200A Hall sensor based PM for Pixhawk / PX4 - RC Groups
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Oct 17, 2015, 06:05 AM
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MaoChris's Avatar
New Product

200A Hall sensor based PM for Pixhawk / PX4


After I had a few problems with the standard power module, like falling off resistors (overheated) and burned out BEC from voltage spikes, I finally designed my own PM module.

Specification:

Sensor Board
- 200A current hall sensor (ACS758-200U), no more falling off overheated stunt resistors
- Maximum cable size AWG10, with a bit squeezing up to AWG8
- Current measurement output voltage to PH = 20mV/A ~ 1V=50A
- Voltage measurement output to PH = 1/10 of LiPo voltage
- Supply voltage to PH = 5.35V/3A
- Cable connection to board via soldering pads to easily adjust requested cable length.  Cable should be secured with 5min epoxy or hot-gun glue.
- 28mm x 31mm x 11mm / 8.5g without cables and shrinking tube

BEC
- Input 2-6S LiPo / max. 28V
- Output 5.65V/3A
- Input wrong polarity protection, as well as Panasonic FM 220uF/35V input capacitor to prevent burn out of BEC from voltage spikes.
- 47mm x 18mm x 11mm / 9g with cables and shrinking tube

If somebody is interested about to get one of these boards, then send visit www.mauch-electronic.com and go to the web shop.
Last edited by MaoChris; Nov 06, 2015 at 06:39 AM.
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Oct 23, 2015, 03:52 AM
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MaoChris's Avatar

V2.0 is out


Newly out is now V2.0 of the 200A Hall Sensor with the following changes:

- With only 18mm x 29mm approx. 35% smaller than V1.0 (Sensor Board)
- The soldering points on the boards are replaced by DF13 connectors
- 10cm / 4pol. cable from UBEC to sensor board with DF13 connector
- Two cables (one spare) for from the board to the FC, one with 10cm and one with 20cm. So you can choose what is the right cable length for you, depend on the multicopter.
- One spare shrinking tube for the sensor board in case you want to exchange a cable.
- AWG12 / 2x10cm is now standard size for main battery cable

I was able to cut down the price of some parts, so the price stays at $25 for the sensor board inclusive the UBEC and worldwide shipping is $8. (This only to your information)

Version 2.0 will be available in the 1st week of November.
Nov 03, 2015, 07:38 AM
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MaoChris's Avatar

1st batch of V2 is ready for shipment !


The first batch is out of production and ready for shipment !

It was requested by many people to get some more or combined information about the sensor board and UBEC… here it is.

Sensor Board:
- Current sensor is a “true hall sensor” up to 200A (ACS758-200U).
- 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.
- Supply voltage to Pixhawk / APM = 5.35V/3A
- Bright blue LED as power on indicator.
- 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.

UBEC:
- Input 2-6S LiPo / max. 28V
- Output 5.35V / 3A -> +/- 0.05V –> Ripple 5.5mV (0.1%) 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.

FAQ:

Why change so fast from V1 to V2 within only a few days ?
- In the beginning the main target was to have a flexible board with just soldering pad’s to connect the cables, but it makes the board a bit bigger in size. Furthermore, some people just don’t have the skills to solder a wire (REM: why somebody in god’s name own an MR if he can’t solder a wire?). So it was decided to install DF-13 connectors with two different cable length, to adjust the distance to the FC (10cm or 20cm). Any other length possible on request and without increasing costs, but might be with a delayed shipping date.

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 ?
- Visit www.mauch-electronic.com and go to the web shop.
Last edited by MaoChris; Nov 06, 2015 at 06:40 AM.
Nov 03, 2015, 09:11 AM
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just4funxwing's Avatar
So the BEC is seperate from the current sensor?
Nov 03, 2015, 09:50 AM
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MaoChris's Avatar
Quote:
Originally Posted by just4funxwing
So the BEC is seperate from the current sensor?
Yes it is... you can find the reason in post #3 under FAQ.

Christian
Nov 03, 2015, 12:51 PM
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Subscribed for future builds!
Nov 03, 2015, 02:28 PM
DroneWorlds - TEAM NEW ZEALAND
jackosmeister's Avatar
I like it! If the sensor is good for 50V, any plans for a HV BEC to match?
Nov 03, 2015, 04:59 PM
Made in Germany
@MaoChris:

I should be mad, because youre pointing at my fears: Fried several ESC and despite of this, never thought of my BEC with tiny caps, probably operated off specs. Although I already had a brown out due to a ferrite vibrating of a cheap Aliexpress Power Module..(bye bye Vcc > bye bye Quad), I forgot about other potential risks.

Have to admit, the separate BEC and its size (although also an issue of the first pics you published), did irritate me as well. But it is true, safety counts @ my expensive MR builds.

Additionally my Atto sensors PCB shunt always reminds me of a fuse (born to get fried), so Im pretty happy about your Hall sensor board, promising some sort of extra insurance.

Good job, Im sold !
Nov 03, 2015, 06:17 PM
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MaoChris's Avatar

Up to 12S is comming in January


Quote:
Originally Posted by jackosmeister
I like it! If the sensor is good for 50V, any plans for a HV BEC to match?
At the moment the UBEC only support up to 6S, but the sensor board has NO limitation, even up 380VAC (not a joke) as long as you provide your own HV / UBEC to replace my one. Recommended output voltage of such BEC is 5.35V, but it will work also with only 5.2 or 5.0V.

However, the upper resistor of the voltage divider (for LiPo voltage measurement) must be replaced (on the sensor board) to match the required voltage range.
Last edited by MaoChris; Nov 03, 2015 at 06:27 PM.
Nov 03, 2015, 06:18 PM
AMA 697691 / FAA 13675
What is the reason for measuring current? To gain a sense of the capacity used? This can be determined by the battery charger and transmitter flight timer.

On my Power Modules, I do not run the battery lines through them and only use them for a regulated voltage to the flight controller and to measure the voltage by APM.

The voltage reading can be used for failsafe conditions and the reduction of connectors needed for passing current through the PM has its own benefits.
Latest blog entry: Greg's Web Hangar
Nov 03, 2015, 07:11 PM
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MaoChris's Avatar
Quote:
Originally Posted by Greg Covey
What is the reason for measuring current? To gain a sense of the capacity used? This can be determined by the battery charger and transmitter flight timer.

On my Power Modules, I do not run the battery lines through them and only use them for a regulated voltage to the flight controller and to measure the voltage by APM.

The voltage reading can be used for failsafe conditions and the reduction of connectors needed for passing current through the PM has its own benefits.
I was surprised to read your post and I was thinking a lot, before I send you any reply... So let me ask you first something back.

Why does you don't use the PM module for current measurement ?
Are you not interested in the actual current, or is it that you don't trust these tiny PM boards with high current ?

There are several benefits for current reading during flight:
- Calculation of used capacity from the LiPo.
- Fine-tuning of LiPo/motor/propeller combinations.
- Set up of an maximum allowed current controlled by the FC.
- Figure out the current change of the MR with different payloads.
Nov 03, 2015, 07:16 PM
Registered User
just4funxwing's Avatar
Quote:
Originally Posted by Greg Covey
What is the reason for measuring current? To gain a sense of the capacity used? This can be determined by the battery charger and transmitter flight timer.

On my Power Modules, I do not run the battery lines through them and only use them for a regulated voltage to the flight controller and to measure the voltage by APM.

The voltage reading can be used for failsafe conditions and the reduction of connectors needed for passing current through the PM has its own benefits.
I like to know how much current I am pulling...

It is the first clue some thing is wrong,

It is how I decide if one motor or prop is more efficient than another.

I like this information in real time.

Confirming this information on the ground is nice, but after the fact.
Nov 03, 2015, 07:54 PM
DroneWorlds - TEAM NEW ZEALAND
jackosmeister's Avatar
Would you do away with the fuel gauge in your car, because you normally only use a tank of gas a week?


Will be in touch MaoChris, have a swag of attopilot 180s I don't have much love for....
Nov 03, 2015, 08:57 PM
Registered User
Quote:
Originally Posted by Greg Covey
What is the reason for measuring current? To gain a sense of the capacity used? This can be determined by the battery charger and transmitter flight timer.

On my Power Modules, I do not run the battery lines through them and only use them for a regulated voltage to the flight controller and to measure the voltage by APM.

The voltage reading can be used for failsafe conditions and the reduction of connectors needed for passing current through the PM has its own benefits.
You must know nothing about this hobby, which is totally fine, but I have to ask: How did you end up in this thread???
Nov 04, 2015, 02:59 AM
Made in Germany
Im sure that Greg, whos a nice guy, doing great support for lo end Witespy RTFQ stuff beginners, has had his target audience in mind, which probably doesnt care too much about logs, COMPASSMOT , current related EMI impacts or stuff like this:

Quote:
There are several benefits for current reading during flight:
- Calculation of used capacity from the LiPo.
- Fine-tuning of LiPo/motor/propeller combinations.
- Set up of an maximum allowed current controlled by the FC.
- Figure out the current change of the MR with different payloads.
This audience is rather getting confused with off spec connector assignment of the cheap RTFQ Power Module and the only benefit for it would be sth. like a flight time to go indicator . We have to realize, that there lots of users around, who dont care at all for the details...

Btw. , by the time I used the VR uBrain, Ive been missing my current readings pretty bad. (although I first did not realized this) Only one input. (I/U by choice). Although this cute FC has been designed for very small copters, VR should have better skipped the JTag...
Last edited by gervais; Nov 04, 2015 at 03:12 AM.


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