New drivers for Denford Mini mill

[robertjenkins]

Hello

I have a Denford Minimill (aka Sherline in the US). I have fried the main control board (long story) and despite replacing lots of the components I'm still not making any progress in getting the thing moving again.

Since the mechanics, motors and power supply are all in good order, I'm wondering about the feasibility of replacing the electronics with new driver boards. But I am not sure what I need. The steppers are sanyo denki 103h7123-0440. They have 6 wires and I think they are unipolar rated at 2A. Does this sound ordinary enough that I can use cheap generic driverse, and if so - any recommendations?

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[dazp1976]

Are these them?
https://docs.rs-online.com/63cc/0900766b8141d50c.pdf

Generic drivers tend to be 4 wires these days. Rarely see a six and I've no clue about wiring unipolar.
However,
Page 87 shows you how to wire them Bipolar.

[Toinvd]

Unipolar needs the six wires, three for each winding . The central wire is connected to the + of the power and one of the others is pulled low by the driver.
For these motors, White and Black are the two central wires. by pulling down orange, the magnetic field of the winding will be in a direction. pulling down blue will reverse the field.
This makes the driver board using less components., but the motor a bit more complicated.
Now the electronics are that cheap we make less complicated (cheaper )motors ( no center tap wire ) and electronics that reverse the direction of the current in the coil.
For your setup,
next, isolate the central wire ( black and White ) and use Orange an Blue for the A+ and A- and Red and Yellow for the B+ and B-
If you need more speed, try using White and Orange for the A+ and A- Black and Red for the B+ and B- this will only use half of each coil, but you have a much lower self inductance.
Run the motors for 10 minutes, and check the temperature cold means you can increase the current. if they are real hot ( you can hardly touch them ) decrease the current.
You should check your power supply output, and find drivers that can handle the voltage.
If the voltage is below 40V you can go for the cheap TB6600 on Aliexpress Even if they don't use the original chip, it's fine for the low current that you need. don't go for the TB6560

[robertjenkins]

Fantastic, thank you. According to the datasheet the correct voltage is 24V so this is what I will give them.

[robertjenkins]

In fact, although the datasheet says they are unipolar, the documentation for the mill says that only four of the six wires are used: red, black, orange and white. Blue and yellow not connected. So how would i wire them?

[dazp1976]

In fact, although the datasheet says they are unipolar, the documentation for the mill says that only four of the six wires are used: red, black, orange and white. Blue and yellow not connected. So how would i wire them?

According to data sheet bipolar.
Looks to me like
red blue yellow orange.
A+ A- B+ B-
Can't be certain but looking at other 4 wire motor types datasheets, that's how it looks to me.
May need trial and error.

[Toinvd]

If your mill uses 4 wires for each stepper motor, so it will be Bipolar. Your motors can be connected Bipolar
A+ and A- are the connection for one coil, Connect White to A+ and Orange to A-
B+ and B- are for the other coil, connect Black to B+ and Red to B-
If you motor turns in the wrong direction, you can reverse it by connecting Black to B- and Red to B+
Take care, NEVER disconnect or connect a motor wire while power is on. ( it's one of the best ways to kill a driver )

[robertjenkins]

OK thanks. (What could possibly go wrong? ...)

[Toinvd]

The motor connections are coils connecting or disconnecting them can give high peak voltages, and that's what blows the electronics in the driver when power is on.
As long as you don't do that, there is hardly anything that can go wrong.
put the settings at 2 A and start running the motor at a low speed.
If the speed is to high, the motor won't turn, but makes a sound and vibrates. This won't hurt your motor or driver, just stop and try a lower speed.

[robertjenkins]

Well something is not right. I connected the wires as suggested. I am sending the pulse from the BOB to pul+ and the direction to dir+ These are getting through as shown by the 'scope. I don't have pul- or dir- connected.
There is no movement from the motors but there is 18V on all A/B wires.
I tried connecting the ENA+ and ENA- to 5v and GND but it made no difference.

[dazp1976]

Well something is not right. I connected the wires as suggested. I am sending the pulse from the BOB to pul+ and the direction to dir+ These are getting through as shown by the 'scope. I don't have pul- or dir- connected.
There is no movement from the motors but there is 18V on all A/B wires.
I tried connecting the ENA+ and ENA- to 5v and GND but it made no difference.

Why don't you conect the drivers properly before playing with the motor wiring? 1 thing at a time! and you wonder why you had no movement!.
Generally:
Pul+, Dir+, Enabl+, ALL connected in parallel to 5v+ on power supply (or 5v bob output if it has it).
Now for bob:
Pul- to axis pin xx, Dir- to axis pin xx, Enabl- to output pin xx. (xx being whichever pin you programmed for these functions.

(Most times enable is not nneded as drivers are generally enabled by default but we'll stick with it for now).

Now you have that sorted. You can ignore the drivers and fiddle with the motor.
Connect 4 of the wires AABB, power on and test.
No good?
POWER OFF.
Try another connection combination AABB power on and test.
No good)
POWER OFF
Try again etc.
If you look at a few datasheets from some bipolar 4 wire motors and compare the coil sequencing you may be able to figure your bipolar wire combination straight away.

You won't damage anything doing this as long as you power the driver OFF completely inbetween. All I've ever had is a loud buzzing, that's it.

My veiw is you'll do more damage pissing about with the scope as you are, with only this little bit and that little bit connected. You may already have done.

[Toinvd]

Good that you mention that you didn't connect pul- and dir-
Like Dazp1976 said, Pul+ and Pul - both need to be connected, the same for Dir+ and Dir- the same for Enable
For test, even when pull and dir are not connected, check if your stepper motor is energized. you know this because the motor should be locked in position.
Switch of the power and you can rotate the motor by hand.
If the motor is not locked with power on, make a picture of your connections and tell us the type of driver you are using

[robertjenkins]

I don't quite understand the criticism. I connected the driver, connected the motor, turned everything on, nothing moved. I measured the voltage on the A and B pins - a constant 18V. I switched off, disconnected the motors and used the scope to see whether a signal was getting in (it was) and whether a signal was coming out (since the motor might have been faulty and potentially grounding a signal when connected. However, even with no motor there was no signal on any of the output pins). I'm not sure any of this was illogical or counts as "pissing about". Anyway, I will try the wiring you suggest, for which thanks.

[Toinvd]

Good that you mention that you didn't connect pul- and dir- This is no criticism, but a positive thing, we know this way that you didn't know Pul+ and Pul- are always both needed.
There is a LED connected to these two connections ( with a current limit resistor ) if - is connected to Gnd and + to the +5V the LED is on and that's the positive signal.
But let's go on getting this to work.
Take one motor and disconnect the wires. don't let any of them make contact to each other.
and then feel how much force you need to rotate the motor by hand.
Connect White and Orange together.
rotate the motor again. It should be realy much harder to rotate. if so, then this is one coil
Disconnect these and connect Black and Red together.
rotate the motor again. It should again much harder to rotate. if so, then this is one coil
Disconnect these and connect white and black together.
rotate the motor again. It should be easy to rotate. if so, then this is not a coil
If this test does as described, you can connect White to A+ and Orange to A- and Black to B+ and Red to B-
Leave Pul+, Pul- Dir+, Dir- EN+ and EN- disconnected, only connect power to the driver. Set the driver for 2A
Power up and try to rotate the motor by hand. If this goes easy, the driver is not enabled or bad.
If it's trying to hold position, that's fine the driver is enabled.
Next step. power off
connect Pul + to +5V from the controller and Pul- to the Pul output of the controller.
Power up, and see if you can rotate the motor from the controller program.
Let me know the results and we will follow up.

[robertjenkins]

OK thanks for that.
White/orange and black/red are definitely coils. As you say, they resist turning when the pairs are shorted. Also my inductance meter shows 3.5mH each which is the right ball park
But when power is connected, they do not seem to be energised - they are still reasonably easy to turn.
The driver unit is getting 24V OK.
Unless you have a better idea it seems like the driver might be dud

[Toinvd]

Which drivers are you using, are they separate drivers for each motor and do they have Enable input. if possible, make a picture of the driver
If yes they have Enable, is anything connected to the enable ( check voltage between En+ and En- )
If there is no voltage, supply 5v between En+ and En - power up and verify is the motor is holding position.
24V should at least be enough for the driver to hold position rather strong .

[robertjenkins]

I'm using separate drivers like this
https://www.ebay.co.uk/itm/352981992806
At the moment just using one, for one motor.
There is no voltage on the EN+/EN- pins. (There is also no voltage across any other pins)
I tried putting 5V across them. No change. The whole unit is drawing about 25mA which is obviously not enough to drive anything

[robertjenkins]

OK - the driver module was faulty! (Maybe I blew it up but I don't think so).
With a new module, it's driving the motor fine. Now I have to get my head round the microstep settings but that can wait ...
Thanks for all help.

[hanermo]

Great stuff !.
Congrats on getting life aka"hello world" movement.

Usually, with steppers I found that connecting disable meant the stepper stopped resisting manual movement.
This was really good for manual use.
No cogging.
I mean, with gecko 201, 203v, 231 (iirc, the small ones), the disable signals being connected,
even with no power to the drivers, means the steppers run smoothly with no cogging when the disable line is connected.

Likewise, connecting the steppers powered up, but even with no pc or sw to direct them, was a great electromagnetic break aka hold.
The disable line stopped all axis movement, very firmly, very accurately, and with a soft-fail option.
Having the disable line connected reduced the cogging of a stepper, drastically.

Even with no power to the stepper drivers.
The back emf energises the gecko series drivers.
Not so with the better chinese drivers.

With newer, better, e.g. 542-line, chinese stepper drivers, the disable line is likewise useful.
It also allows for a very very good em break, and mostly avoids the screws turning or position being lost or moved even while powered off.

I´m using ac servos, now, and the above is mostly from memory and experience over 4 types of drivers and past 16+ years.

Most important advice.
Connect the disable line !
It makes for a great break and a great reduction in cogging otherwise.
A stepper with a disable line connected DOES NOT cog like it normally does.

Disable connected but off means the stepper turns smoothly.
On means it´s locked.
Disable not connected makes the stepper turn very chunky, about 1/16 per turn and resisting manual turns.
Connect the disable line !

I use disable to lock my lathe axis, when needed, for semi manual machining.
Even with ac servos, these days.
Works extremely well.

[dazp1976]

Hello

I have a Denford Minimill (aka Sherline in the US). I have fried the main control board (long story) and despite replacing lots of the components I'm still not making any progress in getting the thing moving again.

Since the mechanics, motors and power supply are all in good order, I'm wondering about the feasibility of replacing the electronics with new driver boards. But I am not sure what I need. The steppers are sanyo denki 103h7123-0440. They have 6 wires and I think they are unipolar rated at 2A. Does this sound ordinary enough that I can use cheap generic driverse, and if so - any recommendations?

I just came across this. I did not know this and is helpful:
https://www.omc-stepperonline.com/do...per-driver.pdf
If you look on page 9 section 4.3 it shows 2 ways to connect a 6 wire motor to a 4 wire driver
1 is half coil mode for higher speed
2 is full coil mode for more torque

It suggests: Orange, White, Red, Black, AA- BB- for option 1. (speed)
It suggests: Orange, Blue, Red, Yellow, AA- BB- for option 2 (torqe)