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1  Using Arduino / Project Guidance / Re: Help a Noob out? Marine application of robotix on: September 04, 2012, 11:07:49 pm
Have you looked at the pros and cons of bluetooth and re-establishing a network after getting out of range, plus it's limited range?

If you're saving your images to a card and not hoping to transmit them programming a micro over the air would be a suitable application for a zigbee module (like Xbees).

Have you mentioned what kind of range you hope to aquire?  Is this a pool you're playing around in?
2  Using Arduino / Project Guidance / Re: Arduino has some strange reactions on: September 04, 2012, 10:38:31 pm
ideally when using AC loads you want a device that can time the shut off to the point where the wave makes the zero crossing or choose a DC Solenoid due to all the pain AC loads cause. DCs are easy to rectify.

If nobody has mentioned it yet try winding/twisting the pair of wires going to your solenoid as tightly as possible (if you do not have enough slack to do so run new longer wires) chock the wires up in a cordless drill and spin. This will have a magnetic cancelling effect that will help impede the inductive spike, while you're at it loop this wire through a couple ferrite beads.

To repeat what others are saying, separate your power supplies and keep your signal and power wires as isolated from each other as possible.

and this app note repeats what others have been saying, coil suppression is a common application in relays because the same voltage causes arcing and welds relay contacts shut.

http://relays.te.com/appnotes/app_pdfs/13c3311.pdf
3  Using Arduino / Project Guidance / Re: Arduino Leonardo- I want to change VReg to 3.3V on: September 03, 2012, 09:14:06 pm
FWIW, I have a board where I can jumper Vdd for either 3.3V or 5V, and I've
never had a problem running Duemilanove or UNO chips with a 16-Mhz xtal.
I think the specs may be a little conservative. I suppose it might not run so
well at -40C or 150C.

If you check the table on page 308 of the datasheet under "Speed Grades" for the Atmega328 you'll see you're right on the edge of stable for 16Mhz at VCC of 3.3V. CrossRoads is giving good advice here.

Works right now isn't good enough, from personal experience troubleshooting crystal instability is extremely frustrating.
4  Using Arduino / General Electronics / Re: Digital pin trigger level on: September 03, 2012, 02:54:45 pm
Are you looking for a low voltage sense? 10.8VDC?

If so one of these might be an option for you.

http://www.ti.com/product/tl7700

http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=tl7700&fileType=pdf
5  Using Arduino / Project Guidance / Re: Creating a form of GUI on: September 03, 2012, 01:56:34 pm
Arduino's sister program Processing would be perfect for this.

http://processing.org/

Arduino comes stock with example code that interfaces with this.
6  Using Arduino / Project Guidance / Re: brainstorming: how can I detect if the AC is on? on: September 03, 2012, 01:53:01 pm
Actually current sensing wouldn't be the worst idea seeing as the compressor would draw a measureable amount of current more than when just the fan is blowing.

Also, if this AC unit is anything like mine when the compressor kicks in the thing will vibrate enough that you could couple an accelerometer to the unit to give you detection. 

http://www.digikey.com/product-detail/en/DKSB1002A/876-1002-ND/2074103

when they're gone they're gone...
7  Using Arduino / Project Guidance / Re: Arduino Leonardo- I want to change VReg to 3.3V on: September 03, 2012, 09:08:36 am
Quote
For sake of not having to translate 5V TTL down to the xbee's 3.3V, I'm going to swap out the VReg on the board to a 3.3V.
An XBee shield that does that seems like a much simpler solution. The pin spacing on the XBee is not compatible with the Arduino or breadboard, so you need something between the XBee and the Arduino anyway.

2mm pitch does not concern me, however, the size of an entire shield does. I have 2mm protoboard, 10 Pos 2mm female headers and xbee socket breakout boards at my disposal, but after I proto this up it's going to be a board spin shield with it's own Xbee socket.

Thanks again!
8  Using Arduino / Project Guidance / Re: Arduino Leonardo- I want to change VReg to 3.3V on: September 03, 2012, 08:15:04 am
You bring up an excellent point. Before their U suffix became the norm I never liked 16Mhz for stability purposes anyway. I'll pop that crystal off and change that out while I'm at it.

Thank you.
9  Using Arduino / Project Guidance / Arduino Leonardo- I want to change VReg to 3.3V on: September 02, 2012, 10:56:10 pm
Hey y'all.

I'm making a FSR drum shield for the leonardo, it's wireless, will be using Xbees.

For sake of not having to translate 5V TTL down to the xbee's 3.3V, I'm going to swap out the VReg on the board to a 3.3V.

I know my way around AVR Studio enough that this will not be a problem with fuse bits and all that but I'm looking at the schematic for the board and wondering about all this 5V Autoselect jive and wondering if there might be a trace I need to cut or something or if this will not be a problem.

Any input in the matter is greatly appreciated.

10  Using Arduino / General Electronics / Re: ATX Power supply as bench power supply on: July 09, 2012, 12:19:43 am
for future reference, since you cut off your connector, the Panel Mount mating housing to a 24 Pin ATX connector would be Molex PN:

39-01-2241

http://www.digikey.com/product-detail/en/39-01-2241/WM1029-ND/284603

The older 20 Pin ATX power supply types would be Panel Mount mating housing PN:

39-01-2201

http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=39-01-2201

Some older ATX power supplys, and switching power supplys in general, do not like no load on the output and auto-shut down. I put a low ohm 25 Watt resistor on my 5V rail, I forget what value I used, but I'm covered by the 25 Watts.

Maybe the power supply isn't liking no load before you turn your amp on?

I threw on fuses/fuseholders rated roughly 5A below my 5V and 12V output ratings (something rediculous like 30A that I do not need) and put on some nice banana accepting binding posts on the bad boy, otherwise Sparkfun sells a kit do do all this...

http://www.sparkfun.com/products/9774
11  Using Arduino / General Electronics / Re: What could be possible reasons for Atmega-chip and Xbee heating up? on: July 08, 2012, 11:51:19 pm
If you're streaming data you're producing around three quarters of a Watt of power. Power = Amps * Voltage.

Add say, 20mA of microcontroller power to your 215mA...

235mA * 3.3V = 775.5 milliWatts

An Xbee Pro even at idle is going to raise temperatures a little running at 55mA, add your microcontroller and you're already at a quarter Watt.
12  Using Arduino / Installation & Troubleshooting / Re: Arduino UNO Rev3 Windows 7 Unknown Device - SOLVED! (for me at least) on: December 29, 2011, 10:25:49 am
Thank you!

I've been struggling with this for two days.

I followed the instructions up until:

Choose Arduino LLC (I didn't have that option listed)

However, if you leave the option > Standard Port Types

and select

Have Disc

and point to the recommended Arduino Uno.inf file it works.

This is for problems with 64bit Windows 7 installation.

Thanks again!
13  Using Arduino / General Electronics / Re: arduino on new PCB timing is not right... on: August 06, 2011, 01:53:25 pm
Swapping out caps on your crystal and now it works doesn't necessarily mean your cap was broken (unless you have a really good meter and can measure 22pF accurately, even then stray capacitance in your circuit...)

It could be the capacitor's percentage tolerance (+/-20%) in addition to the stray capacitance of your ground trace added up to breaking a camel's back. I've seen this in the field doing repair work. This is common if there is stray capacitance on the traces or the crystal's capacitor values are ill suited for the Load Capacitance value of the crystal, or you have ceramics with extremely sloppy temperature coefficients.

Replacing the capacitor and now it works could mean you're safe, but barely and may still have instability down the road. I would possibly consider reducing your capacitor values to factor in stray capacitance. THe best possible method to find stable values is to buy a number of values say, from 10pF up to 30pF and test to see what the bottom and top of your ranges are and pick a value that is dead in the middle (the average of your bottom and top limit) Or, just try a lower value, say 16pF, and if it works, stick with that...

Or you could've had a cold solder joint on the cap. Or, maybe you did burn it out...

To get back to your bypass/filter issue... It is standard practice on all digital chips to filter/bypass VCC to Ground with a .1uF ceramic capacitor directly (as close as you can get the component to the VCC pin and the components Ground Pin. It is why they designed this chip with the VCC and Ground directly adjacent. You could finagle the leads of a through hole .1uF cap into the pads of your VCC and Ground. You really do need this one...

14  Using Arduino / General Electronics / Re: Looking for options: Small, bare AC/DV 12V 1.5A PSU on: August 06, 2011, 01:34:04 pm
Have you considered what effect 15 Watts is going to have in an enclosure that small?


This one might meet your requirements, though it'll take a little finagle'in with PC Pins.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=945-1090-ND

CONV AC/DC 20W 12V OUT 1.65A
2.06" L x 1.07" W x 0.93" H (52.4mm x 27.2mm x 23.5mm)
 
15  Using Arduino / General Electronics / Re: arduino on new PCB timing is not right... on: August 06, 2011, 12:05:58 pm
If you're able to upload code on an Uno board it's probably not the chip, but the board...



If I may, a little critique of your design,

I'm not seeing a .1uF bypass capacitor going from the VCC on your chip to GND. (edit: I just spotted it, it wouldn't be filtering/bypassing that far away from your VCC Pin, it's effectively not there doing it's job)

Also, ground trace should not daisy chain from one component to the next, especially if one of the components on there is a crystal. Noise from internal switching on the microcontroller will get introduced to your ground all over that trace and will raise the 'potential', basically you won't have a true ground to reference anymore. Also, it's one long electromagnetic antenna, picking up radio frequencies. This could potentially effect your timing.

If you were to redesign, I would recommend either learning about polygon ground pours or, at the very least, draw one huge fat ground trace up the middle of your board and have all components that need to reference off it connect straight to that, not each other.

Second, to advise on your problem, if you could kindly provide the following:

The settings you used for fuse bits ( or if it was a prebootloaded chip)
The speed of your crystal.
The part number of your crystal and values on your crystal capacitors might actually help as well.

I'd assume you're using the latest bootloader Uno, Decimilia...

What method (programmer) did you use to program your chip (if it wasn't pre programmed with bootloader) ? Can you go into:

AVR Studio>
Tools>
AVR Programming>
Fuses

to read them?

AVR Studio is a free tool available from Atmel if you don't already have it.

If you  keep your current design, if you're using a 16Mhz Crystal you're going to need to replace it with a much more stable 8Mhz.

 16Mhz Chyrstals aren't that stable, and the fuse bit arduino uses for them isn't optimized for noisy boards like yours. If you insisted on keeping 16Mhz (I would not recommend it) learn about the FULL SWING fuse bit settings available. You'd have to overdrive your crystal.

To get back to speed of crystal and values of your capacitors, if I had to wager, the stray capacitance of your long ground trace would bump up the capacitance values via stray capacitance on your crystal caps making things very unstable. An scope would be very helpful in this regard.


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