What Limit Switches?

**Neale** · 12-12-2016

Originally Posted by Chaz

Thanks. Good info. I'm using 24V, so this will help.

Can you link what you bought please?

Sorry - it was sufficiently long ago that that seller doesn't seem to have them any more. They were "LJ12A3-4-Z/AX NPN NC 4mm Inductive Proximity Sensor Switch DC 3-wire 200mA", which are available from quite a few other suppliers. I paid £23 for a box of 10 but again, prices vary and that was a couple of years ago.

**Chaz** · 12-12-2016

Originally Posted by Neale

Sorry - it was sufficiently long ago that that seller doesn't seem to have them any more. They were "LJ12A3-4-Z/AX NPN NC 4mm Inductive Proximity Sensor Switch DC 3-wire 200mA", which are available from quite a few other suppliers. I paid £23 for a box of 10 but again, prices vary and that was a couple of years ago.

Thanks.

**Chaz** · 12-12-2016

https://www.amazon.co.uk/LJ12A3-4-Z-.../dp/B0053FA8B8 Seems to be the same?

**Neale** · 12-12-2016

Not absolutely sure. These specifically say "iron sensing" or somesuch. Because I don't have the original listing for mine, I can't say what they are. Proximity switches are sometimes iron only, sometimes anything metallic (although with reduced sensitivity, as I understand it). Mine certainly trigger on aluminium. Of course, if your trigger component is iron or steel, then that's not important.

**Chaz** · 12-12-2016

Originally Posted by Neale

Not absolutely sure. These specifically say "iron sensing" or somesuch. Because I don't have the original listing for mine, I can't say what they are. Proximity switches are sometimes iron only, sometimes anything metallic (although with reduced sensitivity, as I understand it). Mine certainly trigger on aluminium. Of course, if your trigger component is iron or steel, then that's not important.

Ive ordered 3 of them to test and see. They should be fine.

Thanks

**Kardacian** · 13-12-2016

Originally Posted by Chaz

Ive ordered 3 of them to test and see. They should be fine.

Thanks

Would you consider using Hall Effect sensors? No moving parts extremely accurate and will outlast mechanical switches. Take a look at these, they run on 5 Volts but I can modify to use higher voltage if needed. They operate in the same manner as a NO switch. However a NC can also be created and will not be expensive.

https://www.tindie.com/products/Kard...ll_prod_search

**Boyan Silyavski** · 13-12-2016

Originally Posted by Kardacian

Would you consider using Hall Effect sensors? No moving parts extremely accurate and will outlast mechanical switches. Take a look at these, they run on 5 Volts but I can modify to use higher voltage if needed. They operate in the same manner as a NO switch. However a NC can also be created and will not be expensive.

https://www.tindie.com/products/Kard...ll_prod_search

Great but 5v and not shielded = Problems

**Kardacian** · 13-12-2016

Originally Posted by Boyan Silyavski

Great but 5v and not shielded = Problems

The voltage problem can be solved easily, what voltage do you need to support. I run these without shielding and have had no issues. What would be an ideal shielding for your environment?

**m_c** · 13-12-2016

Originally Posted by Boyan Silyavski

Great but 5v and not shielded = Problems

That's actually a bit of a generalisation, as it depends on exactly how you're powering things. I keep meaning to do a post on the why and how the problem can be mitigated to a certain extent.

Regardless, IMO limit switches should always be fail safe I.e. NC, as you want to minimise the risk of a wiring fault causing the switch detection to fail.
Plus, magnetic switches on something that could potentially be machining steel?