Tachymeter design

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
AJH wrote:
> On Tue, 25 Apr 2006 18:09:37 +0100, Steve
> <[email protected]> wrote:
>
>> Here is a circuit we use with a water flow sensor. Its a pretty useful
>> universal frequency to voltage converter and is very linear. It drives a
>> moving coil panel meter from SKT 2. Pin 7 on Q2 drives an alarm o/p,
>> whose trigger point is set by R10. The output will need to be buffered
>> to do anything but light an LED.
>
>
> Thanks Steve but 'scuse my ignorance, what are the op amps?
>
> AJH

The little triangles Q2 on the picture, holds two of these "Operational
Amplifiers" in one 8 pin box. Like I said, if you just want frequency to
volts, forget them. An op-amp is just a very simple amplifier, with a
lot of amplification, unless you turn it down with external resistors.

Steve
 
Steve wrote:
> AJH wrote:
>> On Tue, 25 Apr 2006 12:49:43 +0100, Steve
>> <[email protected]> wrote:
>>
>>> A crude RPM to volts detector needs only a single transistor, a
> couple of diodes and a capacitor, with sundry resistors. Would you
> like to see the circuit ?
>>
>> Yes I would, I have a small anemometer with three wires coming off it
>> so would like to know how to connect it to a readout. I'm guessing it
>> contains a hall effect transistor that counts the metal blades as
>> they go past.
>
> Here is a circuit we use with a water flow sensor. Its a pretty useful
> universal frequency to voltage converter and is very linear. It
> drives a moving coil panel meter from SKT 2. Pin 7 on Q2 drives an
> alarm o/p, whose trigger point is set by R10. The output will need to
> be buffered to do anything but light an LED.
>
> If you ignore everything after Q2 pin 3, volts on R2 is directly
> proportional to Frequency, and you can do what you like with it. Keep
> the load on the pin very low, or you WILL need the opamp.
>
> The time constant of R2/C2 affects the scale and range. As shown here,
> it will work with the 1000 RPM signal nicely I think, but otherwise
> make R2 a bit bigger.
>
> Here is the picture of the circuit.
>
> http://www.thetaylorfamily.org.uk/cmine/displayimage.php?album=8&pos=0
>
> The input is shown as +12, signal and ground. In fact the input pin
> SKT 1 pin 2 can be driven with anything from about 1V to 12V, or you
> can add another little transistor amplifier.
>
> Steve

The picture I was looking at doesn't appear to have a pin 2 on SKT1.

--
If Your specification is vague or imprecise, you'll likely get what you
asked for not what you wanted!

He who says it cannot be done would be wise not to interrupt her doing
it.


 
GbH wrote:
>
> The picture I was looking at doesn't appear to have a pin 2 on SKT1.
>

That should be pin 1. Ooops.
Steve
 
On Tue, 25 Apr 2006 19:25:20 +0100, Steve
<[email protected]> wrote:

>>
>>
>> Thanks Steve but 'scuse my ignorance, what are the op amps?
>>
>> AJH
>
>The little triangles Q2 on the picture, holds two of these "Operational
>Amplifiers" in one 8 pin box. Like I said, if you just want frequency to
>volts, forget them. An op-amp is just a very simple amplifier, with a
>lot of amplification, unless you turn it down with external resistors.

Sorry I hadn't realised you meant I could leave them out when you said
ignore them.

AJH

 
On or around Tue, 25 Apr 2006 13:57:12 +0100, Ian Rawlings
<[email protected]> enlightened us thusly:

>On 2006-04-25, Steve Taylor <[email protected]> wrote:
>
>> Nah, it'll bounce like the clappers.
>
>Would the switch even have time to switch in the first place, let
>alone bounce? Perhaps with a large-ish curved magnet?

too big a magnet and you'll have an unbalanced propshaft...
--
Austin Shackles. www.ddol-las.net my opinions are just that
Confidence: Before important work meetings, boost your confidence by
reading a few pages from "The Tibetan Book of the Dead"
from the Little Book of Complete B***ocks by Alistair Beaton.
 
On Tue, 25 Apr 2006 20:03:27 +1000, "Karen Gallagher"
<[email protected]> wrote:

>Can any electronics whizzes help me out with a simple design for a
>tachymeter to display the RPM of a propshaft?
>
>I'm looking to monitor the output of my rear PTO so it does not over-rev
>while negotiating rough terrain - mostly a creek bed I have to drive through
>frequently while weed-spraying. Max RPM needs to be kept below 1000, but
>sometimes seems to sneak up well beyond, judging by the odd sounds coming
>from the rear.
>
>I'm pretty handy with a soldering iron, but gave up on modern electronics
>when they replaced valves with these new fangled transistors :)
>
>Karen

I've got a slightly different requirement, which people here may have
ideas on...

I need a very accurate odometer fitting to a vehicle (mine). I'm not
sure how accurate car ones are, but I want 1% tolerance. I don't want
a kit - I want someone to fit, calibrate and test it, and ideally give
me some kind of certificate. I'm aware that the calibration will
drift as the tyres wear etc...

Anyone know anyone who can do this?

--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'03 Volvo V70
'06 Nissan Navara aka "The Truck"
 
On Tue, 25 Apr 2006 21:17:44 +0100, Tim Hobbs <[email protected]> wrote:

>I need a very accurate odometer fitting to a vehicle (mine). I'm not
>sure how accurate car ones are, but I want 1% tolerance.

Blummie - is that actually possible without having one of those extra
wheels on a frame at the back and only driving at <30mph?

>I don't want
>a kit - I want someone to fit, calibrate and test it, and ideally give
>me some kind of certificate. I'm aware that the calibration will
>drift as the tyres wear etc...

Talk to your local weights and measures bods, or the nice people from
HMR&C. They will know who produces such equipment. Any GPS based
system will be too far out IMO.


--
"We have gone from a world of concentrated knowledge and wisdom to one
of distributed ignorance. And we know and understand less while being
increasingly capable." Prof. Peter Cochrane, formerly of BT Labs
In memory of Brian {Hamilton Kelly} who logged off 15th September 2005
 
On 2006-04-25, Austin Shackles <[email protected]> wrote:

> too big a magnet and you'll have an unbalanced propshaft...

So another wedge of metal on the other side, or alternatively drop the
reed switch and use solid state like a sensible person ;-)

--
Blast off and strike the evil Bydo empire!
 
On Tue, 25 Apr 2006 21:39:52 +0100, Mother <"@ {mother} @"@101fc.net>
wrote:

>On Tue, 25 Apr 2006 21:17:44 +0100, Tim Hobbs <[email protected]> wrote:
>
>>I need a very accurate odometer fitting to a vehicle (mine). I'm not
>>sure how accurate car ones are, but I want 1% tolerance.
>
>Blummie - is that actually possible without having one of those extra
>wheels on a frame at the back and only driving at <30mph?
>
>>I don't want
>>a kit - I want someone to fit, calibrate and test it, and ideally give
>>me some kind of certificate. I'm aware that the calibration will
>>drift as the tyres wear etc...
>
>Talk to your local weights and measures bods, or the nice people from
>HMR&C. They will know who produces such equipment. Any GPS based
>system will be too far out IMO.

I was thinking of a propshaft-based transducer, then calibrated over a
measured number of wheel revs (or on a rolling road or similar).
Certified for x miles until tyres wear to a certain amount.

Definitely don't want a GPS-based system, 'cos that's what I'm
testing!

--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'03 Volvo V70
'06 Nissan Navara aka "The Truck"
 
On Tue, 25 Apr 2006 21:17:44 +0100, Tim Hobbs <[email protected]> scribbled
the following nonsense:

>On Tue, 25 Apr 2006 20:03:27 +1000, "Karen Gallagher"
><[email protected]> wrote:
>
>>Can any electronics whizzes help me out with a simple design for a
>>tachymeter to display the RPM of a propshaft?
>>
>>I'm looking to monitor the output of my rear PTO so it does not over-rev
>>while negotiating rough terrain - mostly a creek bed I have to drive through
>>frequently while weed-spraying. Max RPM needs to be kept below 1000, but
>>sometimes seems to sneak up well beyond, judging by the odd sounds coming
>>from the rear.
>>
>>I'm pretty handy with a soldering iron, but gave up on modern electronics
>>when they replaced valves with these new fangled transistors :)
>>
>>Karen
>
>I've got a slightly different requirement, which people here may have
>ideas on...
>
>I need a very accurate odometer fitting to a vehicle (mine). I'm not
>sure how accurate car ones are, but I want 1% tolerance. I don't want
>a kit - I want someone to fit, calibrate and test it, and ideally give
>me some kind of certificate. I'm aware that the calibration will
>drift as the tyres wear etc...
>
>Anyone know anyone who can do this?

Terratrips can be set up fairly accurately IIRC, given that they are
used on competition vehicles. Not sure about certificates though.

Would have thought Warren might know someone?

Failing that, see if the plod know anyone.

--

Simon Isaacs

Peterborough 4x4 Club Chairman, Newsletter Editor and Webmaster
Green Lane Association (GLASS) Financial Director
101 Ambi, undergoing camper conversion www.simoni.co.uk
1976 S3 LWT, Fully restored, ready for sale! Make me an offer!
Suzuki SJ410 (Wife's) 3" lift kit fitted, body shell now restored and mounted on chassis, waiting on a windscreen and MOT
Series 3 88" Rolling chassis...what to do next
1993 200 TDi Discovery
1994 200 TDi Discovery body shell, being bobbed and modded.....
 
On 2006-04-25, Mother <"@ {mother} @"@101fc.net> wrote:

> Talk to your local weights and measures bods, or the nice people from
> HMR&C. They will know who produces such equipment. Any GPS based
> system will be too far out IMO.

I had a quick google about for doppler radar systems that point at the
ground, but got bored.

--
Blast off and strike the evil Bydo empire!
 
Simon Isaacs wrote:

> Failing that, see if the plod know anyone.

That's probably your best bet. The guys who do the NZ Police speedo
calibrations will also provide the same service to anyone else - not
much use to you being 12000 miles away but I expect there's someone
similar in the UK.

Otherwise the people who calibrate taxicab meters normally have the
technology to at least test the mileage covered and give you an
indication of what the error is.

Incidentally, which of your vehicles do you want to fit this to? If
it's the Navara (which IIRC has an electronic speedo) it should be easy
to hook in to the signal wire for that with a pulse counter that can
then be easily calibrated to show distance travelled.


--
EMB
 
On Wed, 26 Apr 2006 09:29:29 +1200, EMB <[email protected]> wrote:

>Simon Isaacs wrote:
>
>> Failing that, see if the plod know anyone.
>
>That's probably your best bet. The guys who do the NZ Police speedo
>calibrations will also provide the same service to anyone else - not
>much use to you being 12000 miles away but I expect there's someone
>similar in the UK.
>
>Otherwise the people who calibrate taxicab meters normally have the
>technology to at least test the mileage covered and give you an
>indication of what the error is.
>
>Incidentally, which of your vehicles do you want to fit this to? If
>it's the Navara (which IIRC has an electronic speedo) it should be easy
>to hook in to the signal wire for that with a pulse counter that can
>then be easily calibrated to show distance travelled.

Yep, it's going on the Navara. Part of the purchase rationale was a
truck with plenty of room to fit 'toys'. The space under the back
seat is filling up nicely....

--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'03 Volvo V70
'06 Nissan Navara aka "The Truck"
 
On or around Tue, 25 Apr 2006 21:46:09 +0100, Tim Hobbs <[email protected]>
enlightened us thusly:

>On Tue, 25 Apr 2006 21:39:52 +0100, Mother <"@ {mother} @"@101fc.net>
>wrote:
>
>>On Tue, 25 Apr 2006 21:17:44 +0100, Tim Hobbs <[email protected]> wrote:
>>
>>>I need a very accurate odometer fitting to a vehicle (mine). I'm not
>>>sure how accurate car ones are, but I want 1% tolerance.
>>
>>Blummie - is that actually possible without having one of those extra
>>wheels on a frame at the back and only driving at <30mph?
>>
>>>I don't want
>>>a kit - I want someone to fit, calibrate and test it, and ideally give
>>>me some kind of certificate. I'm aware that the calibration will
>>>drift as the tyres wear etc...
>>
>>Talk to your local weights and measures bods, or the nice people from
>>HMR&C. They will know who produces such equipment. Any GPS based
>>system will be too far out IMO.
>
>I was thinking of a propshaft-based transducer, then calibrated over a
>measured number of wheel revs (or on a rolling road or similar).
>Certified for x miles until tyres wear to a certain amount.

try taximeter types, too - they're mostly driven form the speedo cable and
calibrated over a measured mile. Whether they do as well as 1% I don't
know.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"The breezy call of incense-breathing Morn, The swallow twittering
from the strawbuilt shed, The cock's shrill clarion, or the echoing
horn, No more shall rouse them from their lowly bed."
Thomas Gray, Elegy Written in a Country Churchyard.
 
On Tue, 25 Apr 2006 22:01:52 +0100, Ian Rawlings
<[email protected]> wrote:

>On 2006-04-25, Mother <"@ {mother} @"@101fc.net> wrote:
>
>> Talk to your local weights and measures bods, or the nice people from
>> HMR&C. They will know who produces such equipment. Any GPS based
>> system will be too far out IMO.
>
>I had a quick google about for doppler radar systems that point at the
>ground, but got bored.

Yes that was my first thought, there used to be a company called
something like RDS that fitted this kit to tractors so you could
measure the wheelslip (wheelslip is a function of efficiency in
getting traction into the ground). Too late for me to google now but
integrate the velocity and you have distance.

AJH

 
Steve wrote:
> Karen Gallagher wrote:
>> Can any electronics whizzes help me out with a simple design for a
>> tachymeter to display the RPM of a propshaft?
>>
>> I'm looking to monitor the output of my rear PTO so it does not
>> over-rev while negotiating rough terrain - mostly a creek bed I have
>> to drive through frequently while weed-spraying. Max RPM needs to be
>> kept below 1000, but sometimes seems to sneak up well beyond,
>> judging by the odd sounds coming from the rear.
>>
>> I'm pretty handy with a soldering iron, but gave up on modern
>> electronics when they replaced valves with these new fangled
>> transistors :) Karen
>>
>
>
> Martyn suggests a reed switch as a sensor, but at 6000 RPM
> =10msec/rev - its pushing it for a reed to have had time to stop
> bouncing around before it has to move again, and a glass tube next to
> V8 is not going to be too happy.
>
> It would be better to pick it off with a hall switch instead.
>
> A crude RPM to volts detector needs only a single transistor, a couple
> of diodes and a capacitor, with sundry resistors. Would you like to
> see the circuit ?
>
> Steve

Yes please Steve, I'd appreciate that - [email protected]

--
"I'd far rather be happy than right any day."
- Slartibartfast


 
On 2006-04-25, AJH <[email protected]> wrote:

> Yes that was my first thought, there used to be a company called
> something like RDS that fitted this kit to tractors so you could
> measure the wheelslip

That's why I had a peek at it, with the idea that if it's good enough
to measure speed accurately enough for tractor applications then it
should do the job. ISTR it being fitted as standard to some models.

--
Blast off and strike the evil Bydo empire!
 
On Wed, 26 Apr 2006 09:29:29 +1200, EMB <[email protected]> wrote:

>Otherwise the people who calibrate taxicab meters normally have the
>technology to at least test the mileage covered and give you an
>indication of what the error is.

Acceptable margin is 5 percent, most will get away with 8, 9 or (at a
push - and if they're not too stroppy) 10 percent.

Not really that good for Tim (or taxi passengers!)


--
"We have gone from a world of concentrated knowledge and wisdom to one
of distributed ignorance. And we know and understand less while being
increasingly capable." Prof. Peter Cochrane, formerly of BT Labs
In memory of Brian {Hamilton Kelly} who logged off 15th September 2005
 
Mother wrote:
> On Wed, 26 Apr 2006 09:29:29 +1200, EMB <[email protected]> wrote:
>
>
>>Otherwise the people who calibrate taxicab meters normally have the
>>technology to at least test the mileage covered and give you an
>>indication of what the error is.
>
>
> Acceptable margin is 5 percent, most will get away with 8, 9 or (at a
> push - and if they're not too stroppy) 10 percent.
>
> Not really that good for Tim (or taxi passengers!)
>
>

Ah ok. Here in NZ the rules are <1% tolerance on the odometer part of
the taximeter.

--
EMB
 
On or around Wed, 26 Apr 2006 20:29:31 +0100, Mother <"@ {mother}
@"@101fc.net> enlightened us thusly:

>On Wed, 26 Apr 2006 09:29:29 +1200, EMB <[email protected]> wrote:
>
>>Otherwise the people who calibrate taxicab meters normally have the
>>technology to at least test the mileage covered and give you an
>>indication of what the error is.
>
>Acceptable margin is 5 percent, most will get away with 8, 9 or (at a
>push - and if they're not too stroppy) 10 percent.
>
>Not really that good for Tim (or taxi passengers!)

ISTR the meter being potentially more accurate than that. worth asking the
taximeter makers.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"Remember that to change your mind and follow him who sets you right
is to be none the less free than you were before."
Marcus Aurelius Antoninus (121-180), from Meditations, VIII.16
 
You must log in or register to reply here.

Similar threads

Nodge68
Freelander 2 (LR2) LR trouble codes.
Replies
6
Views
38K
Keith Kernow Kernewick
Keith Kernow Kernewick
300bhp/ton
Driven: New Defender - On & Off Road. Is it a Pretender?
2 3
Replies
50
Views
8K
Squonker
S
P
Freelander 1 Fuel rail Connector.
Replies
12
Views
2K
blodge
blodge
Dr_evil
Series King Cab
61 62 63
Replies
1K
Views
144K
discomark10
discomark10
The Mad Hat Man
Rust Removal Using Electrolysis
Replies
15
Views
39K
Paul D
Paul D
Back
Top