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Survey : Weight vs. battery life for bike computer?
On Tue, 08 Jul 2003 20:42:12 GMT, "Cleanbean"
wrote: 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 I wouldn't use a computer with the weight of a AAA or AA. Consider using 2 large watch type batteries. Funny how non-engineer types so blithely recommend something. I got a real kick out of this one. Doug |
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Survey : Weight vs. battery life for bike computer?
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Survey : Weight vs. battery life for bike computer?
On Thu, 10 Jul 2003 05:39:58 GMT, Doug wrote:
On 8 Jul 2003 16:02:56 -0700, (Reza Naima) wrote: Or are you planning to derive speed from GPS? As a user, I'd worry about accurate speed readings in that case, due to signal lock loss. Ooh, Shiny! I just got an idea: If you have GPS anyway, and a wheel-rev counter, you can derive the wheel diameter automatically. A few miles in should be enough to get at least as close as regular bike comps will, and if conditions change (say, you let your tire go flatter or a bigger rider is on) it adapts to that. Dunno if it's computationally feasible, though. Probably is. Just every mile or so (either GPS indicated or revcounter indicated) adjust the wheeldiameter value to match the two. Though there is one problem I can see: If you're, say, doing circles in a parking lot, the GPS, especially at multiple seconds sampling rates, won't be accurate at all. The same goes for if you round a corner: the GPS trail will take the straight diagonal from last-point-before-corner to first-sample-after-corner, whereas you would have had to go around. Perhaps you should just have it as a special "calibrate wheeldiameter now" function to be used in initial setup with a long (nearly) straight piece of road, in addition to the option of setting wheeldiameter manually. For the shinyness factor, flightdeck style gear indications are of course also cool. I wonder if you could make your computer compatible with a flightdeck wiring harness? That'd give you cadence and wheelrev sensors as well as (perhaps most importantly and very hard to do any other way) gear sensors and a couple of control buttons in a useful place, if I remember that wiring harness right. Dunno if that's either practically or legally feasible, though, they probably have patents. Ask your lawyer. factor. You did say "next gen" after all. But I practically described the display a PC would give analyzing the data, so perhaps that's unrealistic. Well, I dunno what chip they're gonna use, but with their energy budget they should have room for one hell of an embedded risc CPU. Certainly on the level of what a Palm uses, possibly on the level of a PocketPC, even. With that kind of processing power, what you just said should almost all be eminently feasible IMHO, up to at least the display resolution of a Palm or pocketPC screen. Various numbers and average of them over last x minutes should be trivial, grahical ride height profile, well, slightly less trivial but should be doable just the same. GPS style mapping would probably be fairly hard, mostly for storage space reasons. OTOH, painting your trail on the map should again be trivial compared to doing the map itself. The user configurable screen layout would probably be best done with the associated PC software -- like the Philips Pronto universal remote controls. What processor is driving all this? How many pixels in the LCD? Indeed. If you wanna do it for a shoestring price, you might need to consider using LCDs from other massmarket appliances and developing your own driver hardware if that's not usable. The cost there is that development costs go way up. Graphical LCDs in the black/white 128x64 pixel format are available pretty cheaply, but relatively small (as a direct relationship, of course). Jasper |
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Survey : Weight vs. battery life for bike computer?
On Thu, 10 Jul 2003 05:39:58 GMT, Doug wrote:
On Tue, 08 Jul 2003 20:42:12 GMT, "Cleanbean" I wouldn't use a computer with the weight of a AAA or AA. Consider using 2 large watch type batteries. Funny how non-engineer types so blithely recommend something. I got a real kick out of this one. My cyclocomp does just fine on one large watch type battery, for years on end. This seems to be a simple case of a misunderstanding of the type of device being discussed (which isn't hard to do from the opening post), rather than any profound misunderstanding. So don't be a selfrighteous prick about it. Jasper |
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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 |
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Survey : Weight vs. battery life for bike computer?
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? |
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Survey : Weight vs. battery life for bike computer?
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Survey : Weight vs. battery life for bike computer?
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 |
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