Batteryless bike computer?

I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,
with probably ten pulses per turn, the sidewall drive is
likely to be around forty pulses per turn.

The sidewall drive might slip insignificantly, the hub
unit would be as good as it gets.

Thanks for reading,

bob prohaska

On Wednesday, October 23, 2013 10:09:39 PM UTC-4, User Bp wrote:
I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,
with probably ten pulses per turn, the sidewall drive is
likely to be around forty pulses per turn.

The sidewall drive might slip insignificantly, the hub
unit would be as good as it gets.

Short answer: I don't know of any.

Longer answer: I recall that Jobst Brandt was heavily involved in the design of the Avocet cyclometers, and that he also had used and worked on Sturmey-Archer Dynohubs at one time. That may account for the "coincidence" that the magnet ring that triggers the Avocet has 20 poles, same as the Dynohub. ISTR hearing that the Avocet's pickup coil (unique among cyclocomputers) worked fine if mounted next to the side of a Dynohub. I haven't tried it myself, though.

Anyway, if that happened to work with your Shimano, that might take care of the signal. It's probably a different number of poles, but you could account for that by adjusting the calibration number.

Now about the power source: Unless you find a cyclometer already designed to get its power from a dynohub, I doubt it's worth playing around with the concept. You'll need some sort of battery (or perhaps super-cap) to maintain memory when stopped. Given that, it's far easier to just use a battery large enough to last a year, and change it for a few bucks at year's end, than to send a few rectified micro-amps to the computer while riding. IMO, anyway.

- Frank Krygowski

Frank Krygowski wrote:
You'll need some sort of battery (or perhaps super-cap) to maintain
memory when stopped. Given that, it's far easier to just use a battery
large enough to last a year, and change it for a few bucks at year's end,
than to send a few rectified micro-amps to the computer while riding.
IMO, anyway.

With the advent of flash memory is a battery needed? Diodes
are essentially free, if the bike's moving faster than balancing speed
there's plenty of power to run the computer and display.

bob

On 24/10/13 14:04, User Bp wrote:
Frank Krygowski wrote:
You'll need some sort of battery (or perhaps super-cap) to maintain
memory when stopped. Given that, it's far easier to just use a battery
large enough to last a year, and change it for a few bucks at year's end,
than to send a few rectified micro-amps to the computer while riding.
IMO, anyway.

With the advent of flash memory is a battery needed? Diodes
are essentially free, if the bike's moving faster than balancing speed
there's plenty of power to run the computer and display.


If it's a USB chargeable computer, like a Garmin, there are ways to
charge those from a dynamo, AFAIK. E.g.;

http://www.rosebikes.com/article/b--...tor/aid:620049

--
JS

On 10-23-2013, 22:09, User Bp wrote:
I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,

What kind of power do "bike computers" take? I studied

http://www.rei.com/category/4500105?version=V2

and I suspect they charge by USB (the third one definitely does.

My "bike computer" is an iPhone in a modified OtterBox.
(modified to be super easy to mount and unmount from the stem).

I plan to build a regulator to turn my generator's output into
the USB-spec power the iPhone requires.

If that's a little beyond your skills, there's probably someone near you
who can do it. In fact, I think it VERY likely that someone already has
done it.

A twelve-volt generator like

http://www.ebay.com/bhp/12v-dynamo

could easily be connected to a converter like these

http://tinyurl.com/lbstqe3

Shimano hubs are six-volt, as far as I know, and USB is five. So
provided sufficient power is available, a converter wold not be hard
to make. But some of the Shimano hubs say "will power most six volt
bulbs." If it can't do ALL, then it must have a pitifully poor power
output.


--
Wes Groleau

Always listen to experts. They'll tell you
what can't be done and why. Then do it.
— Robert A. Heinlein

On 24/10/13 14:47, Wes Groleau wrote:
On 10-23-2013, 22:09, User Bp wrote:
I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,

What kind of power do "bike computers" take? I studied

http://www.rei.com/category/4500105?version=V2

and I suspect they charge by USB (the third one definitely does.

My "bike computer" is an iPhone in a modified OtterBox.
(modified to be super easy to mount and unmount from the stem).

I plan to build a regulator to turn my generator's output into
the USB-spec power the iPhone requires.

If that's a little beyond your skills, there's probably someone near you
who can do it. In fact, I think it VERY likely that someone already has
done it.

A twelve-volt generator like

http://www.ebay.com/bhp/12v-dynamo

could easily be connected to a converter like these

http://tinyurl.com/lbstqe3

Shimano hubs are six-volt, as far as I know, and USB is five. So
provided sufficient power is available, a converter wold not be hard
to make. But some of the Shimano hubs say "will power most six volt
bulbs." If it can't do ALL, then it must have a pitifully poor power
output.


Try running your dynamo with a 12V 6W bulb.

You will need to be riding faster before it is at full brightness, but
it will produce that much power quite happily.

Or, hook up a multimeter set to AC volts and measure the dynamo output
with no load. You might be surprised just how high the voltage gets.

The bottle dynamo might slip more because of the increased power
transmission from the tyre to the dynamo.

http://www.baldurdash.org/OtherStuff...de/12vinfo.htm

--
JS

chiroptophobia

On 10/23/2013 7:09 PM, User Bp wrote:
I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,
with probably ten pulses per turn, the sidewall drive is
likely to be around forty pulses per turn.

The sidewall drive might slip insignificantly, the hub
unit would be as good as it gets.

Look into the CatEye solar. It has rechargeable coin cells inside so you
should rarely have to change the batteries. It includes both a sensor
for the wheel and for the cranks (cadence).

The manual is at
http://www.cateye.com/files/manual_dl/7/755/CC_2000_E.pdf. You may
have trouble buying one as it's a discontinued model. Not sure where you
could buy the SR44R batteries anymore.

Really, the batteries on newer bicycle computers last so long that
there's no need to power then from a dynamo or from a solar cell.

On 10/24/2013 9:15 AM, sms wrote:
On 10/23/2013 7:09 PM, User Bp wrote:
I've got two bikes with always-on generators, one hub
mounted and the other sidewall friction driven. Are there
any bike computers that can take their signal and power
from this kind of setup? The hub generator is a Shimano,
with probably ten pulses per turn, the sidewall drive is
likely to be around forty pulses per turn.

The sidewall drive might slip insignificantly, the hub
unit would be as good as it gets.

Look into the CatEye solar. It has rechargeable coin cells inside so you
should rarely have to change the batteries. It includes both a sensor
for the wheel and for the cranks (cadence).

The manual is at
http://www.cateye.com/files/manual_dl/7/755/CC_2000_E.pdf. You may
have trouble buying one as it's a discontinued model. Not sure where you
could buy the SR44R batteries anymore.

CatEye solar worked very well. I had one for years.


Really, the batteries on newer bicycle computers last so long that
there's no need to power then from a dynamo or from a solar cell.



Garmins require USB charge. A friend was just telling me that she had
issues keeping hers charged when she did one of those 3 day challenges.
She was camping and had to find power to charge her Garmin.

I'm not sure that she'd install a generator even if it would work to
charge her computer. Maybe Garmin should look into solar charging...

On 10/24/2013 8:06 AM, Duane wrote:

snip

She was camping and had to find power to charge her Garmin.

I'm not sure that she'd install a generator even if it would work to
charge her computer. Maybe Garmin should look into solar charging...

Right, I wasn't thinking of a GPS, just a simple bicycle computer.

Could a hub dynamo keep an operating Garmin fully charged or is the
Garmin drawing too much power? That's an issue with some of the better
battery powered lights, they're drawing more than the 3-5 watts that a 3
watt dynamo can provide. But with lights, you can be charging them even
when they're only in flashing mode in the daytime, and flash mode
doesn't take much power. The computer will presumably be operating all
the time. It may require one of those 6 watt tire-driven dynamos. Too
bad no one has come out with a 12V/6W hub dynamo yet. It would enable
riders to have sufficient power for a good set of lights or it could be
used to charge more power-hungry devices.

For camping I think I'd have a hub dynamo charging a battery pack of six
AA NiMH batteries during the day, then charge devices from that pack at
night. Six Sanyo Eneloop AA cells would provide about 15WH of energy.

Allowing for losses you'd need probably 6-7 hours of riding, generating
4W per hour to charge that battery pack if it were completely drained,
but it's unlikely to be completely drained.

Put the output of the battery pack through an 80% efficient DC-DC
converter to 5V and even with the losses you'd be fine.

The Garmin Edge batteries appear to be 4-5 WH batteries. So even with
additional losses, a 15WH battery pack would have the capacity to charge
the Garmin Edge.

Now if you could design a charger that would charge two 3.7V Li-Ion
batteries, in series, from a dynamo, that would be even better. The 6VAC
from the dynamo is about 8.5VDC, and Li-Ion batteries should be charged
at about 4.2V per cell, and charger ICs require 9V minimum input. So you
might need a boost regulator to get the voltage high enough to run the
charger, which would reduce efficiency.