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Old Dec 21, 2012, 10:43 AM
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Dennis Frie's Avatar
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Originally Posted by Nosepo View Post
One question, I use the Bts555 for turn on/off my multicopter and this part have a Ampere sensor built-in. Do you think i can use it for Ampere count in your OSD system?

Datasheet:
http://www.datasheetcatalog.org/data...n/1-bts555.pdf
The current-sense should be an analog voltage at 0-5 volt max. I don't know what output-range BTS555 have and how it's scaled, but it should be possible.
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Old Dec 21, 2012, 10:49 AM
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Dennis, may I ask please, is there a better way to measure battery voltage other than using a resistor voltage divider? What about using an comparator op-amp with a precision voltage regulator as a reference voltage? If so, would you have a sample circuit?

Thank you.
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Old Dec 21, 2012, 10:55 AM
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Originally Posted by rimshotcopter View Post
Dennis, may I ask please, is there a better way to measure battery voltage other than using a resistor voltage divider? What about using an op-amp with a precision voltage regulator as a reference voltage? If so, would you have a sample circuit?

Thank you.
Why would you use any other solution to measure the voltage? A voltage-divider is a very easy way to scale the voltage, completely linear and the accuracy only depends on the resistors (with normal 1% resistors the accuracy is quite good).

If you have noise on the measurements etc. that's another problem.
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Old Dec 21, 2012, 10:59 AM
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Originally Posted by Legot View Post
Without breaking open the NAZA gear and going directly off of the component contacts, there isn't really a good way to talk to them.

I don't believe it is possible to have an AVR talk to the CAN bus (which is what the Naza sensors connect to) without some external CAN bus ICs. IMO, it wouldn't be worth it to add compatibility with the Naza because of the protocol hacking and extra component cost/space that would be required. Especially considering that Naza isn't inherently open source, and its so expensive that most people considering this nature of OSD wouldn't go for it.
The new Arduino Due has native support for CAN bus. It's also fast enough and has enough RAM to keep more operations as floating point. Kind of expensive, though.
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Old Dec 21, 2012, 11:02 AM
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Originally Posted by Ace4 View Post
The new Arduino Due has native support for CAN bus. It's also fast enough and has enough RAM to keep more operations as floating point. Kind of expensive, though.
That's a 32 bit CortexM3 ARM processor, which is quite another league
But I gotta admit, the new ARM-processors begin to look more and more interesting as the prices gets close to the normal 8-bit controllers.
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Old Dec 21, 2012, 11:03 AM
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Originally Posted by Dennis Frie View Post
Why would you use any other solution to measure the voltage? A voltage-divider is a very easy way to scale the voltage, completely linear and the accuracy only depends on the resistors (with normal 1% resistors the accuracy is quite good).

If you have noise on the measurements etc. that's another problem.
Well, the best reason is the resolution of the ADC on the Arduino. With the OPAMP, I assume it can be scaled to 0-5 volts.
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Old Dec 21, 2012, 11:10 AM
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Originally Posted by rimshotcopter View Post
Well, the best reason is the resolution of the ADC on the Arduino. With the OPAMP, I assume it can be scaled to 0-5 volts.
If you use 0 - 15 volt you will have a resolution of:
15 V / 1024 steps = 0.0146 V ~ 15 mV resolution.

For the purpose of measuring the battery-voltage on a plane, better accuracy is not needed at all.

If you really want to have better resolution, you can use a differential amplifier with a reference-voltage. Then you should be able to get a resolution around 5 mV instead.

At the moment I only show 1 decimal on the voltage-measurement. That's approximately 5 times worse than the ADC accuracy with standard voltage-divider.
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Old Dec 21, 2012, 11:37 AM
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What I had hoped for and sooner or later, I will find it, is a means of measuring voltage regardless of the number of cells connected. Example: the circuit would have a voltage selector for 2,3,4, etc and the output would be 0-5 volts regardless indicating full(4.2 volts per cell) to empty (3.3 volts per cell).
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Old Dec 21, 2012, 11:43 AM
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Originally Posted by rimshotcopter View Post
What I had hoped for and sooner or later, I will find it, is a means of measuring voltage regardless of the number of cells connected. Example: the circuit would have a voltage selector for 2,3,4, etc and the output would be 0-5 volts regardless indicating full(4.2 volts per cell) to empty (3.3 volts per cell).
I would recommend just to change resistors instead, unless you really need the accuracy. Even with 10S li-po (lets say 50 volt max), you will have an accuracy of 50 mV which is still better accuracy compared to what's being shown.

Using an OP-AMP with a gain of 0.1 or similiar will give the exact same result as the resistors. If you use it as a differential amplifier and a reference voltage you can use the top (say 9 - 13 volt for 3S lipo), which will off course give better accuracy.

but with all the switching-noise etc. you will need quite an anti-aliasing filter to use it for anything practical.
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Old Dec 21, 2012, 11:47 AM
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Thanks Dennis.
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Old Dec 21, 2012, 11:48 AM
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Originally Posted by rimshotcopter View Post
Thanks Dennis.
No problem. Let me know if you decide to try anyway and need a quick schematic
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Old Dec 21, 2012, 01:24 PM
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Hi guys ! i'm following this thread since is begin, and i have to say that you've done a great job !

i'm not new to arduino, but not expert too =p i just receive my breakboard MAX7456 and i want to give a try to this beautiful project !

first i dowloaded your last release v.07 and send it to my arduino (I own a MEGA 1280)

i wire the breakboard like the pictures on the first post of this thread. Now i see the pictures from my camera, but nothing.. no text or number on screen ?? it is normal ? and i have to do something ?

thanks again guys !
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Old Dec 21, 2012, 01:37 PM
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Originally Posted by BillyJo View Post
Hi guys ! i'm following this thread since is begin, and i have to say that you've done a great job !

i'm not new to arduino, but not expert too =p i just receive my breakboard MAX7456 and i want to give a try to this beautiful project !

first i dowloaded your last release v.07 and send it to my arduino (I own a MEGA 1280)

i wire the breakboard like the pictures on the first post of this thread. Now i see the pictures from my camera, but nothing.. no text or number on screen ?? it is normal ? and i have to do something ?

thanks again guys !
Great to hear we have another one giving it a try
The Arduino mega with Atmega1280 have different pin-output.

One solution is to use the ISP-header. It provides all the connections you need except SS.

But here is what you need on Arduino Mega (1280 version):
SS = 53
SCK = 52
MOSI = 51
MISO = 50

Uno have:
SS = 10
MOSI = 11
MISO = 12
SCK = 13

So if you just use the drawing as reference but use the pin-change written above you should be good to go
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Old Dec 21, 2012, 01:50 PM
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thanks for your fast answer, but nothing again.... did i have to change these pins number into functions.cpp ?
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Old Dec 21, 2012, 01:59 PM
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Originally Posted by BillyJo View Post
thanks for your fast answer, but nothing again.... did i have to change these pins number into functions.cpp ?
Oh, that's right. You don't have another Arduino by any chance? As it's an Arduino Mega the pins is also different on the chip itself.

If you wanna try with the mega:

In functions.cpp you can find this:
#define CS 2 //PB2 Select
#define MOSI2 3 //PB3,
#define MISO2 4 //PB4,
#define SCK2 5 //PB5, clock output

I THINK it should be like this for the mega:
#define CS 0 //PB0 Select
#define MOSI2 2 //PB2,
#define MISO2 3 //PB3,
#define SCK2 1 //PB1, clock output
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