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Laptop with on-board POE RS485

For programming devices used in Home Automation I can plug in RS485 devices into the laptop and have them powered over the CAT5.

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To program certain devices I need an RS485 adapter. This meant a clunky setup that needed a desk (to provide strain relief to the USB port), a laptop, a USB to RS485 adapter cable, a DB9 to RJ45 converter, and a 24VDC POE Power Supply with a couple of CAT5 patch cables.

It was an unwieldy mess and had resulted in broken USB ports in the past, since the RS485 cable is a bit heavy and it was plugged into a chain of stuff. So with a recent cheap laptop purchase I realized that I had a lot of room inside of it where an optical drive could go (a plastic blank was all it had). So now I can operate away from any electrical outlets and plug the devices directly into the back of the laptop with a single CAT5 patch cable.

I have been working with and programming these RS485 Home Automation accessories for several years now, and have made improvements in the crap I have had to carry along the way. I have modded my Asus EEE PC 701 with a touch screen, I had an early Lenovo laptop that converted to tablet mode, and I was about to also try a cheap Win8 tablet as a way to run the simple Windows programs and have portability.

I then picked up this Acer Laptop for about $175 on sale and I looked into adding RAM or an SSD to slightly improve performance. Once I saw the YouTube video below I realized there was room inside of it to add other components. Ideally I could do without a touchscreen if I had the ability to eliminate the following things I carry: a serial adapter, a POE power supply, a couple of CAT5 cables. Besides carrying these parts, I have to find a place to plug them in to mains and a clean area to lay it all out. Sometimes my jobsites are not that clean or don't have mains power available.

So a Laptop that could power an accessory that draws 10mA at 12-24V and communicate RS485 directly would make my life easier.

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    Step 1

    This video sort of shows some basics on opening up this laptop. Essentially you'll remove all screws from the bottom, then gently pop open the snap-clips around the perimeter of the top. Careful, the clips are delicate, screws are small, and 2 ribbon cables are still attached. Gently lift up just enough to get to the two ribbon cables connected to the motherboard. Detach them by opening each connector as shown with arrows below (small one flips up):


  • 2
    Step 2

    The ACER Aspire ES1-512-C12D Laptop has is a good amount of open space between the WiFi card and the charger port and the area where the optical drive blank goes is right inline with it. BONUS!

  • 3
    Step 3

    Begin by removing the RS485 adapter's over-mold. They typically some off relatively easy if you can start the cut right on the seam. There isn't any glue used on the inside and there is clear plastic clam-shell hood protecting the circuit board, but still you should be careful. Of course you can start with a different, bare RS485 converter board, but I used this $35 USB one from CommFront.

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Arsenijs wrote 09/14/2018 at 00:06 point

Awesome project! Congrats on the successful mod =)

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