One random question: Would it make sense to power the system from an RC NiMH battery? I found one that outputs 1700mAh of 4.8V for the same price or less as a bunch of eneloops to do the same thing with less mAhs here.
How do you charge these batteries, though?
BTW, I don't think I'll want an in-bike charging circuit, as I have read that Nickel batteries should only be charged at room temperature, and, well, winter's coming. I am thinking just to be able to alternate between dynamo and battery mode, without ever connecting the battery to the dynamo itself, instead taking it to my room to recharge.
Another thing I'm considering is using a hub dynamo, since apparently they don't cost extra effort while pedaling, therefore could always be engaged, and the need for batteries would be eliminated. I could use a supercap to power the system during stops. And the cost is about EUR 30 (40 dollars). Any comments?
One random question: Would it make sense to power the system from an RC NiMH battery? I found one that outputs 1700mAh of 4.8V for the same price or less as a bunch of eneloops to do the same thing with less mAhs here.
How do you charge these batteries, though?
BTW, I don't think I'll want an in-bike charging circuit, as I have read that Nickel batteries should only be charged at room temperature, and, well, winter's coming. I am thinking just to be able to alternate between dynamo and battery mode, without ever connecting the battery to the dynamo itself, instead taking it to my room to recharge.
Annoyingly, the computer I am on will not let me view that link so I'll have to look at it later... Most RC NiMH batteries can be bought with a charger and that would probably be the easiest option. If you can get one that it over 5v then it would be better (6v ish). As the voltage of that battery is less than 5v, you are going to need a DC step up circuit still...
I just found an old LiIon cell from a pocket PC (R.I.P.) rated 1,5 Ah @ 7.2V
I still have the pocket pc itself as a charger, I will be conducting some experiments with it in the next couple of days.
one obvious possibility for a waterproof display IS a bicycle computer. It's fairly easy to drive one from an arduino, especially if you only want to display numbers in the range of ordinary bike speeds.
I have been reading that thread with interest but I hadn't really thought of using a bike computer as the display mainly because I don't think I could fit all the data I want on it... I wouldn't have thought it was that simple to connect to... Any hints of how you do it?
When they are done on bike computers they are incredibly inaccurate. You would need a pressure sensor on each pedal at least to make it more accurate...
I am testing the tachometer using interrupts to record the pedaling frequency (right now simulated by button presses).
I salvaged two LiIon cells from an old PDA, powering Arduino with 7.2V!
Also, I ordered MAX6955 and 6956 ICs, now driving a row of LEDs and one 7 segment display over I2C! ;D And they include five general purpose I/Os which I can use for buttons in the handlebars. Perfect!
Small test video here.
Next step: Order some more 7 segment elements, attach the control buttons, write the UI.
It's an arduino set up. I use it on a motorcycle to count and store pulses from the speed sensor. With the count(pulses/second) stored on the sd card, the card can be removed from the arduino cktry., then plugged into my computer.
The data can then be loaded onto a spreadsheet, such as excel, then the data can be used to calculate things that happened over a period of time, speed, acceleration, rpm, make curves on the spreadsheet, calculate derivatives or integrals from the various curves.
I haven't been able to calculate torque or hp yet, but I can graph speed and acceleration curves. If I make any mechanical changes to the bike, those curves will give an indication of any changes in performance that might have resulted from my mech. changes.
I was thinking of taking some old speed shifter levers (I'm converting one of my bikes to single-speed) and trying to convert them to electrical switches - although I haven't thought of the waterproofing question yet :-/
I would have thought that it is too big. How big is the internal diameter of your handlebars?
The lithium ion battery I am thinking of using definitely won't fit in though...
I was thinking of taking some old speed shifter levers (I'm converting one of my bikes to single-speed) and trying to convert them to electrical switches - although I haven't thought of the waterproofing question yet
I don't have any space to fit extra levers on the recumbent I am going to be mounting this on (I made the recumbent too so I may re-make a carbon fibre seat with a space for all of this to be connected which will be difficult to get to with the seat on and will be waterproof).
