Universal ring distributor for stepping motor - Solutions - Huaqiang

Probe domestic switch needle KG-300K, with a head diameter of 3.0mm, is a normally open switch needle.

Single chip microcontroller STM32L151CCU6

Photocoupler

1. Introduction Stepping motors are commonly available in three, four, five, and six-phase configurations. The operating mode varies between single-phase excitation, where each phase is energized sequentially, and double-phase excitation, where adjacent phases are energized alternately. For five and six-phase motors, additional excitation methods exist. The excitation pattern is determined by the ring distributor, a specialized circuit that converts single-phase pulse signals into multi-phase control signals for the motor. Currently, only three-phase ring distributors come in dedicated integrated blocks, which are cost-effective. However, most ring distributors use logic circuits like counters and flip-flops, resulting in complex structures and limited flexibility. This paper presents a universal ring distributor that can be adapted to various stepping motors and any excitation method. 2. Circuit Design Idea For three to six-phase stepping motors, the power-on state can be represented as a six-bit binary number called the status word. These status words are continuously output to control the motor’s operation. The sequence of these status words cycles in a loop, with the period (number of status words in a cycle) and each individual word depending on the motor's phase count and excitation mode. The time between consecutive status words determines the motor’s operating frequency and speed. Table 1 lists common excitation patterns for different phase motors, from which the status word sequences in Table 2 can be derived. Notably, the status word periods for various modes are 3, 4, 5, 6, 8, 10, and 12, respectively, with their least common multiple being 120. A 120-cycle sequence can unify all excitation methods. The general-purpose ring distributor selects the appropriate 120-step sequence based on the selected mode. 3. Circuit Principle The implementation of the universal ring distributor is shown in the diagram. Two 4516 ICs and gate circuits are cascaded to form a 120-count up/down counter. When counting up, the U/D pin is high, and the CLR pin remains low from 00H to 77H. Upon reaching 78H, the CLR pin goes high, resetting the counter and starting the next cycle. When counting down, the U/D pin is low. Once the counter reaches zero, the borrow signal becomes active, triggering the next cycle. It is important to note that both 00H and 78H are flipped within one step. In the diagram, a 2K memory chip (2716) stores the status words for different excitation modes. A 4-bit toggle switch provides the upper 4 bits of the address, dividing the memory space into 16 zones. Each zone corresponds to a specific excitation method. The address ranges and selection words for various modes are listed in Table 2. For example, in the single-three-phase mode, the selection word is 0000B, with an address range from 000H to 07FH. The three-phase status word repeats 40 times in the first 120 units. Although only 120 bytes are needed to define a mode, it is recommended to fill all 128 bytes for smoother transitions between cycles. The lower 7 bits of the memory address are generated by the 120-counter. Each time the counter increments, the memory outputs the corresponding status word. By continuously cycling through the counter, the system generates the desired sequence of status words, with the excitation method determined by the selection word. A small capacitor at the CLR terminal helps eliminate noise caused by counting transitions. 4. Final Status Word Data The final status word data stored in the memory can be programmed using a single-board computer. The 120-counter can also be implemented using PAL or GAI circuits. Testing has confirmed that the universal ring distributor operates reliably and performs stably. Additionally, the storage space and excitation methods can be flexibly adjusted according to specific needs.