Buy or build - mating old sensor to new display

[macorro]

Thought this might be an interesting first project, but my knowledge is very basic.

A 12v old (1988) boat speed indicator with its paddle wheel sensor. I have a new display which can read the old paddle wheel but interprets the speed at close to twice the proper value. Calibration on the new display is limited to about 15%. I guess the paddle wheel sends a signal each time a paddle induces a current.

I think if I can find a way to lose every other signal from the paddle wheel then I can use the two together. Such a circuit doesn't sound too complex - is this something I can buy? Otherwise could you give me some pointers, please?

 

[Randy Day]

In article <260773c5-4568-4409-8be3-b912c224190d@googlegroups.com>,
chris.macorro@googlemail.com says...

Thought this might be an interesting first project, but my knowledge
is very basic.

[snip]

I think if I can find a way to lose every other signal from the paddle
wheel then I can use the two together. Such a circuit doesn't sound
too complex - is this something I can buy? Otherwise could you give me
some pointers, please?

If your paddle wheel puts out good clean
digital pulses, a simple (digital)
divide-by-2 circuit uses a D or JK
flip-flop (i.e. CD4013 or CD4027).

If the paddle wheel puts out analog
waveforms, it might be a bit trickier...

 

[Jasen Betts]

On 2015-05-31, macorro <chris.macorro@googlemail.com> wrote:

Thought this might be an interesting first project, but my knowledge is very basic.

A 12v old (1988) boat speed indicator with its paddle wheel sensor. I have a new display which can read the old paddle wheel but interprets the speed at close to twice the proper value. Calibration on the new display is limited to about 15%. I guess the paddle wheel sends a signal each time a paddle induces a current.

I think if I can find a way to lose every other signal from the paddle wheel then I can use the two together. Such a circuit doesn't sound too complex - is this something I can buy? Otherwise could you give me some pointers, please?

I expect that you can buy something from a place that does automotive
speedometer customisation, but you may want to add some extra
waterproofing. eg: http://www.abbott-tach.com/era.htm (I searched on
"electric speedometer ratio")

you're correct that a circuit to halve the number of pulses would not be very complex.

but as another approach perhaps you can modify the paddle wheel,
eg: if the wheel has two magnets in it replace one of them with a matching weight.

--
umop apisdn

 

[George Herold]

On Sunday, May 31, 2015 at 11:05:34 AM UTC-4, macorro wrote:

Thought this might be an interesting first project, but my knowledge is very basic.

A 12v old (1988) boat speed indicator with its paddle wheel sensor. I have a new display which can read the old paddle wheel but interprets the speed at close to twice the proper value. Calibration on the new display is limited to about 15%. I guess the paddle wheel sends a signal each time a paddle induces a current.

I think if I can find a way to lose every other signal from the paddle wheel then I can use the two together. Such a circuit doesn't sound too complex - is this something I can buy? Otherwise could you give me some pointers, please?

Do you have a 'scope? It may be that you are getting transients on both edges,
and maybe just some RC filtering will be enough.

George H.

 

[Jim Thompson]

On Mon, 1 Jun 2015 07:50:52 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Sunday, May 31, 2015 at 11:05:34 AM UTC-4, macorro wrote:
Thought this might be an interesting first project, but my knowledge is very basic.

A 12v old (1988) boat speed indicator with its paddle wheel sensor. I have a new display which can read the old paddle wheel but interprets the speed at close to twice the proper value. Calibration on the new display is limited to about 15%. I guess the paddle wheel sends a signal each time a paddle induces a current.

I think if I can find a way to lose every other signal from the paddle wheel then I can use the two together. Such a circuit doesn't sound too complex - is this something I can buy? Otherwise could you give me some pointers, please?

Do you have a 'scope? It may be that you are getting transients on both edges,
and maybe just some RC filtering will be enough.

George H.

The "new" display probably does what I did back in the '60's... sees
both lobes of the magnetic transducer. I did it to reduce ripple.

A schematic of the new display would tell all.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[macorro]

On Monday, June 1, 2015 at 3:50:59 PM UTC+1, George Herold wrote:

On Sunday, May 31, 2015 at 11:05:34 AM UTC-4, macorro wrote:
Thought this might be an interesting first project, but my knowledge is very basic.

A 12v old (1988) boat speed indicator with its paddle wheel sensor. I have a new display which can read the old paddle wheel but interprets the speed at close to twice the proper value. Calibration on the new display is limited to about 15%. I guess the paddle wheel sends a signal each time a paddle induces a current.

I think if I can find a way to lose every other signal from the paddle wheel then I can use the two together. Such a circuit doesn't sound too complex - is this something I can buy? Otherwise could you give me some pointers, please?

Do you have a 'scope? It may be that you are getting transients on both edges,
and maybe just some RC filtering will be enough.

George H.

No scope - only a multimeter. Am thinking of a 2 channel scope that uses wifi for a tablet display. Would this do for an entry level scope.As you can see I am starting from scratch.

 

[macorro]

On Sunday, May 31, 2015 at 6:26:06 PM UTC+1, Randy Day wrote:

In article <260773c5-4568-4409-8be3-b912c224190d@googlegroups.com>,
chris.macorro@googlemail.com says...

Thought this might be an interesting first project, but my knowledge
is very basic.

[snip]

I think if I can find a way to lose every other signal from the paddle
wheel then I can use the two together. Such a circuit doesn't sound
too complex - is this something I can buy? Otherwise could you give me
some pointers, please?

If your paddle wheel puts out good clean
digital pulses, a simple (digital)
divide-by-2 circuit uses a D or JK
flip-flop (i.e. CD4013 or CD4027).

If the paddle wheel puts out analog
waveforms, it might be a bit trickier...

How can I tell the difference between Analogue and digital. My tools are limited to a multimeter for now.

 

[Bob Masta]

On Tue, 2 Jun 2015 00:23:08 -0700 (PDT), macorro
<chris.macorro@googlemail.com> wrote:

On Monday, June 1, 2015 at 3:50:59 PM UTC+1, George Herold wrote:
On Sunday, May 31, 2015 at 11:05:34 AM UTC-4, macorro wrote:
Thought this might be an interesting first project, but my knowledge is=
very basic.
=20
A 12v old (1988) boat speed indicator with its paddle wheel sensor. I h=
ave a new display which can read the old paddle wheel but interprets the sp=
eed at close to twice the proper value. Calibration on the new display is l=
imited to about 15%. I guess the paddle wheel sends a signal each time a pa=
ddle induces a current.
=20
I think if I can find a way to lose every other signal from the paddle =
wheel then I can use the two together. Such a circuit doesn't sound too com=
plex - is this something I can buy? Otherwise could you give me some pointe=
rs, please?
=20
Do you have a 'scope? It may be that you are getting transients on both =
edges,
and maybe just some RC filtering will be enough. =20
=20
George H.

No scope - only a multimeter. Am thinking of a 2 channel scope that uses wi=
fi for a tablet display. Would this do for an entry level scope.As you can =
see I am starting from scratch.

Since this project seems to involve "audio" frequencies, you
may be able to use your computer's sound card inputs. Sound
cards are AC-coupled, so you can't measure DC voltages
directly. But you should be able to look at waveforms just
fine, and it won't cost you a thing to get started.

Sound cards are limited to about +/-2.5 V signals max, so
you may need a simple voltage divider on the input. If you
want better protection, you can use 2 parallel reversed LEDs
as the bottom leg of the divider to convert it into a
voltage limiter. See <http://www.daqarta.com/dw_0all.htm>

If you are actually working on the boat (not on your bench)
you may want to use a laptop running on battery to avoid any
ground reversal issues.

You can probably do your entire project within the 30-day /
30-session trial period of Daqarta, saving you $29. Or look
around for one of the free scope programs out there.

Feel free to ask any questions about Daqarta via Email, or
using the Contact page on the site.

Best regards,


Bob Masta

DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

 

[Randy Day]

In article <989c853f-ac70-49db-89e0-e600feab81a7@googlegroups.com>,
chris.macorro@googlemail.com says...

[snip]

How can I tell the difference between Analogue and digital. My tools
are limited to a multimeter for now.

Can you find info on-line about the
device? A datasheet or service manual
may describe how the paddle operates.

Alternatively, (and it's not a
definitive test, but...):

You can try monitoring the output with
the meter, then turn the paddle as
slowly as you can while watching the
meter. If the voltage 'snaps' from
high to low as you rock the wheel back
and forth across a tiny distance,
there's a good chance it's digital.

If you observe a more gradual voltage
change as the wheel rotates, it's
analog.

Just out of curiosity, is there physical
contact as the paddle tips pass the body
of the sensor, or does it rotate freely?

Are there magnets on/in the paddles?
That would indicate a reed switch or
Hall-effect device as the position sensor.
They're both popular as waterproof
non-contact sensors.