2/27/2015 4:46 PM | |
Joined: 11/22/2014 Last visit: 4/29/2024 Posts: 23 Rating:
|
Hello guys!
How do you generally decide if the load should be directly connected to the transistor output or an additional relay is to be put. I am asking about other factors, apart from the 0.5 A current limitation. What is your practical experience? Attachmentpictures.zip (592 Downloads) |
This contribution was helpful to
1 thankful Users |
3/2/2015 9:20 AM | |
Joined: 11/22/2014 Last visit: 4/29/2024 Posts: 23 Rating:
|
Hello guys and thank you for your answers. In my previous post, I forgot to mention this is my first project with Siemens so it is still a little bit hard to guide through the whole "ocean of documentation" available online. However, I have experience with several other brands so the logic is already here :). @eisenpferdreiter, maybe your are right about the diode. However, my case is having 600 transistor outputs(through 21 output expansion modules), located on a machine, with very little place for anything. In addition, 14 expansions for inputs are also present. With all this explanation, I just want to insist on the fact I don't have much space, even for terminals. My great wish was to have no terminals so that valves and sensors are wired directly to the S7 expansion modules but realized I don't have enough "+" and "-" terminals for the supply of these sensors/actuators. Even if I wire several in the same push-in terminals, I still have to use very small cross-section so that they all get in. All this is inside a 1000x800x250 mm enclosure panel. And what's worse, there is place for just one more panel like this and it is for the power supply - SITOP, UPS, fuses, etc... My latest idea is that a second mounting plate is added, above the Siemens modules, for terminals. If I do it like this, maybe I will have enough space for terminals with diode for protection. In addition, distribution boxes will be used so that it's more suitable for sensors/actuators to take power and signal. As for the power, it is 0.9W mainly. You have said "low". With 24V, this means 37mA current consumption. The output has a capability of 0.5 A. Is it low enough, what do you think? Even if the start-up current is 10 times higher(some sort of rule of thumb), it is still in the permissible range. @Pegaia, I followed your advice and checked the technical data for this property "work with inductive yes/no" but there is no such thing. Happily, inductive load is mentioned on two other places with the following meaning: * inductive shutdown voltage (max 53V - for S7-1500 and ET200 MP modules, 50V for ET200 SP modules) * switching frequency for inductive load - 0.5 Hz for S7-1500 and ET200 MP modules, 2 Hz for ET200 SP modules. So, my general feeling is that inductive load is supported and therefore should be protected. What I can see from the internal wiring diagrams, there is one zener diode per group, which means 4 in total. I don't know if this is enough for protection, I don't have practical experience with Siemens :). Here are the links to the two technical datasheets: https://support.industry.siemens.com/cs/#pd/462650?pdti=1&lc=en-US https://support.industry.siemens.com/cs/#pd/29756?pdti=1&lc=en-US I checked in the ET200SP manual collection and the connection diagram of the module 6ES7132-6BH00-0BA0 doesn't show much of protection, or at least I am not looking where I should. In the ET200MP/S7-1500 manual collection, as I mentioned above, a zener diode is shown at each potential group. The module type is: 6ES7522-1BL10-0AA0 The modules for the ET200SP have no problem with space - they are for other machines and devices from the process and I can install diodes/external relays and everything else - space is no factor. However, the ET200MP/S7-1500 modules are 21 outputs + 14 inputs modules and they are inside a 1000x800x250 mm panel. They are located on three rows (one S7-1500 row and two ET200MP rows). I can't install a bigger panel unfortunately as the machine space is limited. As I mentioned above, the idea is to put a second mounting plate and make the panel "somehow double". That's why I am asking if protection is to be put. If diodes have to be put, this means special terminals (which support diodes) and thus more space will be needed. Check the attached file for the preliminary design with modules, system power supplies. I know the system power supplies are not to be mounted like this(at the most right) but this is just a quick preview to check if space will be enough. It is enough for PLC modules but no space left for terminals :) Anyway, now you know why I am asking, as every diode matters. Not in terms of money, in terms of installation space. |
3/9/2015 8:35 AM | |
Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating:
|
I did not burn not a single output in my career. |
Follow us on