnace. The tester simulated the thermostat
activation with a relay, which in turn, started the ignition phase
with its characteristic snapping sound, something most of us have
heard in our kitchens or basements. During the ignition phase, the
tester measured the ignition voltage, in the 10 kV to 25 kV range,
to ensure it working properly. After a few ignition pulses, the
tester simulated a flame and then tested the igniter to ensure it
stopped the ignition pulse train.
If the igniter-under-test passed every step in the sequence, a
green light was lit. If it failed any phase of the test, a red light
was lit.
I designed the tester to work with Honeywell, Robertshaw, and
Johnson igniters. I built one unit, got it working properly, and
delivered it to my client.
