Enable pins on Stepper driver, are they required?

[Neale]

The Huanyang VFD is controlled by the CSMIO and I have been assuming that this will stop on e-stop although I have not checked this. However, I do have a primary Pilz contact going spare and I could wire the VFD run signal via that for belt-and-braces. I have more-or-less finished the control box, apart from some small odds and ends, but the machine isn't quite at the same state. Once I have limit and e-stop switches fitted and wired, I shall be going through the safety functionality that I have. For example, I haven't yet checked the VFD braking characteristics and tuned things like deceleration.

When I say that safety is a compromise this is, obviously, I hope, tongue-in-cheek but we do have to be sensible about this. I am building a hobby machine for a home workshop, and not expecting idiot bystanders to wander by and poke fingers in it. However, I am also moving from the mark 1 built from MDF which is just about strong enough to stand up to its own weight(*) but would self-destruct in the case of any foul-up, to the mark 2 which is all welded steel, including gantry, and could do itself and anyone in its path serious damage. So, for example, accessible e-stops and limit switches all round, but no "open door" detector for the control box. Just trying to steer a sensible course between extremes.

(*) I exaggerate - in fact, it is not quite strong enough to stand up to its own weight...

[cropwell]

(*) I exaggerate - in fact, it is not quite strong enough to stand up to its own weight...

I hope to start a steel gantry build soon - I hope it will stand up to my weight, but I am not light.

Serious question - does anybody use braking resistors on VFD's ?

Cheers,

Rob

[Clive S]

Rob I am sure they do but for the ones we tend to use I personally don't think they are a necessary. But you can alway connect it to the 3 bar fire under the bench

[magicniner]

The Huanyang VFD is controlled by the CSMIO and I have been assuming

My Siemens VFDs have Stop and E-Stop wired inputs, it's this input and not a peripheral device which should be relied upon to implement the E-Stop.
Most good E-Stop switches have at least two circuits to facilitate direct control of the nastiest component of a machine, if it's all nasty then it usually operates a mains cut off but for most lathes and mills killing the spindle removes the most risk, the motor cannot start while the wired E-Stop to the VFD is active.

[njhussey]

I thought I read somewhere in a discussion that cutting power to the VFD whilst it was running was not a good idea and that the best thing to do was fit a timer to then switch off the power after it has been told to stop by the controller?

[magicniner]

I thought I read somewhere in a discussion that cutting power to the VFD whilst it was running was not a good idea and that the best thing to do was fit a timer to then switch off the power after it has been told to stop by the controller?

That's why the decent manufacturers have an E-Stop input on the VFD, you can configure different ramp down and braking for Stop and E-Stop, if you have a braking resistor the E-Stop can be startlingly fast.

An electrical engineer I used to talk to was discussing ramp down time for a circular saw E-Stop with his boss and was instructed to make it stop as fast as possible, his boss arrived later that day for official commissioning and a demo an was surprised to find Chris outside the workshop door with the E-Stop on a long lead, his boss paid for the replacement blade and the floor, wall and ceiling repairs.

[Neale]

I've found a reference to e-stop in the HY VFD manual - it seems that it's possible to define one of the digital input pins to accept an e-stop signal. I need to go through the manual in more detail to find out which of the many parameters will control things like e-stop ramp-down time, or if it just chops output and uses DC braking. I also assume (I'm doing a lot of assuming at the moment) that it will need an external braking resistor to give best results. More research...

My current e-stop switches are built from modular components and are single pole at the moment but could easily have a second pole added, wired either as an independent mechanism or via the second channel of the safety relay. But again, I have to come back to the appropriate level of protection. But then, I'm the guy who removed the chuck guard from his vertical mill as the first action after installing. Instead, I bear in mind that it would be an error to insert finger into revolving cutter.

This thread has drifted some way from the original question about enable pins on drivers, but I don't think that there has been a definitive answer to that one yet...

[cropwell]

Instead, I bear in mind that it would be an error to insert finger into revolving cutter....

Been there, done that, lost a fingernail (but it has regrown, albeit lumpy). This is why I asked about braking resistors, as my little trip to the world of pain was taken while the cutter was on run-down.

Cheers,

Rob

[Neale]

This is why I asked about braking resistors

I've done a bit of googling of HY VFDs and braking resistors and there doesn't seem to be much folk wisdom out there. Plenty on how to make it spin up but very little on how to stop it again. The standard HY stop mechanism (if you just remove "run" signal) is to run down from current frequency to some pre-defined stop frequency at a rate given by a specified parameter, and then either coast to a stop or use "DC braking" according to another parameter. I can't find any specific description of how emergency braking works, but I haven't been through the manual word by word yet. I would have expected "cut power to motor and use DC braking", but in any case it sounds like there is a need for an external braking resistor. The manual does give recommended values for this, and it looks as if they are available from eBay or AliExpress for £20 or so.

[Clive S]

Been there, done that, lost a fingernail (but it has regrown, albeit lumpy). This is why I asked about braking resistors, as my little trip to the world of pain was taken while the cutter was on run-down.

Cheers,

Rob

Rob you should see this then https://www.youtube.com/watch?v=eiYoBbEZwlk they are made commercially they wreck the saw though I think there are types that clamp the blade with an explosive charge like a air bag.