TB6600 / HY-DIV268N-5A Problems, and possible solutions

For better, for worse, I've been trying to sort problems with my mill (heavily modded Denford Starmill), lately rebuilding the control cabinet from scratch. For reference, I'm using a cheap Chinese Ethernet motion controller (NVEM 5-axis) and the TB6600-based HY-DIV268N-5A controllers, with 40V/600VA drive supply.

Part of the reason for the rebuild was cosmetic, but I was concious that pre-rebuild I suffered occasional skipped steps; post-rebuild (and the introduction of the HY-DIVs) I was getting substantially more missed steps.

The obvious solutions - replace the PSU and stepper drivers, but that's £300 in anyone's money for 4-axis so I thought it worth having a look at what's actually going on.

Firstly, the NVEM controller manual suggests feeding the stepper driver from a constant +5V and switched pulse/direction lines (-ve going). The steppers were losing about 50% of all pulses and the steppers sounded awful.

Measuring the actual signalling the pulse/direction lines were positive-going pulses vs common ground. Rewired for this and the situation was much improved, but still losing a random number of steps (example was on 4th axis, running 0-90 degrees I'd lose 3-8 degrees, clearly still useless). The improvement, however, got me wondering about the stepper driver's opto-isolated inputs and whether these were struggling with saturation of the photo transistor and/or switching speeds.

Now, scoping the signals from the NVEM controller, the step pulses were 2.25us in length. Tearing one HY-DIV apart and examining the circuit revealed the inputs for step/direction were based on 4N25 opto-isolators. Now, these are not exactly fast devices, with the datasheet quoting an optimal rise/fall times in the order of 2-3us (depending on configuration and manufacturer) and supply voltage across the phototransistor. Throwing a scope on the transistor-side of the opto-isolator showed poor transfer performance (and, accidentally touching the base-connection of the transistor miraculously improved the stepper performance greatly. That was enough to make me think hard about whether my problems were due to the short pulse period from the motion controller.

Now, with a normal parallel BOB you can tweak the pulse width, but not with this cheap motion controller.

So, one idea - if people are losing steps with these drivers, try increasing the pulse-width to 5us to see if this improves your situation.

For me, though, I was starting to think of solutions such as pulse stretcher (hint: Do NOT search for that term on eBay, especially if at work. Sometimes I wonder how innocent and naive I am).

However, another solution presented itself. The TB6600 is capable of stepping with 2us pulses, so all I needed was a faster opto-isolator. Problem is, they're like hens-teeth to find.

Instead, I came across the 6N137 device. This is a logic-level high speed buffer device. It's 8 pin DIL, compared to the 6 pin DIL 4N25, but pin compatible if you sit the device 2-1, 3-2, 4-3, 5-4, 6-5, 7-5 on the pads for the 4N25, and you then only have to source a +supply for the pin 8. Don't worry, a picture later will make that clear.

One other problem exists, that the driver had a 51k resistor from the opto-isolator's transistor's base to 0V. This pin on the 6N137 is the enable input, and needs to be floating, or pulled high for the 6N137 to work properly. Simple solution - remove the resistor.

So, for example,

Attachment 22107

Here, you can see that I've remove the 2 6-pin Opto Isolators (lower-right) and the two base-pulldown resistors (just above each opto isolator). I've soldered in 2x3 pin SIL headers for each opto-isolator to accept the replacement 6N137s.

Attachment 22108

Here, I've inserted the 6N137's, bending pins 1&8 away from the PCB (no holes for these). Pin 1 is N/C, pin 8 is +5V. Also, according to the datasheet the 6N137 requires a 100nF capacitor between VCC and ground (pin 5). So...

Attachment 22109

I've strapped capacitors across the supply to the 6N137 and sourced a +5V supply from the SMD resistor near the TB6600.

Reassembled the driver, and tested. A-Axis was perfect - responding to much quicker acceleration and max speed than previous and faultless in terms of lost steps. Tried one of the remaining drivers - back to the usual poor performance. So, an evening in the shed later and I've upgraded all 4 of the drivers and reassembled the cabinet. Operation is now perfect, as far as I've been able to test.

So, lessons:

1) Buy different stepper drivers.

2) Or, if that's too late, start looking at just WHAT your problem is. Don't discount the pulse width from your controller.

3) If you think you are losing steps and increasing the pulse-width doesn't help, have a look inside the stepper driver, and read the spec on the opto isolators on the step/dir inputs. If these are slower than your preset-able pulse-width then think about replacing them.

I can't promise my solution for my problem fixes anyone else's but the solution above has given me what I think is solid performance for very little money.

Happy to discuss further with anyone interested, this was a very brief description of my problem/solution.

Mike

Nice write up Mike looking forward to the next instalment

Nice work Mike good write up

I have a problem with the HY-DIV268N-5A, the 2 Led's turn red with nothing but the power cables connected to it. I have a 48v 10A power supply. My other DQ860 MA driver work great from this power supply. Any suggestions?

Well documented write up, well done!! any news on reliability I assume you have done more testing?


edit: Ok I have purchased one of these as they are cheap as chips!!!!

fully expecting that I have to mod it to make it into something more reliable!! but I have just opened it up after delivery and it has 6N137's fitted already (no caps across the supply pins though) - time for some testing.....

earle


Earle

Quote:

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Originally Posted by Earle

Well documented write up, well done!! any news on reliability I assume you have done more testing?


edit: Ok I have purchased one of these as they are cheap as chips!!!!

fully expecting that I have to mod it to make it into something more reliable!! but I have just opened it up after delivery and it has 6N137's fitted already (no caps across the supply pins though) - time for some testing.....

earle


Earle

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Sorry, I missed this, probably too late now. But, to answer your question re. reliability - yes, totally reliable now, although only just started using the machine again last night but managed to machine a face-plate for a project box without any problems.

Quote:

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Originally Posted by darius12

I have a problem with the HY-DIV268N-5A, the 2 Led's turn red with nothing but the power cables connected to it. I have a 48v 10A power supply. My other DQ860 MA driver work great from this power supply. Any suggestions?

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Hello Darius, I have exactly the same problem with the same driver that I bought 2 days ago. Did you find a solution ? Where you able to solve that problem ? Thx.

Hi,

I'm also using TB6600 based controllers... these super-cheap ones:
Attachment 23660
and they're fine apart from after about 10 minutes any of X/Y axes will die, all indicator lights off on driver, until I power cycle it. They don't seem very warm and they don't auto-recover as you might expect if it were overheating. It's perhaps too different from your circuit but maybe someone here recognises the problem.

Over current? Totally dodgy circuit / waste of money?

Any suggestions appreciated!

(36v 15A power. driving fine using GRBLv1.1. Failed on highest power and the one down from that)

Phil

Phil,

If you could remove the cover and take/post a photo of the circuit board I'd be interested in comparing. Only advice is - when reassembling only tighten the case screws lightly (the plastic mould form for the screw hole tends to float inside the case - so if you tighten the screws too much it will snap the plastic.

Happily! Here it is:

Attachment 23661

the back showing the tiny chip:
Attachment 23662

and the block that sits on it (connected by some purple mat to the actual heatsink):
Attachment 23663

I expected it to be like the 6560 in size! It's labelled S109AFTG - I've been sold a totally different board :grumpy:

Attachment 23664

OK looking into datasheet, the TSD and ISD modes on this chip require more than just disable/enable to recover, so it's probably one of those, and since it's happening towards the end of a job it's maybe pointing more towards TSD error. Will reset heatsinking and try again.

OK, opened all the boxes, reduced clearance to heatsink and replaced foam pads with silicon grease. Heat sinks now getter hotter and no fail yet...

-Phil

Phil,

Useful info there and it sounds like you're making headway into solving this - if so it would be invaluable to add your findings to this thread as you go, for the next poor soul who buys these (I also have 5 of these lying around... definitely not TB6600s, despite the eBay ad claiming them to be so - I think there's a hint as to the max voltage printed on the enclosure - I think (I'm at work at the moment) that the TB6600-based ones advertise themselves at upto 48V operating, whereas your's (and mine) at 40V are the little SMD devices. I'll also caution that the opto-isolators on that board are (according to datasheet) pretty sluggish devices - but chase one problem at a time and see if your thermal solution resolves your problems.

Well, I did the thermal treatment on Y and it didn't overheat and the heatsink got a lot hotter, which is great. I then did the same job on the other axes and put them all back (in different order, probably), this time the Z failed. Now I've heat-treated a spare and swapped that in, so trying again.

Ultimately I'd like to actually buy a real TB6600 controller and try that, anyone know of a good supplier for those? Not seen one in the UK yet that looks pucker, but Far East will do!

Thanks,
Phil

Phil,

These are the ones that I bought...

https://www.ebay.co.uk/itm/Single-Ax...vbgiYCPuIMIsVA


Although my seller went under the name of "bigger*gift", but we all know the Chinese are a little agile with their naming. I think the discriminator is the 50V and 5A rating.

I'd caution, however, the subject of this thread and that mine, bought April/17 required the opto-isolators replacing.

OK thanks, I just bought two that look just like that, with the higher voltage and current rating. I can replace the optos as this thread details.

Meanwhile, I just ran a large job at 2x speed and it made it through the job twice without tripping, so maybe I'll be OK for milling polystyrene - will wait a while before putting the actual lump of wood under it though!

-Phil