Spoke sensor for bicycle

On Tuesday, June 14, 2022 at 3:04:05 PM UTC-4, whit3rd wrote:
> On Tuesday, June 14, 2022 at 11:32:03 AM UTC-7, Ricky wrote: 
> > On Tuesday, June 14, 2022 at 2:21:58 PM UTC-4, whit3rd wrote:
> > > ... a reluctance
> > > sensor on a gear-cluster tooth? There's some DC insensitivity, unlike with Hall 
> > > sensors, but maybe a low-speed signal dropout isn't going to be a bother. 
> 
> > Does it have to be magnetic? A conductor moving in a magnetic field creates a current which also creates a magnetic field which can be detected, no?
> A nonmagnetic gear tooth will (in motion) disturb a magnetic field, and make a pulse. 
> The eddy current response, though, is less than a ferromagnetic material's, and has a time decay 
> of its own, added to the coil's DC insensitivity. 
> 
> An IR (modulated? polarized?) source, aimed at a retroreflector on a spoke, has good range and sensitivity, at a cost 
> of some power usage. Rejecting ambient light and dirt are other issues there.

I know they use induced currents in aluminum cans to separate them using a magnet.  The magnet spins under the conveyor belt making the cans jump off the end, while the rest of the stream simply falls off.  A friend who worked in the industry complained that my crushing cans made this not work as well.  But my cans are sold as aluminum, not mixed into the all-in-one stream. 

-- 

Rick C.

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On 6/14/2022 6:07 PM, whit3rd wrote:
> On Tuesday, June 14, 2022 at 5:22:18 PM UTC-7, Don Y wrote:
>> On 6/14/2022 1:39 PM, whit3rd wrote:
> 
>>> A better solution would be to instument a hub and axle, but the axle diameter is fixed by the bicycle frame, and
>>> the hub by the wheel-builders. That means redesigns of the mechanical bits unless one lucks out and
>>> finds a compatible generator hub off-the-shelf.
> 
>> The biggest win is it gets you away from the wheel. E.g., you could affix a
>> bar magnet to the end of the cable-in-cable and detect it's rotation (to
>> whatever extent you desire) as well as using its motion to generate *power*
>> for the circuit (esp with the ultra low power technologies now available;
>> think about the tire-rubbing generators that used to power headlamps...)
> 
> Yeah; those delivered 2 or 3 watts; enough for a halogen flashlight lamp,
> and to charge a 6V lead/acid battery for standstill lighting.

I've not seen one in decades.  They seem to predate the "10 speed" time in
my life.

But, I recall them as putting lots of drag on the wheel.  And, as a
"rotation sensor", they would be inadequate as I doubt the signal
would "integrate" well.

> If you use
> one built into a wheel hub, the dynamo pole count determines the AC cycles per mile travelled.

OK.  That would be similar to my "spinning magnet" idea.

> The friction type can be precalibrated easily (the drive drum circumference is better known
> than the tire's) if  it engages the tread  rather than the sidewall of the tire.

I don't think the output would translate into "revolutions" well, across the
range of possible speeds.  Likewise, I imagine it would still produce an
output when the wheel moved *backwards* (?)

On 6/14/2022 7:03 PM, rbowman wrote:
> On 06/14/2022 06:22 PM, Don Y wrote:
>> The biggest win is it gets you away from the wheel.  E.g., you could
>> affix a
>> bar magnet to the end of the cable-in-cable and detect it's rotation (to
>> whatever extent you desire) as well as using its motion to generate *power*
>> for the circuit (esp with the ultra low power technologies now available;
>> think about the tire-rubbing generators that used to power headlamps...)
> 
> What a wondrous invention they were... All that aggro for a one candlepower 
> headlamp. Somehow I associate those with the Sturmey-Archer three speed hubs.
> 
> I suppose driving a generator that way is better than driving the bicycle with 
> a 26cc motor in a similar way:
> 
> http://bumblebeebolton.com/front_instructions.html
> 
> I thought the concept might have been relegated to the trash bin of history but 
> I've seen a similar design for a DIY low rent eBike.

I've been looking for an "alternate" form of transportation for the
little jaunts -- to the library, post office, etc.  Just a couple of
miles, likely off-road.

Things like bicycle, Segway, one-wheels, etc. come to mind.  But, none
have really checked all the boxes (e.g., carrying a bag of groceries
on a bike or Segway is really not ideal).

But, recently, I'm liking the idea of a small gas powered generator
tucked in the battery compartment of my electric wheelchair (!).
This would eliminate the maintenance issue of the batteries
($400/set) as well as increase the possible RELIABLE range of
the chair.  (of course, you couldn't use it indoors but that's fine)

Building on that idea, a gas powered Segway?  <grin>

On 15/6/22 16:02, Don Y wrote:
> On 6/14/2022 7:03 PM, rbowman wrote:
>> On 06/14/2022 06:22 PM, Don Y wrote:
>>> The biggest win is it gets you away from the wheel.  E.g., you could
>>> affix a
>>> bar magnet to the end of the cable-in-cable and detect it's rotation (to
>>> whatever extent you desire) as well as using its motion to generate 
>>> *power*
>>> for the circuit (esp with the ultra low power technologies now 
>>> available;
>>> think about the tire-rubbing generators that used to power headlamps...)
>>
>> What a wondrous invention they were... All that aggro for a one 
>> candlepower headlamp. Somehow I associate those with the 
>> Sturmey-Archer three speed hubs.
>>
>> I suppose driving a generator that way is better than driving the 
>> bicycle with a 26cc motor in a similar way:
>>
>> http://bumblebeebolton.com/front_instructions.html
>>
>> I thought the concept might have been relegated to the trash bin of 
>> history but I've seen a similar design for a DIY low rent eBike.
> 
> I've been looking for an "alternate" form of transportation for the
> little jaunts -- to the library, post office, etc.  Just a couple of
> miles, likely off-road.
> 
> Things like bicycle, Segway, one-wheels, etc. come to mind.  But, none
> have really checked all the boxes (e.g., carrying a bag of groceries
> on a bike or Segway is really not ideal).

Cargo bike? Or trike? Possibly electric?

> But, recently, I'm liking the idea of a small gas powered generator
> tucked in the battery compartment of my electric wheelchair (!).
> This would eliminate the maintenance issue of the batteries
> ($400/set) as well as increase the possible RELIABLE range of
> the chair.  (of course, you couldn't use it indoors but that's fine)
> 
> Building on that idea, a gas powered Segway?&nbsp; <grin>

You could carry a genset on a cargo bike.

Ch

On a sunny day (Tue, 14 Jun 2022 21:00:44 +0300) it happened Dimiter_Popoff
<dp@tgi-sci.com> wrote in <t8aicd$2uq$1@dont-email.me>:

>On 6/14/2022 20:43, Jan Panteltje wrote:
>> On a sunny day (Tue, 14 Jun 2022 18:51:21 +0300) it happened Dimiter_Popoff
>> <dp@tgi-sci.com> wrote in <t8aapr$ab6$1@dont-email.me>:
>> 
>>> I started cycling again (used to as a kid...) some 4 years ago.
>>> And while I know there are plenty of super cheap "bicycle computers"
>>> I have been thinking of making my own.
>>> Thus so far 4 years no speed/mileage indicator for me, obviously.
>>> While this may likely remain the case forever I am still thinking
>>> about it - not the obvious things like the MCU, display etc., just
>>> the rotation sensor. They all use a magnet placed somewhere on one
>>> of the wheels and some sensor, I have used a Hall sensor for
>>> pretty precise positioning of the rotor of our TLD reader etc.,
>>> but I only still keep on thinking of making the thing because I
>>> imagine it sensing just the spokes, i.e. making some inductive sensor.
>>>
>>> I know what I will try out etc., I may even get to designing one before
>>> the millennium is over but well, these thoughts seem to be on topic and
>>> I am sure there are people with more experience making inductive
>>> sensors than I have.
>> 
>> Or you could make something like my gm_pic2:
>>   http://panteltje.com/panteltje/pic/gm_pic2/
>> 
>> It uses GPS and writes to SDcard or EEPROM where you were at any time, logs radiation there too
>> There is software to replay the trip on google maps.
>> After all the GPS talk here ..
>> Simple maaz using the space and time between data points will allow you to find speed and distances.
>> A GPS module and a Microchip 18F14k22 + EEPROM is all you need.
>> Oh and a battery...
>> Now been working 24/7 for 8 years... As clock mostly.
>> No tinkering with your bike needed.
>> Also logs trips per bus or train.
>> 
>> 
>
>Is the GPS accuracy/latency of the speed measurement close to that of
>a car's speed indicator?

You will have to average here and there I suppose.
Seems reasonabale to me, but have not tried on a bike.
Latency is very low.

On a sunny day (Tue, 14 Jun 2022 22:01:01 +0300) it happened Dimiter_Popoff
<dp@tgi-sci.com> wrote in <t8altd$uqm$1@dont-email.me>:
>The Hall sensors I have "in the drawer" are some with hysteresis though,
>they need such a magnet really close (within 1mm if not less) to work,
>would need some other kind but that should be the easiest part.
>But well, it looks I am not going to start the project any time soon.
>And I did download some biking app to the phone, this makes the
>project's prospects even more bleak...

An other way would be a laser diode shining through the spikes and a photocell picking it up on the other side.
Be careful not to burn out eyes of some kids.
The acceleration sensor would work nice too,
some code is on my site that uses a 6 axis accelerometer but not for speed.. math seems easy enough though.
Did I not write code for a  navigation system using only such accelerometers, yes,
needed an oven, some uni redid the experiment .. its on Usenet..


  

On a sunny day (Tue, 14 Jun 2022 17:56:50 -0400) it happened Joe Gwinn
<joegwinn@comcast.net> wrote in <4a0iahhpmhi9ocv7ig0k1nidjn95mqbbg1@4ax.com>:

>Well, there is also Wiegand-wire sensors:
>
>.<https://en.wikipedia.org/wiki/Wiegand_effect>
>
>.<https://en.wikipedia.org/wiki/Wiegand_Sensor>
>
>But as others have noted, the spokes may be non-magnetic.  This can be
>solved by adding a bit of zinc-plated mild steel tubing (automotive
>brake line) glued to at least one spoke with a silicon rubber
>adhesive.  The spoke would pass through an inch of tube, with silicon
> rubber filling the gap between tube and spoke.
>
>Joe Gwinn

Just thinking, use a camera looking down
The speed can be derived from the moving pattern it sees
Almost like a computah mouse...

On 14/06/2022 18:09, Dimiter_Popoff wrote:

<snipped>
> 
> Hmmm, but will that work at really low speed (like when pushing the
> bike uphill)? It is an idea to do it this way (I did not even know the
> name of the method so the idea is more than welcome), yet what I was
> thinking was more in the line of changing some oscillation frequency
> (thus detecting the spokes also&nbsp; "at DC").

A former colleague used a clever method for an impeller type flow 
sensor.  He used a small unshielded inductor with a parallel capacitor 
connected to a PIC pin.  Set the pin to be an output, kick the LC with a 
pulse, then set the pin to be an input and count oscillations.  In air, 
you get a few counts, near metal, you get fewer counts.  I don't know 
details, but he was able to sample sufficiently quickly for it to work.

My guess is that it wouldn't be practical over the clearance distance 
you'd need for a spoke, but it's a neat method.

-- 
Cheers
Clive

On 06/15/2022 12:02 AM, Don Y wrote:
> Things like bicycle, Segway, one-wheels, etc. come to mind.  But, none
> have really checked all the boxes (e.g., carrying a bag of groceries
> on a bike or Segway is really not ideal).

There are quite a few cargo bikes or if you already have a bike, 
trailers. A friend has a BOB Yak that worked out well. It's easy to 
disconnect if you don't need it and the single wheel means it tracks on 
the same path as the bike if you ride single track.

The low cost solution would be looking for one of those child trailers 
at a yard sale.

There are also bike panniers but you wind up repacking the groceries to 
get everything to fit. Two wheeled grocery shopping on either a bicycle 
or motorcycle tends to limit impulse purchases.

On Wednesday, June 15, 2022 at 2:56:59 AM UTC-4, Jan Panteltje wrote:
> On a sunny day (Tue, 14 Jun 2022 22:01:01 +0300) it happened Dimiter_Popoff 
> <d...@tgi-sci.com> wrote in <t8altd$uqm$1...@dont-email.me>: 
> >The Hall sensors I have "in the drawer" are some with hysteresis though, 
> >they need such a magnet really close (within 1mm if not less) to work, 
> >would need some other kind but that should be the easiest part. 
> >But well, it looks I am not going to start the project any time soon. 
> >And I did download some biking app to the phone, this makes the 
> >project's prospects even more bleak... 
> 
> An other way would be a laser diode shining through the spikes and a photocell picking it up on the other side. 
> Be careful not to burn out eyes of some kids. 
> The acceleration sensor would work nice too, 
> some code is on my site that uses a 6 axis accelerometer but not for speed.. math seems easy enough though. 
> Did I not write code for a navigation system using only such accelerometers, yes, 
> needed an oven, some uni redid the experiment .. its on Usenet..

Optics get dirty and stop working.  They also are impacted by precipitation.  No one wants an intermittent speed-o-meter. 

I think the clear winner in this contest is the playing car against the spokes.  

Actually, I think people have trivialized away the variable reluctance sensor.  While the spoke may not be magnetic, it's no trouble adding a small piece of metal to the spoke or spoke nipple or even the hub.  I believe spokes on most bikes are arranged to cross and form an X.  The crossing point may be a good place to put the metal badge.  

-- 

Rick C.

--+ Get 1,000 miles of free Supercharging
--+ Tesla referral code - https://ts.la/richard11209