CHARGER DURING TRAVELLING

I m just a begginner for microc n microp.And I have a project idea as follows:-there will be an instrument in travelling buses which will provide certain amount of electricity for charging lapi,mobiles,battery chargers etc.certain number of coins will be inserted into that instrument and for specific corresponding time, the equipment will be charged accordingly.For eg:-a mobile needs to be charged for 15 min,then Rs.5 coin will be inserted and it will provide charging.(It may analyse the weight of that Rs 5 coin).
Please help me out in this product oriented project....

Thanking you

hi ssp123
nice idea weight of a coin is gud suggestion but if anyone insert coin type thing then
it consider it also a coin anyhow think about weighting for simplicity to get start