Car sequential shift lights wanted

[Homer]

Hi,
I'm looking for a circuit or pointers where to start to build a sequential
shift light for a car.
I need to be able to set an upper rev limit, for example 7000rpm. As the
engine approaches this speed I need a series of lights to illuminate i.e.. 1
at 6500rpm the next at 6100rpm and so on until 7000rpm.
I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Thanks
Homer.

 

[Active8]

On Thu, 1 Apr 2004 20:53:10 +0100, Homer wrote:

Hi,
I'm looking for a circuit or pointers where to start to build a sequential
shift light for a car.
I need to be able to set an upper rev limit, for example 7000rpm. As the
engine approaches this speed I need a series of lights to illuminate i.e.. 1
at 6500rpm the next at 6100rpm and so on until 7000rpm.
I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Thanks
Homer.

Freq - voltage out (scaled) into LED bargraph display or just a quad
comparator for 4 lights. Or you can try getting a PIC to run amidst
all that auto electrical noise
--
Best Regards,
Mike

 

[John Woodgate]

I read in sci.electronics.design that Homer <feckinstupid@hotmail.com>
wrote (in <c4hrul$2hgerd$1@ID-163076.news.uni-berlin.de&gt about 'Car
sequential shift lights wanted', on Thu, 1 Apr 2004:

I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Find LM3914. With the LM2907, that will give you up to 10 shift
indicators.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Jan Panteltje]

On a sunny day (Thu, 1 Apr 2004 20:53:10 +0100) it happened "Homer"
<feckinstupid@hotmail.com> wrote in
<c4hrul$2hgerd$1@ID-163076.news.uni-berlin.de>:

Hi,
I'm looking for a circuit or pointers where to start to build a sequential
shift light for a car.
I need to be able to set an upper rev limit, for example 7000rpm. As the
engine approaches this speed I need a series of lights to illuminate i.e.. 1
at 6500rpm the next at 6100rpm and so on until 7000rpm.
I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Thanks
Homer.
The normal way would be to measure the delay between the pulses.

You could use some softloop, and test for loops < n.
So, basically you need no f-to-v converter.
You only need a PIC.
Some PIC freq counter and rpm counter aplicatioons are on the net.

 

[Tim Wescott]

Active8 wrote:

On Thu, 1 Apr 2004 20:53:10 +0100, Homer wrote:


Hi,
I'm looking for a circuit or pointers where to start to build a sequential
shift light for a car.
I need to be able to set an upper rev limit, for example 7000rpm. As the
engine approaches this speed I need a series of lights to illuminate i.e.. 1
at 6500rpm the next at 6100rpm and so on until 7000rpm.
I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Thanks
Homer.


Freq - voltage out (scaled) into LED bargraph display or just a quad
comparator for 4 lights. Or you can try getting a PIC to run amidst
all that auto electrical noise

Noise issues aside (and you can get around those) this cries out for a
PIC, AVR or other small microcontroller.

Particularly when your buddy with the flathead wants one with a redline
at 4K.

--

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

 

[Geoffrey Swales]

I think a PIC would probably be the low-cost solution.
If you used the classic 16f84 then you can get programmers and compilers
free off the web.

Have one of the pins set to interrupt on rising edge. You may want to use
some kind or RC filter on this pin so you don't measure noise. In this
interrupt simply get the pic to increment a counter called, say, rev_count.

Next you have a second interrupt that is driven by a timer. This interrupt
copies the content of rev_count to a second location called final_count. It
then clears the content of rev_count.

The main body of the code can simply look at the value in final_count and
decide how many LEDs to illuminate. These threshold values can be define at
the start of the code, so they can easily be changed to match the
characteristics of the engine/application; high, low, logarithmic, etc...

Best Regards,

Geoffrey
http://www.biodigital-ltd.com

"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:c4i048$116u$1@news.wplus.net...

On a sunny day (Thu, 1 Apr 2004 20:53:10 +0100) it happened "Homer"
feckinstupid@hotmail.com> wrote in
c4hrul$2hgerd$1@ID-163076.news.uni-berlin.de>:

Hi,
I'm looking for a circuit or pointers where to start to build a
sequential
shift light for a car.
I need to be able to set an upper rev limit, for example 7000rpm. As the
engine approaches this speed I need a series of lights to illuminate
i.e.. 1
at 6500rpm the next at 6100rpm and so on until 7000rpm.
I've found information on a LM2907 frequency to voltage converter and can
more or less work out how I could use it to illuminate a single LED at a
single rpm but other than using 5 identical circuits set at the different
rpm steps I'm not sure how to light the LED's sequentially with a single
circuit.

Thanks
Homer.
The normal way would be to measure the delay between the pulses.
You could use some softloop, and test for loops < n.
So, basically you need no f-to-v converter.
You only need a PIC.
Some PIC freq counter and rpm counter aplicatioons are on the net.

 

[mikem]

Lots of PIC suggestions:

Here's mine.

Set up a Counter in the PIC to count up on the Clock, possibly
prescaled. Rate to be appropriate, see below:

Use conditioned Spark Pulse (like you were building a tach) as
an interrupt input to a PIC. The Interrupt service routine
latches the timer value and resets it.

The latched value is proportional to the SparkPeriod (time between
sparks).

Export the SparkPeriod as a global variable visible to the Main loop.

Set up a series of tests which set Port Pins if the
SparkPeriod is less than a Constant. "SparkPeriod < C"
is equivalent to "RPM > some Trip Point".
You can have as many trip points as you have IO pins.

The SparkRate is depenent on 2/4 stoke and number of Cyls.

MikeM

 

[Homer]

Thanks, this seems the best solution with my limited knowledge, will have to
investigate PIC's when I have more time.
I have another question. If the LM3914 takes a 0v-5v signal from the LM2907
to light the full range of 10 LED's, how would I get the LM2907 to give an
output of 0v upto 6500rpm and increase from 0v to 5v between 6500 and
7000rpm?

Thanks
Homer.


"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:rnKvfBLTdHbAFw1F@jmwa.demon.co.uk...

Find LM3914. With the LM2907, that will give you up to 10 shift
indicators.

 

[John Woodgate]

I read in sci.electronics.design that Homer <feckinstupid@hotmail.com>
wrote (in <c4mffo$2k03v5$1@ID-163076.news.uni-berlin.de&gt about 'Car
sequential shift lights wanted', on Sat, 3 Apr 2004:

I have another question. If the LM3914 takes a 0v-5v signal from the LM2907
to light the full range of 10 LED's, how would I get the LM2907 to give an
output of 0v upto 6500rpm and increase from 0v to 5v between 6500 and
7000rpm?

You need a simple op-amp circuit to provide the offset. I don't have the
LM2907 data sheet, so I can't give you detailed instructions. But IF the
output is 5 V at 7000 rpm, it's 4.64 V at 6500 rpm. You need a gain of
14 to boost this 0.357 V change to 5 V, and an offset of 4.64 V applied
to the - input of the op-amp.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Mark Zenier]

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in message news:<nPMs1AFLxsbAFwG5@jmwa.demon.co.uk>...

I read in sci.electronics.design that Homer <feckinstupid@hotmail.com
wrote (in <c4mffo$2k03v5$1@ID-163076.news.uni-berlin.de&gt about 'Car
sequential shift lights wanted', on Sat, 3 Apr 2004:
I have another question. If the LM3914 takes a 0v-5v signal from the LM2907
to light the full range of 10 LED's, how would I get the LM2907 to give an
output of 0v upto 6500rpm and increase from 0v to 5v between 6500 and
7000rpm?

You need a simple op-amp circuit to provide the offset. I don't have the
LM2907 data sheet, so I can't give you detailed instructions. But IF the
output is 5 V at 7000 rpm, it's 4.64 V at 6500 rpm. You need a gain of
14 to boost this 0.357 V change to 5 V, and an offset of 4.64 V applied
to the - input of the op-amp.

The LM3914 doesn't have to have zero as the bottom of its range. By
putting the right voltage on pin 4, RLo, you skip the op amp in favor
of a trimpot or voltage reference.

Mark Zenier mzenier@eskimo.com