Advertisement

Posts Tagged ‘small dc motor control’

Toy Motor Driver Circuits

This is an actual reverse engineered circuit diagram of the one transistor circuit most commonly used to drive Permanent Magnet DC motors in childrens’ toys. This type of circuit almost always uses the 625mW version of the ubiquitous 8050 or 8550 transistor. It is vital to note that there are two different varieties of each of these two transistors, and although they are often stamped with the same part number, they are not interchangeable because one is a 625mW part with a higher VCEsat, while the other is a 1W part with a lower VCEsat. This is very confusing because you often have to run tests on these transistors to tell them apart! The important feature to note about this circuit, is that the maximum power delivered to the motor is normally designed to be limited by the VCEsat of the transistor, and almost never by the HFE or base current. [...]

Read more source:

http://www.members.shaw.ca/novotill/ToyMotorDrivers/index.htm

Small DC Motor Speed Regulator

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