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Long Wire Effect On The Output Of An Industrial Controller

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Saif.Manaseer

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Dear All,

I've been a visitor to this site for over a year now.
I just made this account I need your help on this issue. Hopefully, soon I'll contribute to this society :)

I'm working on an elevator electronic control board, which is already established and working, but for the indicator display (7-segment) the driver IC is obsolete (L6221A) and I need to change it.

Now, the IC is definitely over sized, it has 1.8A continuous current capability, and there's 16 channels (4x4) but the power supply of the board is fused with a 4A fuse and also an indicator (LED) can't take that much of current even if there was 7 of it (6 floor building, more than that and we use a relay card), of course not all will work the whole time, but as a full load, the IC is over sized.

Now, the problem isn't in the load, but in the interference on the long wire connecting the load to the board, it can at moments reach very high currents. The previous IC was a UDN2559 which has continuous 700mA output current, over current protection and thermal protection, but during the elevator operation, it would fail due to previous reason. What really bothers me is that the protections can't keep the IC safe, it seems the transition is faster than the IC's protection.

So, what can the solution be? Can an external filter circuit protect the outputs? Is ferrite bead a good option?
Any advise is truly appreciated!

Regards,

Saif
 

HTA

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Hi Saif,

I think long lines are a capacitive load when turned on, causing a this high inrush current. Only a build in shortage protect could help. If you switching off long lines with an open collector driver you are faced with the inductance of the line and can cause high voltage spikes. Maybe you take a look at the way the industrial 24V line driver are dealing with this problem. Here is an article about it: https://eetimes.com/design/industri...rs-to-save-energy-for-long-transmission-lines . Different +24V industrial line drivers you can find at the iC-Haus under: https://ichaus.biz/24VLineDrivers. Another option might be to look at: https://ichaus.biz/mcu_interface .

Enjoy your design work!
 

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