iPhone measuring Watts produced by a bicycle? :O

[Fluence]

I'm with a project in my hands, that i need to build a bicycle that generates electricity with a dc motor and a on-grid inverter. There's no problem here, since i know how to do it.

The problem, is that i need to connect a iPhone on the bicycle to measure the watts produced.

My thoughts are:
How can i connect an iPhone to measure watts?
Is there some software already built to use on iPhone, or i need to make it?
The iPhone only have to measure from 0 to 250W.

I wonder if it's possible...

If it isn't, maybe creating somekind of system, that measure the Watts produced by the bicycle, presents them on the internet, and the iPhone access that page and presents the user with the Watts produced on real-time.

 

[blueroomelectronics]

After you design the current sensor and microcontroller you could either transmit it via WiFi as HTML (no software needed on the iPhone just Safari) or BlueTooth (you'd need to write a custom iPhone app so you'd need a Mac too)

It's an advanced level project.

PS your bicycle will only generate a few Watts. Not a practical electrical generator.

 

[birdman0_o]

Why do you think it will only be a few watts? I think at a good pace he could generate maybe 100W for an hour (after all the loses).

 

[Sceadwian]

blueroom, if the motor is large enough and it's geared properly it will make plenty of electricty, mind you 100 watts for an hour is more than just a minor workout that'd leave the average person dead exausted if they were even able to do it. I'd say a more reasonable goal with a generally fit person would be closer to 25 watts for any extended period of time, more than 30-45 minutes even on that kind of a load you'd need someone in good physical condition.

 

[blueroomelectronics]

Ok 100Watts produced is 0.1kWh or about 2 cents worth of electricity. How much food is required after an hour workout? I also saw the 25W figure for human powered generators, we just don't make efficient power sources.

 

[birdman0_o]

Well if your working out on the machine anyways... I think feeding into the grid is a waste of time, but maybe if you charge your cell phone, you feel as if your workout meant something?

 

[Sceadwian]

Blueroom, no one said a word about efficiency, or mentioned anything about the cost of the electricity we could generate, but your mention of 'only a few watts' is drastically different from the realty of 25-100 watts. I think we're more efficient than most electrical only systems. Sure we can make robots that can put our movement abilities to shame, but take a look at their electrical power usage =) Also keep in mind the bulk majority of human energy is spent heating our own bodies. We might be doing only 100 watts of 'work' but we're putting out DRASTICALLY more total power.

birdman I'm not sure you know what 'feed the grid' means. The houses electrical system is part of the grid, if you're running a bike that's feeding the grid in your home you're supplementing the houses electrical system, so you would be charging your phone if it was fed from the grid.

 

[birdman0_o]

Author mentioned grid-tied inverter, just pointing out that unless you live on a very lonely island, not much point as Blueroom pointed out (energy is 'cheap'). Was suggesting maybe using power to charge a phone, or something "useful".

 

[Nigel Goodwin]

Why do you think it will only be a few watts? I think at a good pace he could generate maybe 100W for an hour (after all the loses).

As I recall, a fairly fit man can usually generate about 60W for an hour - and he might do 100W for short peaks.

 

[carmusic]

then at 60w he could power a small lcd television!

 

[Nigel Goodwin]

then at 60w he could power a small lcd television!

Yes, he could - I couldn't

However, he'd probably be too knackered to watch it

 

[3lectrokid]

If your trying to get money by giving electricity back into the grid it would be a waste of time. even if you could theoretically create about 100watts its still only 0.1kw. Here in the UK we pay around 10p per kwh so to save 10p we would be riding on the bike for 10 hours and that is almost impossible because we are not fit enough and we need to eat and sleep.

If you still want to do this you can use a shunt resistor and measure the voltage drop and amplify it with an OP amp to input as an analog value. You can then use the iphone's TX and RX pins in the connector for serial communications. If it needs to be wireless you can use a XBEE to transmit serial data. Software will then need to be written to read the serial data and decode it and present it to the user

I hope this gives you help on what you are trying to do

 

[peufeu]

Lance Armstrong in his glory days was measured at about 550 watts mechanical power output in endurance mode ; professional cyclists often reach 500... and they can do that for hours. That's 2/3 horsepower, exceptional for a human, especially if you compare the size of a cyclist to the size of a horse ! So those guys do about 9 W/kg.

A fit adult will do about 250 watts endurance for a few hours, 1 kW sprint for 1 minute. Those were about my figures for last summer on the bike. Since I weigh a lot more than a pro cyclist I had about 2.5 W/kg.

An adult bureaucrat will do about 80 watts endurance for a short time, this corresponds to fast walking, most people will start to breathe strong at this level, let's just say modern lifestyle and all-car society really turned us into wimps

If you want to measure your power, no need for fancy equipment, just time your ascent on a known altitude difference. E=mgh, P=E/T

With generator efficiency, if you're in the "fit adult" category you'll get maybe 200W electrical power, of course it makes absolutely no sense to do that as an electrical powerplant (and the electricity generated would be prohibitively expensive), but it would be fun !

At this power output your body (which is very inefficient) will burn about 600W as heat, so you will sweat insanely. If you do indoor cycling without a fan blowing a LOT of air (not too warm) in your face you'll be limited by body temperature (ie you will faint) not by your endurance ! Incidentally the fan would use quite a lot of power ...

Charge batteries with the bike, and power the TV with them, makes the "couch potato" moments a lot more deserved ! lol.

As for the iphone link, here's an idea :

Free2move Bluetooth Serial Port Plug: Amazon.fr: High-tech

your microcontroller can probably speak RS232, so if your iphone can associate with a bluetooth serial port you can easily make them communicate, without knowing anything about bluetooth protocol. You'll need to rip out the MAX232 in the serial port dongle to get a uC-friendly voltage.

 

[jbeng]

Everyone seems to be concerned about how much power a human can generate and efficiency and all that... but from reading the original post, I get the idea this is a school project. I don't think the resulting power output, efficiency and such is all that important to him. I think "getting it to work" is the important part here.

Personally, I like Blueroom's HTML page scheme.

 

[Fluence]

I don't want to make this project to "earn" money from the electricity produced, as you've said before that's totally unthinkable.

I just want to do it, for the marketing.
And to achieve the maximum impact, i need to be able to connect an iPhone (or a "normal" cellphone), to measure the watts produced by the user.

Right now i think the idea it's:

Build a electronic component, that can measure the Watts and send the data to a HTML or PHP webpage.

I have no idea how to make such a device. Can someone give me some ideas?

I'm a web designer i know how to program in HTML, PHP, etc. if, by some means, the electronic component could for example write in the variable $watts and update it in real-time, the Watts produced, i could make a webpage to display and refresh that value in real-time too... and every iPhone and cellphone with internet could visit the page and view the Watts produced. It's a good idea i think.

 

[3lectrokid]

As I said in my earlier post you can use a shunt resistor and measure the voltage drop and amplify it using an OP amp. If you have never used a micro controller before you can have a look at the velleman kit K8055 which is a board that you connect to the computer and you can read voltages and set outputs etc. you will then need to create a program that simply reads the value and then can create a web page for people to see

You cannot do anything like this without either micro-controller programming knowledge or without computer programming knowledge because you need to do decoding of data.

If you can just show the amount of watts used on LED's or similar you can just use the output of the opamp which is just a voltage signal and connect it to an input of a LM3914 and connect some LED's to it

 

[blueroomelectronics]

First start with a digital Watt meter. You're best bet is a microcontroller based solution. Pick a microcontroller to start.

 

[peufeu]

The solution that requires absolutely no technological expertise :

Put a wattmeter on the generator ; put a webcam in front of it.

> velleman kit K8055

That's exactly the solution you don't want : it only works on windows, you need a special DLL, a special driver, you can only use cumbersome languages like C or Delphi, etc.

> the electronic component could for example write in the variable
> $watts and update it in real-time

Hm, your explanation is a bit fuzzy. You have no (or little) knowledge of electronics so you'd be better off with a simple solution ...

Amazon.com: V&A Auto/Manual Ranging Digital Multimeter with USB Interface, VA18B: Home Improvement

"digital auto-range digital multimeter with a USB interface, which can be conveniently connected to your computer to monitor the real time measurements"

This could be a way for you to do it with minimum effort, and you get a free multimeter.

This exact model is probably not the one you want though, because the comments mention you have to use their software (and not your software). But it seems to emulate a serial port so there's probably a way to hack it. Google for "usb multimeter" for more options.

Note this will give you the volts (or amps) not the watts.

You could also use a cheap "USB data acquisition" (google those words) kit with 2 analog inputs, current and voltage, multiply this and you get power. Try to get one which is supported in an easy to use scripting language (some support python which is nice) so you don't have to learn C.

 

[3lectrokid]

If you want to go with the multimeter option there is a way to read the data being sent from it. i forgot the web page but someone hacked the data coming off of it. However I remember the display's digits were sent in text form so it is easily readable by a terminal.

 

[peufeu]

Injecting the power in the electricity network is not only useless, but also pretty difficult to do. Instead, I suggest powering something useful, and noticeable, from your generator. The human motor would be a lot more motivated if seeing visible results ! Like : try some high power LEDs (LUMINUS SST-90) and also a fan to cool the cyclist... you'll come up with ideas.

However I remember the display's digits were sent in text form so it is easily readable by a terminal.

excellent.