stepper driver

I'm building an electronic dividing head, pinching ideas from contributors to the forum, principally John Haine for the mechanical design and Silly Old Duffer for the electronics. My stepper driver is as photo. I think that 'excitation mode' means microsteps, and Stop current is the current through the motor whilst it's not moving. I also think "1" means on. Can anyone confirm? Any idea what I should set Stop Current to? Any idea what Decay Setting is, and what it should be set to?

Last thing I want to do is release the magic smoke!

Excitation is microspepping as you say. Stop current would be standby or holding current when not stepping. Set as low as you like to provide enough of a 'detent'. It's a worm drive so it's unlikely to move anyhow.

Don't know about the decay setting. I'd set it to 25% and see how you go. (tune for minimum buzz and check you are not losing any steps. What's the part number?

regards Martin

It's one of these TB6560

This link will explain what fast , mixed and slow decay rates do .

**LINK**

i think you will find 25 or 50 % will do you for a rotary table .

1 is on 0 is off ( they are using the 0 and 1 as used in logic instead of off and on ) .

Today I finally got all the loose ends together, joined the various bits and switched it on. Surprisingly it worked first time. Now to fit a motor to a rotary table. Watch this space.

Thanks to all who came up with the mechanical and electrical design, and helped with setting up the driver board. Here's a photo of the completed box

Very neat Duncan....

Looking forward to seeing the rotab conversion...

There's a well documented issue with these inexpensive stepper driver boards., The fact is the designers of those boards did not follow the recommendations set by Toshiba for the power-up and power-down sequence.
There are other minor design faults but this is the one that can lead to total TB6560 failure.

In simple terms the logic (5v) supply onto the IC should be established and stable before the stepper drive voltage is applied to it and should be maintained until the stepper drive voltage is removed . These boards derive the logic voltage from the higher voltage via a 7805 (or similar) making this impossible as supplied.

There are mods that can be done to overcome this problem but they involve cutting of PCB tracks and the construction of a delay module.

The solution to the issue may be to hand by using spare pins of the Arduino, a MOSFET and a few more lines of code.

In depth discussion here. https://www.cnczone.com/forums/stepper-motors-drives/139306-can-tb6560-driver-design-violate-chips-specs.html

Good luck

Edited By Brian Oldford on 15/04/2019 16:08:56

Might be a red-herring Brian. The thread started in 2005 and the last post is dated 5th November 2013. It says:

Hi, has anyone used these cheap single axis TB6560 drivers?

The reason I ask is because I traced both ENABLE and RESET pins to a RC net that will hold both pins low until Vm and Vdd stabilize...

The board looks like Duncan's. My guess is that someone fixed the problem between 2005 and 2013. I'm sure Duncan will tell us when his board blows-up!

Dave

I don't think that's the issue. The datasheet clearly states that the power supplies need to be sequenced, VDD first and then VMA/B on power up and vice versa for power down. The control inputs need to be low as well during power up, for which an RC circuit might help. But the RCs don't solve the problem of power supply sequencing.

Getting the power sequence wrong, mat have no effect, it may result in incorrect operation, or it might fudge the IC. The datasheet talks about internal parasitic diodes and how they are used. I expect that powering up in the wrong sequence causes uncontrolled currents to flow in the parasitic components, which may, or may not, let out the magic smoke.

Andrew

Mine is arranged so that 5v to the driver board is supplied as soon as you plug the whole thing in, and nothing is sent to the control connections until you've gone through the setup routine. Unless you unplug the power supply before it's finished, no signals can be sent after 5v is removed. I hope this is OK. No doubt SOD will confirm or deny (he wrote the software)

Edited By duncan webster on 15/04/2019 18:04:09

Duncan

Is the 5v derived directly or from the higher voltage supply?

Andrew's point is taken.

The software wasn't written with this particular module in mind, though now I'm wondering if the type I tested it on is OK or not! It hasn't blown up yet, fingers crossed.

Anyway, the software starts with a loop that does nothing apart from list what the keypad does on the LCD. No control signals are output until the user presses a key to enter command mode. So far so good, except at least one version of the circuit diagram shows ENA permanently connected to +5 supply; to maintain the start sequence it should be connected to Pin 13, which is coded for that purpose already. (My ENA is permanently wired but it proves nothing - it's a different controller.)

Apart from that, I think power up is OK. Not sure about power-off though because the code doesn't do anything special. I'll have a think.

Dave

This may well be a theoretical problem with the 6560 drivers but I have been using a number of these for quite a few years and have never had one fail. Even if one did fail they are so cheap it would hardly be the end of the world. Also they seem to withstand back emf's when manually turning the stepper motor ( can be very handy with double ended motors when you also want manual control )

Doug

Looking at it more carefully what I said before is wrong. I have a 24v supply which is connected to the driver board and via a 5v regulator to the Arduino. The 5v from the regulator is connected directly to the CLK+, CW+, ENA+ and ENA-. It will be easy to connect these last 4 to pin 13 and arrange a time delay between the Arduino receiving power and pin 13 going high, I'm awaiting SOD comments on power off. Can't see how to make control signals go off before the 24V in the event of pulling the plug out or a power cut. Not sure what Andrew means by VMA/B, mine has +24, gnd, A+, A-, B+, B- on one end EN-, EN+, CW-, CW+, EN+, EN- on the other end

More recent info on these boards here. **LINK**

VMA and VMB are the power pins on the IC that drive the two output stages, in this case 24V. VDD is the pin on the IC that supplies the internal logic, in this case 5V.

Andrew

Having pondered power-off, I think the answer is lemon flavoured. Ideally what's needed is some circuitry to control the power supply and a soft OFF switch. Not rocket science but unwelcome complexity almost certainly costing more than a new controller module!

In Duncan's place I'd be inclined to risk it: although the spec says damage is possible I guess magic smoke is less likely when power is removed.

The module I used is based on the TB6600 chip. It seems more resilient. Although the spec defines a start-up power sequence, it uses the word 'should' and there are no dire warnings as given for the TB6560. In the event Duncan's module blows, I suggest replacing it with the 6600 type.

Oh dear, why is nothing ever easy...

Dave

Things can be easy, it's just that things are rarely Cheap AND Easy!