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1  Using Arduino / Storage / Re: For expert - flash question on: August 06, 2012, 07:14:38 am
See here: (for the multitude of other people who keep asking this question)

http://hardcoreforensics.com/blog/2012/01/02/arduino-mega-direct-reading-of-a-nand-flash-memory-chip

It Is NOT a viable solution, it will take between 1-2 days to fully extract a current technology Nand-Flash chip. (see my timings using HAND crafted assembly code)
And WEEKS to do the latest devices even using a Arduino Mega.


And NEXT TIME search the forums.
2  Using Arduino / Storage / Re: [code] Nand Flash 4Mbit (512 Kbytes) - S71295 (SST on: August 06, 2012, 07:10:04 am
This is NOT NAND-FLASH, this is SERIAL FLASH and they are completely different........
Which means that the code is WRONG for a Nand-Flash chip.

see here: http://www.sst.com/dotAsset/40490.pdf
and here: http://hardcoreforensics.com/blog/2012/01/02/arduino-mega-direct-reading-of-a-nand-flash-memory-chip


3  Using Arduino / Programming Questions / Re: On startup, start loop at beginning of next minute on: March 19, 2012, 01:20:14 am
I am reading multiple sensors with the arduino and logging that data to an SD card. I do not have a real time clock, so to set the time on startup I send a message over the serial port from the unix terminal. However, I do not want the main loop to start reading the sensors until the start of the next minute once the time value is received by the arduino (i.e., if the time sent over serial port is 11:41:25, delay the start of the loop until 11:42:00).

I've looked around the forum for a while to find an answer to this, but cannot seem to get a solution; it's entirely possible I am just not searching with the correct terminology. Any ideas or directions would be appreciated. Thank you.
-Dave

Really easy........
Sloppy way to do it...
1. Read minutes. (1)
2. Read minutes (2)
3. if minutes1 = minutes2 goto 2.

4. dropdown into main loop
4  Using Arduino / General Electronics / Re: Flyback diodes on: March 18, 2012, 11:58:25 pm
but I'm curious how the current can be the same if the voltage is thousands of times higher?  It seems like you ought to have to trade current for voltage.

Actually it is related to the inductance & resistance of the circuit, on an unloaded circuit it can be tens of KV. but the current will be very very low.(you CANNOT reliably measure it with a multitester)
One thing to note is that there is ALWAYS back emf from a motor even when it is running under power, it occurs whenever a magnetic field collapses or is cut by a metallic object.
If you have a very fast scope you can see this as the motor rotates under power. try scattering some 10nf or 100nf ceramic capacitors about the circuit, as well as the back emf diodes, but note that rectifier diodes really are too slow for this.




5  Using Arduino / Networking, Protocols, and Devices / Re: IP address of Ethernet shield on: March 05, 2012, 10:46:18 pm
I am totally new to Arduino and, of course, new to the Ethernet Shield. I decided to try and run the  Web Server tutorial code http://arduino.cc/en/Tutorial/WebServer  .

Obviously the code needs to be changed to reflect the MAC address of the shield and the IP of the shield. I expected to be able to simply plug in the shield (attached to the Mega) to my router and then log into the router to check out the “attached devices” page to find the IP and MAC addresses. I can see my computer, cell phone and  Tablet but not the Shield. Activity lights appear to indicate the Shield is properly attached but it does not show on the attached devices list.

What am I doing wrong?
Thanks.
There should be no need to change the mac address, unless there is a clash

You MUST change the ip address to match your network:

change this line:

Code:
IPAddress ip(192,168,1, 177);

So that the first 3 numbers match your network and subnet....

so if a device on your network is on 192.168.0.xx

Change above line to :
Code:
IPAddress ip(192,168,0, 177);

if your device is on network 192.168.5.xx change the line to:

Code:
IPAddress ip(192,168,5, 177);


The reason you cannot see the device is because, whilst it may be connected, it is not  'within' the domain your router is looking at.

If you get stuck, then  post the addresses your computer/tablet show up at.

6  Using Arduino / Displays / Re: Help With wiring 1.8" color lcd on: February 25, 2012, 08:46:36 pm
Quote
well if you looked at the page you linked you would see the download that includes documentation and example code. it's in  a zip file.

You must be using Internet Explorer.  Try finding that file and most of the pictures when using a real browser.  

The W3C HTML Markup Validation Service reports 291 errors on that page.


Don

Nope....... it works fine with both Safari & firefox, just requires two skills   "Ability to read" "Ability to observe"

For anyone else lacking the rudimentary skills to use the internet, I have attached the re-compressed file for arduino, after stripping out other C++ demos not needed
7  Using Arduino / General Electronics / Re: Capacitor acting like a wire on: February 21, 2012, 09:34:23 pm
One of the parts I scavenged was a 470 uF/6.3V capacitor. I noticed it had two crevices on the bottom where it used to be connected by wires, so I stuck my own wires into it.
Quote
Am I doing something wrong? Is the capacitor messed up because I just stuck some random wires in it to replace the ones that were used to solder it to its previous board?

Is this capacitor an SMT part or is it a traditional part (any picture, or find something similar on the web as a reference for us), because it could be that the part was torn from a pcb and the terminals have been ripped out.
If the terminals were ripped out, then you need to throw the part away, because sticking wires back in, will not work, and would result in a 1:1 short. (possibly resulting in what you are seeing)

8  Using Arduino / General Electronics / Re: Cheap/easy/efficient way to switch 5A without a 5A switch? on: February 21, 2012, 07:56:10 pm
Devils advocate

Not cheap or small, but easy:

Bistable or latching relay.
9  Using Arduino / General Electronics / Re: Maximum current in wires. on: February 21, 2012, 07:49:33 pm
Quote
Their listed "current carrying capacity" seems VERY low compared to common practice. (<4A for 16g wire?  Nor do I have any 1000W hair driers with 12g cords...)

Normally cable manufacturers quote the resistance on either 1Km lengths or 1000ft,
The reason they have quoted the table like that, is that once a cable gets warm its resistance INCREASES.
http://www.allaboutcircuits.com/vol_1/chpt_12/6.html

Also the resistance depends on where your cable is from.
Most of the 'good' crap out of China is low quality copper, the real copper cable crap out of China, often has aluminum or steel strands that have been chemically treated to look like copper that is mixed in with the real strands.

Sometimes it pays to get 4 core 16A then parallel two of the cores to give 50% of the single core resistance and double the current, and not worry about temperature rise.

10  Using Arduino / General Electronics / Re: Ok to share capacitors between voltage regulators? on: February 21, 2012, 07:25:47 pm
Quote
The other day I asked in another thread if I had to use tanatlum with my regulators because they're expensive and I wanted to use ceramic, and Grumpymike said I should avoid their use because they can catch fire. 

My toaster can also catch fire: tants usually do this when they are abused or used in the wrong way, I can honestly say that one design I worked on shipped over 2 million parts and for that product range I NEVER once saw a tantalum that caught on fire, but that does not mean it cannot happen.

Cost is relative.
Quote
Capacitors other than tantalum or aluminum can be used at
the adjust pin and the input pin. A 10uF capacitor is a
reasonable value at the input.
You are not talking 10uf you are talking 47uf, as I said before electronics is like cookery, also be aware an electrolytic can be  +-50 - +-50% of the marked value.

Quote
I understand that.  I was just concerned that the 3.3v reg might overheat if the supply is 12v.


but looking at the data-sheets, it maxes out at 16v input
and the other maxes out at 27 or difference depending on the model, why not use the same range parts (LM1085-3.3) for the 3v3.

You are still within the spec, but ultimately it depends on WHAT load you are driving.

Quote
Also I seem to be getting conflicting information here.  On the one hand you're saying it's critical I use the capacitor values in the datasheet for stability, and on the other you're telling me to add two more caps which aren't in the datasheet.

The data-sheets cover what is around the regulator for optimum operation of the regulator, my recommendation was related to the fact that I did not know the power supply and cable length, also note that an IC is a 'microcosm' linked to components around it, once you get a few inches of copper between your IC's and power points, you will be glad of a bit of storage near your connector, before you hit the inductive load/Choke that is commonly called a power cable.


Quote
Your suggestion also goes against my own experience with voltage regulators.  I've built a number of circuits with only a .1uf on the input and a 10uF on the output of my regulator, and running off a 9v battery.  These circuits were driving a couple noisy servos and reading analog inputs and I haven't had any problems.  Are you sure you're not being overly cautious?  I could understand sticking a larger cap on the input if I was running off something like a wall wart, but that isn't likely with this circuit.

Then go with what you know, personal experience trumps free advice (especially with engineers). As regards capacitors after regulators, I'm used to seeing idiots slapping 1000uf or 2200 uf after them, but issues generally start at about 100-220uf.
Also consider that electricity does not just appear at a component, if you are driving a servo, then you will need some storage prior to the regulators, before they hit the power cable.

Quote
Are you sure you're not being overly cautious?
I have designed for millions of 'items' shipped, so yes when a simple choice can push your failure rate up .02 of a % and your ass is on the line you do get a bit cautious.

Also looking at your  circuit design, route BOTH regulators supply rails (VCC, VSS) separately to the input terminals, ensure when the copper is routed that they are not daisy chained (if this is a single layer pcb)


11  Using Arduino / Programming Questions / Re: Stand Alone Arduino? on: February 21, 2012, 08:22:32 am
Really no need to make it this complicated with linux libraries and pc's and udp & http.........

Sql server allows stored procedures, you can install an email interface to send and receive emails in the database (well documented).

The arduino has an ethernet shield.....(well documented)

Email is just text commands and bytes sent to a pre-defined port (well documented)
There is at least one thread recently on sending emails from arduino. (user: zoomkat I think)

Package up all your data as an 'email' and pop it off to either :
1. Your sql database directly (you need to handle corrupt deliveries/non delivery)
2. To a relay remailer (the system does it all for you.)
12  Using Arduino / General Electronics / Re: Ok to share capacitors between voltage regulators? on: February 21, 2012, 07:23:52 am
Normally a capacitor is chosen for a reason, you need to try  and follow the requirements in the data-sheets, specifically because the values are chosen to prevent the voltage regulators from oscillating and also the distance from the regulator can make a big difference.

Also note the data-sheet uses tantalum close by the regulator & not electrolytic, (electrolytic caps are the bitches of the electronics world), the tantalums have nice high frequency characteristics and a tighter tolerance.

As regards the  3.3 and 5v,  do not supply the 3.5v from the 5v regulator, there is no such thing as a free lunch, you would simply increase the dissipation of the 5v regulator and cause additional ripple on its output.

Drive them separately , but stick a reasonable size electrolytic BEFORE them, and a 0.1uf bypass capacitor, generally it is not a good Idea to stick your big storage capacitors AFTER the regulators (capacitors can be considered 'shorts' until they get a charge).

It is unlikely your design is going to fail badly or blow up by the use of the electrolytics, consider that electronics is very much like cooking as regards ingredients, but it is also unlikely to perform with the sort of  tolerances one would expect from modern components if you don't follow the manufacturers requirements.

One last point, the higher the working voltage of an electrolytic, the more it 'leaks'.


13  Using Arduino / Displays / Re: LCD text corrupts after Arduino runs for length of time on: February 21, 2012, 03:07:09 am
ok, a TVS is a little different........

If it is a coil type load, you will be looking at back EMF, best way is either a  diode (for DC) across the coil, or an inline inductor (for AC) in series with the coil. and  if you have a relay in there, you need a resistor+capacitor (Snubber network) across the contacts.

14  Using Arduino / LEDs and Multiplexing / Re: Driving two different devices off a single pin on: February 20, 2012, 10:33:01 pm
try them in series.
15  Using Arduino / Displays / Re: LCD text corrupts after Arduino runs for length of time on: February 20, 2012, 10:08:44 pm
My Arduino is powered from a small isolated AC-DC switching converter (a 9VDC wall wart).  The converter is supplied with mains power less than a foot (as the crow flies and along the wires) away from the devices with the coils.

I put a diode across the AC input leads at the converter to snub the high spikes on AC mains, and this has cut the instances of problems way down.  But I still get a confused LCD now and again when the pump or solenoid are switched.  So I would love to find a more robust solution...

Jim

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I put a diode across the AC input leads at the converter to snub the high spikes on AC mains

Sorry that is incorrect and potentially dangerous,  if it is AC you should be using a Transorb, or if it is an AC switch, a resistor and an X2 capacitor in series across the contacts.
You ONLY put a reversed diode across a low voltage DC feed with a 0.1uf capacitor ,and possibly an inductor in the  Arduno & low voltage control feed.

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