kolyur
Lifetime Supporting Member + Moderator
The Banner SC22-3 safety controller is a product that I've become quite familiar with over the past few weeks--I'm using one on my latest machine project. I wanted to share my experience on PLCS.net because overall I think it's a good product, but I don't think the Banner literature represents its capabilities very well.
Here is Banner's page for the SC22-3:
http://www.bannerengineering.com/en-US/products/6/Machine-Safety/52/Safety-Modules-and-Controllers/442/SC22-3-Safety-Controller/
The SC22 seems to aim for a market somewhere between a mechanical safety relay and a full-fledged safety PLC. In my mind, the greatest benefit of this device is that you can connect a variety of guarding switches, each with different wiring requirements. In my case, we had a number of traditional NC interlock switches, as well as a handful of magnetic and hinge switches using complementary logic (one NC and one NO contact per switch for redundancy). And some dual-channel E-stops of course. I was able to configure the SC22 to handle all of these devices without a problem.
I had no trouble installing the Banner software and communicating with the SC22 using a USB cable. The software is basic but pretty straightforward. To configure a safety input, for example, you just specify the type of safety device and terminals to be assigned (based on the number of channels and wiring logic of the device). Supposedly you can do all the configuration using the onboard keys and display, but I wouldn't recommend it. The 128-page manual goes into great detail explaining general safety concepts and requirements, but should really provide more information about the operation of the SC22.
The SC22 has three safety outputs, and in my mind the Banner literature doesn't do a very good job of explaining exactly how these outputs are related to the inputs. The fact is that each safety input is assigned to one of the safety outputs, and the state of each output is an AND combination of all assigned inputs. If you're thinking that you can develop some logic to control the outputs, think again. I realize that Banner doesn't market this as a safety PLC, but since they call it a safety "controller", you would think that you'd have more control over the outputs. You can set each input to require either a manual or automatic reset when tripped.
What has really been frustrating me about the SC22, however, is the limitations of some of the advanced functions. My current application requires two bypass keys. The first is a technician-only key that bypasses all guards and does not restrict any machine functions. The second is an operator setup key which bypasses some of the guards but also locks out certain machine functions (by dropping out some contactors). In the past we have been able to accomplish this with a traditional safety relay and hardwired setup. Although the SC22 specs claim that you can configure "bypass switchES", in reality you can only set up one bypass input. The muting function could potentially be used to simulate a bypass switch, but I discovered that you can't use both a muting and bypass function on the same inputs (this is not mentioned anywhere in the manual). As far as dropping an output when the bypass mode is activated, well I've come up with a few ways to do that but they're all kludges.
In short, I think the greatest strength of the SC22-3 is its ability to accept switches with a variety of wiring configurations. If your application doesn't require anything beyond that, the SC22 would be a good choice for its $500 price tag. However, for my project I think I'll end up having to add a second safety relay to handle the bypass functions. I'd be interested to know if some of these limitations could be rectified by future firmware and/or software updates from Banner.
If anyone else has experience with the SC22-3, I'd really like to hear your thoughts.
Here is Banner's page for the SC22-3:
http://www.bannerengineering.com/en-US/products/6/Machine-Safety/52/Safety-Modules-and-Controllers/442/SC22-3-Safety-Controller/
The SC22 seems to aim for a market somewhere between a mechanical safety relay and a full-fledged safety PLC. In my mind, the greatest benefit of this device is that you can connect a variety of guarding switches, each with different wiring requirements. In my case, we had a number of traditional NC interlock switches, as well as a handful of magnetic and hinge switches using complementary logic (one NC and one NO contact per switch for redundancy). And some dual-channel E-stops of course. I was able to configure the SC22 to handle all of these devices without a problem.
I had no trouble installing the Banner software and communicating with the SC22 using a USB cable. The software is basic but pretty straightforward. To configure a safety input, for example, you just specify the type of safety device and terminals to be assigned (based on the number of channels and wiring logic of the device). Supposedly you can do all the configuration using the onboard keys and display, but I wouldn't recommend it. The 128-page manual goes into great detail explaining general safety concepts and requirements, but should really provide more information about the operation of the SC22.
The SC22 has three safety outputs, and in my mind the Banner literature doesn't do a very good job of explaining exactly how these outputs are related to the inputs. The fact is that each safety input is assigned to one of the safety outputs, and the state of each output is an AND combination of all assigned inputs. If you're thinking that you can develop some logic to control the outputs, think again. I realize that Banner doesn't market this as a safety PLC, but since they call it a safety "controller", you would think that you'd have more control over the outputs. You can set each input to require either a manual or automatic reset when tripped.
What has really been frustrating me about the SC22, however, is the limitations of some of the advanced functions. My current application requires two bypass keys. The first is a technician-only key that bypasses all guards and does not restrict any machine functions. The second is an operator setup key which bypasses some of the guards but also locks out certain machine functions (by dropping out some contactors). In the past we have been able to accomplish this with a traditional safety relay and hardwired setup. Although the SC22 specs claim that you can configure "bypass switchES", in reality you can only set up one bypass input. The muting function could potentially be used to simulate a bypass switch, but I discovered that you can't use both a muting and bypass function on the same inputs (this is not mentioned anywhere in the manual). As far as dropping an output when the bypass mode is activated, well I've come up with a few ways to do that but they're all kludges.
In short, I think the greatest strength of the SC22-3 is its ability to accept switches with a variety of wiring configurations. If your application doesn't require anything beyond that, the SC22 would be a good choice for its $500 price tag. However, for my project I think I'll end up having to add a second safety relay to handle the bypass functions. I'd be interested to know if some of these limitations could be rectified by future firmware and/or software updates from Banner.
If anyone else has experience with the SC22-3, I'd really like to hear your thoughts.
Last edited:
