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Electronics for CNC apparates

Last update: 31/07/2015

tb6560 toshiba

It is, nowadays, very common on the market (ebay for instance) to find a lot of controllers based on a very cheap ic: the Toshiba TB6560 considered a modern replacement of the old TA8435HQ. 

 

This IC it is a bipolar stepper sinusoidal motor driver and it is characterized by an internal traslator, microstepping, 3A/phase current, 34V max of power supply, pwm, driven by the usual step/dir/enable pins. A driver IC at first sight perfect to build a cnc machine but with some limits.

Many boards using the tb6560 got broken in few seconds (sometimes even less :-) ) due to small mistakes or misundestandings on the procedure of use of such ics mainly dued to an incomplete reading of its datasheet and application note.

Honestly speaking we have to say that this is a very delicate ic:

  • the power supply must be very well filtered, and a fast fuse on the power supply line must be used;
  • better not exceed the supply of 24V particularly using 3A/phase motors;
  • attention must be payd to the design: grounds must be connected in a single point, if possible, away from the ic;
  • the logic of the ic must be powered before the motors (this is a normal situation for any other driver/controller)
  • the ic must be connected to a large heat sink cooled, if possible, by a small fan because the heat generated could be important.

In very few words it must be used with care.

Here follows a simple schematic for a test board (studied to be easily milled):

tb6560 schema

Schematics are quite simple. Please remember:

  • the value of the resistors connected to NFA and NFB sets the current for the motor according to the following simple formula: Imot=0.5/R therefore using a 0.5ohm the current for the motors is set to 1 Amp;
  • the capacitor C5 sets the frequency of the internal clock. This frequency is related to the lenght of the clock input pulse. Using a 330pf capacitor the frequency will be around 130Khz and the clock lenght necessary to recognize the pulse around 30uS while using a 100pf capacitor the frequency will be around 400Khz and the minimum pulse lenght of 10us.

JP settings table: JP1 (Torque) JP2 (Decay) JP3 (excitation mode):

 

JP1 JP2 JP3
TQ1 TQ2 Torque resulting DC1 DC2 Decay value M1 M2 Excitation mode
L L 100% L L 0% L L 1
L H 75% L H 25% L H 1/2
H L 50% H L 50% H L 1/8
H H 25% H H 100% H H 1/16

 

This is the testing board:

 

tb6560 brd

Unfortunately there are 10 small bridges to be solded but this is a single side pcb.

 

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