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1  Using Arduino / Project Guidance / Re: 434 MHz Antenna on: August 07, 2012, 03:17:52 pm
Appreciate the thoughts.

2  Using Arduino / Project Guidance / Re: Wedding project idea on: August 07, 2012, 03:17:08 pm
With "professional quality" sensors and gear and an unlimited budget this would be a simple project.

However, using the "unprofessional sensors and gear" I am limited to by my budget this would be such a miserable project I would move on to planning other things.

That's what the comments above say too I think.

By the way -- for Mrs. -- use missus (in the vernacular) -- misses is something you don't want to occur on your wedding day. I was going to write out a bunch of bad taste puns -- then thought better of it.  smiley-eek

Concentrate on having a happy day and spend the money on a really good bottle of champagne. Or maybe buy his-and-hers matching Maega 2560s for wedding presents. And you can both work on a project on your honeymoon.


3  Using Arduino / Project Guidance / Re: Engine Radiator Coolant Level & Temperature on: August 07, 2012, 03:09:30 pm
Temperature and pressure sensors might do everything needed.

They do need to fit in so as not to drop the pressure. On a diesel (commercial, truck) I am pretty sure those sensors are already there -- at least on modern engines.

4  Using Arduino / Project Guidance / Re: 434 MHz Antenna on: August 07, 2012, 03:05:09 pm
How do you do that? Find that distance apart at which you can communicate -- but with difficulty. Shorten the antennas slightly -- test for improvement -- if you see improvement shorten some more.

If it gets worse -- you need longer antennas -- start over. Sorry about that -- try 18cm -- then shorten as per above instructions.

No this is not quite right.
The antenna needs to resonate. The 17cm length is approximately 1/4 of the wave length of the frequency in use. The antenna should be cut for the frequency being used. If a 1/4 wave whip is not sufficient, then you can add a ground plane. The ground plane would be a few wires at right angles to the whip and 20% longer. Someone mentioned a dipole. That's two legs, each 1/4 wave long, one fed from the center fo the feed line and the other connected to the braid. These are directional, with signal radiated off their sides.

If this is not adequate, you can build more complex directional antennas.


One could say that anything is not quite right. smiley-twist

Amirra is an engineering student. She rarely asks a second question in any area. She can read and figure things out for herself. Never ever give an engineering student too much information -- they take great pride in their ability to figure out things that don't yet know.

I pointed her to places that would fill in all the details I left out and that everyone else left out.

So... Those radios are never quite on the the freq. you expect. One would think if shortening the antenna does not work -- lengthening might work. However un-cutting the wire is not that easy -- starting over again with a piece "too long" seemed simpler to me.

I do think I got it right -- but I did get a chuckle.

You made my day.
5  Using Arduino / Project Guidance / Re: guidance for pre-newbie on: August 07, 2012, 02:41:54 pm
Let's see -- 25 sensors means 3X25 =75 Analog ports to read -- quickly... On an arduino? And send the results elsewhere? My Mega 2560 bogs down with four sensors  1 ADC connected -- the rest connected to the I2C interface, the data sent via UDP to my PC. My 32MHz ARM 7 is not that much better.

I say it's a waste of time on an Arduino.

On a CORTEX-M3? Maybe! The TI Stellaris line will sample up to 500,000 times a second (500KSPS) on all LM3Sxxxx series boards and 1MSPS on a higher end processor -- like the LM4Fxxxx series.

But then you have to add extenders for Analog ports -- so Multiple TWI/I2C extenders would be better.

I think this is a very advanced project -- just because of the synchronization required -- but what do I know -- I just do arithmetic.

My recommendation is that you do the arithmetic first -- purchasing second.
6  Using Arduino / Networking, Protocols, and Devices / Re: Review of DS1307 Libraries and Sample Sketches on: August 06, 2012, 10:21:47 am
Did you find the one I reworked?

I added access to the RAM on the RTC chip and made some fixes in the Arduino Library.
7  Using Arduino / Sensors / Re: Measure distance or direction with accelerometer? on: August 06, 2012, 10:20:04 am
It''s not a brain teaser. It's a "Do you have some particular knowledge" question?

Do you know and understand vector math differentials and integrals? Is this just about decoding dynamic position as opposed to static position?  The the answer is yes and you can do it.

So yes -- there are seismic algorithms as has been pointed out. They are an analog to what you want.
8  Using Arduino / Sensors / Re: Processing 2 Analogue Inputs To Create Differential Value on: August 06, 2012, 10:16:22 am
Always, always always, model make and years(rev).

If you don't tell us what you have you will always get answers whoich might work -- but might not be the best or what you want. Maybe they are what you want. How would you know?

This is from the Mega 2560 Manual -- a comparator is built in. Surprise!

The Analog Comparator compares the input values on the positive pin AIN0 and negative pin
AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on the negative pin
AIN1, the Analog Comparator output, ACO, is set. The comparator’s output can be set to trigger
the Timer/Counter1 Input Capture function. In addition, the comparator can trigger a separate
interrupt, exclusive to the Analog Comparator. The user can select Interrupt triggering on comparator
output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is
shown in Figure 24-1.

The Power Reduction ADC bit, PRADC, in “PRR0 – Power Reduction Register 0” on page 56
must be disabled by writing a logical zero to be able to use the ADC input MUX.


The you can decide if you want to use the comparator or not.
9  Using Arduino / Project Guidance / Re: 434 MHz Antenna on: August 06, 2012, 10:03:58 am
You could also google it and find this:
http://www.csgnetwork.com/antennaedcalc.html

A dipole is two side -- so that would be twice as long -- cut in the middle and fed to coax or twin lead.

I used "One Side" on that screen -- which tells you how long to make a Vertical "Ship antenna" -- which is just 1/2 a dipole.

So the answer of 17cm is pretty close. Start there and maybe play with a couple of antennas -- trimming them to see if they work better.

How do you do that? Find that distance apart at which you can communicate -- but with difficulty. Shorten the antennas slightly -- test for improvement -- if you see improvement shorten some more.

If it gets worse -- you need longer antennas -- start over. Sorry about that -- try 18cm -- then shorten as per above instructions.

Wiki has a reasonable answer --
http://en.wikipedia.org/wiki/Dipole_antenna

See frequency vs length -- remember that is a dipole formula cut in half for a "whip".

l= 143/f (meters) or l = 468/f  (feet)
10  Using Arduino / Project Guidance / Re: Want to build automatic closet [total newbe] on: August 05, 2012, 06:52:25 pm
Quote
I'll create a DB (yaml) which the arduino will read
Really? How will you do this?

Making the Arduino talk to a PC that is running an application that is listening/talking to the serial port, that that knows how to talk to the DB is possible. Writing DB software for the Arduino is much more challenging, given the small amount of SRAM available.

UDP over Ethernet. I have done this -- it's not a big deal. I suppose I could have done USB or serial -- but I used the Ethernet card.

It is back and forth communication and I collect up to 2M points of data a day (4 items per point -- Mega 2560)
11  Using Arduino / Project Guidance / Re: Advice starting my first robot on: August 04, 2012, 08:32:25 am
Go here and type the word "books" into the search bar. There is a book on robot drive trains.
http://www.robotshop.com/ca/home.html


I have been designing computer processors and autonomous systems all my life and been in this business over fourty years. I was thinking of being a Radiologist. Is there anything you think I could do for under $1000 to join your field?  smiley-roll-blue

I think you are doing fine. It takes a while to gain the knowledge. Surprisingly, your incredible knowledge of anatomy may become your greatest asset. How do I know what you know? Never mind...

One more point. a Mega2560 with Ethernet or Bluetooth for the Control link might be a far better choice because of the extra I/O and ADC pins. Just an opinion.

PS: By the time you are finished your wife may wish you just had an affair. It might be cheaper and less time consuming and more forgivable.
12  Using Arduino / Programming Questions / Re: running more than one program on: August 03, 2012, 10:17:23 am
The framework I mentioned and the FreeRTOS will both meet your (unstated) requirements.
http://www.freertos.org/

I assume that the FreeRTOS framework would not be compatible with the Arduino IDE environment.

Never assume anything...
http://www.freertos.org/a00090.html#ATMEL
http://www.freertos.org/AVR_IAR.html

I have not tried -- I just got FreeRTOS running (correctly) on my LM3S811 -- so if I get bored -- maybe I will try my Arduino Mega 2560 -- it should work -- sort of.

You might have to change an if statement here and there....  smiley-roll

I would look at the State Machines Framework first though -- he has a specific version for Arduino.

See here and here:
http://www.state-machine.com/arduino/
http://www.state-machine.com/arduino/AN_Event-Driven_Arduino.pdf

hth...


13  Using Arduino / Programming Questions / Re: Measuring 12 Volts on: August 03, 2012, 10:11:14 am
Just do the ratios so they agree with reality. It should be fine.
14  Using Arduino / Sensors / Sensor Selction Aid on: August 03, 2012, 10:01:58 am
Quite a few posts are "What sensor do I use to...?" or Could you explain how Sensor XYZ works?

I ran across this Digikey resource while taking the Design News tutorials.

Digikey Sensors:
http://www.digikey.ca/ca/en/techzone/sensors/index.html

Other sites have similar tools -- I just happen to know of this one. I finally gave in and opened an account with them -- not the cheapest but the service is reasonable and the resources are phenomenally good.
15  Using Arduino / Programming Questions / Re: running more than one program on: August 03, 2012, 08:26:12 am
Yup -- that's the way computers work all right -- in polled mode. But that is the programmer -- not the machine.  My Arduino definitely has Interrupts available. (Mega 2560)

Are you looking for an Interrupt Driven Real Time Operating System?

The framework I mentioned and the FreeRTOS will both meet your (unstated) requirements.
http://www.freertos.org/

Now what exactly do you want?

This inquiry is pretty vague.
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