On Jun 30, 2:07 pm, Sjouke Burry <burrynulnulf...@[EMAIL PROTECTED]
>
wrote:
> Mike H wrote:
> > I would like to data log commanded spark events for my vehicle. It
> > uses a Distributorless Ignition System which consists of a engine
> > control computer, a control module, and a coil pack. The coil pack is
> > fed 12v and has control wires. When a control wire is brought to
> > ground by the control module, current can flow through a coil primary
> > winding. The control module holds the ground for a ECC demanded dwell
> > at which time the ground is raised, causing the coil to discharge.
>
> > I want to monitor when each control wire is being held to ground.
>
> > My monitoring device can take a 0-5v DC input.
> > Do I need to be concerned with the current in the primary circuit that
> > I will monitor voltage on?
> > Is there a circuit design, or a discrete component that will scale the
> > 12v on/off signal into a 0-5vDC output I can push into my DC input?
> > This will need to operate fairly quickly.
>
> > Other suggestions?
> > Thanks
>
> You have to deal with very high voltages(hundreds), when the ground
> connection opens.
> I would advice 100k to 1 megohm in series with two 4 volt zenerdiodes
> anti parallel, to clamp voltage to 4 volts.
> to make more of a divider, shunt 30k accross the diodes and a small
> capacitor of 200 pf.(the last to stop capacitive coupling accross the
> 100k to your input).
> Then maybe your electronics will stay alive :)
Perhaps I didn't describe my intention fully or am understanding what
I see incorrectly.
In the case of my ignition system, an electronic control module
receives 12v. A pack of 3 coils receives 12v (6 cylinder motor,
wasted spark system). Each coil primary thus has 12v but the
primaries are not grounded. Ground is achieved by a switch inside the
electronic control module which provides a ground to the primary of
each coil as necessary.
Note that these are ignition events, thus such events occur in
hundreds of microseconds.
My understanding is that
When the electronic control module brings a coil primary to ground,
current will flow through the primary. When the ECM lifts the ground,
an electrical field in the primary will collapse creating a large
induced voltage in the secondary winding of the coil.
If I just want to monitor when the ECM drops a line to ground, and
then lifts it again, will the voltage not be limited always to 12v at
the primary?
My idea.. thus far is to create a voltage divider that sits in
parallel on the control line. When the ECM drops the control line to
ground, my voltage divider will output 4.5v. When the ECM raises the
ground, my voltage divider will output 0v.
New idea, that I used aaCircuit to show.
Could I not use a 5vdc power source for my input to my data logger.
Then have the sensor ground for that input be tied to the ground on
the primary control wire to the Coil? Thus when that becomes grounded
my 5vdc flows through my other circuit?
'-----------. .----------------------------o----------------
o
| | | | 12v DC
|Spark Plug | | .---------------. |
.'. | Coil | ' .-----'
| | | | | ECM |
| | C.---12v DC- '--' |
| | C| | '-------o-------'
| | C| | |
'.' |'-------o-----' |
| | ECM Switched Ground |
'-----------' | |
| | |
| | |
| | ===
=== '-----' GND
GND |
|
|
|
VCC |
+ _ |
| 5v DC / \ |
'------------------(_/_)-'
\_/
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
|
