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Electronics for CNC apparates

Last update: 31/07/2015

A really interesting ic to drive, even with microstepping, a unipolar stepper motor is producted by Sanyo, the STK672-080. This is not a real ic but it is a small module, using small surface components inside a resin case. It is really interesting because can manage upto 2.8 amp/phase without heatsink (3.3 amp/phase with heatsink).

 

Sanyo STK-62080

 

It is a common component used mainly for japanese copy-machines. It is characterized by:

  • microstepping (upto 1/8 step);
  • upto 45V supply voltage;
  • upto 3.3A (2.8 without heatsink)
  • step - dir - enable command pins (internal traslator);
  • built-in sensing resistors;
  • pwm;

and it needs almost no external components at all, only a couple of capacitors (for filtering) and a pair of resistors (for Vref settings) will complete the circuitry.

 

There are some limitations:

  • 1/16 of steps it is not a true 'microstepping' because it is obtained generating a step on the rising and the falling edges of the signal pulse. In our environment (CNC machines), therefore, it is useless (we can consider, for this reason, a max of 1/8 step);
  • max input pulse frequency is 50Khz. It means that using a 1/8 microstepping with a 200 steps motor we can obtain, at max, a theoretical 31,25 turns per second.

This is an honest driver anyway, very simple to manage, useful in many circumstances.

sanyo stk-62080

 

stk 62080

 

This is the introduction schematic proposed by Sanyo in the datasheet of the component.

To obtain a safer and pratical schematic we are going to propose a few modifications according to the  suggestions proposed by the application note.

The max input voltage, for safety, has been reduced to 40V, the phase/current is set through the Vref voltage level (from 0 to 2.5V).

The led shows the excitation state monitor.

Excitation table:

JP1 (M1)   JP2 (M2)  
 0  0  full step
 1  0  half
 0  1  1/4
 1  1  1/8

 

 Bom Parts

Value 

C1  1uF
C2  150-220uF 63V
D1  1N4148
JP1, JP2  jumpers
LED1  LED3MM
R1,2  100
R3,R4  1k
R5,R6  10k
R7  2.2K R-TRIMM64P
SV1   MA05-1 pins
IC1  Sanyo STK672-080
X1   W237-136 wago screw connector

 

 

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