Buy or build - mating old sensor to new display

[snip]

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...

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:

(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

ery basic.

e a new display which can read the old paddle wheel but interprets the spee d at close to twice the proper value. Calibration on the new display is lim ited to about 15%. I guess the paddle wheel sends a signal each time a padd le induces a current.

eel then I can use the two together. Such a circuit doesn't sound too compl ex - 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 ed ges, 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  |             | 
| Voice:(480)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.

very basic.

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.

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?

edges,

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.

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

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

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

Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE Signal Generator, DaqMusiq generator Science with your sound card!

[snip]

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.