Cascading AB light curtains

[python01 1]

I would like to cascade AB light curtains. Was thinking about cascading two sets of 440L-P4K1280YD but it seems that one set will have to be 440L-C4K1280YD for this to work. Does anyone know if this can be done with P4K type only? Or there is no way to do it without C4K in the mix?

[AndrewG 13]

Based on the Allen Bradley website, P4K is "standard" and C4K is "cascadable". So, it seems you need C4K. Even if there was some way you could get it to work without C4K, is it worth the risk, given that it is a safety application? If something ever goes wrong with the light curtain in the future, I would want to make sure I can prove my design was foolproof. If the manufacturer says cascadable is C4K, then I would use C4K. Website link: http://www.ab.com/en/epub/catalogs/3377539/5866177/3377569/6388297/2875466/3379609/tab3.html Edited 6 Jun 2014 by AndrewG

[panic mode 246]

yes, of course there is a way to do it even if light curtains are not "cascadeable". someone did it for example to make them cascadeable are you just trying to guard some corner of the machine or workspace? based on circuit in link posted by AndrewG, it is a standard type4 light curtain with EDM. this means that you can use two of them and - use both of them to disable whatever you are guarding. since each receiver has EDM, you can directly drive safety relays and let EDM monitor them, then connect NO contacts of both sets of safety relays in series (basically an AND function). if you need different or more complicated logic, use safety controller for that, use light curtains as safety inputs.safety circuits are not that complicated, it is just that most people get spooked and never even try to see what is going on. few tips: - safety circuit is only as strong as it's weakest link (using cat4 safety relay or light curtain to drive FSD without monitoring does not make it cat4 circuit). - using control relay instead of safety relay does not make it safety circuit, even if monitoring is used. - even though circuit is redundant (dual channel OSSD, pair of FSDs etc.) single EDM input can be used to monitor both FSDs (or more). each FSD needs NC contact wired into EDM input monitoring loop - solid state outputs tend to include "diagnostic pulse" which is fine when driving FSDs etc. (but is problematic when connecting to safe inputs of safety PLC) - any device adds delay and increases reaction time of the safety circuit (generally 10-50ms) so you want to minimize cascading (adding interposing safety relays) if possible (longer response time has negative impact on safety distance to a hazard). etc. example safety relays (note safety marking): - AB:700S -Omron: G7S etc.

[ASForrest 12]

Use the above information with caution. While correct, it's incomplete - whether or not you can do this depends on a number of factors, and if you're not sure about the standards and legislation, best to seek professional advice. Send me a PM if you want further info.