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Science Forum Index » Electronics - Basics Forum » basic question
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| Mike_in_SD |
 Posted: Mon Feb 12, 2007 8:37 pm |
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Guest
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the speed sendor/sensor on my streetrod transmission turns on and off
(pulses) 12v sending it to the speedometer.
I have an old scope that I barely know how to use .. and it shows
a nice square wave
with the speedo disconnected my fluke reads 6v
so I guess I am measuring average voltage.
now the problem
Im working on a project where I feed these pulses to a microprocessor
If I dont have the speedo connected and just connect the sender
to the micro .. it works fine.
but ..
when I connect the speedo and "tap" into the signal line
I only measure 1v and its not enough to trigger the micro
not sure what to do ..
thanks for any help
mike |
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| ehsjr |
| Posted: Mon Feb 12, 2007 10:35 pm |
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Guest
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Mike_in_SD wrote:
Quote: the speed sendor/sensor on my streetrod transmission turns on and off
(pulses) 12v sending it to the speedometer.
I have an old scope that I barely know how to use .. and it shows
a nice square wave
with the speedo disconnected my fluke reads 6v
so I guess I am measuring average voltage.
now the problem
Im working on a project where I feed these pulses to a microprocessor
If I dont have the speedo connected and just connect the sender
to the micro .. it works fine.
but ..
when I connect the speedo and "tap" into the signal line
I only measure 1v and its not enough to trigger the micro
not sure what to do ..
thanks for any help
mike
Opamp?
Ed |
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| Bob Masta |
| Posted: Tue Feb 13, 2007 9:50 am |
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On Tue, 13 Feb 2007 02:35:08 GMT, ehsjr <ehsjr@bellatlantic.net>
wrote:
Quote: Mike_in_SD wrote:
the speed sendor/sensor on my streetrod transmission turns on and off
(pulses) 12v sending it to the speedometer.
I have an old scope that I barely know how to use .. and it shows
a nice square wave
with the speedo disconnected my fluke reads 6v
so I guess I am measuring average voltage.
now the problem
Im working on a project where I feed these pulses to a microprocessor
If I dont have the speedo connected and just connect the sender
to the micro .. it works fine.
but ..
when I connect the speedo and "tap" into the signal line
I only measure 1v and its not enough to trigger the micro
not sure what to do ..
thanks for any help
mike
Opamp?
CMOS buffer would be easier and better for square waves.
The ever-popular CD4049 has 6 in one package. These are
inverting buffers, so if polarity is important (which I doubt here),
use one of them to invert the sensor signal, and feed it to
the rest, which invert it back. You'll then have 5 copies of the
signal to use. You can parallel these as needed if one
destination needs more drive current.
Best regards.
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card! |
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| Mike_in_SD |
| Posted: Tue Feb 13, 2007 1:25 pm |
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Guest
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NoSpam@daqarta.com (Bob Masta) wrote in <45d1c06f.2054715
@news.sysmatrix.net>:
Quote: On Tue, 13 Feb 2007 02:35:08 GMT, ehsjr <ehsjr@bellatlantic.net
wrote:
Mike_in_SD wrote:
the speed sendor/sensor on my streetrod transmission turns on and off
(pulses) 12v sending it to the speedometer.
If I dont have the speedo connected and just connect the sender
to the micro .. it works fine.
but ..
when I connect the speedo and "tap" into the signal line
I only measure 1v and its not enough to trigger the micro
not sure what to do ..
thanks for any help
mike
Opamp?
CMOS buffer would be easier and better for square waves.
The ever-popular CD4049 has 6 in one package. These are
inverting buffers, so if polarity is important (which I doubt here),
Cool Bob .. I'll check that out .. thanks
mike |
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