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5791  Using Arduino / Programming Questions / Re: DS1307 and writing problem into 56 internal ram on: March 04, 2013, 05:49:16 pm
Can you clarify which library and version?  And do you already have code (its much easier to
give concrete examples relating to existing code)

Conceptually the DS1307 looks like a 64 byte non-volatile RAM with special behaviour of the
first 8 addresses.  The I2C interface allows specifying a starting address and then writing or reading
consecutive bytes from that point.
5792  Using Arduino / Sensors / Re: analogRead() reading non-existent fluctuation? on: March 04, 2013, 10:57:11 am
You probably need low-pass filtering on the sensor inputs - something in the range 1nF to 10nF to ground for both
green and white wires ought to help - the leads to the sensor may be picking up noise, the sensor itself may
be noisy.

Multimeters use integrating ADCs so they effectively low-pass filter down to 1Hz or less bandwidth - the ADC on
the Arduino has a bandwidth more like 10kHz.
5793  Using Arduino / Motors, Mechanics, and Power / Re: Long range PTZ turret on: March 04, 2013, 07:16:18 am
The DC motor has no encoder so no accuracy at all.  The actual precision of the stepper motor will be limited by
the backlash in the gear system (which I believe is not 64:1 as they claim, but a ratio very close to that - I seem
to recall a thread about this a year ago).
5794  Using Arduino / Motors, Mechanics, and Power / Re: dc motor as a variable resister? or potentiometer? or encoder on: March 04, 2013, 07:11:55 am
Not a normal motor.
Perhaps a brushless motor, but I'm not sure.


Not really - although for a constantly turning shaft you can measure the number of electrical cycles
and act as an encoder - but stationary motors produce no signal, and very slowly moving one's almost
nothing.

What are you trying to detect/measure?
5795  Using Arduino / Displays / Re: SSD1963 controller with 7" TFT (horizontally mirrored image) on: March 04, 2013, 07:04:18 am
The most promising option seemed to be:

0x36 Set_address_mode

BUT

NOTHING happens no matter what I change the value to, in fact if I comment out the line it makes no difference.

Address mode only changes the behaviour on sending multiple pixels - IIRC the UTFT library sets up bounding
rectangle before drawing lines / blocks and then sends the right number of pixels - the bounding rect ensures
all the pixels end up in the right place whatever scan-direction is used.

The gate-scan and source-scan bits are what you need to find.
5796  Using Arduino / Displays / Re: Uno and 7" LCD on: March 04, 2013, 06:59:26 am
21 level shifters???
5797  Using Arduino / Displays / Re: Uno and 7" LCD on: March 03, 2013, 07:03:12 pm
That display is 3.3V logic and 16 bit parallel only, so you'll need 21 pins to talk to it....

A 5V display with 8bit parallel support would be easier...

One way to reduce the pin count is a couple of 74HC595 shift registers (run at 3V3) to drive the 16 bit databus
using the Arduino SPI hardware, and then you'll only need about 8 level shifters rather than 21.
5798  Using Arduino / Displays / Re: OLED Library Messing Up RFID on: March 03, 2013, 06:56:21 pm
Also check if there's enough spare memory perhaps?
5799  Using Arduino / Displays / Re: SSD1963 controller with 7" TFT (horizontally mirrored image) on: March 03, 2013, 06:52:39 pm
All these LCD drivers have a bit to control gate-scan direction and a bit to control source-scan direction,
check the datasheet for where these are in the registers.  Don't change the RAM addressing unless you
want to switch landscape <-> portrait - if I remember correctly.

Again if I remember rightly the usual set up is that the RAM addressing bit simply transposes X and Y, which
means a reflection about a diagonal.  There are 8 combinations of these 3 bits giving access to every
rotation and refection sense.  Rotating by 90 degrees involves changing the RAM addressing and one
of the other reflection bits.
5800  Using Arduino / General Electronics / Re: M7 Diode on: March 03, 2013, 06:46:23 pm
The series protection diode should ideally be a schottky diode, then the voltage drop would be more like 0.3 to 0.4V

In fact there are few circuits where a silicon diode is preferred over a schottky diode - schottkys' main weakness
is higher reverse leakage at high temperature, but is generally superior for most uses below 60V or so.
5801  Using Arduino / Motors, Mechanics, and Power / Re: Stepper motor shield supporting 4 or more stepper motors on: March 03, 2013, 06:36:31 pm
Hi,

I'm currently trying to build a DIY pick-and-place machine as was wondering if there is a motor shield compatible with the Arduino Mega2560 that supports 4 or more stepper motors. I've searched the web for days and have not found anything that does. The closest I've come is the Makerbot Motherboard, but it doesn't seem to be compatible with the 2560. I am new to this so any help would be greatly appreciated.

Regards,
Lee

How big are your motors - over 1A or so is going to be more problematic.  NEMA 17 size is likely to be
fine with this (make sure you get low-resistance low-inductance bipolar motors for these A4983 and A4988
driver boards)
5802  Using Arduino / Motors, Mechanics, and Power / Re: arduino with DE10 Programmable Brushless ESC on: March 02, 2013, 09:16:19 pm
Yes, Servo.  You need to find out what arming sequence the ESC needs too (trial and error - but often min-throttle for several seconds
will work).


[edit:  oh yes, watch out for that 6V BEC - don't try connecting it to 5V logic!]
5803  Using Arduino / Motors, Mechanics, and Power / Re: Help with stepper motors? on: March 02, 2013, 09:13:54 pm
Quote
I'm powering it with 12V, as necessary, and have the four wires from the stepper going into pins 8-11.
Stop right there. That arrangement will damage your arduino from both excess current and excess voltage.
You need some sort of driver.

Indeed - you also need to test pins 8 to 11 to see if they are still working properly - directly connecting an inductive
load (all motors are inductive loads) to sensitive electronics is a recipe for fried components.
5804  Using Arduino / Motors, Mechanics, and Power / Re: Will these boards power larger stepper motors? on: March 02, 2013, 09:10:33 pm
There's some info on that motor in this thread: http://arduino.cc/forum/index.php/topic,19958.0.html

I think the easystepper ought to handle it - check the winding resistance is the same.  What are the dimensions
of the motor - similarly sized steppers tend to have roughly the same power (I-squared-R) ratings since often
the design is thermally limited.

Although the EasyStepper claims to go upto 0.75A it will run mighty hot at that level from what I can see
of the specs - start at a smaller current and work your way up checking the temperatures are sensible.
5805  Using Arduino / General Electronics / Re: Differential amplifier noise on: March 02, 2013, 08:58:54 pm
Filtering out any RF on inputs is always a good idea for sensitive DC circuits like this - 1nF ceramic across all the load-cell input leads
should kill any RF pickup without affecting the frequencies of interest.  Ferrite toroid on the whole lead close to the breadboard is
also another possibility.

Definitely keep all the wiring on the breadboard short and neat and supply decoupling capacitors are _obligatory_
for a high-gain amplifier, otherwise it is very likely to oscillate via supply-rail feedback.  A ground-plane would be nice,
though obvious difficult on a breadboard.  One can add a grid of ground wires across the whole breadboard to
improve matters.

Reducing the gain in the circuit will reduce risk of instability/oscillation BTW.
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