Hi folks,
decided to chime in after blowing :-( my "China Bang Board" as well and finding later your very helpful thread. Now waiting for the delivery of parts to replace.
Thanks a lot to all individuals sharing the fruits of your personal effort! :-)
After studying the schematic and reading all posts I understand more of the blowing of my drivers and want to forwad my notions:
1.
The 6560 requires to get the 5V first and later it will accept the motor voltage. The schemtic of this board reverses this requirement! :-( Constantly! Let me explain:
The 12V and 5 V regulator along with their capacitors perform a delayline for the 5V supply. It takes some milliseconds until the 5V is stable on the drivers.
Ignoring this the Motor supply is directed to the drivers instantly.
So accept my good advice: DO NOT do what I did - to set a switch between 24V supply and the board. It will blow soon your drivers because of this weakness mentioned above.
If you switch the mains at the input of your power supply you still do not face the power requirements but usually the drivers seem to accept this - most times. But this is still not a recommended use case!
Cause of damage:
The transistors in the output driver are aranged in an H-bridge. It is essential to GARANTEE at every time that within one pole of the H there is only one single transistor switched on at a time. This can not be done without the 5v being stable on the driver! So it is very probable that the too early voltage for the motor drive will open both transistors by itself and a short circuit will occure.
In my case it occured long enough to damge the whole driver. In other cases (switched mains) it will probably crack some parts of it so the output might still do some performance but not full spec or it will be killed later on.
An extra problem seems to be if a motor output is not conneced. My 4 channel bord was connected to X,Y,Z leaving C open. This open channel was blown first. Later Z while not being connected ..... I remember that one of you experienced the same kind of bang. This can be promoted by the heat sink not being connected to GND.
But PLEASE accept my advice. Do not connect the heat sink anywhere to GND. The currents will disturb on their trace other entities of the schematic. It is not just DC current! The best way would be to connect a lead from one screw of every driver to the corresponding ground Pin 10 or/and 15 but NOT pin 6 (this is the 5V-GND - it should not be disturbed by additional driver currents!)
I believe that this power problem is the main problem of all blown drivers. I shared my notions instantly in order to hopefully save some of your boards - wold wide :-)
Give me some days to evaluate some suggestions to face the power on issue.
2.
Reset schematic:
It is good practice to add a diode in parallel to the pullup resistor (cathode connectod to capacitor side and anode connected to supply). This is necessary in order to discharge the capacitor soon when the supply is switched off. If this is not performed you will get no reset after short interruptions of the supply. Proper reset is essential!
3.
Ther were some quesions around regarding the diods in the power input trace to the board. These are usually used in order to protect the board when reversing power and GND acceidently. Omitting these diodes will blow your board in a very very reliable way - in case of pwer reversal.
4.
Some facts reagerding my setup:
- ISEL mill with cutting area of app. 50cm x 50cm, all ball nuts, 2 Proxxon Motors 300 Watt with power supply (bought defect 200 € - only defect = Z home switch :-)
- all stepper motors 4A
- 4 channel china board (this blue one most of you have) - now blown
- PC tower case with PC living downstairs
- in the upper floor live the PC power supply, the driver board just under the roof with component side down and the 20-30V supply in the CD-drive compartment. The case provides an additional blower for this compartment - i will gladly use this support.
Adavantges of this setup:
While feeding this all in one unit through one single cord the unit has a good genuine GND condition. (I hope to omit optos completely later on) It depends on measurements - to be done.
This setup allowes to supply the on board blower with teh 12 V from the PC power supply.
4.
I feel sad because these china men convert such a good motor driver into a problem zone world wide.
Joke: What about Toshiba sponsoring them in order to increase the world wide demand for parts (spare parts) :-)
If you have additional hints for my setup please feel free to comment. It is good practice to screw an idea through different brains :-)
Regards
John