This is a small voltage and current sense PCB. DC current is determined by measuring a voltage drop across a pair of parallel 1 mOhm shunt resistors, then converted to a final analog voltage output by the TI INA-169. Voltage sense is accomplished by scaling to 3.3V ADC range by a precision resistor divider.
The PCB is supplied without leads or connectors. The pad sizes are large enough to accommodate 12 gauge heavy duty leads (see datasheet) but care must be exercised in soldering. Smaller gauge leads are considerably easier to solder without creating shorts.
From the datasheet,
“The output impedance of the INA169 OUT terminal is very high, which permits using values up to 100kΩ with excellent accuracy. The input impedance of any additional circuitry at the output must be much higher than the value of RL to avoid degrading accuracy”.
If a you are seeing crazy current readings, this is the likely cause. An impedance converting circuit, such as an op-amp, will probably solve those issues. See this thread => https://forums.openpilot.org/topic/37838-attopilot-battery-monitor/#entry331962 .
Example used an AD8066 SO8. From the thread,
“Pin 8 (V+) is soldered to the shunt resistor. Pin 4 (GND) is soldered to the sensor board ground plane (I scratched off the solder resist only in this area. This was the trickiest part for me because your have to be sure not to scrape off too much and thus short-circuit with Pin 3 later). Pin 3 (+IN) goes to I-out of the AttoPilot, and the wire to the [microcontroller] Board (which is normally soldered to the I-out of the AttoPilot) goes to Pin 1 AND 2.
I first soldered Pin 1+2 and Pin 3 and then placed the opamp on the sensor board and soldered Pin 4 and 8. After all I secured everything with plastik spray which crawls even in the darkest corner (low viscosity superglue should also do the job)."
Here is an image of the modified current sensor => https://drive.google.com/open?id=0B0jwgLkjMWzDUTNLdTR5ZFRmQlE
The designer is aware of this, see comment => https://www.sparkfun.com/products/9028#comment-5367a7fbce395fdd458b456f ] .
This skill defines how difficult the soldering is on a particular product. It might be a couple simple solder joints, or require special reflow tools.
Skill Level: Noob - Some basic soldering is required, but it is limited to a just a few pins, basic through-hole soldering, and couple (if any) polarized components. A basic soldering iron is all you should need.
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If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.
Skill Level: Competent - You will be required to reference a datasheet or schematic to know how to use a component. Your knowledge of a datasheet will only require basic features like power requirements, pinouts, or communications type. Also, you may need a power supply that?s greater than 12V or more than 1A worth of current.
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Based on 5 ratings:
The first board that I bought I changed my setup three times, the last time I used a little too much solder and too much heat that I shorted out the ground trace. (you can see the trace in the picture directly under the N in GND where the ground power wire is soldered to the board) By simply adding a jumper from the power lead ground and the instrument ground lead made for an easy fix, thanks to the great documentation that has been made available.
It takes a beating from ham handed soldering and still works flawlessly. I bought two more of these, since this little board will make for one of the cheapest 90A current probes for general multimeter use that I have ever seen.
If you follow the instructions on the Ardupilot wiki:
It works perfectly. Thanks guys!
Even with the heat required to solder the large gauge wires, the pcb lands showed no sign of delaminating. Then correction factors in the example code worked well and verified against test equipment. I will purchase again.
Works Exactly As Advertised