Board Mount Safety Relays

[srtest 0]

A product I oversee currently uses a DIN Rail Safety Relay (SR103AM01). This safety relay interfaces with a PCB that we designed. To avoid the need to make custom cabling to connect our board to this DIN rail device, I would like to find a module that comes in a board mount package.

Does anyone know if such a device exists?

I have located relays like the Omron G7SA Safety Relay, but these are individual force guided relays, which do not seem to have the same functionality as the Safety Relay Modules.

[Joe E. 259]

I'm not aware of any such products. I know they go through a lot of testing and certification to be allowed for safety applications. For what you're doing, you might reach out to the safety relay's manufacturer representative to see if they could work out something like an open frame model that could attach to your board, but I would be really surprised if they did that unless your volume is really high.

[panic mode 246]

individual safety relays can be used as atomic(low level) building blocks to make own safety products but you need to follow the guidelines and design the circuit for certain functionality yourself or implement existing one if found (two hand control, EStop control, light curtain control, safety mat control...). 

word of warning, there is a reason one does not do that any more and instead buys ready to use modules.

the first and most obvious one is that such designs need specialized knowledge that goes well beyond following instructions in a datasheet of ready made module. also this need to meet safety standards and be independently tested by approved labs. one can see examples of that in many older products (FE207 board in KUKA KRC1, ESC board in KRC2 etc.). and as already stated doing things like that is absurd unless dealing with huge volume. 

so today, groups of individual safety relays are used at most for contact expansion for ready made safety products (that already have all functionality and approvals). even there, one would really need to think hard about using individual relays rather than ready made expansion modules. 

another issue is that products like SR103AM0 are only meant for the very simplest uses (monitoring or control of a single safety point). typical cell likely may need to use dozens of them (or more) so very often this is just not practical. that is why there are safety networks. they allow one master (usually a safety PLC) to connect to numerous safety devices, even those that are complex on their own. an example is safety PLC monitoring some production line with many cells, each cell containing one or more robots, own PLCs and dozens of safety devices.

there are some hybrid products for different scales but ...

safety modules like SR103AM0 are the lowest building blocks currently on the market that would allow you to make circuit without need for lab evaluation and certification. 

so the best you can do that i am aware of is to have product that is easy to find and replace. for example you can have them with removable terminal blocks. that way you can build own wiring assemblies that allow quick connection between safety module and your board.

[panic mode 246]

here is an example of "internal circuit" and operation of one safety module

https://www.utmel.com/blog/categories/relays/what-is-safety-relay

but... this is not the real internal circuit. it is a simplification used to explain how it works. for example it does not have second channel depicted and shown circuit has no way to detect cross channel faults. The better version is shown for Omron G9S301 or G9S501 and it used to be shown on the side of the module.

here is another "approximation" of such circuit. note, while this does show both channels etc., this too is not able to detect cross channel fault. also note that fuse is a key component of such designs (need to be a fuse and not circuit breaker). on some products like G9S it may be even accessible.