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ME 445 – H05
Name _________________________
1) A 10 50 W heating element and a TIP 122 Darlington transistor with gain hFE = 1000 are
used in an adjustable heater as shown below.
a) Determine mean power from the heating element when the pot is set at 15 K. __________
b) What should the pot setting be for maximum allowable power? __________
c) How should this circuit be modified to prevent problems if the pot gets turned to 0  ?
Sketch your modification on the schematic below.
d) Repeat a) above using a 24 VAC supply. __________
e) Attach the first page of a TIP 122 spec sheet. How much does a TIP 122 cost? __________
f) Which vendor did you investigate for the spec sheet and price? __________
10 
50 W max
heater
+24 VDC
5A max
supply
POT
TIP 122
Darlington
hFE=1000
NC
2) The Unite MY1016Z3 gearhead motor is designed to operate at 24 VDC. It draws 1.4 A at
no-load speed of 375 rpm. Stall torque is 445 in.lbf with current draw of 103 A.
a) Determine maximum output power in HP and W as well as the speed at which it occurs.
HPMAX _______________
WMAX _______________
at rpm _______________
b) Determine maximum efficiency, the speed at which it occurs and power out at that speed.
MAX _______________
at rpm _______________
HP at MAX _______________
c) Provide MATLAB graphs for torque, current, input power, output power and efficiency as
functions of speed.