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.

Bengaluru cyclothon

I was so excited to join this rally that I registered very early, a month, before the D-day Oct 11th 2009.

Participating previously in Midnight marathon and completing a half-marathon of 21.95kms was quite a arduous running task!

I felt cycling is far more easier than running on foot or maybe its because I had enough practice commuting to office for past few days and dropping my cycle at Koramangala indoor stadium (for it to be transported to venue) riding it from my home near Hebbal, the day before the event took place.

Having reached the place a little late due to misadventures(?!) of the volvo buses arranged for us to the venue, I collected the cycle from hangar-2. Stretching the thigh and calf muscles and hydrating enough, We all started off from the same place. We were sent in batches and I noted my time of start to be 9:12am to be precise.

It was an exhilarating experience to be a part of this great event. A "young"old man(you will know the reason soon why i call him "young"),above 60 years of age was cycling a hero jet and rode past me when I had stopped to hydrolyze myself with electral after an hour of journey. To my surprise he was not wearing a BIB but had put a writing on his back which interested me and soon I chased him to find out what was on his back and captured it in my cell phone. It said - "I will never be an old man. To me old age is always 15 years older than I am."(See one of my pics) WOW! That one moment in my life,I enjoyed the spirit of life more than the fun ride of 36kms.

Sad part of the whole cyclothon was I saw fellow cyclists who were carrying broken chains and even pedals of the rented cycles(BSA Mach) which droped off!! after 15-20kms of ride.. There were not many mechanics(or were there any!?) who could get those fixed. And even more irritating was to see the condition of my cycle after transport to the venue. Damn! They had damaged a few parts Handle was not turning fully and freely.. but thanks for not doing any odd-tuning with gearbox.

Volunteers did a good job providing water for every 10-12 kms of ride. It took 1:40 mins to reach back to the base, after completing the 36Km ride. I met a couple of cycling clubs GoGreenGoCycling and Bangalore-bikers and joined them. Raghu Dixit's songs were rocking the crowd when elite race was going on. Actress Pooja gandhi, Actor Manjunath and lots of other celebrities were present in the occasion. BMX stunt biking was a nice attraction. Manipuri boys did great on extended studs of the wheel axle doing a 360 spin. I left the venue after getting refreshed with banana's and plenty of water. Pedaling again back home from BIEC to my place at Sahakarnagar was really cumbersome as I hit Nelamanga's "bad" traffic for the first time in riding cycle. Many cyclists were forced to choose the odd terrains off-road where even two-wheelers can't tread. But to be honest cycles are always faster than cars in such traffic. It was nice to see cycles participating which costed upto 91K(Trek fuel 5-5) INR :)

Hope to join weekend cycling in and around Bangalore. Catch ya guys. Later :)

Operation Manyatha

I always say - "People should have at-least one craze for keeping themselves alive, not as in breathing-air-alive but something like happy-contented-motivated-energetic-alive" :)

Okay, here I go. On evening of this good Friday, I had this crazy idea to commute daily by cycling to office which is at Manyatha embassy tech park and that's the reason why I choose this deluxe title of the post!

To test the feasibility of the above and start this Operation as a successful one, I took the test ride starting from home straight to the office on Saturday evening at 4:00 pm. The cycle was in good shape even after my 80+ kms of pedal-a-thlon :P, a few months back. Inflating of the tires was all that the "food" that it needed this time.

Ears plugged with the I-pod touch speakers which was buzzing the top 25 songs played on it, I traveled in the hot sun which was shining so mercilessly even after mid-noon! As my heart raced (but below the limits :P) It pumped more blood to my brain and amplified my thoughts after a few kms of cycling! I looked back and asked myself..The very 1st question on your mind too by now ;)

What am I going to achieve by commuting on a Saturday evening, just to the gates of office and coming back for about 15 kms of round trip travel without a drop of water with me?

I don't know the reason - What! Why!, But I enjoyed giving a mocking smile at the petrol bunks in my OWN cycle(The first thing I bought from my salary!) where I usually get my bro's bike or my dad's car refueled.

I spread the awareness to use fuel free alternatives and it was like a solo-campaign to save the world from air pollution and depleting natural resources :'( Hope everyone implements it sooner before the D-day arrives.
Having said about pollution, I regret to say that I have found so many plastic bottles, covers and sachets thrown all around the beautiful mountain terrains while trekking.
I learnt from one of our guides during Kerala trip, a few years back, who himself picked up all plastic to put it in nearby dustbin while trekking. No doubt about the literacy rate there.
This reminds me of the quote - "We do not inherit the earth from our ancestors. We borrow it from our children."

Coming back to the cycling, I took the service roads to escape the yamadhooth-like Leyland trucks and for safer journey. They was lot of rush and parking problem that people were facing near Lumbini gardens at Nagawara as it is a new place for holiday outing within the city limits. Dodging all the traffic I came to my office and It is more farther than I expected. Total round trip to-n-fro home costed about 15 kms of pedaling. It took a total of 45 mins and I was back at home by 4:45pm. It was pretty fast indeed!

I will make it a exercise/habit to take this seriously and continue my good deed :D Hope I will keep myself fit till next weekend to say whether "Operation Manyatha" was a success or failure ;)

Cheers,
Karthik Bharadwaj H

Cycling expedition to MaakaLidurga on 26-12-2008

After few days of preparation and amidst my parent's strong opposition, I set out to my longest cycling excursion (till now) in my all new "Hercules ultima shox dx" geared cycle. Actually it was MADE all new, since both tubes were out a few days back and got replacement with a long seat rod to ease my legs. "Total Overhauling" cost me around 230 bucks(looks like I had kept it in good shape). Motto: Take care of your companion so that it takes care of you :)

It was pure fun and most important of all I had been a long way far from all the bondages with this real world for few hours.

Preparation was the most important of all the phases. So I tested myself before setting out by taking it around 20 kms per day within the city for the last weekend.(20th,21st December 2008). Also, I had been to my friend's place on 25th December riding it about 24 kms to and fro Kalyan-nagar from where we went to morning show-ghajini movie. Its going to be all different post so not detailing it out here ;)

Thanks to "The Nomad" and "roastedneutons" travel blog which helped me out in route and also mentally get prepared for this journey.

I packed up the following things before :
1. Lunch (Puliyogare from home)
2. Water (2 bottles of water)
3. 1 pack Glucose + 2 Electral sachets
4. Dates (very rich in minerals)
5. Hand Pump (heaviest of them all)
6. Knife as a tool and also for safety
7. Bandages
8. Relispray
9. Hexagon tool and spare tubes in case of puncture
10. Digicam
11. Cap
12. Towel
13. Torch

Having checked out the route on google maps and having visited Ghati subramanya (10kms from maakaLidurga) a week back, it was not a problem in finding directions.

I started at 5:45 am in the morning and it was still a bit dark coz it is still winter now. As i reached Yelahanka it was getting brighter and soon the orange sun exposed himself at the horizon, behind the trees amidst the fog. It was beautiful to see... time around 6:30am.

(Sunrise view soon after crossing Yelahanka)
(The morning life had already started in the country side by that time.)

The roads were not bumpy and actually were in good condition, properly asphalted. However, It did make me sing the song "bum bum bole" after a while though!So far so good ;) Re-hydration was done every half an hour till I reached Dodballapur at around 8:30am. I had breakfast(4 idlis+coffee+2 bananas) on the way at around 9:00am and again carried on my long journey. Water was not a problem till then as some or the other village approaches for every 3-4 kms of travel.(The only thing is that you should not be totally dependent on mineral water.) I reached destination at around 10:15am.
(My companions on State Highway No. 9)(Bangalore-Hindupur Train leaving from MakaLidurga station as soon as I arrived)(Destination MakaLidurga)(Red mud roads- A deviation to the hill base)(Perfect Countryside)
(Really broadguage!)
(Meet me @ Infinity)(Untouched lake nearby)
(That somebody's me!)
(Bunch of BMS Mech 2nd year students who had camped there a day before my arrival)(Got company for trekking)(The same lake view from half way climbing of hill)
(A centipede-like train below)
(MakaLi Fort still standing)
(Small temple atop)
(Myself, second from right with awesome cook next to me!)
(Supposed to be the birth of the lake water, It was too deep like a well!)

There was a small ganesh temple at the base of the hills. People of the temple are so sweet that they even offered me Ragi balls for lunch after climbing down! They also took care of my parked cycle till I came back (without removing any of the nuts and bolts or monkey testing of working gears or the air in the wall tubes).

After Cycling for about 50kms+Bathing in lake for half an hour+Trekking nearly 3kms+having lunch+sleeping for 45 mins and then climbing down, with half the glucose packet empty, 1 electral sachet remaining and my lunch box empty... I had lost time to plan my journey back and thanks to lorry driver who hitchhiked me back to Dodaballapur(for about 16 kms) which saved me more than an hour and a half or so in my return back to Yelahanka-towards hebbal-back to my place. I took very few breaks and pedalled at constant speed on my way back and reached home at around 5:45pm. It was a memorable 12 hour butt-wrenching journey but(t) also my best ever. I had traveled around 80+ in my cycle! I feel good after the journey. It has increased my appetite a lot ;)

I would like to go for long distance cycling expeditions seriously along with some cyclists/trekkers organization to keep up my passion. Can anyone help me out please?

Cheers,
Karthik Bharadwaj H