Drafting (vehicle)

Drafting is a technique of reducing the drag co-efficient of your motor vehicle by travelling after  the lead vehicle slip stream, the biggest  advantages of drafting is the fuel consumption, which is considerably reduced , I have experimented drafting on highways and I was surprised by the results of the drafting, I sync with a big truck traveling at 60 km/h with a distance of just 5 feet from its bumper, after sync with it I immediately deviated to the other track, keeping the throttle same, and my speed was reduced to 45 km/h which means 25% decrease in speed however there are some tips and tricks for the drafting:

   Always draft with the vehicle of size comparable  to you vehicle size

Keep an adequate distance.

Make sure that the lead vehicle brake lamp is functioning correctly

Never draft in rainy weather. Because the friction of road and tire in reduced thus needs a larger distance to slow down a vehicle.

If the lead vehicle is big as compared to yours, then you can easily keep a large distance.

   If you are on a bike, the best is draft along with a truck. Because in winter season you can avoid the cold breeze easily J

Portable cell charger circuit

If you got a cell phone which you loves, but it don't have enough battery time then this circuit is for you, unfortunately in some 3rd world countries where there is large load shedding this circuit is a must. For making this circuit you dont have to be a circuit genie, its really simple :)

Here is the list of thing you need :

Solder iron (of course :p )
breadboard or vero borad
female nokia or micro usb pin
two way double toggle switch
2x 3.7V betteries (Li-ion)
100uF electrolytic capacitor
330uF electroltyic capacitor
LM2575 regulator IC
1N5819 zener diode
330uH inductor

Now lets get to the point, Here is the circuit diagram,

It uses two li-ion battery, the input is from the cell phone charger pin, the switch is used to toggle between series and parallel connection of batteries, for charging the batteries must be connected in parallel mode, for the operation of the regulator they must be connected in series so that their voltage add up to provide the adequate input for the regulator, the regulator is a switching type regulator which is very power efficient and dont need a heat sink unless you are using it for charging mutilple cell at the same time.