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31  Using Arduino / Project Guidance / Re: How to control DC motor forward and reverse with one potentiometer on: December 05, 2012, 07:56:22 pm
Replacing the pots might be a better idea. But if you want to change the resistors you just need to reduce them by the same factor. ie, your 5k pots are 1/20 of the original pot's value. So the top 100k resistor will become 5k, and the bottom 10k will become 500R. That's going to increase the current through that leg but it's still only 1.1mA or so.
32  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 05, 2012, 03:50:22 am
I fly paragliders for a living so I'm familiar with thermals.
That's not a job. It's getting paid to have fun smiley
I was looking at the KK boards since you mentioned them several days ago. But I can't find much info on firmware etc.
33  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 05, 2012, 03:33:41 am
The way I'd approach this is similar to the algorithm used for NTP
Is that Marzullo's algorithm you're talking about?
34  Using Arduino / Project Guidance / Re: How to control DC motor forward and reverse with one potentiometer on: December 05, 2012, 02:20:54 am
Also, don't I also have to make sure the pots on the joystick are the same resistance as the pots that were originally on the speed controller?
It's a 100k pot. Looking at the schematics it's not simply connected to V+ and ground. There is a 100k resistor on the high side and a 10k connecting it to ground. So yeah it won't act the same unless the joystick pots are 100k. Or you change the resistors to compensate.
35  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 04, 2012, 01:24:53 am
I am considering to make a similar demonstration using the same 2 sensors.
Please do! I haven't got a quad yet but want to make my own and write all the code for it myself. So I've done a lot of research and wrote a simulator to test some ideas.

Since you only want an accuracy of 10ft or so, you may not need to do complex sensor fusion. But I'm thinking you'll need the accelerometer to limit the vertical speed, in the cases where the baro gives incorrect readings. I've got to buy a baro sensor so I can play.

BTW what are planning to do with the fixed wing? I was thinking of making an autonomous glider which would detect and stay in thermals. But alas it's already been done:
http://diydrones.com/profiles/blogs/thermopilot-project-a-thermal-hunter-glider-drone
36  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 04, 2012, 01:01:53 am
Its working well for roll and pitch, but I have a lot of problem to stabilize on the yaw axis, did you succeed?
Can you explain how you're trying to control yaw?
37  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 03, 2012, 03:57:03 pm
How about this code to fuse Ameter and pressure? 
Have a read of this. It's not that simple and the Aeroquad guys still haven't got it working reliably. You can get it working on a test bench:
 

But it's a totally different story on an actual flying quad.
38  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 02, 2012, 03:37:29 pm
I agree with PeterH that the sampling rate should be higher. But then you say 10ft accuracy is all your after so who knows.

If you have a look at the Aeroquad code you'll see getting decent altitude hold isn't as simple as taking readings from the baro sensor. They run the sampling rate at something like 50Hz, filter the readings, adjust with temperature compensation, and combine the baro with accelerometer readings. Maybe you're already doing this in your code? It's hard to tell from the pseudocode you posted.
39  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: December 01, 2012, 06:09:22 pm
Ideas for improvement?
How are you measuring altitude, and what sort of accuracy in the altitude hold are you trying to achieve?
40  Using Arduino / Project Guidance / Re: Measuring change in magnetic flux via Arduino and MAG3110 sensor on: November 27, 2012, 01:36:52 am
For measuring orientation won't you need an accelerometer as well?
41  Using Arduino / Project Guidance / Re: variable air solenoid control on: November 23, 2012, 04:04:39 pm
Electronic proportional flow valves do exist but they're expensive. Some work like you're thinking - basically a stepper operated valve. And others use a PWM signal to control a solenoid valve:

http://www.omega.com/ppt/pptsc.asp?ref=FSV10&Nav=prel03

Would pulsing the air cause any problems for your rocket? Because I was wondering about driving a simple air solenoid with a PWM signal. Higher the duty cycle the more net flow you'll get.

EDIT: Thinking about it, a cheap but relatively fast switching air solenoid may not pulse all that much when driven by a PWM signal. Have a look at this paper:
http://advantech.gr/med07/papers/T06-001-456.pdf
42  Using Arduino / Project Guidance / Re: CNC Sewing Machine with Arduino - is it possible on: November 22, 2012, 03:11:18 pm
I think the digital potentiometer will do the trick. Seems simple enough and I'm not really worried about efficiency so don't necessarily want to go down the PWM route. I guess the question with the digital potentiometer is can I vary the resistance (ie. voltage) and syncronise it with the speed movement of the XY table? So, if the sewing machine sews slower, the XY table moves slower and if the machine sews faster, the XY table sews faster.
Couldn't you just put a sensor (IR, hall effect etc) to detect the position of the needle bar? That way the single sensor would allow you to detect both the needle position (whether it's up or in the fabric) and sewing speed.

BTW what are you sewing? Just simple built-in machine stitches or more like the proper embroidery machines do? A friend of mine recently bought one of those machines and it's amazing what they can create.
43  Using Arduino / Project Guidance / Re: Need an air flow generating unit for automatic wind instrument on: November 22, 2012, 01:22:10 am
Isn't the flow keeping the ping-pong balls aloft, not the pressure?  I have seen in vacuum cleaner shops where they have a beach ball hovering above their latest model cleaner.  I would think it would not require very much pressure at all, but a decent flow rate.
Sort of. Something has to create that high speed flow. And that is pressure. We were putting bits of blu-tack on it to make it spin and stuff. There's no way I could've made that ball stay floating with my lungs. Anyway I tried a 4.5 watt squirrel cage out of an old HP computer today. I had no recorder so made a ghetto one. It seems to work fine. Pretty sure this is more about decent flow rather than high pressure. It would be different if trying to play a trumpet or reed instrument.

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What about a CPAP machine?  One would think that it's capabilities would mimic those of a human's, due to the way they function.
That's a really good idea. The fixed pressure versions seem to put out enough pressure. The problem though is the cost. They're damn expensive.
44  Using Arduino / Project Guidance / Re: Need an air flow generating unit for automatic wind instrument on: November 21, 2012, 02:42:30 am
The fan needs to be an impeller type and not squirrel cage. Even a ~250W furnace blower (which are squirrel cage) don't do anything for static pressure (DAMHIKT).
I used to think that. A few years ago I hooked up a 100mm centrifugal fan to a high speed mini drill motor and passed the outflow through an 8mm orifice. We were levitating ping pong balls a good few feet above it. And the noise wasn't all that bad.

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To your question on CFM for a refrigerator compressor it looks like they're in the 1 CFM  (28 liter/minute) range and capable of ~100 PSI. Surprising number of examples of "homemade air compressors" on Youtube using these pumps. They are oil piston compressors just like typical large compressors so I suppose it does make sense.
I don't think 1 cfm will be enough. But if it was then you'd want to build a buffer tank to smooth out the oscillations. And if you're going to do that, then just buy a cheap 2hp compressor.

BTW, even these 2.4 W fans can pump 9.5 cfm with a static pressure of 6.5 inch-aqua. And only produce 32dBA.
http://www.jaycar.com.au/productView.asp?ID=YX2530
45  Using Arduino / Project Guidance / Re: Arduino UNO won't stay connected on: November 21, 2012, 01:47:58 am
What happens when you try a different sketch?
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