Micro switch safety do not want 240v in micro switch

David Waldron · Nov 18, 2024

Hi there, I have a donkey saw (hacksaw) that I have restored, new wiring etc, and put on a KEDU NVR on/off switch. There is an emergency stop button and I believe it is a relay that controls on/off (Am new to this so relay may not be the correct word). The relay has 13 (neutral in) and 14 (Neutral out, from motor) and 23 (power from stop button) and 24 (power to motor) on it.

What I would like to do is safely wire in a micro switch, so that when the switch closes, the motor to the machine cuts off. The micro switch I have has common, NC and NO connectors available.

How best to wire this up to minimise any risks.

Spoon · Nov 18, 2024

Not wanting to put a downer on your efforts, but when the word "safety" is used it's best to leave alone.
Depending on what category of safety is required depends on the wiring and what electrical items are needed.

Not that I fully understand what you are trying to do with this micro switch or how you are going to wire it into the existing circuit....

Andy™ · Nov 18, 2024

Spoon said:
Not wanting to put a downer on your efforts, but when the word "safety" is used it's best to leave alone.
Depending on what category of safety is required depends on the wiring and what electrical items are needed.

Not that I fully understand what you are trying to do with this micro switch or how you are going to wire it into the existing circuit....

sounds more like the bottom switch that's triggered once its finished the cut to switch it off automatically. not a 'safety' device as such

David Waldron · Nov 19, 2024

Andy™ said:
sounds more like the bottom switch that's triggered once its finished the cut to switch it off automatically. not a 'safety' device as such

You are cprrect Andy, should have explained a bit more. The machine is cutting, engagement is achieved through a dog clutch, when the cut is complete the blade lowers a small amount further, around 1cm, and the dog clutch disengages, this means the machine stops cutting. However the motor is still going and the belt is still going around. There is a safety shroud on the whole belt and motor mechanism, so this is safe. i dont like the motor still going, and would like to turn this off. I could wire the live through the micro switch, but the reason was in wiring the live in this manner it is taking high voltage through the micro switch (it is designed for this). Was just wondering if there was a cleaver way to access the on/off switch relay through the micro switch, rather than using the micro switch to cut the live.

UNG · Nov 19, 2024

I think an industrial limit switch would be a bit more robust than a microswitch for this application

David Waldron · Nov 19, 2024

UNG said:
I think an industrial limit switch would be a bit more robust than a microswitch for this application

I was thinking of something like this. When machine body lowers it would push the switch down. My main concern is running 240v through this. No wires would be exposed, but would rather have the switch trip the on/off relay that is part of the main mechanism, but not sure if that is possible.

mainline · Nov 19, 2024

A contactor that uses a lower voltage to switch.

You would need to add a power supply, but cost is minimal.

David Waldron · Nov 20, 2024

mainline said:
A contactor that uses a lower voltage to switch.

You would need to add a power supply, but cost is minimal.

Thanks, looked it up, some are integrated, take 240, and switch on 12v. I did not know the word of the thing I was looking for !, this will do it I think, will do some testing.

Geoff1946 · Nov 20, 2024

I was wondering if these devices guaranteed isolation of the low voltage side, but when I look up that part number it has a 220volt coil (?).

UNG · Nov 20, 2024

You have provided no information on the motor you are using on this machine and having looked up the NVR control you are using it is looking like you are creating a disaster that is waiting to happen
The relay you link to the switching duty of AC7b which is rated at 7A is probably not sufficent for your requirements also I doubt a donkey saw fits into the category motor loads for household applications
What you are proposing would be better handled by an appropriately sized motor starter with a 24v control circuit that any safety and control devices you need can be integrated into

UNG · Nov 20, 2024

Geoff1946 said:
I was wondering if these devices guaranteed isolation of the low voltage side, but when I look up that part number it has a 220volt coil (?).

It is available in a range of coil voltages when you dig into the specs

Geoff1946 · Nov 20, 2024

UNG said:
It is available in a range of coil voltages when you dig into the specs

I obviously didn't look deeply enough. Still wondering about isolation though.

Micro switch safety do not want 240v in micro switch

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