Losing steps/position, again

[AndyUK]

Steppers are generally all rated 2-3Vdc yes?.

My understanding is that if you give a coil on the stepper the rated voltage (2-3V) it will draw the rated current.

If you give a stepper a higher voltage, the current will also increase and the thing will burn up.

But we're not doing that - we're using stepper drivers. These give the motor the full voltage in "punches" to limit the average current to a set value. Therefore its entirely reasonable that the voltage supplied to the driver is important for the reasons Jazz sets out.

Blanket recommendations are dangerous either way - you need to consider all the factors like the steppers inductance and current limits to determine what will blow and what won't. NEMA 17 or 23 is just a mounting size, and has no real effect on this.

[ngwagwa]

See my previous post on this. I have same board.

Is the 5v feed not to the top right of the BOB?

[Doddy]

It's recommended to use a bare ended usb cable from a psu to the board header in order to both avoid PC usb noise and keep board protection.

Have you a link to this recommendation - I have two identical cards in my machine fed from the local supply so I'm interested if I have a dormant problem or not.

[JAZZCNC]

Steppers are generally all rated 2-3Vdc yes?. So if said nema 17 / 23 or 34 (2-3Vdc) were put on the same driver why would I only blow the 17? (unless I didn't change the current output).

I didn't say it would blow it up, I said it would destroy them and this is true. They couldn't handle the heat and that would kill them eventually depending on voltage.

Also inductance. There are Nema 34's out there that are abysmal running on 60V supplies and ideally need at least 120Vdc to work reliably.

Also there are now drivers on the market with direct 240Vac input connections so no need for psu's anyway. These are aimed at nema17-23 size. Why would these not burn them up either?

You'll find that many of the drives that use 240Vac won't run small motors for the same reason I mentioned before, most don't even limit current below 5a. The drives you speak of which use AC voltage and can run Nema 17/23 use Low AC voltage which you transform down from 230Vac and that gets rectified to DC in the drive.

I fit 230 Vac drives all the time and I can tell you that if I fitted those little motors or nema 17 motors to the drives they would be fried within hours. Even with small (4nm) Nema 34 motors you have to be very careful and make sure you limit current correctly because current it proportional to Voltage and you cannot limit the voltage so they get hot.
This is physics it's not me making shit up and just because you haven't experienced it doesn't mean your correct it what your saying. Unless you know it to be true then I suggest you STFU because it's hazardous to components life and even dangerous in some circumstances.

I and many others use 60Vdc at least using larger 34 size drivers to run nema17 & 23 size motors. Even that goes against the grain and it's worked for years.

No it's doesn't go against the grain and it's perfectly acceptable because the voltage is much lower and the motors can handle it. Again physics comes into play and there is an ideal voltage where motors run with-in safe tolerances, most people running more than 60vdc with NEMA 17/23 motors are running past the motor's ideal voltage but only just so it's not a problem. Think of it like overclocking a PC, it works but will shorten the PC's life unless it's cooled better, same shit here.! . . . Running higher than ideal voltages your actually shortening the motors life but who cares because it's going to take years if only 10-20v over but double the rated voltage or more and it won't take long. (unless cooled massively)

[JAZZCNC]

Pictures of currrent control box - I was wrong I don't appear to have a 5v supply.

Can we have a overall pic of the complete box as it will help make things clearer.

[ngwagwa]

https://lozharroplures.co.uk/my_images/11.jpg

I have removed the V5 spindle controller and the driver for the 4th axis.

[JAZZCNC]

Ok looking at that then the original transformer is being used to power the original board at the top. The transformer says 28V (this is AC voltage) which is about right for the drives ending up around 36V when rectified.
The original board will also probably transformer it down to 5V and that's where the BOB is getting it from. Trace the wires from the 5V terminals on the BOB and you'll probably find they route back to this board.

[ngwagwa]

JAZZ - yes the 5v to the BOB is fed from the vertcal 42 pin connector on the Baldor card. I think I would prefer to by a 5v transformer which should then make the Baldor redundant, just have to work out how to do the E-Stop.

I have found the BOB axis controls, they also feed into the 42 pin connector and am looking for the feeds from the board to the steppers (4 found and 2 to go)

[dazp1976]

JAZZ - yes the 5v to the BOB is fed from the vertcal 42 pin connector on the Baldor card. I think I would prefer to by a 5v transformer which should then make the Baldor redundant, just have to work out how to do the E-Stop.

I have found the BOB axis controls, they also feed into the 42 pin connector and am looking for the feeds from the board to the steppers (4 found and 2 to go)

These boards are usually wired as this below. Trace the wiring back just to double check it to be sure.

Shows 5v in on the bottom 3 right connectors. This is likely how it's powered atm.
e-stop P10, limits P12-15, spindle switch+speed all run off the seperate 24v input on the right.

Was at least 5 years ago when I was advised against using the bottom connectors for 5v. Told it's more ideal to modify a usb lead instead due to the protection circuitry.
Trying to re-find information on the net is a pig.

[JAZZCNC]

JAZZ - yes the 5v to the BOB is fed from the vertcal 42 pin connector on the Baldor card. I think I would prefer to by a 5v transformer which should then make the Baldor redundant, just have to work out how to do the E-Stop.

I have found the BOB axis controls, they also feed into the 42 pin connector and am looking for the feeds from the board to the steppers (4 found and 2 to go)

That should be easy enough just follow wires to steppers. If there was a better picture of the original board i could probably tell you. There will be 4 wires per stepper. So look for blocks of 4wires that will probably be same colour wires.

The E-stop is easy enough and you have relays and contactors in there but first, you will need to find their voltages and what other things you need to control. I see what looks like a spindle Speed controller board so this will need to be incorporated into your wiring and safety etc.

To be honest, if you are going to start again with a new controller and drives then I suggest you trace wires and label them, then rip out everything else in the control box and start afresh. It's often quicker more reliable and less confusing.

If you inventory what you have and find the voltages etc and tell me what controller you are going to use I will happily help you work out a wiring schematic.