View Full Version : Pilz Relay info

07-06-2013, 12:08 PM
Hi all

I need some advise on the workings of Pilz relay's , namely a PNOZ 1 with 2 channels.

I purchased it as used item from a gentlemen on this site, but i cannot remember who, what with getting older and failing memory, and losing my laptop in a small fire, along with all my info and contacts, so i am starting all over again, and before someone say's it, i will take a back up copy this time.

I have nearly finished wiring my new CNC control cabinet, i followed the instructions given to me on how to set it up the Pilz, but for the life of me i cannot get it to work.

When pressing the reset button, i have installed, i can hear what i think is a relay clicking in and out, but i cannot get the channel lights to come on, therefore the Pilz is not energizing, can anyone help?



07-06-2013, 03:14 PM
Hi Ray,

That would be me.! You didn't actually purchase from me, I purchased it for you from Ebay if I remember correct.?
I tested it before sending to you so know it works so suspect you have something wired wrong.?
The first place to check would be that there's a Jumper wire between X1-X2 if this is not present then it won't energise. (Think I left one connected actually.?)

Next check the switches and/or E-stop connections between T12/T22 and T11 are NC (normally closed) type and working correct.
Both T12 and T22 need to connect to T11 for the Relay to Work.

Now when the Momentary Reset button connected between T33 & T34 is pressed the Relays should energise switching the contacts and the Channels light up.

Best way to test the relay is to disconnect from switches etc and put jumper wires between X1-X2 and Between T12-T22 to T11. Then when T33 & T34(reset) are shorted the relay will energise and stay energised until any of the above connections are broke.
This is how I tested the Relay before sending to you.

If you tried to contact me and I haven't replied then very sorry but unfortunately serious family health issues have kept me off the forum with little time for anything else, even answering emails with lots getting missed or put to the wayside for later but unfortunately getting forgotten about.!!

23-04-2014, 01:44 PM
Many Thanks

I was having a senior moment, i new i had asked that question before, but i could not remeber well.


08-05-2014, 08:09 PM
What's special about the Pilz safety relays? Looking at their web site, it looks as if, electrically, it's "just" a relay. I'm guessing that it is specially built for reliability (no chance of welding contacts, that kind of thing?), and it's used as an alternative to wiring things like BOB enable out to the drivers and VFD, etc., to minimise the amount of circuitry involved in e-stop operation and hence improve reliability. In particular, it takes the control PC out of the loop.
Is this right? What have I missed? How important is it to fit something like this rather than rely on e-stop->BOB->PC->BOB->drivers?

08-05-2014, 08:34 PM
It's a much bigger picture. It starts with law and making equipment safe, such as the Machinery Directive.

Then you have to make an assessment of the required safety category based upon the criteria here, although in practice it's much more involved.
Standards for functional safety - Pilz - GB (http://www.pilz.com/en-GB/knowhow/standards/standards/functional_safety/articles/00238)

Only then can you choose the appropriate safety equipment to achieve that level, basically 4 categories.
To achieve a safety level, relays such as the Pilz have to demonstrate that they will not fail within certain criteria and they have increasing levels of self checking, only then can they be certified as meeting the standard.

So to answer your question, the relays are designed to achieve a particular safety category to satisfy the requirement by law to make machinery safe.
Your PC, bob, standard relays, have not been certified to meet the standards required. In a domestic setting at home in your shed these safety requirements do not apply but because these relays can be found on ebay at good prices I don't see any reason not to use them, and they can simplify the control circuit too.

08-05-2014, 10:16 PM
Thanks - I had a feeling that that was the answer. Essentially, electrically, they are "just a relay" but they are manufactured to high standards, have some special features to "guarantee" reliability, and are certified as such. My impression is that some people fit them, probably a majority do not, but you pays your money and you takes your chance - in a home workshop environment, anyway. I was a bit put off when a quick google search took me to the Farnell site and saw prices from 100+VAT and up. Then I took a look at eBay, and that makes it look a bit more sensible! In the overall scheme of things, especially if I go down the external motion control board route, it's not going to add an enormous amount to the overall cost.