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.

"Mute" spectator

Today, I left the office at around 6pm and took the way out of campus via the rear exit of Manyatha Tech Park as this avoids me hitting bad evening traffic on Outer ring road. It was a beautiful dusk. A bit sunny as sun was still visible at the horizon shining over the yet-to-be-completed tall concrete buildings around.

I dropped at nearby shell service station for refueling my Enfield Bullet. After top up of fuel tank, I reached out to get a filling of the tires with Nitrogen gas. There was a guy, station worker at that Shell petroleum outlet, who was busy doing his work of setting the PSI units to prescribed values and filling up the front and rear tires as fast as he can. He waved at us and called upon all two wheelers in the queue as he was working parallel on all front tires of all bikes at once and then setting the pressure to a higher value for the rear tires to work smarter. (A nice efficient scheduling algorithm indeed!) But there was a man with his scooter who was in need to break this algorithm and wanted to be FCFS! (First-come-first-served). He was very upset of the way he was waved and asked to wait for filling up of every other bike's front tires to get his rear tire done. He went to manager with a complaint that this worker is showing hands at him and asking others to move ahead of him and break priority. Manager rushed to the place as the guy was still continuing doing his work of filling air. Manager revealed that the guy is deaf and dumb and does show only hand signals to communicate. I said to the man in scooter that he was doing his work in parallel so that it saves a lot of time. But the man left grumbling over the petty issue making a big fuss. The manager who stood next to me said that even though god has given him everything, he shouts over this poor guy who is deaf-mute. At least this guy isn't begging or stealing but doing a service at station for earning some money. The man was already long gone with his two-wheeler to even lend an ear to those words. I stood a "mute" spectator after listening to what manager said as my thoughts lingered around the same but the guy was busy filling up gas for the next car in queue without knowing what all had happened until now.

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

Freedom ride

Sunday - 16th August 2009, One more memorable day in my life.

I didn't know what to name this post, but since my "independent" ride was soon next after independence day I aptly named it so.

I was having one more of a lazy weekend (as usual)... sleeping, sleeping and more sleeping, stuck to my couch, wrapped up in bed, not sure of sunrise or sunset! maybe even the clock had doubts in displaying AM/PM! with awesome drizzling weather outside..this Saturday.

Few of our college friends tried to meet-up for lunch on Sunday noon but in vain. :( So nothing much fun this weekend, I thought and again pillow was my "best friend" till 10.30am on Sunday morning.

Mom called me up to get up and wash my face to come out of just-now-got-up look, for her elder brother had come home to bless her with arishina/kumkum (A custom which is usually observed, similar to Raksha bhandhan in North, I suppose) for the Gowri festival, Next Sunday. How sweet of him to come to our place, I thought.. and so sooner did the thought of me going to my cousin sister's place crossed my mind and that is when I decided to goto Mysore!!! It was already 11am on Sunday morning. Me, not yet having a bath or breakfast, realizing my thought was far from reality but I always am game for making probable things possible :)

Having no commitments/meetings, I had all the time in the world to get ready for 100 mile journey from Bangalore. I got it all arranged in quick time. Had a quick-short bath and light breakfast and bidding a tata :) to my parents I started my bike after a long time. My companion, bullet doesn't give up on me in crisis like this.. It started smooth as if I had "buttered" the inside of the engine the day before! Off I leave to Mysore at 12:15pm packing an extra set of clothes and fueling up in a nearby service station off the Mysore road.

I drove slowly for about 20-30 kms for getting the engine hotter. It was around 2pm when I reached kamat(not a Kha-Mat :P) restaurant, 11 Kms behind Maddur. Jowar roti meals with Brinjal curry(they call it ennegai) is too good a feast when you are really really hungry. I called up my mom to say that I was having lunch at Maddur and mom couldn't believe her ears as she had heard my words as a foolish thought and wouldn't do such a thing in reality to drive away so far!

I disturbed my mechanic a couple of times to guide me to tighten brake nuts(The splashing of rain water to rear brakes lessen the effect of drum brakes) and to check the need for topping up of engine-oil, dust in carb-valve. His solutions worked out well.

It was 3pm already but I enjoyed the ride and scenic beauty around as it was drizzling for few moments and bright sunshine the next. There was no need to rip my bike and go fast as I had already plans to come back next morning. Slow and steady, I dodged some bad part of Mysore road on the way and soon I reached the "royal" city of palaces.

Mysore is not the same as before when me and our family used to live there a decade back. It is stretching outwards just like Bangalore with coming up of ring roads and bypass roads. Those were the days where every road had a -puram attached to it! now replaced by large blocks of vast sites called colony.

It was not difficult in finding way to my uncle's place as I had already known the landmarks. I surprised everyone by my untimely visit and It was nice to see everyone at home. It was a almost a year since I had been to their place. I had loads of fun at uncle's place that evening. We played pagade (desi version of dice game - ludo) which I used to play with my late Grandma during school-days. It brought back a lot of memories. Aunt prepared nice onion bajji.. too good for the chilling weather :) Great to know that little sister's education is going well. Nice to know her ambitions of completing BBM with CS and taking up further MBA in Bangalore university. Youngest sibling sister of all in our family is in her 10th grade and kudos to see that she has joined Bharathanatyam senior in dancing classes. I spent a lot of time looking out for myself in uncle's marriage album and had hearty laugh at "young myself" :D

I went back to childhood looking at the cute barbie doll sisters treasured in their photo-album. Sad, that I dont have my own photos when I was a little kid. I seemed like more of Kamsa rather than Krishna when they used to get me fancy dressed for a photo shootout :P

It was late and heavy lashing rains outside with a bit power cuts in between, we could not go out for strolling around famous Mysore palace. Also I had to leave early next morning back to Bangalore. So I was forced to sleep at 11pm to get up early at 4:30am. Its been ages since I slept so early.. I am quite nocturnal type who usually does not go sleep without seeing 1:00am on clock. But due to the tiredness of treacherous journey biking for hours made me sleep like a baby. I do get sleep anyplace,anywhere in this world, even on a stone bench, when I want to rest ;)

Over-cautious of missing my work on Monday, I got up before the alarm. Ready at 5am, I left back to Bangalore and drove all the 140+kms at one strech without a break! till I reached home. This was my longest non-stop journey. Poor engine had to bare all the torture but I accelerated "with care" :).. I didn't care about my back pain and I couldn't stop anywhere because there was torrential rains from the beginning till the end of this journey and I was half drenched!! Not even Niagara falls come close to seeing of such a beautiful rainfall!

I reached back home at 8:15am and had hot shower to ease my cold numb fingers. But my mind was still numb in memories enjoying a memorable day gone by. I had enjoyed each and every single moment, A real bliss!

The Monsoon ride

We, THE bulleteers scaled a new milestone few weeks back, riding through the everlasting rain and hairpin bends of the western ghats. The treacherous journey was worth the pain.

It was a beautiful friday morning(3rd of july)..an extended weekend "spirit" had already arouse- all set for long distance driving to Ooty(Ootacamund),TN.

It all started with Arvin, Visakh, Jai, Sunil and others organized by crossworks/travel-life with sponsors like Red Bull and Wranglers.

After preparing a list of to-do items like RC book update, Fitness certificate, Insurance, money, fueling up for the ride, the actual ride! then finally comes the last thing on my list(after the ride) a travelogue about the memorable journey. I have been updating and saving this as draft all these writings during weekends as i didn't have time to complete and post it. You know how worth is a weekend for an adventurous Software engineer like me ;)

Anyway, coming back to the thumping and roaring of engines on the state/national highways.. I should say this was my first long bike trip on my first bike which i had driven less than what 900 odd kms that we covered in those three days. Just a month after buying and riding in city conditions, it's a daring task to climb the ooty hill but with guidance of 20+ other bulleteers it was a good experience. It wasn't a drag of any kind but we enjoyed the ride.

Day 1, We met first in the country club resort on Mysore road,(Next to Raja-rajeshwari dental college, kumbalgod) to munch the breakfast, idli-vada-sambar and sandwich. After fueling ourselves with heavy breakfast we got our bike's tuned for long journey. Our mechanic Mubarak (AKA Mumtaz :P), got our bikes ready for long road ahead. Tighting of break nuts, adjusting of carburetor timing.. we reached Maddur cafe coffee day for our introduction session, then we set to our next destination - Gods own country. True to its name. I have been there 4 times now and trust me, Its the most beautiful place in south India i have seen.
Leaving the tread-marks on the Mysore road we passed through the hump-ty dump-ty roads of Gundlupet where our bikes fork oil(for suspension) got warmed up. Landing in the MC resorts of Bandipur we had our lunch and set out to Panamaram, Wayanad for our home stay called ente veedu (meaning "Our house" in Malayalam). We bikers lost time in fixing up of our bikes and cleaning up of rain water logged fuel tanks(Yup! it rained as hell all three days long) and we had to drive all drenched in rain as we touched the borders of Kerala. Following only the boards available but no one else to ask in midnight we somehow reached the place and thanks to the good roads of Kerala. The best roads ofcourse promotes tourism there than anything else. The worst roads can be found in TN and in Karnataka roads are okie but not at all places though..
Finally reaching the place we found our dorms and rooms very comfortable but some continued merry in fueling themselves up with hot beverages. Of course you know I am non drinker, non smoker and Veggie, So i didn't afford any of the "so-called luxuries"! But a lot of caffeine in Red Bull energy drink had its own side effects in going to sleep. I advice not to drink more than 2-3 red bulls per day or you are gonna stay awake even on bed for more than 48 hours, Losing your brain cells instead of liver cells :P

Day 2, was a really round about way of going to Ooty from Kerala. We missed our route-maps and end-up 120 kms away from ooty after riding for severals hours which was actually more than what we had to cover if we started that properly in correct directions. But it is a part and parcel of every motorcycle diary to get lost in country roads and enjoy the serene beauty around or else where is the adventure without getting lost!? We visited a friend of Visakh whom we foLLowed all the way in Manjeri and Chungam..macha.. Chungam Chungam.. :P ( like I repeat.. repeat repeat.. Funny the way he reapeated every place while answering the phone call) Sorry dude for posting it here.. but you made our day of grand leg pulling!
It was 8pm already and 100+ kms of night driving ahead very few retreated but courage, adventure and challenge took over the fears and we hit the roads non-stop till we reached Ooty hill. It was damn cold and misty all the way up the hill. We couldn't see past each other in the heavy precipitation around. Snake-like taillights ahead on the curvy roads was so good to see.. equidistant from each other we followed each other up the hill to reach our place. As planned we couldn't goto Avalanche, in Ooty as we lost time on the way.

Day 3, Getting up late and relieved of the body pains after refreshing bath, We made our way into Holiday Inn @ Ooty, and occupied the whole of car parking lot! I suppose, We scared away a bunch of people who were having breakfast when we came drenched to the luxurious hotel. Food was awesome and we billed around 7000 for a breakfast! We had made it temporary residence in the morning hanging our rain coats and riding jackets around and helmets everywhere.. :P After a photo-shootout in the parking lot we buzzed again riding down the 36 numbered hair pin bends of the ooty hill to reach Madhumalai forest range, a continuation of Bandipur forests in TN. It seemed like we brought rains along with us all the way back to Mysore, as we could see blue-black clouds on our back heavily loaded with water which showed us no mercy even after getting out of the Ooty! We saw elephants with their cubs, Fox, Lots of deers, wild boar on our way back in the morning which is very rare to see even if we go for night safari! Hitting the Mysore road SH-17 again.. It was pretty pathetic to see youngsters trying hard to race our constant speed Enfields which were going past 100 kmph all the way back till we reached Maddur coffee day again for a break. We cheered the other bulleteers we found on the way enjoying the ride more. At last bidding farewell to all those who accompanied three days, i reached back home at 00:00 hours on monday morning.

I slept on my couch with the thumping still ringing in my ears asking me the question "where next?" I wish to do cross country biking for 20-25 days - K2K ride (Kashmir 2 Kanyakumari), I dream to cover the highest motor-able roads in the world on the way from Himachal Pradesh - Leh-Ladakh, some fine day.. I wish I stay true to my childhood dreams, I wish the biker in me still prevails "for years to come in near future" in spite of escalating fuel price/nagging Girl Friend/Fiancée/Wife ;)

Aloha!