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1  Using Arduino / Motors, Mechanics, and Power / Re: How can I use Arduino Uno control a stepping motor? on: Today at 12:31:12 pm
Arduino communicates via USB-serial port.  Many programs can drive that.

Which stepper motor?  There are basically two kinds and they are not
really the same.  Low-impedance bipolar steppers have high performance and
need a constant-current chopper-drive controller (the Pololu A4988
is a common example for small steppers).  High voltage supply allows
faster operation.

Unipolar steppers with high impedance windings are the other sort, and
often a ULN2803 or 4 BJTs is all that's needed to interface them.  The
supply voltage is fixed and maximum motor speed is modest.

There are libraries to drive steppers, called, appropriately Stepper and
2  Using Arduino / Motors, Mechanics, and Power / Re: More efficient than a L298... on: Today at 12:27:42 pm
Anything except an L293D....  The problem is none of them
are cheap except for the surface mount chips.  LMD18200T
I've used and its 0.3 ohm MOSFETs I think, for significantly
better performance Pololu have the co-packaged MOSFETs+driver
in the form of the VNH5019 and similar.

BTW the lower limit for integrated DMOS H-bridges is about 0.25 ohm
per switch, this is fundamental to DMOS process I think.

Discrete power MOSFETs go down to 0.001 ohm and below.
The VNH5019 has 4 MOSFETs and a driver chip co-packaged
(power MOSFETs use the substrate as the drain, so you need
at least 3 chips (the high switches can share substrate).

With good modern superbeta BJTs you can build a decent H-bridge
in the 1..5A range with low Vsat (< 0.3V) - however they are
nearly all surface mount.
3  Using Arduino / Programming Questions / Re: array without delay on: Today at 12:14:20 pm
"nextCount" is a poor choice of name for a constant that is a time delay.
How about "display_delay"?

And "lcdCount" can be "lcd_time" much clearer...

You need to subtract before compare if comparing time values as
they wrap-around, whereas the difference cannot wrap if the delay
is reasonable.

void loop()
  if (millis() - lcd_time >= display_delay) // subtract before compare
    lcd_time += display_delay ; // move target a fixed delay
    ... stuff ....
4  Using Arduino / General Electronics / Re: Schottky Diode on: Today at 12:06:48 pm
Hi guys,
I´m looking for a high speed schottky diode, had anybody made some experince with these.

Otherwise I´m not sure if these diodes fit to my needs. I like to convert a sawtooth signal to a  square wave signal (round about 30MHz would be nice) .
Are there other simple ways to realize or does anybody knows where to get such diodes with the appropriate properties?

Thank you !!!


They don't make "low-speed" schottky diodes!

Without knowing what circuit you were contemplating its hard to
say anything useful.

What is this sawtooth signal, voltage and impedance, what quality of square wave do you
want from it (it does sound like a job for a high-speed comparator)?

High speed comparators are notoriously unstable and pretty much mandate a
ground plane.

Its not impossible to have a good quality saw or square wave at 30MHz if you know
what you are doing - which means using video amps and transmission line.
5  Using Arduino / General Electronics / Re: Resistor's capacity on: Today at 11:59:34 am
Some value between 150 and 1k for LEDs, practically anything from 500 to 50k for
pull-ups or pull-downs...

BTW "capacity" is a property of containers, resistors have "resistance" and capacitors
have "capacitance".
6  Using Arduino / General Electronics / Re: Which Voltage Regulator use ? on: Today at 11:47:02 am
The OP is looking for a regulator with ultra low quiescent current (20uA or less I guess).

I'd query the need for a regulator at all - use LiFePO4 cell and you have ~3.3V supply
and no chance of battery bursting into flames...  Finding a LiFePO4 in the right form factor
may be tricky though.
7  Using Arduino / General Electronics / Re: DC-DC Converter Step Up Down problem, Gets Very Hot! on: Today at 08:31:44 am
Peltiers are very good conductors of heat when powered down, so for a fridge they
have to be continusously powered otherwise you've just got a coke-can connected
to an external heatsink!

You also need more current to sustain a larger temperature difference across the
device, meaning that running a peltier at 10% nominal level is fairly pointless for
a fridge.   Without some mechanical means of decoupling the peltier thermally
you cannot employ a duty-cycle style cooling regime like a standard fridge.

A peltier coupled to a coolant loop with a pump would permit running the peltier
at best efficiency point on a duty-cycle basis, but even so they are woefully inefficient
compared to standard refrigeration technology.
8  Using Arduino / Programming Questions / Re: Rotary Encoder to measure velocity on: Today at 08:21:26 am
Perhaps you missed the word "mechanical" there?  They do program, but its in Gcode... smiley-wink
9  Using Arduino / Programming Questions / Re: Button interrupts - arduino uno - help on: Today at 08:16:04 am
The Uno supports interrupts on every pin via the pin-change interrupt mechanism,
as well as the two "external interrupt" pins D2 and D3.  Pin change interrupts have
the granularity of a port, not a pin, so you have to write code in the handler
to investigate what change happened.

To detect human input an interrupt is overkill, its much neater just to look at
the pin with digitalRead() in loop().

Interrupts are useful when dealing with frequent or urgent events (think 1kHz
or above, microseconds).
10  Using Arduino / Programming Questions / Re: PIN CHANGE interrupt by software on: Today at 08:08:32 am
If i am not wrong the interrupt type you try to use it is for check  (fire the interrupt routine) when a pin goes from high to low or reverse, but the pin must be as INPUT and not OUTPUT (use external buttons)   if you want every some ms to do something you need the TIMER interrupt.

pin change interrupts fire when any of the pins in that port that aren't
masked-out change, whether or not they are inputs or outputs.

For instance you can use a PWM pin to trigger a pin-change interrupt that
will fire everytime the PWM output transistions.
11  Using Arduino / Programming Questions / Re: Making a DC motor wait for conditions on: Today at 08:03:05 am
Your system has a number of states.  In each state the behaviour (ie the correct
response to various inputs and timeouts) is different.

Thus you need a variable or variables that record the current state explicitly.

So first go and write down the various states, and the relevant inputs or timeouts
that cause particular outputs and state changes.  This is a state-machine and all
non-trivial sketches tend to be written this way because it allows different things to
be controlled in (pseudo) parallel.

loop() ends up being a big switch statement dependent on the current state.
12  Using Arduino / Programming Questions / Re: PIN CHANGE interrupt by software on: Today at 07:57:27 am
PCINT0 does port B (pins 8 to 13)
PCINT1 does port C (pins A0..A5)
PCINT2 does port D (pins 0 to 7).
13  Using Arduino / Programming Questions / Re: RSA Or ECC Library on: Today at 07:54:44 am
Well its a tight fit for RAM I think - certainly for RSA with secure keylengths being
what they are now.

ECC takes less space but you'll have to implement discrete elliptic curve operations
over at least one of the NIST curves, which I doubt anyone trusts any more with
the Snowden revelations.
14  Using Arduino / Motors, Mechanics, and Power / Re: Help with: Stepper Motor Power-off when not in use on: Today at 07:36:23 am
Perhaps you should tell us some details like which stepper motor,
which stepper motor driver, how they are powered, which library(s)
you are using (your code?)....
15  Using Arduino / Motors, Mechanics, and Power / Re: Steppermotor and serial.print and read combined on: Today at 07:34:52 am
Curious what I do wrong.

Button currrently controls up and down movement of the stepper motor.
Code works but as soon as I uncomment a line related to serial.print it also stops to work correctly.
You need to explain what working correctly and working incorrectly means for
your code, and to tell us which line you commented/uncommented.

Am I asking to much from this combo?
Perhaps explaining exactly what you want would be a start.

And why are you setting the enable pin of the stepper motor low - it would normally
just be tied to 5V and left that way.

Is there a reason you forgo the AccelStepper library btw?
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