Survey : Weight vs. battery life for bike computer?

"Cleanbean" wrote in message
.. .
I wouldn't use a computer with the weight of a AAA or AA. Consider using
2
large watch type batteries.

John in Texas

Why? You don't even know what features it would have. I suppose the original
article should have at least hinted at what was on offer for the proposed
costs. I did not answer because for me it would really depend on what I am
getting. I would like to see a modular system. The disply could be designed
like the SRM head unit and it could have some kind of open standards bus to
add on peripherals. Let's say you have something comparable to the 710 but
with a superior pixelated display. The add ons could incluse power from any
of the systems currently available (or at least more than one). A GPS unit
could be added for certain applications and otherwise left at home.



"Reza Naima" wrote in message
om...
I'm working on designing a "next generation" bike computer. We're
trying to figure out what would be the optimal tradeoffs for the
batteries. We are looking at the following options (With
non-rechargeable batteries you can get 2x the performance):

1 AAA NiMh Rechargeable Battery : 2 hours, 12 grams
2 AAA " : 5 hours, 24 grams
1 AA " : 4.5 hours, 27 grams
2 AA " : 10 hours, 34 grams


Note that the product is designed to store ride information to be
downloaded to a PC. Thus you would want the batteries to last the
entire trip. However, you could always carry extra batteries with you
in a separate pouch for extended trips.

Let me know what you think...
Reza

Let's say you have a reasonable NiMh AA cell, say 1600 mah.
You have to draw 180 ma to run it down in 10 hours. That's
a lot of current.

1600mah at 1.2volts. Most electronics want 3.3v, so you're looking at
581mah at 3.3v, which at a burn rate of 150ma comes to 3.8 hours based
on our initial calculations. Since then, we've started doiong some
measurements, and we're looking at a more reasonable 70-80mah
including the LCD display. This doubles the expected time to ~8 hours
which we think is sufficient for most riders.

The big catch is that enthusiasts with high disposable income
will view this as too heavy. An easy fix is to have an initial
version with 2 D cells. Then switch to AA's and advertise "xx grams
lighter."

True Or, we can post the device weight w/o batteries and state it
as such.

Seriously, you need to budget power way better. Where is it all
going? Are you using a linear regulator?

Into the FLUX CAPACITOR!! I did mention the device is capable of time
travel, right? We've made improvements from the 1.31 gigawatts
required

More seriously, a DC-DC voltage converter. Linear regulators can only
reduce voltage.


And finally, if you use USB for PC downloads you can sponge off of USB
power and save or recharge the internal batteries.

And that was the design before we consulted FCC regulations. Seems
that it becomes much more complicated once it is attached to a PC.
Having removable flash makes it save us lots of time and money in FCC
testing. Plus, the smallest flash size is 32Megs!! That's a lot of
data you can save!

A future version might include a camera to snap a picture every so
minutes. And the device is designed to be expandible via a
multi-master bus system.

So, who wants to buy some vapour-ware now? If not now, check back
around xmass-time...

Reza


New Question : if the device could have any one "cool" feature, what
would it be?

In article ,
says...

....

New Question : if the device could have any one "cool" feature, what
would it be?

The ability to import your ride data into one of those PC mapping
programs, and plot your times and average speeds along the displayed map.


--
David Kerber
An optimist says "Good morning, Lord." While a pessimist says "Good
Lord, it's morning".

Remove the ns_ from the address before e-mailing.

On Mon, 14 Jul 2003 10:56:58 -0400, archer
wrote:

In article ,
says...

...

New Question : if the device could have any one "cool" feature, what
would it be?

The ability to import your ride data into one of those PC mapping
programs, and plot your times and average speeds along the displayed map.

And the ability to show you sprinting from the Yellow Jersey group at
the end of the ride to leave them in your dust. Even though your ave
MPH is only 18.5!! ;-)

Lindsay
----------------------------
"One of the annoying things about believing in free
will and individual responsibility is the difficulty
of finding somebody to blame your problems on. And
when you do find somebody, it's remarkable how often
his picture turns up on your driver's license."

P.J. O'Rourke