Oscilloscope question

D

Dan Beck

Guest
Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels work
fine, and I use it to probe circuit boards powered up on the workbench. I
now own an old hobby car with the old fashioned plugs/points/capacitor
ignition. Is there any way I could use the 'scope to observe the ignition
signals, and would there be any value to it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan
 
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:UoVyk.685$1l2.242@newsfe27.ams2...
"Dan Beck" <biscuitbecks@*nospam*cableone.net> wrote in message
news:gagld5$erd$1@registered.motzarella.org...
Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels
work fine, and I use it to probe circuit boards powered up on the
workbench. I now own an old hobby car with the old fashioned
plugs/points/capacitor ignition. Is there any way I could use the
'scope to observe the ignition signals, and would there be any value to
it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan


The LT back emf could spike as high as 600V (maybe even higher) if the
scope is all tube you should be OK, but if it uses transistors in the Y
amplifiers some caution might be wise. Study the spec for the x10 probe
and if it isn't rated for that voltage then make a voltage divider
yourself, here again you need to check the voltage rating of the
resistors - if necessary make the dropper section of the divider out of a
number of series resistors.
Click to expand...

It might be prudent to add a neon lamp or a TVS bidirectional zener type
suppressor across the scope inputs. I'm not sure how fast a neon lamp
triggers, but the type of suppressors used in telephone equipment should be
pretty good, and rated about 60 volts.

Here are links:
http://www.onsemi.com/PowerSolutions/supportDoc.do?type=datasheets&category=824
http://www.rectron.com/data_sheets/1.5ke.pdf

Paul
 
On Sat, 13 Sep 2008, Dan Beck wrote:

Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels work
fine, and I use it to probe circuit boards powered up on the workbench. I
now own an old hobby car with the old fashioned plugs/points/capacitor
ignition. Is there any way I could use the 'scope to observe the ignition
signals, and would there be any value to it, besides academic information?

That sort of thing was done in the old days, I've never had a car so
Click to expand...
I don't know how useful it was, or even if it matters now (I gather
a lot of cars are now beyond the ability of the average person to
do much repair work).

It would have been detailed in countless magazine articles, and
likely in all those "101 Things To Do With Your Oscilliscope".
That sort of book can be quite useful when starting out with
an oscilliscope, you might want to dig up a used copy.

Michael
 
On Sat, 13 Sep 2008 08:14:49 -0700, Dan Beck wrote:

Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels
work fine, and I use it to probe circuit boards powered up on the
workbench. I now own an old hobby car with the old fashioned
plugs/points/capacitor ignition. Is there any way I could use the
'scope to observe the ignition signals, and would there be any value to
it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan
Click to expand...
I've used my 1-channel, 5MHz Heathkit to set the dwell on my '71 Vega,
and to diagnose problems with a bad throttle sensor on newer cars. It's
a lot less direct than using a dwell meter, but you get to see more of
what's going on.

Use a 10:1 probe, set the voltage scale to lots -o- volts/division, hook
the thing across the points and -- voila! You can see not only the
dwell, but you can see the profile of the low-tension side of the coil as
it fires.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
 
On Sep 13, 8:14 am, "Dan Beck" <biscuitbecks@*nospam*cableone.net>
wrote:


years ago I was given a 10 MHz Heathkit oscilloscope.
... own an old hobby car with the old fashioned plugs/points/capacitor
ignition.  Is there any way I could use the 'scope to observe the ignition
signals
Click to expand...
Two ways. First, you can look at the primary winding on
the spark coil; the opening of the points will make a
few hundred volts spike (an attenuator probe is wise
here), and the sparkplug firing will determine the trailing
edge of that transient. Imbalance of cylinders in
breakover voltage is clearly visible, can be caused by
obvious things (dirty or misgapped plugs) or unobvious
ones (gas mixture in the cylinder changes the breakdown
characteristic).

Second, you can use a clamp-on transformer to monitor the
current through the HV wires (either the wire to
the coil, OR the distributor wires to one plug at a time).
Be careful about grounding here, of course. A burden
(shunt) resistor on the secondary of your transformer is
VERY IMPORTANT; ten to a hundred ohms should
be sufficient. The transformer can be a pair of ferrite
core halves and a single turn of wire for the secondary.
 
On 2008-09-14, Paul E. Schoen <pstech@smart.net> wrote:
It might be prudent to add a neon lamp or a TVS bidirectional zener type
suppressor across the scope inputs. I'm not sure how fast a neon lamp
triggers, but the type of suppressors used in telephone equipment should be
pretty good, and rated about 60 volts.
Click to expand...
at 60 they'd fire on the ring voltage.

Bye.
Jasen
 
On Sep 13, 10:14 am, "Dan Beck" <biscuitbecks@*nospam*cableone.net>
wrote:
Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope.  Both channels work
fine, and I use it to probe circuit boards powered up on the workbench.  I
now own an old hobby car with the old fashioned plugs/points/capacitor
ignition.  Is there any way I could use the 'scope to observe the ignition
signals, and would there be any value to it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan
Click to expand...
You could take this oscilliscope, and check the rate of transfer
during disconnect of the 12V btty.
This will show you when your wires are degrading. And, might even
indicate moisture due to acidic influence, a common ailment.
 
Tim Wescott wrote:

On Sat, 13 Sep 2008 08:14:49 -0700, Dan Beck wrote:


Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels
work fine, and I use it to probe circuit boards powered up on the
workbench. I now own an old hobby car with the old fashioned
plugs/points/capacitor ignition. Is there any way I could use the
'scope to observe the ignition signals, and would there be any value to
it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan


I've used my 1-channel, 5MHz Heathkit to set the dwell on my '71 Vega,
and to diagnose problems with a bad throttle sensor on newer cars. It's
a lot less direct than using a dwell meter, but you get to see more of
what's going on.

Use a 10:1 probe, set the voltage scale to lots -o- volts/division, hook
the thing across the points and -- voila! You can see not only the
dwell, but you can see the profile of the low-tension side of the coil as
it fires.

And hope the condensor(capacitor) in the ignition system is good as you
Click to expand...
connect your sensitive scope to this potential arching point.


http://webpages.charter.net/jamie_5"
 
Jamie wrote:
Tim Wescott wrote:

On Sat, 13 Sep 2008 08:14:49 -0700, Dan Beck wrote:


Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels
work fine, and I use it to probe circuit boards powered up on the
workbench. I now own an old hobby car with the old fashioned
plugs/points/capacitor ignition. Is there any way I could use the
'scope to observe the ignition signals, and would there be any value to
it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan


I've used my 1-channel, 5MHz Heathkit to set the dwell on my '71 Vega,
and to diagnose problems with a bad throttle sensor on newer cars.
It's a lot less direct than using a dwell meter, but you get to see
more of what's going on.

Use a 10:1 probe, set the voltage scale to lots -o- volts/division,
hook the thing across the points and -- voila! You can see not only
the dwell, but you can see the profile of the low-tension side of the
coil as it fires.

And hope the condensor(capacitor) in the ignition system is good as you
connect your sensitive scope to this potential arching point.


http://webpages.charter.net/jamie_5"

That's why you use a cheap scope...
Click to expand...

Actually, I was trying to figure out if there's a network that one could
make that would use a neon bulb or similar to absorb transients.
Something that wouldn't mess up the measurement too much, but wouldn't
also go 'pip' right before the oscilloscope goes 'pop'.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
Tim Wescott wrote:

Jamie wrote:

Tim Wescott wrote:

On Sat, 13 Sep 2008 08:14:49 -0700, Dan Beck wrote:


Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels
work fine, and I use it to probe circuit boards powered up on the
workbench. I now own an old hobby car with the old fashioned
plugs/points/capacitor ignition. Is there any way I could use the
'scope to observe the ignition signals, and would there be any value to
it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan



I've used my 1-channel, 5MHz Heathkit to set the dwell on my '71
Vega, and to diagnose problems with a bad throttle sensor on newer
cars. It's a lot less direct than using a dwell meter, but you get
to see more of what's going on.

Use a 10:1 probe, set the voltage scale to lots -o- volts/division,
hook the thing across the points and -- voila! You can see not only
the dwell, but you can see the profile of the low-tension side of the
coil as it fires.

And hope the condensor(capacitor) in the ignition system is good as
you connect your sensitive scope to this potential arching point.


http://webpages.charter.net/jamie_5"

That's why you use a cheap scope...

Actually, I was trying to figure out if there's a network that one could
make that would use a neon bulb or similar to absorb transients.
Something that wouldn't mess up the measurement too much, but wouldn't
also go 'pip' right before the oscilloscope goes 'pop'.

Invest in some TVS diodes. They'll work great for your application.
Click to expand...
Just select the ones that hits the limits of your scope input or just
under it.
Get the bi-directional types and lay one of them across the scope's
input.




http://webpages.charter.net/jamie_5"
 
Dan Beck wrote:

Hello all,

years ago I was given a 10 MHz Heathkit oscilloscope. Both channels work
fine, and I use it to probe circuit boards powered up on the workbench. I
now own an old hobby car with the old fashioned plugs/points/capacitor
ignition. Is there any way I could use the 'scope to observe the ignition
signals, and would there be any value to it, besides academic information?

Thank you in advance for any and all thoughts!

Regards,
Dan


If you're interested in the HV current Pulse, You can wrap a couple of
Click to expand...
turns around a plug wire and load the output to a low value resistor.
This will act as a current xformer and provide you a safe a low voltage
reference signal for your scope to monitor the current pulse at the
electrode on the plug.
They make engine scope probes to clamp on plug wires and in line taps
accessories.
At work, we actually use an automotive HV inline coupling to monitor
a signal via a scope on irradiation units.

You could also consider using a HV probe for scopes. The one you
would need could be expensive.



http://webpages.charter.net/jamie_5"
 
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