My cycle dynamo USB charger - design and principle

Much awaited dream of getting my own mountain bike becomes true last month. :) Last month I bought KHS Alite 500, 2012 model from Pedals and Wheels Malleshwaram. Odo reads around 300 Kms and am loving the rides! First I fell in love with Bullet, then I fell in love with Biking as its even more adventurous and fun. A lot of people get this silly idea in their minds that he is doing a vain attempt to save environment, some say he is over-doing a workout and getting thinner, some even kindle the way I look wearing my cycling attire. But I don't care for what people think because more than all that stuff, I bike just for my own enjoyment :)

Coming back to my original title - USB charger using cycle dynamo. This was my last weekend's plan which I got executed this whole week. My room had become a electronics workshop for a while with smell of burnt solder and also a generator room with the sounds of dragging dynamo over the tire treads. I burned a little of  midnight oil during weekdays in completing this project.

The basic drive for coming up with this charger is to charge my Phone/Camera/GPS device on long touring.
All feature-rich-smartphones have got a weak battery life. Mine is Motorola Defy BF5X 3.7V, 1500mAh which lasts for about max 2 days with CPU underclocking governors of 300MHz and 600MHz in action!

Recently bought a MINI DVR 80, sports camera to shoot my biking adventures which will now be usable if have a all-time-charger on the go!


Having worked on basics of 12V electricals in Bullet it was a pretty easy job to design battery charger for my cycle dynamo. Principles involved are the same and anyone can design it in minutes if you had attended your high school class about non-linear circuits.

AC supply from dynamo -> Full wave rectified (double the AC frequency, using 4 diode bridge-rectifier) pulsating DC -> Apply a capacitor as filter to smoothen out the DC output -> Limit the current by a shunt resistor (simplest electric ballast) -> Regulate the fluctuating DC by putting a IC regulator to appropriate voltage (IC78XX series).

This simple circuit below will explain a lot more:

> The output current varies from 0-1A based on the speeds of the cycling. IC7805 starts to give the output at speeds of 6-7Kmph as the input unregulated DC supply should be more than 8V for IC7805 to kick off.

> The power of dynamo itself restricts the capacity of current it can drive to the IC and thus a decent shunt resistor of rated around 2-3W should be sufficient.

> Capacitor could be more better if its rating is something like 25V, 0.1F. More-the-better. Will hold more charge and thus keeps charging for a while even though you stop for a while during the ride.

> This is not a very efficient circuit but just works for me. I saw better designs on web doing similar stuff. Output current should be ideally 1/10th the Ah rating of the battery being charged from the USB, as there will be chances of over charging and also lessens the life of rechargeable Li-ion batteries. You will need to add voltage comparator and make current trickle when fully charged. Then circuit becomes more complex. But to avoid this I usually connect the USB output to a portable battery power which has got protection inbuilt to cut-off the supply when its fully charged. (Note that, this portable battery power can be charged by other power outlets as well)

Further upgrades would be to put a high rated capacitor like 1F and put some 3W LED lighting for the front and the rear which could lessen the value of current limiting resistor.

Things you need:
1. I found the circuit of full wave bridge rectifier in a damaged wall charger adaptor unit of my WIFI modem at home. It had real good diodes IN5400 which can rectify upto 50V, 3A. A cycle dynamo can never reach that power rating to burn them!
2. Regulator IC costs some 8 Bucks (Courtesy: Famous SP road of Bangalore)/ Or you can find it in some old radios/ Or go to local TV repair shop.
3. Most important of all! Bottle dynamo, Just the generator coil with strong neodymium magnet will cost INR 80. (Hub dynamos will be better as there wont be drag/tire wear)
4. A USB Type A socket (Female pin). (A cheap USB adapter cable which was unused at home)
5. Soldering gun + solder paste + solder wire. (You can get soldering done in nearby electric shop if you are not good at working with PCB)
6. Insulated wires (About 2 meters)
7. A Heatsink(+ metal paste) for regulator. I made my own heatsink with several folds of Aluminium foil as the power dissipation will be less if cycling speeds are around than 20kmph ;) And I don't expect to reach constant speeds of 40kmph during touring.
8. Alligator clips for clamping at the dynamo output terminals. (I use them as its flexible for removal. Saddle bag can hold all of the charger circuit when I want to remove)
9. A digital multimeter to verify that circuit is behaving as expected. (An oscilloscope would be better to view it graphically :P)

With an overall cost of around INR 250 anyone can build this circuit.

Even Nokia has come up with bicycle charger kit but at a whooping cost of INR 1500!!
http://thegadgetfan.com/gadgets/nokia-dc-14-bicycle-charger-now-available.html

http://europe.nokia.com/find-products/accessories/all-accessories/power/chargers/nokia-bicycle-charger-kit/specifications

Some pics of my project:

Final housing of all wiring with charger inside saddle bag.

Had kept my cycle upside down for Pedalling, thus the dynamo reversed!

In my first attempt heat sink was bigger than PCB :P

Rectifier circuit

Constant voltage output of regulator with any output load

Avg output current, 440 mA

USB adaptor PIN

My funny packaging in a organic tea box :P

I shall call this device as Organic USB Charger to Go Green :)

Charging in action, Device getting charged while pedaling

Housing of all cables below the seat.

With just about 20 Mins of cycling at 15kmph you could easily recharge the phone for about 30 mins of talk time / 20 hours of standby time! You can disengage the dynamo from wheel by pulling and pushing a lever when you want to stop charging.

Disadvantages:
1. Drag when the dynamo is in action. (Quite a humming sound at rear which makes the nearby street dogs chase you at times! :P)
2. Tyre wear (I don't think much as MTB tyres are built for more worse terrain)
3. Weight of dynamo (around 200 gms). Wont be much of effort to pull that weight along on an Aluminum frame bike.

Engine-eer!

As a kid I very much enjoyed disassembling all of my toys into pieces and trying to fix it back unknowingly that I will be an engineer someday later in my life :P

Old habits die hard! Even till today I do fix most of the household broken things like changing bathroom fittings and taps, regulators of ceiling fan, Fixing of water pump in air cooler, alarm clocks etc., You may get it done by professional but the happiness you get in repairing it is more worth it. Trust me! :)

Recently my cruel eyes have turned towards my "toy", Royal Enfield Bullet :D I bought the pete's manual for my bike last weekend from Nandan, so called Bangalore's bullet scientist :) and have started doing a study/research on my bike to find out how-things-work in it during weekends. Call it passion or insanity or whateva!

No matter how people ridicule me and poke fun at my craze, someday I wish to open up the whole of engine and put it back as it is with even better tuning done with perfect valve train arrangements. I am quite good at tools but I don't have a set of all tools required. Shopping list of spanners, box pliers is quite lengthy! A single change of engine oil requires about 2.2L(INR 440 bucks), leave alone primary clutch-case and gearbox oil. But it is quite a cheap machine from spares point of view to screw-it-up :P

I refreshed all my high school basics about Bernoulli's theorem to know action of carburetor and see it practically working in adjustment of the idling thump. Basics of alternator/regulator to know the use of AMPs meter and how charging is done using DC output of rectifier. Lenz law to know how induction coil works. First of all the physics behind the 4 strokes design of single cylinder petrol engine - about how linear motion is converted into rotary motion by crankshaft and connecting rods. Knowing how overhead camshaft(OHC), pushrods, rocker arms are used in inlet and outler valve timing. Electrical timing of spark soon after compression. It is a lot of fun than you can imagine if you have a feel for it.

You may ask why I am becoming(or rather mere talking) more like a mechanic now than an software engineer :P
Well, In industry, If you write a piece of code you need to stick to the norms of code readability, re-usability and do everything the C++ way in overriding,overloading but you can't hack your own code to make life simple! :( Lost are those college days when you had all the freedom to obfuscate complex sudoku solvers in 3 liners, Solve Tower of Hanoi using bitwise operators and the simple yet famous "hello world" programs into single line and enjoy them all. There is some internet humor @ http://www.gnu.org/fun/jokes/helloworld.html
Behaving as though you are "seasoned professional" even though you are not one is so much painful like an itching somewhere you can't reach! So I am trying to get back to my instinct of gaining knowledge and learn new things while breaking and fixing it up again :)

Even now I have the habit of adding "Thanks and Regards, Karthik" at the end of this blog as in outlook conversation which clearly indicates the other side effects of becoming addicted to office e-mails :P
Anyway,
Thanks and Regards,
Karthik :D

Fmylife!

People nowadays are so busy that they don't have time not even just to think of themselves.

You can call me selfish or the guy who has no work to do or gone nuts! But I always ask myself questions like - Why am I like this? What is wrong with me? How do I spend the rest of my life the best way that I can?

To be frank, I feel lonely most of the time and I am! Even though I stay together with my family, the word together is merely physical because I sense there is no mentally a good healthy bondage in my family even though I participate in this institution. I shouldn't be the one complaining/revealing about all my personal stuff but I feel this as the perfect outlet for my emotions and I don't even know how rudely I am jotting it down or how many of them I am hurting in writing this! I have been crying a lot within me that nobody notices. It hasn't turned so worst as any suicidal instinct or anything but I do feel a lot insecure even at home. Where else do I find comfort? Don't ask me to meet a psychiatrist as I have been thorough this my entire life till now, me being only closest friend of myself. I resolved into all kinds of music, books, movies-illusions of real life and what not but its all temporary diversion to feel I'm still alive. Everyone needs someone to share your feelings with, to fight with, to love, to care, to feel happy for, to be happy with.

I know that the relations that come through the blood cannot be chosen! But neither have I made really close friends whom I can share the feelings that even I don't trust telling it to my parents.

I DO WANT to live my life happily as possible and have always been in the pursuit of that happyness (with a 'y'). I have practiced and learnt to live lonely life which I know is not a socially good way of being a human being but I have been fighting to overcome it ever since I find a little bit of freedom in my way.

I don't know why even at the age of 22 I still am treated as a 13 yr old adolescent! by my parents. To be precise, I am not allowed to take decisions on my own when they are parents around! Why all the nose poking with my life even after I have started to earn my living? Why parenting when we can take care of ourselves? Always trying to force what they couldn't achieve in their life. Not letting me be somebody different. I hate them when they don't trust me. Won't they ever know that I never gonna let them down. All that I expect them is to wish me that my dreams of life never take me out or turn bad and leave me to achieve it. I feel this whole world is mine to fulfill my dreams whatever they are.

I don't know why I have become such a nerd, a geek now but as a kid I was rather forced to take up studies so seriously that I barely remember participating or rather was never allowed to participate in any extra-curricular-activities that I was so much interested in. I regret for all the things I lost in my childhood just to be a product called "yet-another-software-engineer". There are so many ways of earning a living in this world and I have realized it after seeing the industry for about an year sustaining the heat of financial crisis around. Why is that my career was chosen when I was a kid? I want peace in my life rather than running behind money.

Given a choice, I don't want to be what I am right now. I am pretty sure most of them don't want too! as everyone feels grass is always green on the other side.

I don't know many youngsters are suffering similar plight! but so is my F**ked up life! (I had never ever used the F word even with ** in my blog till now)

Seriously! Where are we heading to?

There are certain important things that the current financial situation has made me think of, seriously!

We are all listening to the words like financial crisis, liquidity , recession very often these days and we all only fear of one thing - "How bad can it affect me!?" A few posts back, I had quoted that only "talented literates" can survive this doom, but my next question was - "What about the rest of them?"

I say the problem is all because of "Engineer population explosion"! Didn't get it quite right?
Let me explain - 3 decades back there were 5-8 engineering colleges per state and now there are more than 200-300 colleges! Churning out on an avg 50000 engineers per year which turns out to be a excess of engineers "on bench" and many even unemployed.

A middle-class family like ours will think of making a fortune in "creating" a software/electronics/mechanical brand product called engineer rather than letting himself to make a living in other low earning professions. Rather, the damn politics in this country and unhealthy reservations in all competitive exams force us to choose and be a part of the IT world of MNC's as they are free from all these.

Forced by the US markets and baseless future trends, the "new born engineer" is forced to work in so damn good projects like developing smart-phones which use symbian/android! Vlsi Chips with integrated HDTV-out, Bluetooth, wifi, FM, camera and what not all on the same chipset! Quad/Octa/Decahexa/ (nonsense) cores for gaming consoles!, All touch interface screen innovations!, Chipsets for showing the numerical display of odometer, speedometer and fuel gauge! He is fascinated by the work/project he involves and he is happy till he gets paid with all the perks ;)

Previously it was necessity which was the driving cause but now its changed to -"Laziness is the mother of all invention". People need gadgets to do everything for them. No doubt it makes life easy but there needs to be a limit for this Idiocracy. Have you ever thought of the number of brands and models of cell-phones in the market now? It will exceed the number of people in the world in few years or it may have already exceeded! We must be having enough number of host PC's and Laptops in this world to exceed the IP address range itself. Do you even use all the features that your cell phone provides atleast once in your lifetime? but yet the market sees a future! how and why?

Instead we need to innovate on something useful to humanity, like cost-effective solar energy trapping systems using mosfets and inverters, Effective farming with current technology, Fuel saving alternatives in cooking and travel, superconductors at room temperatures and levitation, LED lights for street lamps and torches, Eco-friendly houses, Recycling of waste water, Rainwater harvesting. Its time to go back to the basics, food-clothing-shelter-water.

I have started doing my part by commuting to office via cycling regularly. There is rainwater harvesting scheme, We have implemented at our house which partially works. I cook most of the times using microwave to save energy as it is efficient than heating up vessel unnecessarily. I preach only after testing feasibility and lots of practice :) Its the little things that makes life great!

In my opinion, the market is just driving people crazy.. and the already crazy people promote it even more!
Was there really a market for small cars in letting the tata nano out? How many middle-class families are going to invest on a car at this time of crisis? I am sure its going into the hands of Richie rich kid's and politician teen-kid's as a toy! Adding more to the traffic and pollution, the situation will worsen soon.

People need to understand that there are other professions too to choose a career and stop working on becoming yet another branded product themselves!
I read this somewhere - "If you throw a stone at the streets of Bangalore, It is sure either to hit a dog or an engineer!"
So wanna be yet another one who gets hurt? ;)