Emergency stop

[savarin]

When I wired up the treadmill motor and speed controller on my 9x20 lathe I added a smack down emergency stop button just in case.
Yesterday whilst parting some 28mm dia bright mild steel the parting blade stuck and the speed (very cheap) controller went "PoP"
It must have been the pot because the speed went to full bore but no fuses blew.
I instantly wound the pot to the off position but nothing happened all the while the motor is speeding flat out, the spindle is jammed but the the spring/ball clutch I made performed its magic and spun screaming like a banshee.
Eventually I hit the mains switch at the wall panel.
Why the hell didnt I hit the emergency stop button, I mean, thats what it was there for.
Why am I telling this?
I think if you have an emergency stop you need to practice using it over and over again so it becomes ingrained and if its required you will do it automatically.
Its right in front of my eyes but I never thought of using it.

Now I have a huge problem, this morning the coffee maker stopped working, oh the horror, what do I work on first.
Happy new year everybody.

 

[JShipley54]

Definitely the coffee maker.


Sent from my iPhone using Tapatalk

 

[silence dogood]

"Out damned stop! Out I say!" Shakesbeer version quote.

 

[benmychree]

Personally, I have found that coffee has little effect on wakefulness in the AM, it is time related, not caffine caused. I can use it or not with little effect on the final presence of mind; accordingly, I'd fix the lathe first, the coffee maker second.

 

[Ulma Doctor]

I’m partial to deadman footswitches rather than ESTOP buttons. The deadman is more intuitive than the ESTOP

 

[Winegrower]

I’m partial to deadman footswitches rather than ESTOP buttons. The deadman is more intuitive than the ESTOP

I really agree…The Takisawa has a foot brake/estop all along the front. It’s slow or fast, depending how hard you jump on it.

 

[savarin]

It was the coffee maker, now working fine.
Off to the shed for the lath now

 

[WobblyHand]

It was the coffee maker, now working fine.
Off to the shed for the lath now

Glad you got your priorities straight. I'd never be able to fix my lathe without coffee!

 

[rwm]

I have the same fear about my estop. I never use it so I would not reflexively reach for it.
R

 

[RJSakowski]

I use the E stop on my lathe as a primary power switch. This is because the AC/DC converter is always powered on. Motor control is via an REVERSE/OFF/FORWARD switch and a potentiometer varying the speed from zero to maximum. I had a similar failure when I was purposely overloading the motor control. The MOSFET transistor shorted out, providing full power to the motor. My reaction was the slow the motor down with the potentiometer with no effect and next to stop the motor with the reversing switch. With the motor stopped, I hit the E stop to remove power to the lathe and finally to pull the plug, absolutely isolating the lathe.

The MOSFET that I am using is rated for 100 amps continuous, 250 amps intermittent @ 500 volts so it is a mystery as to why it shorted but it did. @savarin, my guess is that you had a similar event. A DC motor in a stalled condition will not have the benefit of the motor generated back voltage and will see the full voltage of the supply. and a much higher current draw. A MOSFET has an additional failure mode where the transient voltage created by interrupting the current flow can be fed back to the gate via internal capacitance, exceeding the breakdown voltage and creating the short. I have circuitry in place to prevent that but apparently, it wasn't sufficient for the overload. As I recall, SCR's are more robust but it has been many years since I worked with them and the technology may have changed.