Reverse engineered circuit diagram of a motor speed regulator out of a portable pocket tape recorder containing a single motor for all functions. This circuit works amazingly well, keeping the motor speed constant regardless of shaft load and battery voltage.
Unmaked diodes are silicon so use 1N4148. Top transistor is germanium running at Vbe of 200mV But silicon work perfectly fine as well. Resistors are 1/4W CF 5% except as noted. It’s ok to use 4.7ohm resistor in place of choke. Motor power draw under different loading is:
-32mA at 2.4V under zero load freerunning.
-80mA at 2.8V under normal regulated load.
-200mA at 4V under normal maxiumun load.
-300mA at 4.5V is end of speed regulation.
-460mA at 3.9V shaft frozen motor stalled.
Read Source: http://www.members.shaw.ca/novotill/SmallDcMotorSpeedReg/index.htm
This entry was posted on Sunday, May 31st, 2009 at 3:06 am and is filed under motor speed controller.
