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[ ] 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
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