[ ] May 2, 2012

Name-Surname Ms. Pornprom NisaimunStudent ID. 54261518

Group Name Instinct

Engineering Team Members M, Kung, Boss, Mic, Yui, Arm, Ball, Garfield, Top, Ice

Product Design Team Members

P’JubP’Ploy

Weekly ProgressI have already tested new charger circuit. First time, I set voltage and current to charge

battery is 8 V and 375 mA (0.25C). It still affect to high temperature of LM317. So I decrease current to 300 mA (0.2C). To limited voltage and current, I adjust RV1 and RV2 from calculation as below:

Time period=60min( Battery ' s CapacityCurrent )=60min( 1500mAh300mA )

¿300minutes ¿5hours

Efficientcy loss20%=300min+( 20 x300min100 ) ¿(30060)min ¿360min¿6hours

Ploss = (Vin – Vout) Icharge = (12 V – 8 V) x 300 mA = 4 V x 300 mA = 1.2 W

Vout = 1.25V (1+R2R1

)+ IAdjRV 1

8V=1.25V (1+ R2240 )+(100uA)RV 1

8V=1.25V +1.25 R2240

+(100uA)RV 1

8V=1.25V +(5.208m)RV 1+(100uA )RV 1

8V−1.25V=(5.208m)RV 1+(100uA)RV 1

8V−1.25V=(5.208m)RV 1+(100uA)RV 1

6.75 V = (5.308 x 10-3) RV1

RV 1=6.75V

(5.308x 10−3)= 1271.665411 Ω

RV2 =V BEImzx

=0.6V300mA

= 2 Ω

PRV2 = (V BE) Icharge = (0.6 V) x 300 mA = 0.18 WAfter testing the circuit, I designed PCB, make PCB, put electronic device to the PCB and

test the circuit again.

Figure 1. Charger circuit

Figure 2. PCB

Engineering Analysis

KING MONGKUT’s UNIVERSITY OF TECHNOLOGY THONBURI

[ ] May 2, 2012

Strong Point- The temperature of LM317 is cool down. - Size PCB of new circuit is same as old circuit.- The circuit can be fined current by adjust RV2.

Week Point- When I connect the contactor between the platform and the body, it is not strong and

sometime the contactor is disconnected.

Next Week JobDo the English report.

KING MONGKUT’s UNIVERSITY OF TECHNOLOGY THONBURI