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11896  Community / Website and Forum / Re: Karma on: January 30, 2011, 07:50:53 pm
That's rather negatively worded, retrolefty!

You think? Aren't most poles biased in what and how they present their questions?

11897  Using Arduino / Project Guidance / Re: Power outage sensor solution on: January 30, 2011, 07:45:44 pm
I believe the resistor is only for the onboard LED

That is correct. The pin 13 connector pin wires directly to the output pin on the controller chip. The on-board led and it's series resistor offers no protection from drawing too much current via the shield pin.

What's confusing the issue is that the older Arduino boards (NG and older) from several years ago did have a series resistor wired between the controller chip and the shield pin 13 connection and several of the example pictures on the Arduino site show plugging a led directly into the pin 13 and adjacent ground pin on the shield connector.
11898  Community / Website and Forum / Re: Karma on: January 30, 2011, 07:35:51 pm
Also by making it sticky it will attract people's attention to it and more people will come to read it through and talk about how they feel about the issue.

Just post a pole to this thread:

" Do you think that posting negative Karma count is a really dumb Idea? "

X  Yes, what were they thinking?

X  No, I like upsetting people!

11899  Community / Bar Sport / Re: Karma... on: January 30, 2011, 07:16:57 pm
I'm ignoring it for now. I've got 2 Atmegas says it doesn't stick aroun long in it's current state.

Yea, but I bet they are just ATmega8's  smiley
11900  Using Arduino / Motors, Mechanics, and Power / Re: Charging batteries in series in an Arduino Fio on: January 30, 2011, 07:12:31 pm
Yes, I see a possible problem. Li-po cells need special charging circuits that start out as a constant current charging mode and then switch to a constant voltage mode to top off the charge. How do you propose to charge a 2 cell series connected li-po battery with USB +5vdc voltage? A two cell series connected Li-po battery, fully charged has a 8.4 vdc terminal voltage and should never be allowed to discharge below 6vdc.

Li-po are great batteries with the highest energy density per weight available. However they have special needs in charging and in prevent over-discharging. Ignoring their special requirements results in fire and/or dead cells.

11901  Using Arduino / Motors, Mechanics, and Power / Re: Logic Level MOSFET Question on: January 30, 2011, 07:04:49 pm
Or does this particular MOSFET fully saturate at 5v? How do I work that out from datasheet? I admit my eyes glaze over looking at all that detail. Which is the relevant parameter?

I assumed that Sparkfun wouldn't release a product with a major design flaw, so is there something here I am missing? Will this shield work properly, or is there more to this than meets the eye?

For a N-channel mosfet with grounded source terminal the turn on voltage is the gate to source terminal voltage, regardless of the voltage coming from the load into the drain terminal. A normal mosfet requires +10vdc gate to ground voltage to fully saturate the mosfet on, no matter what the load voltage being switch to ground is (from a couple of volts up to the 60 volt drain limit). A logic level mosfet only requires +5vdc gate to ground voltage to fully turn on, again regardless of the load voltage being switched on and off. The mosfet used in that SparkFun board is the same one they sell individually: which is a logic level mosfet type  RFP30N06LE .

The datasheet for that device is : which states in the opening description that it is a logic level mosfet. Also figure 7 in the data sheet shows a graph of five different gate/source voltages curves (labled Vgs) and how much current each of those values will allow to flow from source to drain. This device will switch on and off just fine with direct connection to arduino output pins.

By the way SF seems to have that same switch board available in a single channel option:

11902  Using Arduino / Motors, Mechanics, and Power / Re: arduino mega + 2x SM-s4303R Servos problem on: January 30, 2011, 06:29:22 pm
I just had an idea, would it be possible to make the servo run in one  direction (for 240 mili sec required to move 90 degrees at 5 V) than halt it for some time and then move it in the other direction (for 240 mili secs again). This should produce the same results int theory respective of the degrees of rotation. Is this correct ?

In theory it would. However you will find in time that the servo wheel will gradually drift it's orentation and you will not be able to keep the stop positions fixed to absolute positions.

Servo are available in all sizes, torque values, speeds, etc. Just stay away from servos that say modified or continuous rotation. Google has plenty of links to servo vendors.

11903  Community / Website and Forum / Re: [SOLVED] Can I attach pics into my post? on: January 30, 2011, 06:03:06 pm
Testing for direct attachments: Look closely, click on thumbnail, making pies!

That should be worth a good Karma or two.  smiley-grin

11904  Using Arduino / Motors, Mechanics, and Power / Re: arduino mega + 2x SM-s4303R Servos problem on: January 30, 2011, 05:39:24 pm
Hi i would like the servos to move the legs of the spider back and forth please see image link. In stationary mode the servos are at 90 degrees. When the spider moves one leg goes forward (180 from 90) and one leg goes backward (0 from 90) to create motion.


Then you have the wrong servos for that job. Your servos have been modified for continous rotation and because of that they are not now using their internal pot as a position feedback sensor and will not perform as you want. The ones you have are designed to continously rotate at a desired speed, in either direction, or stopped.

Your application requires standard unmodified servos.


11905  Using Arduino / General Electronics / Re: New switching regulator on it's way on: January 30, 2011, 05:31:31 pm
I've ordered from Satistronics in the past and they have been quite good. I even have two of the aforementioned DC-DC switching power supplies, if you buy directly from Satistronics, you pay about $3 less each.

Have you been happy with the supplies? Do they seem to meet all the specs given?

11906  Using Arduino / Project Guidance / Re: Power outage sensor solution on: January 30, 2011, 02:27:51 pm
You're going to need a resistor on that red LED.

How did I miss that, me being the resistor Czar and all.  smiley-lol

Yes, please add a series resistor to your red led immediately, 200-500 ohms. As it is your poor output pin 13 is screaming in agony anytime you turn it on and you will soon lose all functionality of that pin.

11907  Community / Website and Forum / Re: Karma on: January 30, 2011, 02:21:41 pm
This is a nerd/geek forum, if a female was brave enough to post a question, Im sure there would be 100+ answers   

And knowing this group, she would just end up giving them all negative Karma and leave, never to return.  smiley-lol
11908  Using Arduino / Sensors / Re: Problem using a "Hall switch" on: January 30, 2011, 02:11:07 pm
If you still have yours available could you let me know what markings it had on it?

 I bought my Allegro hall effect sensors about a year ago from an E-bay seller. I bought both 5 each of their analog sensor and switch sensor. Part number and device markings are:

Allegro analog hall sensor part # A1323LUA-T  Device marking = 23L

Allegro digital switch sensor part # A3213EWA Device marking = 13E

11909  Using Arduino / Sensors / Re: Problem using a "Hall switch" on: January 30, 2011, 01:46:30 pm
I can't explain all the wavy hands and proximity stuff you are seeing. I have used that same sensor and it just worked as expected.

Perhaps you should add a bypass filter capacitor of .1ufd (or larger) between the hall effects Vcc pin and ground pin. I don't see anything wrong with your sketch.

Edit: You might try using a diffenet output pin for the led and change your code to match as maybe you damaged the pin 13.

11910  Using Arduino / Project Guidance / Re: Power outage sensor solution on: January 30, 2011, 01:39:05 pm
Your proposal sounds reasonable to me.

 Another method would be to use a simple 120ac coil relay. Wire the relay coil to your 120vac power and then wire the contact common terminal to arduino ground and the normally open contact to a input pin. Enable the internal pull-up for the input pin. Then when the AC power is removed the pin will read as a HIGH and if AC power is avalible the pin will read as a LOW.


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