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1  Using Arduino / Project Guidance / Re: Arduino based Stereo Canon DSLR Interval Trigger on: February 15, 2013, 05:31:50 pm
No. In MF autofocus is completely disabled.

Correct. It's as if the remote pins are connected to the shutter button. Since if you move AF to a back button, grounding the remote AF wire won't focus either.
2  Using Arduino / Project Guidance / Re: Arduino based Stereo Canon DSLR Interval Trigger on: February 15, 2013, 06:47:40 am
I'd defiantly go for a solid state solution, any bounce on mechanical components like a relay could make your camera do strange things.

We're talking about Canon cameras here. All fine. Sure I'd use a solid-state solution. But there's nothing wrong with what the OP is doing. It's simple and effective.
3  Using Arduino / Project Guidance / Re: Arduino based Stereo Canon DSLR Interval Trigger on: February 14, 2013, 05:00:48 pm
Firstly the diodes D1-D4 are unnecessary. They may even cause problems due to the voltage drop across them. However you should put flyback diodes across the relay coils as explained in the article.

I just checked my 60D and the current that flows through the focus and shutter circuits seems to be less than 100uA. So even some small reed relays will do the job.

Optoisolators aren't really needed here since the relays are isolating your circuitry from the camera.
4  Using Arduino / Project Guidance / Re: Heart-rate measurement using Arduino on: February 14, 2013, 03:15:55 pm
Thus, the IR light goes through the finger rather than reflect off of it.

That may work better though having the phototransistor on the same side should still work. I have a couple of heart rate monitors on my Android phone. You hold a finger over both the camera lens and the LED flash. The camera detects the slight brightness changes as the blood pulses through the capillaries. Works very well.
5  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 07, 2013, 07:17:31 pm
I just pulled my baitcasting reel apart and the cam follower looks like this (crap pic):


6  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 07, 2013, 06:00:13 pm
If I am understanding him right, the stops have the < and > groove to them to redirect the follower into the other track.
Yes.
7  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 07, 2013, 05:43:22 pm
The only limitation to it is that the OP mentions variable widths. This could be solved with a square shaft that he can slide on different lengths of these at different points depending on how many piles he is trying to make and how wide.

I think it's can be simpler than that. Just have a long shaft with the spirals milled all along it. Then you put "stops" along the shaft where required. Bit hard for me to explain but if the stops are just either side of a "X" part of the spirals it basically turns that location into the end of the shaft and causes the cam follower to reverse at that point.
8  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 07, 2013, 05:06:22 pm
smiley
I was hoping you'd see it.
9  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 07, 2013, 04:43:55 pm
This site is also good for viewing animations of many mechanisms:

http://www.mekanizmalar.com/
10  Using Arduino / Project Guidance / Re: Arduino, and Mechanical Movement of Objects - a Newbie Question on: February 06, 2013, 05:29:05 pm
For a purely mechanical option, couldn't you use something similar to the level-winders on overhead and baitcasting fishing reels? I couldn't find a decent image to show you how it works. But the shaft is cut like this:



I'm sure you could use some adjustable (and removable) stops on the shaft to set the end-points for when the hooks need to change direction. And also add/remove them depending how many drums you're filling.
11  Using Arduino / Project Guidance / Re: Challenge: horizontally / inertially stabilize a pizza on motorcycle on: February 03, 2013, 04:35:50 am
Quote
What you want to do is make it so the direction of the total force on the pizza is orthogonal to it's plane.
Which is more or less what happens if the pizza box were rigidly attached to the motorcycle
frame, such that it's horizontal when the m/c is straight up and down, rather than being
"actively stabilized".


Exactly. I was hoping the OP would realize that. In fact his idea would work better for a car which doesn't significantly lean into a corner, which is the opposite to what he's thinking. I wonder if any university has ever obtained government funding to research "Topping Drift on a Pizza En Route"
12  Using Arduino / Project Guidance / Re: Challenge: horizontally / inertially stabilize a pizza on motorcycle on: February 03, 2013, 02:42:26 am
I think oric_dan is right. Keeping the pizza horizontal during a turn is going to create a net force on the pizza and toppings toward the outside of the turn. One way to look at it: Imagine looking down from above and tracing the path the pizza makes during a turn. It's going to be an arc, correct? And that means a change in direction and hence acceleration. Now imagine tying a string to the pizza box and whizzing it around you in a horizontal plane. How will the pizza fair? What you want to do is make it so the direction of the total force on the pizza is orthogonal to it's plane. Just like gravity usually does.

13  Using Arduino / Project Guidance / Re: Quadcopter whit or whitout arduino? on: December 30, 2012, 04:11:11 pm

That's an awesome tutorial and has helped me choose what hardware I'm going for. Definitely a KK2.0 board FTW! The price is amazing considering it has the required sensors for basic flight control.
14  Using Arduino / Project Guidance / Re: PH fish tank on: December 30, 2012, 06:02:29 am
Quote
did you know a borax solution can be used to calibrate near this range? It will produce a buffer solution of around pH 9.2, so this method requires a controller that will allow calibration using arbitrary buffers.That Sparkfun kit doesn't do that.
Because it already has set calibration points.    4.0, 7.0, and 10.0 are very commonly used and widely available buffer solutions. And at $25, the stamp is the cheapest I have found.
But he's only interested in the 10.0 range, the 4,0 and 7.0 is useless. Considering the OP is only interested in a small range of pH values, it would be cheaper to purchase a Ph probe, use a single-chip instrumentation amp and do the calibration on the Arduino itself. The pH 10 buffers don't keep very well as they absorb CO2 from the atmosphere.
15  Using Arduino / Project Guidance / Re: PH fish tank on: December 30, 2012, 01:33:59 am
Also, this is not for fish. It's for algae.

http://www.algaelab.org

Interesting link! Glad you said it was for algae as I was surprised like Delta_G with what fish you were trying to turn into caustic soup  smiley-eek

If you look up aquarium controllers a lot of the pH probes are damn expensive. I'm not sure if that's just because they're made to last while continually in the tank, or also because aquarium equipment is often overpriced. Some of the well-known manufacturers recommend cleaning them at least every couple of months. Many people use undiluted white vinegar or lemon juice for this. Even then the probes only last up to 18 months or so.

As for the buffer solutions, since you're only concerned with a pH of 10-11, did you know a borax solution can be used to calibrate near this range? It will produce a buffer solution of around pH 9.2, so this method requires a controller that will allow calibration using arbitrary buffers. That Sparkfun kit doesn't do that.

EDIT:
I just did some searching and apparently these probes are pretty popular for the price:
http://www.bulkreefsupply.com/brs-brand-ph-probe.html
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