EFI, Vac Motors, 24vdc vs. 120 vac
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Posts: 46,084
EFI
There has been some inquiry on using a BSII of some
flavor to do EFI functions. Be aware that the stamp is
too slow to do everything. If you design some hardware
to take over the critical timer/timing functions then
the stamp can read sensors and load timers that are
triggered by an external event sensor like TDC.
For a stationary engine where loads and other variables
will change slowly all is ok, WITH THE RIGHT HARDWARE
married to the stamp.
To try EFI functions without designing external
Hardware, your efforts will fail.
For the ignition portion do not reinvent the wheel,
fixed timing works fine. Use off the shelf engine
ignition hardware or what ever came with the engine.
*******************************************************
****************
VAC motors
All universal motors will run off AC or DC though the
voltage level required for DC is reduced, just remember
that for total power it is area under the curve.
*******************************************************
****************
24 vdc vs. 120 vac (operator panels)
The real issue here is longevity, the problem with
switching AC power levels through switches in an
operators console is the arc that occurs across the
contacts. The arc rapidly degrades the mechanical
switch. Thus most control switches use 24 volts dc so
that what they control is in essence a signal not
power. All power switching functions occur some place
else. Using 24 vdc one can use flyback diodes to keep
freewheeling currents from arcing contacts and greatly
improve the lifespan of the switch .
Many times in the industrial environment, it is not 120
being switched, it is usually 220-240 or 460-480 VAC,
thus the need to define operator consoles as having
only signal level voltages. In some environments the
switching of 3000 + volt AC on thousand horsepower
electric motors is not out of the question. All of the
above can be accomplished is with a simply 18 gauge
24vdc circuit from far away. Distance is another issue,
would you rather run 1000 feet of 18 gauge or 000 gauge
to switch power. Thus the 24 vdc has a cost saving side
that is not readily apparent.
So quite sweating the regulations, there are reasons
for them, which has obviously been missed in the
previous discussions. Everyone lives longer if we
follow them.
Sincerely,
Ron
There has been some inquiry on using a BSII of some
flavor to do EFI functions. Be aware that the stamp is
too slow to do everything. If you design some hardware
to take over the critical timer/timing functions then
the stamp can read sensors and load timers that are
triggered by an external event sensor like TDC.
For a stationary engine where loads and other variables
will change slowly all is ok, WITH THE RIGHT HARDWARE
married to the stamp.
To try EFI functions without designing external
Hardware, your efforts will fail.
For the ignition portion do not reinvent the wheel,
fixed timing works fine. Use off the shelf engine
ignition hardware or what ever came with the engine.
*******************************************************
****************
VAC motors
All universal motors will run off AC or DC though the
voltage level required for DC is reduced, just remember
that for total power it is area under the curve.
*******************************************************
****************
24 vdc vs. 120 vac (operator panels)
The real issue here is longevity, the problem with
switching AC power levels through switches in an
operators console is the arc that occurs across the
contacts. The arc rapidly degrades the mechanical
switch. Thus most control switches use 24 volts dc so
that what they control is in essence a signal not
power. All power switching functions occur some place
else. Using 24 vdc one can use flyback diodes to keep
freewheeling currents from arcing contacts and greatly
improve the lifespan of the switch .
Many times in the industrial environment, it is not 120
being switched, it is usually 220-240 or 460-480 VAC,
thus the need to define operator consoles as having
only signal level voltages. In some environments the
switching of 3000 + volt AC on thousand horsepower
electric motors is not out of the question. All of the
above can be accomplished is with a simply 18 gauge
24vdc circuit from far away. Distance is another issue,
would you rather run 1000 feet of 18 gauge or 000 gauge
to switch power. Thus the 24 vdc has a cost saving side
that is not readily apparent.
So quite sweating the regulations, there are reasons
for them, which has obviously been missed in the
previous discussions. Everyone lives longer if we
follow them.
Sincerely,
Ron