[rinthesun]

These single driver boards using the TB6560 chip are available from Amazon for $16, so I ordered one. When it arrived I looked online for a circuit diagram with out finding one. In fact these SainSmart products are notorious for poor or no documentation which does not always mean the product is bad. I then spent 3 hours tracing the circuit and now have a schematic. The only odd part of the circuit is the use of the torque setting. I doubt that they work correctly; however, if SW5 and SW6 are left open then during idle times, no step, the torque drops to 20% and then switches to 100% on the first step. Next we will test the board.

We are at a MakerSpace and cobbling a CNC router on the cheap. Are steppers are all bipolar so the TB6560 should work. One thing I noticed about the ST330 there are no protection diodes on the stepper coil outputs, assuming I guess that the internal diodes of the TB6560 are sufficent. Is this true?

[H500]

Does the design include power supply sequencing circuitry? If not, the chip will likely self destruct.

The diodes are not needed. Mosfets have them built in.

You should actually spend slightly more and buy a tb6600 board instead. They are much better.

[rinthesun]

By power supply sequencing, that the logic power is up before or at the same time as the motor power. The 5V regulator is on the board and is connected to motor power, so logic power and motor power come on at the same time which I understand is acceptable. The board also uses opto isolation.

I have been reading the threads on the TB6600 boards and it is not clear which is the best design.

[H500]

Powering the 5v regulator from the stepper supply might be sufficient, but it's not a certainty. If the voltage rises too fast, the chip might not have time to intialize. You seem to have electronic expertize, so if the chip blows, it would be a simple matter to replace it and then add the sequencer.

As for the 6600, I would go with the lowest cost one. It is impossible to ascertain that the higher cost ones use better components or is better engineered.

[lucas]

I always used a normal transformer with a large filter capactor, the output on these will raise much slower than a cheap switching supply with minimal cap's on the output. The 5V regulator follows the motor voltage and the 5V will be present when the motor supply is at +-7V. Never had a problem with TB6560 @24VDC and 2A max.

As for the 6600, I would go with the lowest cost one. It is impossible to ascertain that the higher cost ones use better components or is better engineered.

@H500: Do you want a PCB of my design to evaluate?

[rinthesun]

I have done a Google search and looked at several TB6560 designs and most use a 5V regulator as this design does without any sequencing circuitry. The ST330 does have one odd thing. The reset pin has 10uf to ground and 10K to +5. That's a 100msec rise time. Will this protect the TB6560 during turn on. All I can think is the designer blew a few out and found that this solved the problem. It's all Chinese to me.

I looked at the datasheet and found the sequencing section. It says the Vdd must be present before the Vm is applied, but no timing is given. There are many designs out there using a regulator from Vm and switching supplies for power, that appear to work. I agree with lucas that an unregulated transformer supply with big caps is a solution. What would happen if you added a large cap to a switching supply?

I will order a Hoyau TB6600 board and evaluate it.

[H500]

@H500: Do you want a PCB of my design to evaluate?

Thanks for the offer, but I am confident that your boards are very well designed. My comment was referring to the boards on Ebay. One vendor was charging $25 for the tb6600 chip alone.