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    transient voltage protection for touchscreen

    I have a touchscreen that requires 12V DC. I'd like to power it from a DC power supply about 50 feet away (accounting for voltage drop) to keep the installation as clean as possible. I'm concerned that the long cable could couple to a magnetic field from a nearby lightning strike and ruin the monitor. It seems there should be some sort of transient voltage suppression where the power cable is connected to the monitor to prevent this.

    Is there anything off-the-shelf I could use for this or do I need to cobble something together?

    How do PoE devices keep from getting blown up? The transformers attached to the data lines would inherently protect the data lines but it seems the DC wires would invite disaster for long runs.

    #2
    If you are really concerned use coax and ground the shielding back at the power input end. The shielded twisted pairs in ethernet cable make it fairly immune to inductance. Otherwise the POE pairs would be messing with the data signal pairs.

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      #3
      Thanks for the suggestion.

      It dawned on me that the touchscreen vendor may already have some transient protection built in where power comes in. I don't see anything in the manual or specs. about it. I plan to ask them what's in this particular model and go from there.

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        #4
        Been using POE here for my wintel embedded touchscreens for a while now. One device I utilize is a Tycon managed TP-MS324. It is not a regular POE switch rather it is a POE injector. You feed a network port on the top row of RJ-45's and you have Data and power coming out the bottom. Inside there is a power supply for each bank of 8 ports plus addition power supply inputs on the back. The PITA piece is the extra cost for a regular switch switch. My tabletops are Gb and this device works fine with them. It is robust and made for outdoor powered AP's. It is an oldie but goodie 1U rack mounted device.



        The managed part of it watches the loads per port and you can turn on an off the port via the management page. This is what I purchased for home use and the purchase was less than $100 for a refurbished by Tycon Power. For work always utilize Cisco everything.

        I am currently using DC power for my outdoor LED landscaping lighting. I have a few 200-300 foot runs and see minimal voltage loss on the 12VDC. I chose to utilize MeanWell DIN mounted power supplies. Each is protected and has two outputs. They are commercial style devices. This is very different from the older toroidal multiple voltage transformers where I would always see a voltage drop with more lights / length on the wire (14 guage stuff).
        - Pete

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          #5
          That was a good deal on that Tycon device as it looks like it is over $900 on Amazon. It also makes cable management better as compared to having zillions of power cables everywhere if you use multiple, single-jack PoE injectors.

          My network switch has PoE built in so I use that. After a few years I had one PoE device stop working. It was a 'V1' device and the replacement with the same model number was 'V2'. I wasn't able to tell if the problem was a design defect, manufacturing defect, or damaged due to a transient voltage. I don't think it was a transient that got it since it didn't fail during thunderstorm season and the switch is on a UPS.

          You must be using something else for your Ubiquity AC AP's since they take the 30 watts of power and this Tycon box only does 802.3af?

          I need to measure the drop with the AC/DC converter that came with this screen. It might be fine with a 50 foot run.

          If the touchscreen manufacturer comes back and says they don't have any protection on the input, I plan to cobble together some TVS diodes in line. The one piece of hardware in my setup that I didn't protect promptly got destroyed 2 months after I put it in. I don't want that to happen with this screen. Nature can be unforgiving here in the land of lightning.

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            #6
            Yup; the Tycon devices are very modular and appear to be mostly hand made. At less than $100 it is a good deal for a used one.

            My tabletop touchscreens utilize 1.40A/7.0W with the clock on screen set at Highest brightness. There is a small SMD fuse on the power input of the Jogglers as I have replaced one to date. I started using Tycon 5VDC power POE splitters and went to using the TP-Link ones. The TP-Link POE splitters are smaller than the Tycon POE power splitter.



            I have left my Ubiquiti AP's using the Ubiquiti POE injectors.

            For the long runs of DC utilized for my LED lighting I see a drop to around 11.9X volts DC on the long 200-300 foot runs.
            - Pete

            Auto mator
            Homeseer 3 Pro - 3.0.0.548 (Linux) - Ubuntu 18.04/W7e 64 bit Intel Haswell CPU 16Gb- Mono 6.12.X
            Homeseer Zee2 (Lite) - 3.0.0.548 (Linux) - Ubuntu 18.04/W7e - CherryTrail x5-Z8350 BeeLink 4Gb BT3 Pro - Mono 6.12.X
            HS4 Pro - V4.1.7.0 - Ubuntu 18.04/VB W7e 64 bit Intel Kaby Lake CPU - 32Gb - Mono 6.12.x
            HS4 Lite -

            X10, UPB, Zigbee, ZWave and Wifi MQTT automation. OmniPro 2, Russound zoned audio, Smartthings hub, Hubitat Hub, and Home Assistant

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