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1831  Using Arduino / General Electronics / Re: Better headers on: August 07, 2012, 10:57:50 am
At 2.54 MM pitch you have illustrated the available solution. I have only seen two variations .5 mm/.020" that fit IC sockets and the .66 mm/.025 standard square headers. There are several different standard sizes available but not to the best of my knowledge any others available for a 2.54 mm/.1" pin pitch or spacing.???

Doc
1832  Using Arduino / General Electronics / Re: interfacing 10 turn precision potentiometers to analog In on: August 07, 2012, 10:48:23 am
I am curious about "Mapping" 10000 (100,000 ohms /10 turns) discrete values into 10 bits of available resolution, one turn would have 10 discrete values. If you look at the portion of a "Turn" that can be reported successfully. It would appear that you have large sections of the Pot that are questionable given the granularity of the available precision at 10 bits of resolution and as far as I can see worthless at 8 bits of data.
I  would think that a 10000 ohm 10 turn pot would be more appropriate if still not overkill or just more data that available resolution... Given the restrictions imposed by floating point variables and the available resolution of the A/D converter.

Doc
1833  Using Arduino / Programming Questions / Re: Mega vs UNO on: August 07, 2012, 10:13:35 am
It's as easy as 1, 2, 3...

Doc
1834  Using Arduino / General Electronics / Re: amps volts and power supplies on: August 06, 2012, 11:48:13 pm
Until you do some reading on BASIC electricity... It's' Free on Wiki too. Not even electronics... perhaps the simplest answer is they're like cups, they can only hold so much before the magic smoke escapes.

Doc
1835  Using Arduino / General Electronics / Re: Increasing LED brightness on: August 06, 2012, 11:43:24 pm
Buy a higher powered IR LED... Simple

Doc
1836  Using Arduino / General Electronics / Re: sugestion on where to buy transformer? on: August 06, 2012, 11:41:57 pm
Well  said Sir. It is easy to make a phasing mistake, Very easy because all  the primary start windings must be one side of the line and the finish windings be the other line connection but the secondaries must be connected series aiding as reversing a primary winding is the same as a secondary winding reversed.

Doc
1837  Using Arduino / Displays / Re: this'll be fun... on: August 06, 2012, 11:29:12 pm
Eagle should have an unique wire symbol  it looked like a thick wire and was called a bus that is actually a way of graphically representing net list connectivity to simplify regular schematic drawings such as yours all the leads had either machine or man generated names that were applied to the required nets but the "Special Wire" or bus symbol should be used in your drawing as it can easily represent direction so as to make work on it later easier and to replace that mass of spaghetti decorating your drawing... and one or two other points... Place the pads for the caps as a MUST DO  and use a ground plane even if It's only on the edges of the board. It's not much more work but I think your efforts will be worthwhile.  IMO

Doc
1838  Using Arduino / Displays / Re: KS0108 Noob Question on: August 06, 2012, 10:56:00 pm
Adafruit has Extensive instruction as well as libraries for their products, generally very well done, I got my little 1.8" display working in about 30 minutes... first time I didn't install the directories properly and it took 2 tries have you looked there. Without more than it don't work" there isn't a great deal anyone can do for you. Without the sketch and a very clear schematic and a picture of what you might have done it is very hard to guess... So Yep... It's Probably broke...

Doc
1839  Using Arduino / General Electronics / Re: quick driver current question on: August 06, 2012, 09:40:54 pm
Design 20 will work as well and it can also be PWM'd... The BC547's are 2N222A's. Actually after having re-read the data sheets on both I'd use the 2N2222A's. One other point re: design 19... 1N4148's are TOTALLY inappropriate as back emf diodes, Use 1N5404 3A 400V PIV diodes...

Doc
1840  Using Arduino / Programming Questions / Re: atoi() function where does it come from ? on: August 06, 2012, 07:51:56 pm
I as more interested in the formatted print functions than managing longs or floats. I usually do that myself beforehand. Long way round but it works for me at my poor level of comprehension of the language. It might take a few more lines of code but it works. I have little interest in floats anyway... too much like the job I retired from. This is my retirement hobby not a vocation. B'sides the Arduino is more a teaching platform than any kind of really accurate analog device and those I can buy as peripheral chips and talk to then with one serial bus or another. The Arduino is much better than TV... I don't care for the new stuff and I've seen too much of the old stuff. I noticed my cable box was out of order today and I just unplugged it...  If I get a rountoit... maybe I will do something about it. Rountoits are really hard to come by these days though.

Doc
1841  Using Arduino / Displays / Re: Help with display on: August 06, 2012, 07:12:20 pm
Likely what you have is an annunciator. Just the bare LCD panel W/O the driver as has been pointed out. Driving an LCD is some what complex as a steady DC voltage on any pin VS the "backplane" will damage the LCD "Cell" connected the device is driven by an ac signal where a displayed segment is out of phase with the backplane and a blank one is in phase with the back plane... Go look up a CD4543 It's an old but very useful chip as it will do several different types of devices. I used a LOT of LCD panels in 2006 to 2008 but I really don't remember all I read then as I left the display control to an ICL7106... Just don't remember it was a cheap drop in replacement for a common 200mV Fs LCD panel meter. Mine cost about 7 or 8 dollars in parts while the "store bought" displays were about $50.00... Think I still have some of the PCB's. I just copied a reference design from Intersil. The part is long discontinued though. Wiki should have some good information.

Doc
1842  Using Arduino / Displays / Re: Trouble compiling examples for the UTFT Library on: August 06, 2012, 06:56:24 pm
Did you RTFM? You know... READ That Fine Manual, first?. Henning is as far as I know very approachable as well, You might try there as well. I would.

Doc
1843  Using Arduino / Displays / Re: Voltage reference with LCD on: August 06, 2012, 06:52:33 pm
An LCD panel in of itself doesn't draw much current and a driver transistor to manage the backlight is a simple thing to do.
For that matter You Could just use a PNP transistor from a digital pin on the Arduino to turn off power to the whole LCD panel...
Rather than trying to control the contrast with the Arduino and save yourself a lot of code grief...
For that matter the Arduino Could be the VCC for the contrast pin... or you could simply "Gate" the contrast off with a transistor.
As I remember If you pull the pin about 2 - 3V high it will turn off the LCD contrast as that pin wants to be about .5 to 1V positive and any higher voltage will blank the display...
All are easy things to do and much easier than trying to PWM the contrast pin.
 Although your idea is certainly do-able it is a whole lot more complication than is required... IMO
The methods I mentioned would be my first choice and PWM control of the device would be a method I would study real hard to avoid as it is too much code for too little a problem.
Occams Razor is a useful philosophy, I have found... mostly the hard way thus my tag line.
Here is a good reference from Wikihttp://en.wikipedia.org/wiki/Occam's_razor. Try reading it and see if you can't simplify things...
Fewer things to go wrong in the end, Most likely.

Doc
1844  Using Arduino / General Electronics / Re: Trouble with a boost converter on: August 06, 2012, 05:30:17 pm
Yes IF you state accurately your power supply requirements. This is a link to an easy to use part available in several different current capacities... I used a lot of them from 2003 to 2006 and they all worked very well for me.
http://www.stanford.edu/class/ee122/Parts_Info/datasheets/LT1170.pdf
Figure out what You'll need and let me know. I'll be happy to help as much as I can.

Doc
1845  Using Arduino / General Electronics / Re: atmega328 glitching on and off on: August 06, 2012, 05:23:22 pm
All of what I wrote in my last post is I believe correct... for a device that needs 200 - 300 mA Max current from a 24VA transformer and yes you do need a 24VA transformer to supply 24 VAC @ 1A load current. A "Half Wave Rectifier will give you 1/2 (approx) of the 24V ac or about 12 Vdc. I suggested a large enough diode that the surge resistor might not be needed and that there would be 9 to 10 Vdc available for the regulator.
The best method (IMO) is a switcher and I had very good results with the part i mention next... I made about 100 of them (Not me I just did the design and PCB layout) but they were really quiet and trouble free.
 I built a lot of 24Vac based switchers in 2003 - 2006 I used an LT1170 because I needed about 3A for 10 - 15 seconds to power a 10W transmitter. It was an easy device to use... all the information you will need is in the data sheet. There are three varieties of this device, LT1170 - 1 - 2 for 5A @60 V max input voltage (LT1170 2.5 A (LT1171 and 1.25 A for the LT1172 I used the 5 lead TO-220 and the 5 Lead SMT package and all worked very well. This is the link to the data sheet.
http://www.stanford.edu/class/ee122/Parts_Info/datasheets/LT1170.pdf
an ac transformer and a bridge rectifier work very well with this device for a stable and adjustable buck mode power supply. If you need a lot of current. If you are just doing a small control device then my last post should have more than enough information. I would add that a Tranzorb should be included for transient protection on the secondary of the transformer to protect the diodes. I also included poly fuses to prevent fires in case of component malfunction. I also used tranzorbs on the rectifier output as these were used in Kansas on a Rural Power Grid where KV level spikes were common and some of long duration... 1/2 second spikes were measured... Usually though when the Power company did a "Load Drop", A frequent nightly occurrence as most of the big Agricultural companies used power at night when rates per KW were cheaper.

Doc 
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