Build Your Own Total System Power Analyzer

Overall Score

Building the system can be done in an afternoon. The first step is to layout and plan before doing anything. In this build, the sensors were mounted on two pieces of acrylic glass which in turn are also mounted inside an aluminum project box. Threaded rods were bolted into place and a two tier arrangement of the sensors were laid out as shown below. Six holes were drilled on either side of the project box (one 1/2 inch, 3 3/8 inch, and 2 1/4 inch) , and fitted with grommets. These serve as feedthroughs for the 24 pin ATX cable, the 2 PCIe +12 VDC lines, the CPU +12 VDC line, and an AUX +12 and +5 VDC line for drives and externals and the last for the signal wires to connect to the DAQ system (U3HV). There is also a terminal block mounted on the input side of the project box, and shorted into 2 groups of 4 terminals. One block is the +5 VDC supply from the U3HV which will power the sensors, the other is the common ground for all sensors and connected to the analog input ground on the DAQ device.

Wiring up the sensors is straightward, the header block on top of the sensor evaluation board has 6 pins, only 3 are needed. The Vin is left unconnected (this is for a variable voltage source which feeds the voltage regulator on the evaluation board). The +5 V pin is routed to the +5V supply terminal block, the ground (labeled AGND) is connected to the ground side of the terminal block, while the Vout is the signal that will connect to one of the analog inputs of the U3HV DAQ system. Note on the LabJack U3HV shown below, the terminal Vs is +5 volts and is the same for all terminals labeled Vs as is GND, which is ground — only one connection is needed here, the Vs is the +5 VDC to the power side of the terminal block, while the GND is, naturally, connected to the ground bus on the termal block. A molex crimp style 4 header female connecter was used to create the connector, this also makes for easy addition or removal and changing of sensors.

[img]Fig7.jpg[/img]

The sensors were number 1-8, then wired up for each line by taking an extension cable for each type, cutting it in half, gathering the appropriate line and crimping a connector at the end. The sensor and the connections for reference later is listed below.

  • Sensor 1 – 20 Amp – CPU +12 VDC
  • Sensor 2 – 20 Amp – MB +3.3 VDC
  • Sensor 3 – 20 Amp – MB +5.0 VDC
  • Sensor 4 – 30 Amp – PCIe/GPU1 +12 VDC
  • Sensor 5 – 20 Amp – AUX +12 VDC
  • Sensor 6 – 5 Amp – Aux +5 VDC
  • Sensor 7 – 20 Amp – MB +12 VDC
  • Sensor 8 – 30 Amp – PCIe/GPU2 +12 VDC

The boards have two sets of barrel connectors, one set is simply IP ground, and so the grounds were divided up and distributed across all 8 sensor boards. Each lead for each rail were crimped together, current flows in the direction of positive carriers, so the input side connecting to the PSU is labeled + IP, and the output to the load is -IP as labeled on the boards. The full wiring and internals of the project box as connected is shown below.

Finally, when all is said and done, all the connections made and ohmed out, the device is now ready to be used. Shown is the actual power metering system connected to a open air build, the test bench is a homemade bench constructed by Dremel cutting down an otherwise worthless case for the motherboard tray:

Ok, it’s built so what’s next?

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