Motor sizing

Servo motor(1- For up and down movement of the pen)

Mass of the body to hold (m)=0.03kg

Diameter(D)=0.02m

Acceleration due to gravity =9.8m/s^2

coefficient of friction=0.45

Force

F=mg* coefficient of friction =0.294*0.45 =0.1323N

Torque(T)

T=F*(D/2) =0.1323*(0.02/2) =0.001323 Nm

Considering Factor of safety FOS=1.3

Final torque =T X FOS =0.001323 x 1.3 =0.001716Nm

Therefore,the required specifications of servo motor is tower pro SG 90 @12v

Servo motor(2-For movement of plotter along X and Y direction)

Mass of the bot(m)=2kg

Diameter (D)= 0.03m

Acceleration due to gravity (g) = 9.8m/s^2

Coefficient of friction =0.45

Force=mg*coefficient of friction

F=29.80.45 =8.82N

Torque

Torque=F*(D/2) =8.82*(0.03/2) =0.1323Nm

considering factor of safety (FOS)=1.5

Final torque =Torque X FOS =0.1323 X 1.5 = 0.19845 Nm @12V

By comparing with the table of specification 0.1984 kg/cm rated torque

Required motor specifications : Tower MG90S @12V

Battery sizing

Components	Quantity	Voltage Rating	Current Rating
Servo Motor(2-Tower Pro MG90S and 1-Tower Pro SG 90)	3	12V	700mA
LCD screen	1	5V	200mA
Arduino	1	5V	100mA
Potentiometer	1	12V	2000mA
Buzzer	1	5V	30mA
IR receiver	1	5V	20mA

Total Current drawn: 4450 mA

For Time=2 hrs

Battery Requirement= current drawn * time

For 12V,

Battery Required= current drawn * time =4100*2 =8200 mAh

For 5V,

Battery Required= current drawn * time =350.0015*2 =700 mAh

Total Battery Requirement= current drawn X time = 4450 mA X 2hours = 8900 mAh

Battery Capacity required for 5-12volts = 9 Ah

Therefore,We require Battery of 8900mAh(9Ah),12 V battery to run our bot for 2 hours.