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1  Using Arduino / Programming Questions / Re: Getting a 1us delay on: January 30, 2013, 05:45:19 pm
Does anybody have a working code snippet I could use to achieve that?
2  Using Arduino / Programming Questions / Re: Getting a 1us delay on: January 30, 2013, 09:54:48 am
Quote
I am trying to measure a time of 1us.

Is that the right strategy to capture 1us resolution?

Which?  Measure an elapsed time of 1 us or measure something with a resolution of 1 us?


Hi,

I am trying to measure something with a resolution of 1us. I was thinking that measuring and elapse time of 1us would allow me to do just that.

Jean
3  Using Arduino / Programming Questions / Re: Getting a 1us delay on: January 29, 2013, 08:56:37 pm
Perhaps, I may add that my goal is to make my own "micros()" function that is precise up to 1us rather than 4 us. Since I read that the micros() function is based upon the timers, I figured I had to come up with my own manipulation of the timers to achieve a 1us granularity. I'm just looking for pointers on the best way to accomplish this.

Thank you
4  Using Arduino / Programming Questions / Getting a 1us delay on: January 29, 2013, 08:36:54 pm
Hi,

I am trying to measure a time of 1us. I realized the micros() function is only accurate to 4us. I was trying to use the following code to increment a variable every 1us. So far "MicroSecClock is always equal to 0. Is that the right strategy to capture 1us resolution? Thank you

Code:
uint32_t MicroSecClock = 0;

ISR(TIMER2_OVF_vect) {
  static uint8_t count;            // interrupt counter

  if( (++count & 0x01) == 0 )     // bump the interrupt counter
    MicroSecClock++;              // & count uSec every other time.

  TCNT2 = 253;                    // reset counter 2MHz interrupt rate
  TIFR2 = 0x00;                   // clear timer overflow flag
};
5  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 23, 2013, 02:33:09 pm
Would it not be sufficient to machine-wind one layer of the coil, manually pause it at the end of the layer and note the number of turns, and then program the winder to use the same number of turns for the other layers?

PeterH,

To me and Dan this seems likes a very good approach to the problem. Although it adds a step in the calibration of the spooling machine to get the number of turns (and consequently the theorical diameter); it seems reasonable to think that from that point on a multitude of coils could be wound using the setting acquired during the calibration run.

I am going to give it a try tonight and report my findings as soon as possible.

Thanks for the idea
6  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 21, 2013, 10:51:33 am
Are you trying to determine when a single layer of the coil has reached the far lip (and presumably needs to reverse to form a new layer), or when the layers of the coil have built up to the required outside diameter?

Yes;

I am trying to determine when a single layer of the coil has reached the far lip in order to properly reverse to form a new layer.

Stopping exactly on the far lip is required in order to properly reverse to the new layer and keep a tight packing without overlaps. When using a single average value for the wiere diameter, the accumulation of error over thousands of turns yields inconsistent results (i.e. the wire will stop before or after (spool unto itself) the far lip).

Basically, I am trying to find a way that will guarantee that the wire will always stop exactly at the far lip.
7  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 21, 2013, 10:47:13 am
Hi,
How much variation is in the wire itself or  the thickness of the insulating coating? How would this effect your project?
Goodluck,
jolphil

There is enough variation that taking several 0.001 precision measurements of the wire and using an average to calculate the amount of turns (coil_length / wire_diameter) yields inconsistent results. This can be due to the coating or other imperfection in the wire. This affects my project because I aim to make "multi-layer" coils and so I need to be able to stop exactly at the "lip" of the coil before reversing the direction of coiling.

If there is still a gap left between the wire and the coil lip, the reversal is problematic.
8  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 21, 2013, 08:44:30 am
Hi,

Thank you all for the answers.

My idea is to spool the wire exactly from one "lip" of the coil former to the other without any gaps. To solve the gap problem, lag works quite nicely. However, even if I measure the wire at several place and use that measurement any slight variation of the wire creates problems when it comes to calculating the amount of turns required (coil_length / wire_diameter). Over several thousands of turns even a variation of 0.001mm can amount to a gross gap. I was thinking that actively measuring the wire diameter for discrepancies would allow me to set the number of turns as a "moving target" during coiling so that the wire ends up exactly at the lip.

Perhaps I should be looking for a strategy/some kind of sensor that would be able to sense the presence of the wire when it reaches the coil lip instead of trying to measure the error? I want to minimize contact with the wire as it is coated with a fine layer of plastic (that I want to avoid stripping away).
9  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 11:57:15 pm
This is a nice diagram explaining the difference between accuracy and precision

Yes I understand. I would like to know if there is a technique that would maximize both accuracy and precision when dealing with a wire and target resolution of 0.001 mm.

Any thoughts?
10  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 11:32:07 pm
Quote
measure a very fine wire with 10 µm (or better) precision

But how accurate do you want it?

I would be really happy if I could record the wire diameter within 0.001mm. I'm not sure if that is possible.
11  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 11:02:06 pm
I am interested in tightly spooling the wire on a coil former. The coil will then be used for another project and it has to be well packed. Instead of working form the theorical diameter of the wire when making the coil, I am interested in measuring it as it unwinds from it's original spool (more accurate).
12  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 10:46:35 pm
Are you serious?
You need to be able to distinguish .001mm precision?

What are you doing?

Hi,

10 micrometers = 0.01 millimeters
AWG44 is finest wire gage I would like to be able to measure. I'm trying to read the diameter of the said wire as it unwinds from its spool.
13  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 10:34:46 pm
one approach would be to use the wire to set the gap between two metal plates and measure the capacitance between them.


Thanks for the reply.

I am not familiar with this approach. Would you have some examples or perhaps reading on that technique of wire diameter measurement.
14  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 10:32:02 pm
My goal is to measure a very fine wire with 10 µm (or better) precision using the arduino.

Have you considered using a microscope?

Thanks for the reply.

Yes, but I need to take the measurement automatically and several times per seconds.
15  Using Arduino / Project Guidance / Re: Measuring a very fine wire with 10 µm precision on: January 20, 2013, 10:30:49 pm
It might help if you give an actual dimension for  "very fine wire". 

I'm guessing you are measuring the width of the wire.  Is that true?

How frequently do you need to make the measurement?

Thanks for the reply.

I am talking about a wire of AWG44 around 0.0585 mm in diameter.

Yes, I am measuring the width/diameter of the wire and I would like to make the measurement several time per seconds using the Arduino.
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