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1  Community / Products and Services / 1 x 20 Vacuum Fluorescent Displays, 5v, Serial Enabled VFD on: March 09, 2014, 04:21:37 pm
I will have a few of these displays for sale. 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=271456375021

They are 1200 baud.
They use 5v at around 500ma, so you can run the Arduino from the same supply.
They can also use RS-232 if desired.
Tested to confirm every pixel works.

There are links to a video showing the display in action.

2  Community / Products and Services / Re: Ok to post links to ebay sales? on: February 04, 2014, 09:59:16 pm
... I am a forum member just like you. My yes is valid as much as yours. ...
In other words, hardly valid at all then, since I am not a moderator, nor experienced at this forum.
I don't need any fishing advice. I needed the fish.  What I needed to know, from someone more experienced, was if using this site to sell my stuff was allowed, even though I'm not a paying vendor.  Not a link to 37,000 posts which would take a lifetime of wasted time to wade through.

And as Coding Badly has kindly given me the answer, I'll take his fish, and thank him kindly, since I know he's a very experienced member of this forum.
Thank you.
 
3  Community / Products and Services / Re: Ok to post links to ebay sales? on: February 04, 2014, 10:48:43 am
Yes, but of those, which ones were links by the forum member selling the thing in that link?
I'm on many forums and some forums don't allow this.
I've searched for rules, but didn't come across any regarding this.

But instead of posting a waste-of-time link, a simple yes would suffice.  Thank you.
4  Community / Products and Services / Re: Ok to post links to ebay sales? on: February 04, 2014, 10:34:05 am
Ok, I'll take that as a yes, even though there's no useful info in that link that I can find.
5  Using Arduino / General Electronics / Re: Using Transistors as switches for 9V relays on: February 04, 2014, 10:19:33 am
It's very common to find the emitter and base are swapped on some transistors.  It all depends on the manufacturer's whims.  If you can sacrifice one try it with the outside legs reversed.  Or, do a search on how to determine which legs are emitter and collector.

There are cheapo, $4 meters nowadays, (Harbor Freight) that will have a transistor checker built in.  (Actually designed to measure gain, but will show you if you have the polarity correct.)
6  Community / Products and Services / Ok to post links to ebay sales? on: February 04, 2014, 09:43:59 am
I have some hard-to-come-by hardware that Arduino users may want, but I will probably be selling them on ebay.  Is it ok to post a thread with photos/details here, with a link to the auctions?
7  Using Arduino / Programming Questions / Re: Is there a way to specify the bit depth a math operation returns? on: November 30, 2013, 08:08:26 pm
ok, thanks.   smiley-cry

8  Using Arduino / Programming Questions / Is there a way to specify the bit depth a math operation returns? on: November 30, 2013, 06:54:08 pm
I'm playing around with timing delays and am using an 8 bit version of millis() by calling a function which returns millis() truncated to 8 bits.

My variables are all 8bit, unsigned integers.

However, when I do math within a "while" statement or "if" statement, the value returned is sometimes negative (because the adding or subtracting is done at a higher bit depth).   I assume the math is done at 32 bits.

Obviously it's an easy workaround to create another 8 bit variable, and a couple more lines of code, to handle the rollover correctly.  But in the interest of speed, and using fewer variables, is there a simple way to specify that math (adding and subtracting) should be done at 8 bits only, (or any other desired number of bits)?
9  Using Arduino / Installation & Troubleshooting / Re: Uno does not work with Windows 2000 ? on: October 24, 2012, 01:04:44 pm
Thanks, Yeah, those are the options I considered. I ended up going with option 4, the FTDI basic from Sparkfun.  It can communicate to the 328 chips directly through Windows 2000, even if the chip uses an UNO bootloader.  That's how I usually use the Arduino environment.  I don't use the actual UNO board too often (never on a Win2K computer).

The FTDI basic also lets me use one of those mini-laptops that only have USB ports.
10  Using Arduino / Programming Questions / Re: Arduino TTL to RS232 Communication (interfaced w/ stepper control box) on: October 20, 2012, 03:54:57 pm
What I'm saying is, whatever you are using to talk to the computer (Hyperterminal via serial port) will not work to talk to the stepper control box because the computer and control box have their Rx/Tx pins configured differently.  The computer is wired as DTE, the stepper controller is wired as DCE.  As Nick pointed out, that means Rx/Tx are wired differently, but also hardware flow control lines may also be wired differently as well.  

More info will be needed to know about flow control requirements, but hopefully you can skip all that by using a "No Flow Control" option.  (Maybe that can be set the same way you set Baud, Parity, stop Bits etc.)


If you have the option, I recommend not using hardware or software flow control, and just communicate with "No Flow Control" just for testing purposes, and just give very short commands with a lot of time in between commands so there are no buffer issues etc.   That way you can at least confirm the commands and Rx/Tx are correct.

Wikipedia probably has some details on RS232/TTL communication if you need more info.

11  Using Arduino / Programming Questions / Re: Arduino TTL to RS232 Communication (interfaced w/ stepper control box) on: October 20, 2012, 10:14:56 am
I couldn't get the links to work either.

Based on Nick's quote, the control box acts as a DCE device.  Your computer's port is wired as a DTE device. Thus you cannot use the same cable to talk to both from the Arduino, unless you re-configure the Arduino end.

If you used a null-modem cable to talk to the computer, you need a straight-through cable to talk to the controller, and vice versa.  Or you need to change the Arduino end from DTE to DCE or vice versa.

That's just the tip of the iceberg on settings to check for successful RS232 comm.

I suggest doing what WildBill suggested and communicate with the box using Hyperterminal first to confirm the controller is working as expected.
12  Using Arduino / Programming Questions / Re: loss of precission on: October 17, 2012, 11:23:42 pm
Also, beware that in floating-point math, another phenomenon often shows up known as "Loss of significance". Wikipedia has a page describing it.  I can't tell with a quick look if your formula will suffere from it, but you may want to look into it. 

Basically, it's a problem that arises when you subtract a number from another number of similar magnitude, then multiply it, or square it etc.  All of the significant digits get lost in the subtraction, then you multiply the remaining insignificant digits by some meaningful value. The result is just amplified noise, and can be completely meaningless.

I usually perform a check anytime I perform a subtraction (if the result is to be used for other operations). If the difference is less than some percentage of either (or both) of the first two values, then you have to force it to zero. (And do a check for a divide-by-zero if your next step divides.)

There are probably other ways to avoid this problem for specific purposes as well.
13  Using Arduino / Displays / Re: Sparkfun LCD, ok without backlight, or in sunlight? on: October 11, 2012, 12:18:09 pm
Let me save you the trouble liudr, unless your white-on-blue is a lot different from my Sparkfun white-on-black.

Thanks again, for the input. The black-on-green is going to work perfectly for me.

In direct sunlight,
black-on-green is much easier to read, it is just plain easy to read,
white-on-black requires a little more effort to read at a glance.
In either type, the backlight makes no difference in direct sunlight.

In total darkness,
white-on-black has a brighter result, but is almost too bright at max backlight,
black-on-green is dimmer but totally readable at max backlight.
In total darkness, the white-on-black is much easier to read with minimal backlight, using much less power.

Basically it comes down to:
In the dark, the white-on-black is probably better for saving power.
In sunlight, green-on-black is much easier to read, but there is no power difference since backlight will not matter.
In indoor lighting both are easily readable, but green-on-black will work with no backlight, while white-on-black will require some backlight.

In this composite-photo, the camera makes the ones in total darkness seem a little darker than they are in person. This is just an artifact of my camera. In person the black-on-green is bright enough to read easily, and the white-on-black is a little too bright.

(I also adjusted the contrast on each LCD to optimize each condition, but really, once adjusted, it seemed to be optimized for all conditions without much fiddling. The contrast setting on the black-on-green was far more sensitive to movement of the pot, though. The white-on-black was easier to set)

http://home.comcast.net/~loudgpz/SparkfunLCDcomparison.jpg
14  Using Arduino / Displays / Re: Sparkfun LCD, ok without backlight, or in sunlight? on: October 10, 2012, 04:45:15 pm
Ok, I just went and ordered a black-on-green display.

So for anyone else who may have been wondering, the black-on-green display is totally readable in normal lighting without any backlight.  By comparison, the white-on-black is almost unreadable without some backlight.  

In normal, indoor lighting, the black-on-green display is readable with no backlight at all, in fact, you can't even tell any difference if you turn the backlight on full or not.  In darker lighting conditions, the backlight makes a difference as would be expected.

The white-on-black displays are very very dark, and unreadable, in normal indoor lighting with no backlight. I played with the contrast, but it was already set to the best setting.  The white-on-black simply is not useable without backlight. It is also not great outside in sunlight. It is probably best used indoors. The darker the environment, the better.  

Obviously, if battery power is a consideration, and you have normal lighting, the green-on-black will be a better choice.
Here's some info on the power useage and noise.

On the black-on-green, I measured 3ma without backlight. 14ma with full backlight. 
With no backlight, and using a 10uF filter, while powered from a FTDI basic USB cnverter, the noise on the power supply was about 58mv P-P.
With the backlight at 50%, the noise was a 142mv P-P square wave.

On the white-on-black, I measured 3ma without backlight. 19ma with full backlight. 
With no backlight, and using a 10uF filter, while powered from a FTDI basic USB cnverter, the noise on the power supply was about 56mv P-P.
With the backlight at 50%, the noise was a 172mv P-P square wave.
15  Using Arduino / Displays / Re: Sparkfun LCD, ok without backlight, or in sunlight? on: October 04, 2012, 03:11:12 pm
Putting it back together is the hard part, not taking it off. The conductive rubber and metal tabs are not very friendly to disassembling and reassembling. Try the contrast first.
I was worried about that. I'll definitely try the contrast first.
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