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1  Using Arduino / Motors, Mechanics, and Power / Re: Stepper hisses even standing still. Can current on all coils be normal? on: April 17, 2014, 08:39:37 am
To be clear about coils - should they be powered both at all times?
I had an assumption that they switch.
2  Using Arduino / Motors, Mechanics, and Power / Re: DC brushed motor angle on: April 17, 2014, 07:47:47 am
I guess you'll have to use encoder or magnetic encoder of some sort.
This board seems not to have any feedback except for current.
3  Using Arduino / Motors, Mechanics, and Power / Stepper hisses even standing still. Can current on all coils be normal? on: April 17, 2014, 06:21:07 am
DRV8825 (just like Pololu ones) stepper driver, plugged into RAMPS 1.4 board drive 1.7A 4-wire stepper, both with or without microstepping.
At all times, stationary or moving the stepper produces considerable hissing resembling that of an amplified computer sound card background noise.
Hissing character changes if driver is touched on adjust pot and some other parts by finger or screwdriver. Have 10 drivers, all hiss. Tested on 2a and 30a 12v psu with no difference.
How can I find the cause?

When going slow through steps (full step, 2 sec per step) to check current between stepper-driver, multimeter shows ~1.7A on all steps. Shouldn't coils work in pairs, so current drops to zero on some steps?
4  Using Arduino / Sensors / Re: High sensitivity gyro? on: April 12, 2014, 06:44:44 am
@Chagrin, @michinyon Thanks for information, didn't suspect things are blurry like that smiley
Still, I guess there is even no real need for calibration, as drift is easily obtainable by subtracting known orientation of previous/next encoder steps. And, depending on price, I guess it's worth a try smiley

So, the question remains - Is there anything that is higher resolution in real life, than L3DG20/L3G4200D?
Edit: also, could it be reasonable to use more than one gyro, to increase precision?
5  Using Arduino / Sensors / Re: High sensitivity gyro? on: April 11, 2014, 01:52:56 pm
The idea is to record both - the gyro and encoder. Encoder gives the absolute position, while gyro provides information on how to interpolate the inbetweens of encoder.
But is it really up to 10 degrees/s? That seems unusable for nearly anything. Maybe it is meant as a possible constant deviation, that can be subtracted after finding it in calibration?
6  Using Arduino / Sensors / Re: Problem with Color sensor module TCS3200 on: April 11, 2014, 07:49:23 am
I've got this sensor yesterday too, but didn't run it yet.
A couple of points to consider -
on turning on/off - it takes some time, specified in datasheet to power up;
highest frequency goes beyond what arduino can detect (100% is at less than 10microseconds);
you might try freqcount library to get linear responce, I suspect you get log scale otherwise, because it's frequency not pulse length that is the information.
7  Using Arduino / Sensors / Re: Which hall sensor should I use for a BLDC? on: April 11, 2014, 06:48:47 am
I didn't actually drive sensored motor, but as far as I understand you just  get a sensored motor and connect it to sensor capable ESC. Unless it's out of curiosity I see no practical reason to "invent a bicycle".
Also why use sensors at all? Usual sensorless ESC works great.
8  Using Arduino / Sensors / Re: How to make a distance laser speak with a DC on: April 11, 2014, 06:42:51 am
Well, if you're not into programming, why not solve it with electronics? If conditions are simple, you can make an analog sensor for laser, driving motor circuit.
9  Using Arduino / Sensors / Re: Gyro and Accelerometer angles on: April 11, 2014, 06:40:33 am
Not an expert but:
1. You can calculate where the earth is via gravity sense of accelerometer.
2. Gyro is needed to detect angular speed mostly, it doesn't need to know where is the zero.
3. if you ask such questions, diy stabilization could be not for you at this moment, as it involves quite complicated math. Probably you could be better off looking for a working code to adopt.
10  Using Arduino / Sensors / High sensitivity gyro? on: April 11, 2014, 06:27:15 am
Any suggestion?
I want to record camera rotation to less than a pixel precision.
I'd be happy to get some results at all, but ideally it should detect offset @200mm focal in HD, which gives about 0.001 degrees for quarter pixel.
I don't care about range, as anything over degree per second will be acquired by other means.

I've read that L3DG20 gives 0.00875 d/s. Is that a real figure or noise gets above that?
Are single axis gyros any better? I've seen only analogue ones and I suspect they have awful resolution on arduino ADC. Could an external ADC be a good idea instead of complete multi-axis digital module?
11  Using Arduino / Motors, Mechanics, and Power / Re: Figuring out terminals of washing machine motor on: April 08, 2013, 05:55:36 pm
Could it be normal that the motor gets hot after couple of minutes of idle operation?
Under almost stopping friction load it gets hot in about 30-60 seconds.
By hot I mean about 48 degrees in hotspots on relatively thin cast iron cylinder.
What could be considered a safe temperature margin?
12  Using Arduino / Motors, Mechanics, and Power / Re: Figuring out terminals of washing machine motor on: April 03, 2013, 01:21:48 pm
Ok, I've connected it like this and it seems to work:

Except it works in "slow mode". After belt drive reduction it should be the machine's normal washing speed.
Which seems strange, I was expecting full rpms (of what would be the centrifugal mode) requiring some magic on remaining windings to slow down.
If I connect one or both of remaining windings to phase before or after capacitor the motor slows down to a various degrees and produces various patterns of buzzing.
Moving neutral to one of additional windings produces no really noticeable effect.
I wonder how to get it to full RPM - there was not much of other components in the machine and it did had the centrifugal mode.
13  Using Arduino / Motors, Mechanics, and Power / Re: Figuring out terminals of washing machine motor on: April 02, 2013, 05:21:26 am
It's actually two separate 220vac phases, through two council meters, and apparently was just to try to balance the council's load. Electric stove, for instance, should be on both phases, perhaps oven on one, plates on other, kind of thing. Stoves are supplied with 3 lines and one neutral connection, and a pic showing how to jumper the lines together for 1 or 2 phases.
Same here except voltage. I saved the pic, it says 380V.
14  Using Arduino / Motors, Mechanics, and Power / Re: Figuring out terminals of washing machine motor on: April 02, 2013, 05:04:26 am
You talk about 2-phase.  Do you mean 2 phases plus a neutral from a 3-phase system or do you mean 220 supply rather than 110 as the USA uses.  If the latter then I'm sorry to advise that it's still single phase even if running at 220.
1 phase - 220V
2 phases - 380V. It's a system specific to Dutch (I hope I don't mix countries smiley ) network, not sure how they manage it.
15  Using Arduino / Motors, Mechanics, and Power / Re: Figuring out terminals of washing machine motor on: April 01, 2013, 07:25:04 pm
Thanks, a bulb indeed should be safer.
I'll try that tomorrow - don't want to wake anyone up if something goes out of control smiley
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