estop and controller board - Page 1
Forum section: electronics / beginners

author: RockyJones
author_rank: Newbie
timestamp: August 21, 2025, 03:32:32 am
content: I want to put in a physical e-stop switch in my 3D printer.I want to use both a Soft Stop to the controller board, and a Hard Stop to the mains.Here's what I'm think but I don't know if this is right or exactly how to do it (delay).I plan on: 220V Mains / e-stop / Dual Relay (Relay 1 NO) to 24V Board Pin 1, (Relay 2 NC) to Mains. I whack the e-stop and Relay 1 closes, shorts Pin 1 to GND, effectively sending "STOP" command to the board (this part is all OK) a Soft Shutdown. Meanwhile, Relay 2 opens and physically shuts down Mains.I need to make sure there's a delay somehow though, so Relay 1 can do the soft stop before all power is gone. Hoping for wisdom and observations...

author: Fredderic
author_rank: Regular Contributor
timestamp: August 21, 2025, 04:33:10 am
content: I'm sure you'll get much better responses than mine soon enough, but I'd think you'd want a smaller soft stop button, next to the big red hard stop button. Usually, when someone hits that thing, it's because the soft stop isn't working, or they have a body part stuck in the way and they don't want to wait long enough to see if it is.Unless what you're wanting is just that, a soft stop with hard stop backup, in which case ye' ol' 555 would probably do well enough… But I'd still keep the big red hard stop switch handy.

author: BeBuLamar
author_rank: Super Contributor
timestamp: August 21, 2025, 12:38:17 pm
content: Usually on a machine I would make the EStop not to shutdown power to the controller. It would send a stop signal (soft stop like you do) to the controller. The other circuit of the EStop only shut down power to any moving parts that can hurt someone like motors, pneumatic, hydraulic etc...I don't know much about the 3D printer but I would imagine shutting down power to the servo or stepping motor drive, the heat.

author: thm_w
author_rank: Super Contributor
timestamp: August 21, 2025, 11:25:43 pm
content: I don't see the value of doing a software stop before you remove mains power.But if you must have it, as mentioned you can use a 555:https://www.aliexpress.com/item/1005009431431779.html(with an appropriately sized relay).Estop buttonswill generally have the option of multiple contacts. There is no need for relay going to the 3d printer board, you can just use one of the contacts directly to trigger the stop command signal. I would recommend using a NC switch from one of the board IO to the estop, to gnd.Then your other contact can activate the time delay relay circuitry.

author: rstofer
author_rank: Super Contributor
timestamp: August 23, 2025, 05:27:44 pm
content: Many e-stop pushbuttons are mechanically latching, particularly the ones that require a key to restore power. Others require twisting the knob to unlatch I prefer the e-stop to shut down everything, right now! I don't usually wear a suit when running machines but you can imagine how you would want to deal with your tie getting tangled with the workpiece. Right now is good!Google for "emergency stop mushroom". Look for mechanically latching. They will usually have just 1 contact, normally closed, press button to open.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2025, 05:51:40 pm
content: Quote from: BeBuLamar on August 21, 2025, 12:38:17 pmYes. That's the way it's normally done. That means if the E-stop has been pressed accidentally, the machine can continue from where it was, without any problems.Quote from: rstofer on August 23, 2025, 05:27:44 pmYes, the E-stop shall be latching.The OP might need to use a proper safety relay and maybe two contactors, depending on the required performance level or SIL.https://www.motorcontrolwarehouse.co.uk/media/pdf/E-Stop%20safety%20measures%20-%20MCW.pdf

author: BennoG
author_rank: Frequent Contributor
timestamp: August 23, 2025, 05:54:09 pm
content: don't do a hard stop e.g. remove power.your fans for the filament heater cooling will stop also and overheat the filament with the residual heat in the heater.whatever you do put the cooling of the print head at full speed to remove the residual heat.

author: rstofer
author_rank: Super Contributor
timestamp: August 23, 2025, 09:08:08 pm
content: Quote from: BeBuLamar on August 21, 2025, 12:38:17 pmAnd if the emergency is the controller on fire? In my opinion, e-stop means there is a real Emergency and I don't care if I lose position, I'm not concerned about consequential damage, I want complete power down right now!There are other controls for Stop (without losing position) or Stop Heating but Keep Cooling and that kind of thing but they aren't a proper response to an Emergency. I wouldn't expect the controller to lose position if the mechanism hits a limit switch but I would expect motion to stop. I'd have to think about what to do about the heaters.What if I walk away for several hours? Do I want a relay style e-stop so I can include a heat or smoke detector?So many things to consider and they're all complications.

author: Zero999
author_rank: Super Contributor
timestamp: August 23, 2025, 09:37:25 pm
content: Quote from: rstofer on August 23, 2025, 09:08:08 pmAdequate over current protection will mitigate the risk of fire. The controller also tends to be low power and therefore low fire risk. There shall also be an isolator, to safely remove power from the controller.I've designed machines before which use an E-stop and it's common practice for the E-stop to just turn off the power to the dangerous parts i.e. motors, hydraulics, heater etc. More often than not, the controller is required to ensure it stops in a controlled manner: stop category 1.

author: BeBuLamar
author_rank: Super Contributor
timestamp: August 23, 2025, 10:00:20 pm
content: Quote from: rstofer on August 23, 2025, 09:08:08 pmIf you just want to shut the power off and not worrying about damage then simply shut the power off without having to send the soft stop signal. I wouldn't want to have any delay at all for the action of the EStop. Besides adding a delay which is more electronic circuitry which can fail and fails to shut down. And EStop must be failed safe that is if it fails it must shut down the power. Also I want to keep the controller alive so that the EStop can nofify it as what happened and it should do what should be done like increase the cooling like someone said.