Zener diode to control back EMF on Fuel Injector
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Posts: 46,084
Hi all, I have a quick question, I was discussing driving electronic
fuel injectors with some of you guys. My stamp is currently being
shipped back to Parallax for repair. I'm building some circuits to
try when it gets back.
Assuming that the injector did fry it back through my NPN driver
transistor, might a 12V zener diode across the injector protect the
stamp from the bigger spikes without affecting turn off time
normally like a straight diode would? Or am I going in the wrong
direction?
Thank you,
Bill
fuel injectors with some of you guys. My stamp is currently being
shipped back to Parallax for repair. I'm building some circuits to
try when it gets back.
Assuming that the injector did fry it back through my NPN driver
transistor, might a 12V zener diode across the injector protect the
stamp from the bigger spikes without affecting turn off time
normally like a straight diode would? Or am I going in the wrong
direction?
Thank you,
Bill
Comments
the stamp totaly isolated from the driver transitor
there are high speed versions that should work
--- "billakay <billak@f...>" <billak@f...>
wrote:
> Hi all, I have a quick question, I was discussing
> driving electronic
> fuel injectors with some of you guys. My stamp is
> currently being
> shipped back to Parallax for repair. I'm building
> some circuits to
> try when it gets back.
>
> Assuming that the injector did fry it back through
> my NPN driver
> transistor, might a 12V zener diode across the
> injector protect the
> stamp from the bigger spikes without affecting turn
> off time
> normally like a straight diode would? Or am I going
> in the wrong
> direction?
>
> Thank you,
>
> Bill
>
>
>
>
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>
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kenneth_m_73149@y... writes:
> i would highly recomend using a optoisolator and keep
> the stamp totaly isolated from the driver transitor
> there are high speed versions that should work
>
The opto-isolator is definately the hot ticket....but all of it's gains can
be lost if your stamp and the injector circuit share the same ground.
To get true isolation with the opto-isolator, you will need to power the
stamp from the output of a DC to DC converter. The input power and ground of
the DC to DC converter is isolated from it's output. In this way, you are
completely isolated.....
[noparse][[/noparse]Non-text portions of this message have been removed]
infinite impedance in the forward direction so all the current flows through
the injector coil and zero impedance in the reverse current flow direction
so the collapsing current shorts to ground rather than back into your stamp.
The zener's variable impedance in the forward direction just complicates
things and I'm pretty sure they generally have a higher reverse impedance
which could leak more current back to the stamp.
I wasn't paying that much attention to the start of this discussion. But
you may want to look at the ULN2003 or similar as a driver. If nothing
else, look at the circuit equivalency diagram in their datasheet and you
will see a conventional diode.
-- Al Margolis, founder
www.hobbyengineering.com
The WEB's newest source for robotics supplies and information
Original Message
From: billakay <billak@f...> [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=iUA75sxTaGyj1BH42vYGDyl7BVWKD_yVrmVqZvjVIa7Vu6DsOZF2hgqdR0j-IGyERk-WiyQg7A]billak@f...[/url
Sent: Thursday, February 06, 2003 9:59 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Zener diode to control back EMF on Fuel Injector
Hi all, I have a quick question, I was discussing driving electronic
fuel injectors with some of you guys. My stamp is currently being
shipped back to Parallax for repair. I'm building some circuits to
try when it gets back.
Assuming that the injector did fry it back through my NPN driver
transistor, might a 12V zener diode across the injector protect the
stamp from the bigger spikes without affecting turn off time
normally like a straight diode would? Or am I going in the wrong
direction?
Thank you,
Bill
To UNSUBSCRIBE, just send mail to:
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