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Old Jul 20, 2011, 11:39 PM
mostly newbie
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United States, CO, Centennial
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Wow that is nice work!! Thanks for posting this and sharing the info/code/schematics!
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Old Jul 21, 2011, 04:49 AM
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Dennis Frie's Avatar
Denmark, Capital Region of Denmark, Naerum
Joined Feb 2011
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I don't expect anyone have used the code yet, but;

Please be aware - in code version 0.01 "mahtemp" is defined as an integer (16 bit) and not a long (32 bit). When the total mAh consumed exceeds 3276.7 mAh it will give overflow. This will cause the 17. bit to be written "somewhere". In most cases nothing will happen - but it's not a good idea to write bits at random addresses.
Updated code will follow after further testing.
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Old Jul 21, 2011, 05:21 AM
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Lithuania
Joined Jan 2007
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Nice. Will try to build it soon.
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Old Jul 21, 2011, 08:07 AM
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Denmark, Capital Region of Denmark, Naerum
Joined Feb 2011
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Anyone who have used the Allegro current sensors (ACS755)?

it seem to have about 600 mv offset - and until 5-10 amps load it stays at 600 mv. Any good ideas? Hopefully it's the last thing that needs to be fixed before I can make the final installation in my plane.

It's all connected and works fine so far - except for the current sensing.

EDIT; Tested and calibrated on breadboard - works fine. Will do another test in plane later
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Old Jul 21, 2011, 10:27 AM
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Congratulations on a successful and quick build!
Very cool, thank you.
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Old Jul 21, 2011, 12:39 PM
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Dennis Frie's Avatar
Denmark, Capital Region of Denmark, Naerum
Joined Feb 2011
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Found the problem with the current-sensor. This is what the output signal looks like. That will make the micro-controller will read more or less random values.
A descent lowpass-filter or some extra capacitors in front of the ESC should do the trick.

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Old Jul 21, 2011, 01:27 PM
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Quote:
Originally Posted by Dennis Frie View Post
Anyone who have used the Allegro current sensors (ACS755)?

it seem to have about 600 mv offset - and until 5-10 amps load it stays at 600 mv. Any good ideas? Hopefully it's the last thing that needs to be fixed before I can make the final installation in my plane.

It's all connected and works fine so far - except for the current sensing.

EDIT; Tested and calibrated on breadboard - works fine. Will do another test in plane later
Notice that this part is no longer in production. From datasheet, it has good linearity (2.8% over full range), and 60mV/A sensitivity.

The datasheet gives an offset of 600mV as you've measured. You have to substract it. So for example 600mV is 0A, and 600mV+60mV = 1A, 600mV+120mV=2A etc.

There is also 68 mV noise, but it should be easily reduced with some filtering.
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Old Jul 21, 2011, 01:37 PM
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Dennis Frie's Avatar
Denmark, Capital Region of Denmark, Naerum
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Quote:
Originally Posted by flipflap View Post
Notice that this part is no longer in production. From datasheet, it has good linearity (2.8% over full range), and 60mV/A sensitivity.

The datasheet gives an offset of 600mV as you've measured. You have to substract it. So for example 600mV is 0A, and 600mV+60mV = 1A, 600mV+120mV=2A etc.

There is also 68 mV noise, but it should be easily reduced with some filtering.
Year, the 600 mv offset is no problem at all - the problem was, that it couldn't measure 0-6 A. The capacitor removed the ripple from the ESC, but the current sensor wasn't too happy about the large capacitance. A normal lowpass-filter with a low capacitance works better .
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Old Jul 21, 2011, 02:57 PM
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Lithuania
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Maybe later arduino autopilot?
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Old Jul 21, 2011, 03:18 PM
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United States, IL, Addison
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I <3 you, was going to do the same. Subscribed!
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Old Jul 21, 2011, 04:44 PM
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SW England
Joined Aug 2009
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Dennis,
In your schematic, what values for R1 and C1 ? as I don't see it anywhere else in the thread.

See, I am paying attention

Nigel.
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Old Jul 21, 2011, 06:22 PM
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Denmark, Capital Region of Denmark, Naerum
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Quote:
Originally Posted by vipix View Post
Maybe later arduino autopilot?
I will maybe make an autopilot later, but I don't plan to do anything official, as projects like ardupilot etc. is probably a better choice if you just want to use a finish code.

Quote:
Originally Posted by Devonboy View Post
Dennis,
In your schematic, what values for R1 and C1 ? as I don't see it anywhere else in the thread.

See, I am paying attention

Nigel.
Please play a bit with the circuit yourself. You might want to take a look here aswell;
http://www.viennawireless.org/balloo...rlay/index.php
But i strongly recommend to use a pot as voltage-divider.

If I make another one I will consider a diode with a little higher voltage drop and much lower R2 value. Might also add the capacitor as well.

R2 is 220 ohm (Written in schematic, but not very clearly). The value is not very important, you can try a few different and pick the value/brightness you prefere.
C1 is 0.1 uF, but other values should work fine. I actually tried something like 25 uF capacitor which worked without problems (but not recommended )
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Old Jul 22, 2011, 02:56 AM
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SW England
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Ok, thanks.
I was asking about R1 (not R2 as it is defined in your schematic) but from your link I see 680k is suggested for R1 and I know I have a 1M pot in my parts bin...

Nigel.
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Old Jul 22, 2011, 03:13 AM
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This would be also a compatible board right: http://www.seeedstudio.com/depot/see...?cPath=132_133
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Old Jul 22, 2011, 05:15 AM
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Denmark, Capital Region of Denmark, Naerum
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Quote:
Originally Posted by Devonboy View Post
Ok, thanks.
I was asking about R1 (not R2 as it is defined in your schematic) but from your link I see 680k is suggested for R1 and I know I have a 1M pot in my parts bin...

Nigel.
arh sorry. I have used a 50K pot. 1M pot should work, but it will probably be more sensitive to RF-noise etc.
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