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  • Author Author: jasonwier92
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Custom PDU: Introduction

jasonwier92

First of all I am very grateful and excited to be picked for his challenge.  When thinking about what I could do for this challenge, I thought about how much I could not stand using an APC AP9211 interfaces. The APC AP9211 is a Power Distribution Unit (PDU) that was widely popular around the year 2000. It could turn on and off outlets via serial communications (RS-232) and with an optional card be controlled over TCP/IP, most commonly SNMP and TELNET. While these are doable parameters for automation, I'd like to use more modern protocols. Also running a CAT5e wire to this device is not always the best solution.  So why not gut the box and create my own interface.  New interface would be able to be modern HTML, telnet or best of all MQTT.  Using HTTP, ssh, or MQTT would easily allow integration to automation software such as Home Assistant to control outlets.

 

AP AP9211

So here is a picture of the AP9211 that I will be using. As you can see this device manages power to eight outlets.  Newer units like this have many more options that I would like to bring to older hardware like this, but most are lacking a few things I would like to have in this and the most considerable would be lack of support for MQTT. Here are some features I would like to have.

 

  • MQTT and a modern HTML/AJAX interface to control and get data from this unit
  • Statistics and graphs, because they are cool
  • Ability to monitor and react to the surroundings
    • Temperature
      • Turning on and off heaters or fans
      • Sending messages about temperature
      • Alerts
    • Light level
      • Turn on and off lights
      • Indicate to other systems about lighting level
    • Presence
      • Bluetooth detection of certain devices
      • Motion detection
      • Enclosure monitoring - more about this later
    • Network Watchdog
      • Reboot devices base on network availability
      • Light indications of a problem, ie turn on a swirling caution light
    • Power
      • Ability to indicate if main power is out
      • Message on outage
  • LCD display for messages
  • Optional extra would be a camera to detect motion, record images, control outlets, and send alerts

 

 

I have two options in this build that I am considering.

 

  • Total gut and build from scratch
    • This would be easier as I do not need to interface with what was there
    • Would allow me to use more of the components supplied for the challenge
    • Could allow for more expansion to extra functions
    • Use of Solid State Relays to allow for dimming on specific outlets
  • Use the control board that was in this and replace the functionality of the Smartcard with the Edison.
    • Would be more authentic

 

I think I am going to gut and build from scratch if you cannot tell from my list above.  I have purchased this AP9211 just for this project.

 

Possible uses:

  • Monitor and control my office project desk
  • Monitor and control my workbench in the basement (my current top choice)
    • Like turning off the lights if I was there and have left to do something and never returned
    • Turn off the soldering iron if left on
    • I can add USB ports to the case to supply 5V USB power to devices too.
  • Tower monitor - I have an 80 foot tower.  I have a camera, rent out space to local WISP, and have my own wireless link to the house.  Would be nice to monitor and reboot stuff remotely. I already know when power is out, but with this I could monitor power and turn off non-essentials after a given number of minutes.
  • Entertainment power control. When nothing is in use turn it off. Not a big fan, but it could be useful.
  • Christmas light power station. I have done this in the past with a APC UPS and Raspberry Pi, but it was big and clunky.  This would be smaller and could even be setup to blend in or add a cool feature.  It is nice to not to have to remember to turn on and off lights, have some turn on/off at certain times, or just for effects.

 

I plan on keeping a camera on this project as it is being built.  Most of the time it will not be the most exciting and from time to time other projects will cover it, but it will be fun to share.

  • in reply to jasonwier92

    Based on the pictures I would tend to try and keep the existing power control board, it looks like it already has the power rails you would need, for sure there is 24V available as that is the rating for the coils of the relays.

     

    The board looks like it would be easy to isolate the relay drive and inject your own from whatever controller you want

     

    Keeping the existing board would be the safest thing too as @MCB1 has already stated, it looks to be well designed and has good clearances from mains to low voltage control side, you would be hard pushed to find this with cheap ebay specials.

  • in reply to jasonwier92

    Well done on the investigating.

     

    The voltages you see suggest an open collector device is driving the relays, and the datasheet below confirms that.

    http://ww1.microchip.com/downloads/en/DeviceDoc/mic5821.pdf

     

    As you can see on the board, they have gone to great lengths to seperate the high voltage (mains) from the low voltage side, and that will include earth planes, etc.

     

     

    If you can replicate the signal required to dirive the latches, then you've eliminated a lot of physical work.

     

    The 12v could be used to power the Edison, and the 5v is the chip drive voltage.

     

    Be aware that the native Edison is 1.8v I/O so you'll need to use the Arduino Breakout board or some interface to drive the chip.

     

     

     

    Mark

  • in reply to mcb1

    I will use the idea of using the board as my second BLOG entry soon.  Here is what I have found so far and I do not have a scope to look further into what signals are coming out of the management card. I have scoped out the 14 pin header going to the 20 pin management card and it has two grounds, 5, 12, and 25V.  Then the other pins go to the array of resistors (8 of them) and they have different voltages on them.

     

    The relays when the outlets are off have 25VDC to them.  When turned on there was 0.7VDC on the one end of the diode I was testing at.  I traced that back to a MIC 5821, which is the 8-bit latched driver that controls the relays.  It can handle 25VDC and data is read in serial with a clock. So I could write to it with the Edison.  The other chip is a Quad NOR, not sure yet what that is used for. I would assume the management is putting out a clock, Data, and Output Enable (OE).  

     

    The low voltage part of the board has three different voltages DC: 5, 12, and 25.

     

    image

     

     

    When I unplug the management card, the serial stops working.  I think a blank has to be in the management port to signal that it is empty.  I will continue to research this option.

     

    image

     

    It would not be hard to wire this up to safely replace the 8 port relay with a opto isolated board and put in a nice 12 VDC power (5V step down too if needed). I will keep both options open for now.

  • in reply to COMPACT

    Agreed.

    Also a Solid State Relay will not allow dimming.

     

    Personally I'd be taking a second look at the existing power board side of the unit.

    It has all the safety design already done, and you might be surprised how easy it is to interface.

     

    Mark

  • If you're going to fiddle with mains power ensure that you follow all of the relevant safety procedures and ensure that your build meets compliance standards.

    If the unit is perfectly functional is it possible to build a gateway to drive your switch box?

     

    Just a thought