On Thu, 19 Jan 2017 21:25:11 -0500, wrote:

On Thu, 19 Jan 2017 11:44:40 -0800, wrote:

I figure Clare will know the answer but maybe others will too. I got
my hands on an old Acura fuel injector last night. It is apparently
the high impedence type because it measures 14 ohms resistance and
draws only .7 amps @ 12 volts. This means I don't need a fancy chip,
just a 555 timer circuit. So I put one together using a relay (because
that's what I have on hand) instead of a mosfet to apply power to the
injector. I put a snubber diode across the injector just like I did
for the relay coil. All the injector circuits I have seen online use
either a pretty high voltage zener, 75 volts, or a resistor across the
injector. From what I have read the 75 volt zener seems to be the
most common and it lets the injector close slower to prevent damage to
the injector from slamming closed. I guess the circuits with a
resistor in parallel with the injector do the same thing. I don't have
any 75 volt zeners in my kit but do have lots of resistors in many
different values and watt ratings. Does using just a resistor make
sense? Maybe I misread the circuit.
Thanks,
Eric
A resistor won't do it - it will just make the injector draw more
power. The relay won't act fast enough. I'd use a diode backwards
across the coil - a 1n5404 or 5406 will be plenty. Might get away
with a 1n4004 (400 volt 1 amp)
Thanks Clare. I know that in an engine the injector needs to close
fast but in my application, applying tiny amounts of cutting lubricant
to a spinning tool, I can get by with a slower closing speed. What I
do want is for the injector to last as long as possible. So as long as
the injector isn't closing any faster than it would in a car I'm
happy. I wonder if the higher viscosity of the lube will be cushion
enough?
Eric