Inductive pickup
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Posts: 46,084
Hi all,
I need some help making an inductive pickup for my stamp (BS2).
I'm trying to pickup the rpm from a two stroke kart engine and
display the results on a LCD. I've used the LCDs and BS2 before so
that's no problem, the thing I'm stuck on is trying to get the rpm
signal.
Most of the comercial units have an alligator clip which just clips
onto the spark plug lead and runs back to the micro.
I think I can use a transistor to get the pulse by driving it into
saturation. I'm not sure how exactly to do this though. What sort of
transistor do I use and how is it connected?
I've looked all over the net and can't find any help. Can anybody
here help me? Please I'm desperate for details.
Thanks in advance.
I need some help making an inductive pickup for my stamp (BS2).
I'm trying to pickup the rpm from a two stroke kart engine and
display the results on a LCD. I've used the LCDs and BS2 before so
that's no problem, the thing I'm stuck on is trying to get the rpm
signal.
Most of the comercial units have an alligator clip which just clips
onto the spark plug lead and runs back to the micro.
I think I can use a transistor to get the pulse by driving it into
saturation. I'm not sure how exactly to do this though. What sort of
transistor do I use and how is it connected?
I've looked all over the net and can't find any help. Can anybody
here help me? Please I'm desperate for details.
Thanks in advance.
Comments
lead INSULATION. Then check that signal wrt to ground with a scope. This
will be the input to what ever signal conditioning you choose (transistor,
fet, op-amp). I would put enough turns on the wire to get about a 0.005 to
0.05 volt signal - it would then be easy to set gain or to drive transistor
to saturation for just about any device you chose.
BTW I saw a commercial tach device in great northern catalog for $30. it
measured rpm, had 2 cycle ot 4 cycle option, also measured hours, had 3/4 or
1 inch lcd readout, mount with sticky back tape. nice. so if you spent $40
on a stamp, $40 on lcd, invested 30 hours on development time for a device
that was commercially available -- - - hey, this is starting to sound like
one of my stamp projects.
richard
Original Message
From: <egroups@d...>
To: <basicstamps@yahoogroups.com>
Date: Sunday, February 11, 2001 6:42 AM
Subject: [noparse][[/noparse]basicstamps] Inductive pickup
>Hi all,
>
>I need some help making an inductive pickup for my stamp (BS2).
>
>I'm trying to pickup the rpm from a two stroke kart engine and
>display the results on a LCD. I've used the LCDs and BS2 before so
>that's no problem, the thing I'm stuck on is trying to get the rpm
>signal.
>
>Most of the comercial units have an alligator clip which just clips
>onto the spark plug lead and runs back to the micro.
>
>I think I can use a transistor to get the pulse by driving it into
>saturation. I'm not sure how exactly to do this though. What sort of
>transistor do I use and how is it connected?
>
>I've looked all over the net and can't find any help. Can anybody
>here help me? Please I'm desperate for details.
>
>Thanks in advance.
>
>
>
>
connect it to the transistor (which leads go where)?
From the transistor am I able to sent the output straight through a F
to V converter for a adc to read the data into the stamp?
Thanks again.
--- In basicstamps@y..., "dakota" <rfriedrich@a...> wrote:
> I'd wrap 3 or 4 turns of insulated solid # 22 wire around the
spark plug
> lead INSULATION. Then check that signal wrt to ground with a scope.
This
> will be the input to what ever signal conditioning you choose
(transistor,
> fet, op-amp). I would put enough turns on the wire to get about a
0.005 to
> 0.05 volt signal - it would then be easy to set gain or to drive
transistor
> to saturation for just about any device you chose.
>
> BTW I saw a commercial tach device in great northern catalog for
$30. it
> measured rpm, had 2 cycle ot 4 cycle option, also measured hours,
had 3/4 or
> 1 inch lcd readout, mount with sticky back tape. nice. so if you
spent $40
> on a stamp, $40 on lcd, invested 30 hours on development time for a
device
> that was commercially available -- - - hey, this is starting to
sound like
> one of my stamp projects.
>
>
> richard
>
>
Original Message
> From: <egroups@d...>
> To: <basicstamps@y...>
> Date: Sunday, February 11, 2001 6:42 AM
> Subject: [noparse][[/noparse]basicstamps] Inductive pickup
>
>
> >Hi all,
> >
> >I need some help making an inductive pickup for my stamp (BS2).
> >
> >I'm trying to pickup the rpm from a two stroke kart engine and
> >display the results on a LCD. I've used the LCDs and BS2 before so
> >that's no problem, the thing I'm stuck on is trying to get the rpm
> >signal.
> >
> >Most of the comercial units have an alligator clip which just clips
> >onto the spark plug lead and runs back to the micro.
> >
> >I think I can use a transistor to get the pulse by driving it into
> >saturation. I'm not sure how exactly to do this though. What sort
of
> >transistor do I use and how is it connected?
> >
> >I've looked all over the net and can't find any help. Can anybody
> >here help me? Please I'm desperate for details.
> >
> >Thanks in advance.
> >
> >
> >
> >
>connect it to the transistor (which leads go where)?
>
> >From the transistor am I able to sent the output straight through a F
>to V converter for a adc to read the data into the stamp?
You might take a look at the LM2917 data sheet and app notes from National Semi
<http://www.national.com/ds/LM/LM2907.pdf>.
It is a popular tachometer (F to V) circuit in a a dip package. It
is a "kit" of parts able to implement a variety of circuits.
For use with the stamp you might want to skip the F to V conversion,
and just count the pulses directly with the stamp. The LM2917 is
nice for that too, using its good input comparator and its output
pulses without filtering.
regards,
-- Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
I'm in desperate need on help. I'm trying to make an inductive tacho
pickup for my go kart.
I've seen small units that work by simply wraping a wire around the
spark plug lead to pickup the signal. How do these work?
I've spent weeks trying to find a circuit on the net and no luck.
Is there anyway I can run this wire to some sort of amplifier or
transistor to generate pulses that I could put through a F/V
converter (like a conventional tacho system)?
The kart has no battery, so it has no real ground reference, and
these other units just seem to use the one wire.
Any ideas????
Thanks in advance (again)
Simon
>
> I'm in desperate need on help. I'm trying to make an inductive tacho
> pickup for my go kart.
>
> I've seen small units that work by simply wraping a wire around the
> spark plug lead to pickup the signal. How do these work?
>
I found a couple of discussion threads on Google that might help:
http://groups.google.com/groups?hl=en&lr=&safe=off&ic=1&th=f65a96a2a7510317,16&s\
eekm=4gsjgg%242us%40news.sas.ab.ca#p
http://groups.google.com/groups?hl=en&lr=&safe=off&ic=1&th=f65a96a2a7510317,16&s\
eekm=4gsjgg%242us%40news.sas.ab.ca#p
The URLs are a bit long, you'll probably have to splice them back
together.
From what I read, it sounds like the general idea is to use the
pickup coil to drive the base of an NPN transistor, then clean up
the signal with a 555 timer in monostable mode.
SD
--
/===================================================================\
| Steve DeGroof (http://degroof.home.mindspring.com/) |
\===================================================================/
The National Semiconductor LM2907 is designed to do just what you're
looking for! It's a F/V converter with an inductive pick-up, for use as a
tachometer. The output is selectable as 0-2 Volts or 0-10 Volts full scale,
which ever is best for your application. The data sheets have several
different (great) application circuits. I've built three projects using
this I.C. and like it alot -- it sounds to me like it's just what you need.
It's inexpensive and available through several suppliers - I purchased mine
through Jameco.
Holler if you have questions,
Tim
Original Message
From: egroups@d... <egroups@d...>
To: basicstamps@yahoogroups.com <basicstamps@yahoogroups.com>
Date: Saturday, June 16, 2001 2:35 AM
Subject: [noparse][[/noparse]basicstamps] Inductive pickup
>Hi all,
>
>I'm in desperate need on help. I'm trying to make an inductive tacho
>pickup for my go kart.
>
>I've seen small units that work by simply wraping a wire around the
>spark plug lead to pickup the signal. How do these work?
>
>I've spent weeks trying to find a circuit on the net and no luck.
>
>Is there anyway I can run this wire to some sort of amplifier or
>transistor to generate pulses that I could put through a F/V
>converter (like a conventional tacho system)?
>
>The kart has no battery, so it has no real ground reference, and
>these other units just seem to use the one wire.
>
>Any ideas????
>
>Thanks in advance (again)
>
>Simon
>
>
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>
>
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>
>
A question from a BS amateur:
A commercially available tachometer uses an inductive pickup (just a
9 inch length of wire) wrapped around the spark plug wire. It then
fits into a u-channel in the device's body. 1 spark=1 rpm. Any ideas
how to create a tachometer with a BS2 using this technique?
Thanks in advance, Tim
From another BS2 amateur...
How about cut the pickup off a timing light (cheaper than a tach), then put
a small cap across it, run a motor with the pickup on it, then read the
voltage. If really small, run it to an op amp, then to comparator. Connect
the output of the comparator via a optoisolator to the Stamp. If you don't
want to cut off a pickup, maybe try a buzzer coil with the center removed
and run the spark plug wire through that. With an op amp you don't need much
voltage, so it should work. Since a spark plug runs at pretty high voltage,
only a few turns should be required to detect firing. If you want to be able
to easily take it on and off though, the timing light pickup might be the
way to go.
Never tried it, have no idea if it would work, just a thought.
Regards,
Jonathan Peakall
www.madlabs.info
Another thought...
You could use a phototransistor taped to the timing light itself. That would
avoid cutting up a timing light, and provide built in optoisolation. A lot
less components too. What exactly do you want to do with the device?
> Greetings,
>
> A question from a BS amateur:
>
> A commercially available tachometer uses an inductive pickup (just a
> 9 inch length of wire) wrapped around the spark plug wire. It then
> fits into a u-channel in the device's body. 1 spark=1 rpm. Any ideas
> how to create a tachometer with a BS2 using this technique?
>
> Thanks in advance, Tim
>
What do you want to check the rpm of.. a car or a small gas engine. Small
briggs and stratton engines have solidstate signals in the igniton which can be
easily conditioned to provide a nice pulse. Email me off list to talk more if I
can help.
ohiotim2 wrote:Greetings,
A question from a BS amateur:
A commercially available tachometer uses an inductive pickup (just a
9 inch length of wire) wrapped around the spark plug wire. It then
fits into a u-channel in the device's body. 1 spark=1 rpm. Any ideas
how to create a tachometer with a BS2 using this technique?
Thanks in advance, Tim
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[noparse][[/noparse]Non-text portions of this message have been removed]
From: "ohiotim2" <tweaver@
> Greetings,
>
> A question from a BS amateur:
>
> A commercially available tachometer uses an inductive pickup (just a
> 9 inch length of wire) wrapped around the spark plug wire. It then
> fits into a u-channel in the device's body. 1 spark=1 rpm. Any ideas
> how to create a tachometer with a BS2 using this technique?
>
> Thanks in advance, Tim
I have used a single wire pickup similar, connected through a 100K to 10M
resistor to the gate lead of a mosfet.
BTW if on a plug-wire 1 spark = 2 revolutions if your talking the average 4
stroke engine.
Intake, Compression [noparse][[/noparse]plug fires], Power, and Exhaust. this takes 2
revolutions of the crankshaft to complete.
As for counting how many RPM's you might want to consider using a BS2 series
processor they support the count command which will make timing easier.
COUNT pin,period,variable returns a 16 bit value representing the number of
pulses seen in a given amount of time.
Lonnie - KF4HAZ -
I spark = 1 rpm (2 cycle)
1 spark = 2 rpm (4 cycle)
Original Message
From: Jonathan Peakall [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=MkITYqpbq0FIXy_bOqpd-eV1VJmrFoBUA3tDxZVWf-5HHNHqiD0OdaZ_3EZY8m7HS-sHjonWmqyRESYioafq]jpeakall@m...[/url
Sent: Tuesday, August 13, 2002 2:53 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Inductive pickup
Tim,
From another BS2 amateur...
How about cut the pickup off a timing light (cheaper than a tach), then put
a small cap across it, run a motor with the pickup on it, then read the
voltage. If really small, run it to an op amp, then to comparator. Connect
the output of the comparator via a optoisolator to the Stamp. If you don't
want to cut off a pickup, maybe try a buzzer coil with the center removed
and run the spark plug wire through that. With an op amp you don't need much
voltage, so it should work. Since a spark plug runs at pretty high voltage,
only a few turns should be required to detect firing. If you want to be able
to easily take it on and off though, the timing light pickup might be the
way to go.
Never tried it, have no idea if it would work, just a thought.
Regards,
Jonathan Peakall
www.madlabs.info
Another thought...
You could use a phototransistor taped to the timing light itself. That would
avoid cutting up a timing light, and provide built in optoisolation. A lot
less components too. What exactly do you want to do with the device?
> Greetings,
>
> A question from a BS amateur:
>
> A commercially available tachometer uses an inductive pickup (just a
> 9 inch length of wire) wrapped around the spark plug wire. It then
> fits into a u-channel in the device's body. 1 spark=1 rpm. Any ideas
> how to create a tachometer with a BS2 using this technique?
>
> Thanks in advance, Tim
>
To UNSUBSCRIBE, just send mail to:
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[noparse][[/noparse]Non-text portions of this message have been removed]
From: "Sadler Porter" <porter.sadler@
> First post, depends on it being 2 cycle or 4.
> I spark = 1 rpm (2 cycle)
> 1 spark = 2 rpm (4 cycle)
This would be true if the command used on a BS2 or BS2e was
COUNT pin,60000,RPM ' 1 minute sampling rate
But 1 minute updating is probably going to be a bit slow,
I would suggest something like
COUNT pin,1000,RPM ' 1 second sampling rate
or even
COUNT pin,100,RPM ' 100 ms sampling rate
then do a little math to convert to RPMs
Lonnie - KF4HAZ -
> First post, depends on it being 2 cycle or 4.
> I spark = 1 rpm (2 cycle)
> 1 spark = 2 rpm (4 cycle)
>
True on a conventional automobile engine that uses a distributor, one
spark = 2 rpm but on some of the newer automobile engines utilizing DIS,
they also fire the coil on the exhaust stroke ( on engines with one coil
pack for 2 cylinders ) Also, most all single cylinder engines fire the
coil on each revolution since the magnent that fires the coil or the
signal device for the pickup is on the flywheel.
Dale
--
Dale Harwood [noparse][[/noparse] N4VFF ]
internet> dale@h...
ax.25> n4vff@n4vff.#cha.tn.usa.noam
#include <std_disclaimer.h>
I take it that you want to make a tachomoeter for the car it self.
Another way for this would be to detect the transitions (i.e. 0 ->
12V) on the 'Primary' winding of the HV transformer. This
transformer generates the high voltages needed to generate the
ignition spark.
This way you will get an easier interface to the ignition of the
system, without the need of inductive coupling etc..
I hope this helps.
Regards
Ashfaq
--- In basicstamps@y..., "ohiotim2" <tweaver@i...> wrote:
> Greetings,
>
> A question from a BS amateur:
>
> A commercially available tachometer uses an inductive pickup (just
a
> 9 inch length of wire) wrapped around the spark plug wire. It then
> fits into a u-channel in the device's body. 1 spark=1 rpm. Any
ideas
> how to create a tachometer with a BS2 using this technique?
>
> Thanks in advance, Tim