nkwai Posted October 16, 2013 Report Share Posted October 16, 2013 Hi, maybe this will be a stupid question, but I don't want to burn something. I have a Vision 120 with transistor outputs, two of the outputs are turning on two relays. The relays have a common 0V and then the +VO from the PLC. If I connect a switch using the same +VO to manually control the relays, do I have to put a diode on the wire coming from the PLC? or there is no problem if current comes backwards? There is also the possibility that the output will turn on while using the manual switch is this a problem? Thank You. Quote Link to comment Share on other sites More sharing options...
Michael_P Posted October 16, 2013 Report Share Posted October 16, 2013 Hi Nkwi It is always a good idea to include diodes in this type of system. Provided you have included the appropriate diodes for your system you will be protecting the system from the inverse voltage. This will also be the same type of protection if both the manual switch and transistor are both firing at the same time, the diode will prevent a detrimental condition if you do not exceed the PIV value for ht diode Quote Link to comment Share on other sites More sharing options...
nkwai Posted October 16, 2013 Author Report Share Posted October 16, 2013 Ok, didn't know that... Exist there any diode bar whit screw terminal's to mount on a DIN rail or something like that? Or do I have to solder the diodes on the wires one by one? What type of diode do I have to use? Thank You Quote Link to comment Share on other sites More sharing options...
Michael_P Posted October 16, 2013 Report Share Posted October 16, 2013 nkwai, The diodes will be connected in series with the outputs, the connection parameter, additional equipment and methods to connect will be in accordance with the electrical code in your region. The diode should be sized to handle the maximum inverse voltage. Any type or size will function provided it is for DC and the PIV is above maximum voltage expected on the line. Quote Link to comment Share on other sites More sharing options...
Walkerok Posted October 17, 2013 Report Share Posted October 17, 2013 A standard 1N4007 diode will work fine. It is 1000V 1amp. They are very inexpensive. Keith Quote Link to comment Share on other sites More sharing options...
nkwai Posted October 17, 2013 Author Report Share Posted October 17, 2013 Thank you, but after a little thinking I've decided to bridge the output of the two relays to other two relays and command the other two whit the manual switch, that way the plc will not be in danger :-) Best Regards Quote Link to comment Share on other sites More sharing options...
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