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1  Forum 2005-2010 (read only) / Bugs & Suggestions / Re: Ethernet software bug - SPI access & ext ints on: October 21, 2010, 08:11:18 pm
Turning off interrupts is not something to be done lightly.

Could you explain this? I'm writing code to log RPM's read using interrupts to an SD card. If I shouldn't disable interrupts, what are the reasons?
2  Forum 2005-2010 (read only) / Syntax & Programs / Re: problem with interrupt and writing to sd-card on: October 02, 2010, 08:21:47 pm
Did the issue ever get resolved? I'm trying to build an arduino/datalogger/accel/rpm reading device, and I'm worried about doing SD card work with interrupts going on at the same time.
3  Forum 2005-2010 (read only) / Interfacing / Re: LM2907 vs. LM2917 on: November 02, 2010, 07:16:34 pm
To compute RPM you can then use millis() (or similar) to define a particular time interval, then see how much Timer 1 has changed during that time interval. That can easily be converted to RPM.
That does sound quite elegant, can it be done in the Arduino IDE, or would I have to program that in assembly?

Here is my rpm calc code:
// Sensor Reading-------------------------------------------------------------------------------------

  if (gearCount >= 15) {
    gearRpm = gearCount*25000000L/(micros() - gearTimeold);
    gearTimeold = micros();
    gearCount = 0;
    if (tachCount >= 15) {
    tachRpm = tachCount*60000000L/(micros() - tachTimeold);

    tachTimeold = micros();
    tachCount = 0;
Here are my ISR's
void gear_fun()
  //Each rotation, this interrupt function is run twice

void tach_fun()
  //Each rotation, this interrupt function is run twice

And this is my RPM output (although rpm's are *10- i messed up calculations):

As you can see it is quite noisey, and the acceleration data could be smoother.
4  Forum 2005-2010 (read only) / Interfacing / LM2907 vs. LM2917 on: November 02, 2010, 04:35:38 pm
I'm hoping to read the RPM of a gearbox using a hall effect sensor and a frequency to voltage converter IC. I'm using interrupts to calculate RPM right now, but I think having a dedicated chip count pulses will make life easier when trying to log data to an SD card.

Can anyone help me out choosing the right lm2907 package? The datasheet lists the lm2907 and lm2917, as well as another variation on each of those, which seems to relate to input voltage.

The main difference I see in this project is that the hall effect sensor is like a switch, as opposed what ever (inductive?) signal is measured from an engine's distributor as many other projects do.

I hope to run the circuit off of the Arduino's 5V regulator, and read the input on an analog input.

5  Forum 2005-2010 (read only) / Interfacing / Re: Arduino Stepper Shield on: December 29, 2009, 05:30:17 pm
I've been doing so much stepper driver webbing today, that I've almost lost my mind! After re-browsing quite a bit, I realize that makerbot uses the reprap stepper drivers, presumably, the ones hoeken developed?
6  Forum 2005-2010 (read only) / Interfacing / Re: Arduino Stepper Shield on: December 29, 2009, 02:19:57 pm
@Hoeken Hey, What is the status of this thing now? I know that you have got the MakerBot going, which looks great- Does it run off this, or did this get somewhat abandoned?

I was thinking about making an open source stepper driver, one that would have a bit better performance than the easydriver (also cheaper if possible). I was looking at allegro all in one chips, as opposed to the L297/L298 combo, but I was having a tough time picking between them.

That said, am I right in thinking that you opted for easydrivers in the end?

Anyway, I'd love to know what the status of this is. Thanks!
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