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3496  Using Arduino / Project Guidance / Re: Isolating Multiple Power Sources on: June 30, 2013, 06:02:59 am
That approach is simple enough but you have to consider the voltage drop wich is around 1.5v if there is some resistive load.

Have you set a budget limit for that ? If not there are lots of interesting possibilities

1.5vdc? Most simple silicon diodes have a .7vdc drop approx or less if you use a Shockley type diode.

Lefty
Forward voltage increases with current (~70mV/decade), and most diodes have significant resistance too,
so once you talk about powering a circuit via a diode you may get to 1 to 1.5V territory (the same diode may be
0.6V for a small signal current, but once you get up to larger currents the resistive IR voltage drop starts to dominate).

Choosing an over-rated diode will help a lot (5A diode for instance).

You mean schottky diode, not Shockley (Shockley co-invented the transistor).  Schottky diode is preferred as
the power dissipation is much less likely to be an issue.  The reason schottky diodes haven't completely surpassed
pn-junction diodes is that reverse leakage current is higher (abyssmally so if very hot) and max reverse voltages are a lot less.
They work very well in low voltage circuitry at room temperature though.
3497  Using Arduino / Project Guidance / Re: IMU Digital Combo Board - 6 Degrees of Freedom ITG3200/ADXL345 on: June 30, 2013, 05:48:23 am
Links give 404
3498  Using Arduino / Project Guidance / Re: 24 motorized fader mixer with Arduino on: June 30, 2013, 05:45:01 am


I'm thinking that you want to control these while the music is going through them.
I would create an AC signal, much higher than the audio range, say 100-300khz or more and capacitively always mix that in with the audio.
The audio signal from each fader then gets split.  The high frequency AC signal gets filtered out, full wave rectified and capacitively filtered to provide a DC signal of "where" each fader is.   The faders are non-linear, since they have audio taper, but interestingly that doesn't matter for this app.  Your Arduino simply reads and samples these 24 DC voltages and stores them for re-use.


100kHz is too close to the ADC input bandwidth of professional audio equipment, usually 96, 192 or even 384kSPS.
Surely all the mixing is done in software anyway, the faders just generate a DC signal?  Suppose it depends on the
antiquity of the hardware!

Anyway are there links to the datasheets for some of this hardware?
3499  Using Arduino / Project Guidance / Re: QUADCOPTER AND SERVO SIGNAL on: June 30, 2013, 05:37:39 am


1) What does pwm frequency of esc signifies(WHICH IS 8KHZ OF MY ESC)?
2) ESC's (4 in nos) would be operated by pwm or servo signal with arduino?
3)Does frequency of servo signal in arduino(which is 50hz) has to be changed for controling esc's (4 in nos) in accordance with esc frequency(8khz) in it's datasheet?
4)If so , then how to change FREQUENCY of servo signal in arduino?
5)Is there any library in arduino to control esc??

6)should i buy this IMU for my quadcopter :- http://www.pololu.com/catalog/product/1268  
1) Ignore this, not your problem.
2) Use Servo library to control ESCs.
3) No, nothing to do with it.  You might want a higher servo signal rate for other reasons though
4) You have the source to the Servo library...
5) Servo
6) Wow, that's expensive.  How about 10DoF: http://www.ebay.co.uk/itm/10DOF-IMU-9axis-Indicator-L3G4200D-ADXL345-HMC5883L-BMP085-Sensor-Module-Arduino-/350812675742?pt=UK_ToysGames_RadioControlled_JN&hash=item51ae109e9e
Quote

1)SHOULD I LOOK FOR A BATTERY WHOSE x*y IS EQUAL TO CURRENT DRAWN BY 4 BLDC MOTORS ??
2)If two batteries have same mah and discharge rate product , then should i buy one with higher mah?
3)Which current i should consider in selecting  batteries - max. current specified in datasheet of motor or calculated from it's power and voltage or from ecal???

4)Should I buy 3S OR 4S battery for these motors ??
5)Which brand should I go for?
1) Don't understand "x*y"
2) Depends - weight is important.
3) measure the current the motor _actually_ takes when generating the required lift using the actual prop you will use,
you need to work out a mass budget and characterist your motor/prop combination.
4) Depends on the lifting power, props, etc.
5) Possibly the most important thing is how well behaved the ESC is to rapid correction feedback (consult quadcopter forums for
recommendations).  Most ESCs are designed for aeroplanes, not helicopters, note.
3500  Using Arduino / General Electronics / Re: powering micro controller and circuit through ac mains on: June 30, 2013, 05:14:43 am
You cannot run two full-wave rectifiers from the same secondary winding like that - they each need a separate winding.

You don't have enough separation on the board between high voltage and low voltage parts - minimum of 10mm would
be a good starting point.  (I'm assuming the relay contacts are high voltage).

Also I see no 0.1uF decoupling capacitors on the ATmega, and is there a ground plane for the logic area of the board?
Supply traces should to be thicker than signal traces, and the traces running to a fuse need to be able to carry more
current than the fuse!

Also AREF should not be connected to AVCC, it should just have a ~ 0.1uF capacitor to ground on it.

All the supply connections to the chip should meet underneath it, not run round the edges of the board, (ditto ground) and
both supply pins take 0.1uF ceramic decoupling caps right next to the relevant pin.
3501  Using Arduino / Sensors / Re: Pressure sensitive button like Playstation controller on: June 30, 2013, 05:07:29 am
For instance:

http://www.coolcomponents.co.uk/catalog/button-breakout-p-449.html
http://www.coolcomponents.co.uk/catalog/button-compatible-p-257.html
3502  Using Arduino / General Electronics / Re: Mosfet PNP - Burn on: June 30, 2013, 05:03:01 am
When I woke up I'll go see what the rest of the circuit and it will change.

Quote
p-MOSFETs in a high side-switching circuit have source to the supply, drain to the load
(first major error in the circuit).
In my schematic, Source is the source, drain is to the load ?


Ah, yes, but you connect the drain of one MOSFET to the gate pull-up resistors - this is what mislead
me, and its completely wrong.  pull-ups are always to the supply, otherwise you won't have pull-up
action when the device is off, so it won't turn off properly, so it might be half-on, and half-on means
the device explodes...
3503  Using Arduino / Sensors / Re: MPU6050 returning a null set after working previously on: June 30, 2013, 05:00:04 am
Yes, my guess would be that you are not initializing all the registers you need to, it
may be that some are starting up in a random state perhaps.

Also is the chip getting a proper reset cycle?  Check the datasheet for whether it
needs an explicit reset after power-up.
3504  Using Arduino / Sensors / Re: Inaccurate readings from integration with a L3GD20 gyro on: June 30, 2013, 04:57:55 am

I am currently trying out basic steps, and since it works flawlessly for single axis rotation, I was hoping to achieve something like that for multi axis rotation before I advance...


I repeat:  you cannot treat the axes independently for 3-D rotation, it doesn't work at all, not even slightly,
you will need DCM or quarternion code.
3505  Using Arduino / Sensors / Re: Comparing Accelerometer outputs for redundancy on: June 30, 2013, 04:54:33 am
With an array of accelerometers you are effectively sensing both the overall acceleration and the differential
acceleration due to rotatational forces....

So you method ought to be able to gate out readings from when the assembly is rotating, and hang onto the
steady state readings (gravity plus any linear accelerations).

You can also estimate rotation rates (but not direction) about axes perpendicular to your line of accelerometers!
3506  Using Arduino / Sensors / Re: Analog input readings are totally off on: June 30, 2013, 04:49:22 am
johnwasser: I thought about buying step-up/-down converter, but I thought they are of low resistance on the input side thus they couldn't run from solar cells...

Add a smoothing capacitor to the solar cell output and it'll be low impedance...

The main problem with running DC-DC converters from solar panels is that they are designed to work from
a voltage source, not a current source.   The capacitor will stiffen up the voltage nicely at short timescales
but when the supply current drops too low the whole thing is going to misbehave anyway.  This is why even
a small battery as an addition to a solar panel is a great idea (you can tolerate someone walking in front of
the solar panel!).
3507  Using Arduino / Sensors / Re: Separate power-supply for sensors (+ resistor) on: June 30, 2013, 04:43:20 am
Firstly the datasheet specifies a 1k resistor, not a 10k resistor - that seems to be a mistake
in the LadyAda tutorial (10k will work fine with no cable, but with a long cable its asking for
problems).

You place a pull-up resistor at the receiving end between signal line and Vcc (ie at the Arduino end).
Think of the pull-up resistor as the load that the sensor is driving, so the load must go at the receiving
end.

Ensure you have a decoupling capacitor at the sensor end from Vcc to ground.  Always use
shielded cable for sensors if you can, shield to ground.  Failing that use twisted pair for signal and
ground.
3508  Using Arduino / Sensors / Re: DS18B20 NOT RESPONDING on: June 30, 2013, 04:34:03 am
No luck with parasitic setup, or standard 5v setup with 3.3K pull-up. Maybe the images tell something.

Can't see how the sensor itself is wired.  How long is the cable?  Its not screened so wouldn't expect
it to work well if long.

Have you tried just wiring it up without the cable?

Is there a decoupling capacitor on the sensor (in 3-wire mode)?
3509  Using Arduino / Programming Questions / Re: int to byte to int doesn't return same value on: June 30, 2013, 03:58:58 am
Code:
  bint[1] = (byte) numberbefore >> 8;

was probably meant to be:
Code:
  bint[1] = (byte) (numberbefore >> 8) ;
casting binds tightly...
3510  Using Arduino / Motors, Mechanics, and Power / Re: How to Know if my motor will work with Arduino on: June 30, 2013, 03:47:43 am
Ahem, we still don't know anything about the motor in question...
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