How to make a simple driver for the engine of an old HDD
The device is an electronic commutator and is designed to work with low-power brushless (otherwise brushless) electric motors, provided their windings are connected in a star. A typical example of such units is the disk drive of classic hard drives of personal computers.
It is distinguished by its circuit simplicity and is assembled using non-scarce parts that are well represented in online trading.
Circuit features
The device is made according to the circuit of a 3-phase multivibrator based on field-effect transistors with an insulated gate, the individual single-transistor stages of which have an identical structure and are connected in a ring. Each previous stage of such a ring controls the operation of the subsequent transistor. The drains of the transistors are connected directly to the motor windings.
The time the transistors of the circuit remain in the active state is determined by a serial RC circuit, the voltage from the middle point of which is applied to the gate.
The schematic diagram of the device is shown in the figure.
- high-power field-effect transistors IRFZ44N with N-type channel – 3 pcs. - http://alii.pub/5ct567
- resistors 1 MOhm power 0.25 W – 3 pcs. - http://alii.pub/5h6ouv
- capacitors 10 nF – 3 pcs. - http://alii.pub/5n14g8
The transistors are equipped with a plate radiator, which has a direct galvanic connection with the drain. Taking into account the low power of the controlled brushless electric motor, there is no need to fix the radiator on a housing with low thermal resistance. The pinout and the recommended bending direction of the leads during assembly are shown in the figure.
Manufacturing of the device
The device circuit is quite simple and does not necessarily require the use of a circuit board. Taking into account its in-line structure, a wire bus with a diameter of 1 - 2 mm, which is connected to the plus of the power source, can be used as a power-bearing element. The common terminal of the windings is connected to the minus of the power source.
Connects to a three-phase hard drive motor with a common wire.
During assembly, it is necessary to monitor the absence of short circuits between individual non-insulated connections; if necessary, cambrics are used.
If there are no errors in the circuit, the device begins to function immediately after applying constant voltage. The motor rotor speed can be changed by replacing capacitors or resistors, and all installed passive components must have the same rating.
