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6706  Using Arduino / Storage / Re: Circuit which powers Arduino long enough to save program state to memory on: April 26, 2011, 09:05:11 pm
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The provided code shows that the voltage monitoring must run continously in the main loop.
That's how I understand it. It's a good way to do it with no external hardware but does add that extra task to the code.

You can add a voltage divider to VIN and use that (probably with a comparator like the ADCMP361 or a supervisor chip) to drive an interrupt.

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Rob


6707  Using Arduino / Motors, Mechanics, and Power / Re: trigger for pneumatic 12V solenoid valves and high-speed strobe. on: April 26, 2011, 09:01:39 pm
I haven't looked at the code yet but there's an error in the schematic, you need a current-limiting resistor for the opto LED.

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Rob
6708  Development / Other Hardware Development / Re: Getting Rid of the Arduino Board on: April 26, 2011, 08:52:41 pm
Also the breadboard itself has a high capacitance, I'd plug the crystal directly into the holes near the chip.

There are no decoupling caps either, often on breadboards you can get away without because of the high capacitance, but I'd put a couple of 0.1uF caps right near the power pins of the chip.

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Rob
6709  Using Arduino / Project Guidance / Re: Reading Synchronous Data input on: April 26, 2011, 08:00:10 pm
Yeah good point, make that the second most useful tool...actually the third most, a MIG welder is more useful smiley

BTW, I gather a "Boy Scout" or "horses hoof" have another meaning in your neck of the woods, if not I'm having trouble picturing that scenario.

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Rob
6710  Development / Other Software Development / Re: Event-Based Library for Arduino on: April 26, 2011, 06:38:30 am
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The idea is to increment a variable by 1 during the button was pressed and to stop incrementing when the button is released.
Then I would think you can start incrementing with onDown and stop with onUp.

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Rob
6711  Community / Website and Forum / Re: Too many forum sections on: April 26, 2011, 03:50:48 am
When we changed the forum over a few months ago there was a discussion about having too many topics. I think at the time it was decided to let it run and see how things worked out.

Being both HS and SW I just click on "unread posts" and scan them all, there's often quite a lot but I only look at the title and drill down if it sounds of interest.

So as a reader it hasn't affected me, however there has been a couple of threads I've started where I had trouble deciding where to put them.

I don't think you can ever really resolve this because of the sort of examples you state.

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Rob
6712  Development / Other Software Development / Re: Need some help using the makefile on: April 26, 2011, 03:40:31 am
It won't work with that line removed of course. I would think you reinstate it and point it to where ever your core files are.

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Rob
6713  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 26, 2011, 12:24:02 am
It looks like they only draw 200-450mA max so a large transistor or small relay would do.

If you're dead lucky the servo will do nothing on power up and therefore stay where you left it.

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Rob
6714  Development / Other Software Development / Re: Need some help using the makefile on: April 26, 2011, 12:17:11 am
He he, after 15 years of NOT using makefiles I find that's now my preferred development method with Arduino.

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Rob
6715  Using Arduino / Project Guidance / Re: Reading Synchronous Data input on: April 26, 2011, 12:15:20 am
I'd buy a logic analyser anyway smiley, the most useful gadget you will ever own.

Meanwhile you could feed the signals into the SPI pins, GPIO1 -> SCK, GPIO2 -> MOSI and set the chip up as a slave.

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Rob
6716  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:43:46 pm
As Lefty says, "Their behavior in that condition is not defined" so I guess all bets are off. Another logical option would be to return to the center position.

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Rob
6717  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:15:42 pm
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Should I just set up something to cut off the power?
A bit drastic but maybe.

The trouble is what happens when you re apply the power? Or maybe that doesn't matter to your application.

Anyway let's see if the pulse train stops after detach first, if not then there should be a software method to make it do so. If the pulses stop but the actuator continues on it's merry way then maybe drastic action is called for smiley

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Rob
6718  Using Arduino / Sensors / Re: Sensing tank fullness on: April 25, 2011, 10:05:46 pm
So as the tank fills the pressure in the tube rises. Then falls back to ambient as it empties. That sounds reasonable to me.

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The main problem I see is attaching the pressure tap to the sensor
Then get a sensor with a barb, many of them have built it barbs ready to put a tube onto.

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Rob
6719  Using Arduino / Motors, Mechanics, and Power / Re: Arduino mega 2560 powering lots of 5V relays. on: April 25, 2011, 09:59:51 pm
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How many dpdt 5v relays can I power directly from the Arduino mega 2560?
Not many, and none at all unless they are the really small ones.

You will need to run the relays from a separate power supply (or from VIN if that's an appropriate level) and as mentioned drive them with transistors or driver chips.

Depending on the application it may be better to use transmission gates or FETs or for that matter a digital pot.

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Rob


6720  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 09:51:48 pm
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I'm assuming once the servo is sent the "pulse" to move to a specified angle, even after you detach it,
If that is the case it's not servo compatible as they say it is.

One question, does detach actually stop the pulse train? The documentation is crap (as per normal) and doesn't spell that out. It may just shut the class down but not stop the timer generating the pulses.

One way to find out, pull the wire after doing the detach (or at any time actually).

BTW, that's one sweat actuator, I've filed it for later.
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Rob
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