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The Darlington transistor output has overload protection using a ballast lamp - 12volt 21watt motor vehicle panel lamp. It has a short circuit (power) indicator. The Green power on indicator ia also used to limit maximum speed.
The rectified voltage is stored on a capacitor to smooth out mains voltage variations. The three 1N4148 diodes control the minimum track voltage to about 1.8 volts. This is not enough to drive the average motor and reduces the amount of movement needed of the speed control before the motor starts. The output transistor is a 5 amp rated but must be heat-sink mounted. It should be a TIP142.
---- Running report
Starts a little jumpy and slow speed running somewhat erratic. No feedback used. Some dead band on the control.
The Darlington transistor output has overload protection using a ballast lamp - 12volt 21watt motor vehicle panel lamp. It has a short circuit (power) indicator. The Green power on indicator ia also used to limit maximum speed.
The rectified voltage is stored on a capacitor to smooth out mains voltage variations. The three 1N4148 diodes control the minimum track voltage to about 1.8 volts. This is not enough to drive the average motor and reduces the amount of movement needed of the speed control before the motor starts. The output transistor is a 5 amp rated but must be heat-sink mounted. It should be a TIP142.
---- Running report
Starts a little jumpy and slow speed running somewhat erratic. No feedback used. Some dead band on the control.
LINK TO IMAGE - cab-darl-1.gif
Circuit Schematic
