The model I bought came with internal pull-up resistors and it works just fine. However open collector would work OK with an Arduino if you either activate the internal pull up resistors or wire pull up resistors yourself.

 If you go with a encoder with internal pull-ups just insure you are getting a 5vdc model. If the encoder uses a higher voltage then +5vdc the you will either have to wire a voltage divider for each channel or go with the open collector model.

Lefty

The answer depends of if the board's power is being sourced from the USB connection or the external power jack. You can draw more +5vdc current if you are using the external power input. USB current is limited to anywhere from 100ma to 500ma depending on who you ask. It's not clear to me  if the serial converter chip, FT232RL, being used does the needed negotiations for more then the default 100ma USB current limit.

If using the external power source then the 5vdc current would be limited by the current rating of the reverse isolation diode or the combined current limit of the 2 5vdc 800ma voltage regulators, minus what ever 5vdc current is consumed by the board itself.

So as you can see it is a little difficult to give you a specific answer to how much +5vdc current is available for use external to the board.

Lefty

Is it safe to run motors or etc off of the same battery as the Arduino, so long as it's not actually running out of the Arduino's output power? Or is it the case that those amount to the same thing, and one really ought to run noisey elements off of an entirely different battery than the Arduino?

 It really depends on how much current is being drawn and how "noisy" the load. Best is independent supply, but powering loads from the external power output pin, Vin, often works fine. Last choice is using the internal 5vdc power, however using that voltage is fine for powering low current ICs, pull-up resistors, standard LEDS (if not too many), etc.

By the way, standard 9vdc batteries usually can not supply the current requirements for things like motors and servos, unless they are of exceptionally small current draw types.

Good luck
Lefty

T;

 Sounds like your test meter is toast. There is no way a 9volt battery should measure 18volts. Are you sure you have it set for DC volt function and not some other function?

As far as using the regulator 5vdc for powering off board components, it can be done but special attention has to be given to how much extra current will be drawn. Also some loads like motors are notorious for generating lots of noise and grunge causing problems. It is almost always better to power off board loads like motors, solenoids, servos and high power LEDs with an external power source, but remembering to wire the ground connection between the internal and external circuits.

Lefty

although oddly it does seem to like to revisit the same moment in time more than once

Well time does tend to march on.

What is exactly your expectations here? How often the time is read from the RTC and sent out to the serial monitor is a function of the cycle time of your program, the I2C link speed and the baud rate of the communication channel rather then the RTC module. If you wish each time capture to be unique then you will have to test each recieved and throw away duplicates. Or put a delay of one second in your loop somewhere.

Lefty

It's only a two wire servo.

I would think of it just as a DC motor. You will have to find out it's maximum current specification and then figure out how you wish to control the motor. If you need bidirectional control you will need a H-drive controller, it just single direction then PWMing a power transistor would work. Even at the  unloaded 63ma specification you can't draw that much current from a Arduino I/O pin, plus one really should design their motor drive circuits with either current limiting protection or the ablity to supply locked rotor current.


Lefty

Only in concept. An Arduino (except the latest Mega model) cannot directly control 27 LEDS (not enought I/O pins avalible) so one generally uses external shift register chips to clock out the desired state of the 27 LEDs.

Lefty

I may have misled on the pull-up or LED wired to the clock output pin. It's a open drain output so the current drawn will be from whatever is powering the other side of the LED or pull-up, not the battery.

Lefty

Has anyone else experienced anything like this?  Any spells, incantations, or funny dances I could try?  I just want to finish this project and move on to something else!

Without seeing your complete wiring it's hard to guess what is happening. Just to clear up how the Batt voltage works, it does not power the whole chip, it just maintains the oscillator and basic counters needed to maintain the time until VCC voltage is next applied. I2C communications can only work while there is +5vdc on the Vcc terminal. Also while in the 'battery save' mode you probably don't want the 1hz signal driving a LED or even a pull up resistor as that will discharge the small battery much faster then the design calls for. The battery only needs to supply micro amps of current during the power off period and any electrical load on the clock signal output will increase the battery current significantly.

Any of this help?

Lefty

Also how are your wiring the PC temp sensor to the Arduino board, how many wires? is there a common ground connection, etc.

Lefty

Or does that make no sense for some reason?

As RT posted this won't work. The FT232R is a 'magic' chip that is UART compatable serial data on the Arduino side but a USB device on the PC side, so you can't use the data pins on the USB connector as a serial data stream because it's not serial data there but rather a USB client chip that can only wire to and talk a USB host controller.

Lefty

Once you disconnect from the PC usb port the  FT232RL chip can no longer be used by the Adunio. However you should still be able to use digital pins 0 & 1 which are the ones that wire from the AVR chip to the FT232RL. That make sense?


Lefty

http://www.arduino.cc/playground/Code/Programmer2

To check out the motor I would think that a ohm meter check to make sure all the windings still have continuity (good) and a check to see if there is any continuity between windings and the motor case (bad).

Lefty

Not many temp sensors go that high. A K thermocouple will if made with the correct insulation material. While the basic K couple will measure to 1350F, you have to find one using insulation rated at or higher then the highest temp you will be subjecting it to.

http://en.wikipedia.org/wiki/Thermocouple

Lefty