After I had a few problems with the standard power module from 3DR and the ones from Hobbyking, like falling off resistors (overheated) and burned out BEC from voltage spikes, I finally designed my own PM modules. The sensor boards are compatible to Pixhawk, APM, Pixhawk lite, AUAV-X2, DroTek und CUAV Pixhack.

These modules are based on a true hall current sensor, so heat is no more an issue !!!

The sensors boards are able for continuous current of 100A for HS-100-V2 and 200A for HS-200-V2 (no time limit), the maximum over current is 1200A@25'C and 800A@85'C for 1 second.

Here some details:

Sensor Board:

  • Current sensor is a “true hall sensor” up to 200A (ACS758-200U) or 100A (ACS758-100U)
  • Ultra-low noise power supply (LP2985-4.0) for current sensor and offset shifting circuit.
  • Microchip MCP601 operational amplifier for offset shifting.
  • LiPo voltage measurement with 1% resistor divider in factor 9:1.
  • 2x10cm / AWG12 cable soldered to current sensor as standard size (Up to AWG8 possible).
  • 6 pol cable connection to Pixhawk / APM (both sides DF-13 connector).
  • 1x 10cm and 1x 20cm / 6 pole cable in the box to select a different cable length if necessary.
  • 18mm x 29mm x 11mm / 7g without cables and shrinking tube.
     

BEC:

  • Input 2-6S LiPo / max. 28V
  • Output 5.35V / 3A -> +/- 0.05V –> Ripple 10mV (0.2%) at 1.5A output current.
  • Input wrong polarity protection, as well as Panasonic FM 220uF/35V input capacitor to prevent burn out of BEC from voltage spikes.
  • 4 pole cable to sensor board with DF-13 connector.
  • 47mm x 18mm x 11mm / 8g with cables and shrinking tube.

Installation:

The Sensor board is installed only into the positive main battery wire and the BEC should be installed as close as possible to the battery connector.

Quality control of the finished product:

To post here all the quality control during the production would be a very long story, so all I can say is, that it is carried out and recorded.

The final QC before the boards are shipped, is a setup with an FC (Pixhawk) and connected to MissionPlanner to check the calibration values for current and voltage measurement.
This final test result will be passed to the customer together with the order confirmation and shipment tracking number by e-mail.

REM: Which power module supplier out there actually use the PM to power up a real FC before shipment ?

So I hope everybody understands, that if I say "safety first"... then I mean it.

FAQ:

Why Hall sensor ?

  • The measurement over a normal shunt resistor is not accurate at lower current (<3.0A). For a Hall sensor the measurement starts at 0.5A with an accuracy of +/-0.5A over the whole range up to 200A !
  • A shunt resistor create heat due to the voltage drop, the hall sensor has only an internal resistance of 100uOhm, so there is no power loss.
  • Due to the heat created by a shunt resistor and the power cable, the measurement of the current is not linear and depends on the temperature. This is not happened to a hall sensor, a temperature change (created by the main LiPo cable) will not influence the measurement.
  • The current flows only through the hall sensor and NOT through the PCB. Most other current measurement boards has the main cable soldered to the PCB and then it goes to the shunt resistor -> these boards can’t handle over 60A constant current ?

 
Why only a few supplier use a true hall sensor for current measurement in an MR ?

  • Hall sensors are very expensive, compared to a normal shunt resistor and not everybody out there wants to spend the money to top up for a good measurement system. So the sales quantity and profit will not be within the target.


Why output voltage to Pixhawk /APM is 5.35V and not 5.0V ?

  • Pixhawk has internally a 3-way power selector over an ideal diode chip. The 3-ways are USB, power connector (6pin) and the Output PWM rail on the back of the FC. So it is possible to power up the FC with either one of this power sources, but how do we know which power source right know is powering up our FC if there is USB, a PM module as well as an backup BEC connected to the output (ESC/Servo) rail ?
    The answer is easy: Whichever voltage is higher by 0.25V to any other power source is selected as the internal power supply, as long as this voltage do not exceed 5.70V !
    The result in practice on the field can be different, as there are many components connected to the FC like, GPS, Servos, opto ESC’s… etc., the power consumed by the system is not stable, which means the supplied voltage is not stable as well. The reason for this is the loss in voltage due to small power supply cables and maybe many connectors.
    To prevent the internal ideal diode to switch too often between different power sources, we choose a bit unusual high voltage (5.35V) as a main power supply. Which means only if any other power supply (USB or PWM rail) is in the small range of 5.35V+0.25V=5.60V and the maximum voltage of 5.70V, then the diode would switch over to the other source.


Why the cable from UBEC to the sensor board is 4 pol ?

  • To reduce the resistance in the power line and increase the safety, or should we ask, why does the DF-13 power input of the Pixhawk has +/+/I/U/-/- ?
    There are also two wires, for positive and negative, used to reduce the risk of failure.


Why sensor board and UBEC are separated ?

  • A switching power supply can be a very “noisy” part in the power supply chain and it is very difficult to shield the coils (1.5MHz) from the current measurement board. So it was decided to keep the two away from each other.


 Why is there an additional capacitor installed at the input of the UBEC ?

  • Many people complain that the UBEC seems to be bit big, but fact is that he is only 22mm x 17mm. What makes him BIG are the safety capacitors at the input and output !
    We all had the issues before that any ESC burned out due to the “hammer effect” in the supply lines, but do we consider that the UBEC is sitting on the same voltage source ?
    Does anybody ask himself so far why suddenly his BEC burned out ?
    Why does some people add some capacitors onto the ESC’s to reduce the risk of failure, but in the same time they forget that there is also anywhere an BEC in the supply line which might need some protection too ?
    How good is it if your ESC’s survive a voltage spike, but your BEC didn’t and the MR crashes ?
    If you can answer some of the questions by yourself, then you will also figure out why this UBEC is a bit bigger than others.


 How can I get one of these boards ?

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Very happy, I ordered a 100A version. Really nice piece of work and arrived at my home in the UK within seven days of ordering! Installed and working fine.

Thank you

Clive

I bought one as well on the 16th, having problem with the tracking number.
It doesn't work where ever I try it at.
Did your tracking number actually work? Mine is not working.
I did contact Mr. Mauch and ask for him to check the number
but I think he thinks I am upset and does not want to answer my email.

It has been my experience that when that happens the item is lost or just plain not coming.
Just a few days ago I had this happen again from a buyer in China on ebay.
In fact it is a 1200mm heavy lift frame that I bought to use this item for.

Hi Jim,

Just checked, and yes the ChinaPost tracking number worked up to its arrival in the UK. I hadn't really expected it for a couple of weeks and so hadn't checked whilst it was actually in transit. Looking now it shows it arrived in the UK yesterday and was delivered by UPS today. Considering I placed the order on the 18th and Christian charged no extra for UK shipping I'm quite amazed. I have to say I found Christian very responsive as I bounced a few queries off him by email and he always got back to me quickly.

Ordering from China seems sometimes a bit of a gamble but I have to say I'm generally finding the reliability of kit both in arriving and also actually working is far better than it was a few years ago. Guess the way I look at it is that the aggregate savings compensate for the odd loss. I didn't really have any doubt though in this instance.

Just ordered some STM32 development boards to play with so fingers crossed again! I hope your power module arrives it's a lot more robust than the conventional unit.

Merry Christmas

Clive

Thanks for the information. I hope mine is not lost or something like that.
I am going to get another one if this one make it to me. I am planning on using it with pikhawk on 7s batteries.

Merry Christmas to you
and have a Great New Year.

Jim

Hi,

First tests on a 100A module: everything is working fine. I made tests up to 70A continuous with no worries. Here a fast test for currents increments on 6S battery.

Full power during this test is 1.5kW, don't worry about the current overshoot before steady state, this is because of my resistive loads.

Got mine in the mail today.(12/30/15)
It is well crafted. Can't wait to use it.

If your having problems tracking the
your package it is because it is not a normal tracking number that is sent to you.
It is a registered mail tracking number. It is not intended for actually tracking the package,
You will have to sign for the package when you get it. The tracking number you get is mainly for Mr. Mauch's use not ours. So do not be upset (like I did) if you cannot track the package the normal way that you might be use to.  You will get it, rest assured. And when you do, you will be happy.

Ok.. now someone tell me how to use 7s with this sensor.. The bec that comes with the sensor says 2 to 6s. I need to run 7s.

Jim

Ups... my record says you should got the 4-14S HYB-BEC together with your 200A sensor !

Is it possible I put there the wrong sticker on it... could you please post a picture of the BEC to clarify ?

Christian

No Sir you did nothing wrong.

My bad.... My Bec is for up to 14s..
I was reading on how to plug it all in and
when reading the specs on it in my old mind
I must have thought I was reading about the one that I have
when in fact I was not So I put foot in mouth for about the 50th time this month.

I hope there is a cure for foot-in-mouth disease

Jim

Hi Jim... thanks for the confirmation.

I was already checking all my remaining serial number stickers for any mismatch, but couldn't find one.

Best regards and Happy New Year,

Christian

Hi!

I'd like to buy this sensor for my heavylifter!

Is calibration necessary? Because if I want to calibrate 200A sensor in MissionPlanner I will need 5kW power source. And that's a lot...

Thank you

Hi Adam, calibration is not necessary for this sensor board. As I test each BEC / Sensor combination before I send them out to the customer. The test result and shipping details will be send via email afterwards to the customer.

So just setup the values for voltage and current reading as follow.

1. On the mission planner’s INITIAL SETUP | Optional Hardware | Battery Monitor screen set the “Sensor” to “Other”.

2. Enter the voltage divider from the final test result and press "TAB" or click out of the field. Then the "calculated battery voltage" should be within a few millivolt of the actual battery voltage.

3. Enter the "Amperes per volt" from the final test result (A/V) and press "TAB" or click out of the field.

That's all you need to do... have fun !

Hi Christian!


Perfect! That's all I need to know.

I will use 2x 6S 16000mAh... I'd like to monitor both batteries separately. My octo could consume up to 400A.

Do you know if it is possible to connect two battery monitors to Pixhawk?

Thank you! :)

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