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1861  Using Arduino / General Electronics / Re: Need some help with the concepts of pull-ups/downs. on: August 28, 2012, 12:14:53 am
Well Young Man, It has been my experience that any reasonable education will come in handy, sooner or later... My biggest fear is that I will forget which answers the questions are for... Think about it. My Very last rant on pull downs, I promise other that to question once in a while... Is that I take a different approach... Kill 'em All and let no one but me.. When I am doing something new I usually use 470 ohm "terminators or pull up/down's... I never really worry about current drawn, I use op-amp Voltage followers on analog measurements and when I am through I start the real engineering and that is to remove components until it's operation is either departing from the design spec's or has flat quit... Put that part back and then test it and try to break it... whatever you can think of that it might see in use... If it works good it's good enough to field test... Maybe many times I have had a piece of equipment fail miserably in the field after heat and cold testing both heat soaked and transitioning between hot and cold... Just roll over and die from something I thought could never happen... about 90% of the time. Granted many seem really out there... as far as time and parts, knowledge and experience... have taught me to remember that "Murphy Was an Optimist". What I recommend here worked for me or I wouldn't advocate it. However there is one real final teacher that few of us know to heed regardless of exposure... Pain is the real teacher... It's the one we knee jerk remember rather than the intellectual or reasoning parts we like to think we use...did you ever wonder why people stick their fingers in light sockets... at least once? it's simply because they have been told not to... By someone who was told not to... Why would I want to go to the trouble of finding one to begin with?
Actually that isn't really fair however it might be true... we do things like that because we are constantly testing our boundaries... That's how we learn.
I can't remember but one board I ever produced that went into production with anything as small as 470R But I do use them until I know that the noisy thing I am concerned about is under control.

 I use them and the lesson that taught me their use went out with spare pins tied high or low. It was also the only project I ever put in a nema plastic enclosure... Steel after that. Again I've wasted a perfectly good space somewhere with my blathering... IT Was Fun though. IMO

Doc
1862  Using Arduino / General Electronics / Re: Trying to adapt a schematics with single power opamps to dual power ones on: August 27, 2012, 02:48:11 pm
The pencil drawing used bi-polar power supplies... The Grounded + input will give you some problems trying to realize that circuit... one other point... the symbols you use for the op-amps are grossly incorrect... use the right ones, they were created for a reason. Rather than being able to see at a glance what is intended your drawing has to be interpreted. and much was lost in your interpretation.
If your schematic tool won't reproduce the correct symbol, find one that will. IMO

Doc
1863  Using Arduino / General Electronics / Re: Resistors, many and cheap on: August 27, 2012, 02:39:05 pm
It's not a widely known thing But Walt was a smoker... I remember him alongside a barely nubile Annette Funicello... on The Mickey Mouse Club... Smoking a cigarette or a pipe... Memories, I spoke of was buying a pipe from the Tobacco Shop on Main Street... when I was 22 or 23 years old... for many years I was a baby faced young lad... and a baby faces Auld Phart... Too. I still get a KICK out of remembering what I must have looked like... desperately trying to look older. I did enjoy the pipe for many years and I bought more than a few pouches of tobacco from that little tobacco store on main street...

Doc
1864  Using Arduino / General Electronics / Re: Free (almost) Solder Suckers on: August 27, 2012, 02:29:00 pm
The Don Quixote of solder... I am not being negative here but I should think that MY Lifetime contribution to world waste... Wouldn't add a speck to the backside of a fly... compared to ... China in the 1700's... for example. I fully agree in EVERY respect the bans on solder for ANY NATION... But I am not so conceited as to believe for a minute that any contribution to either side of the argument is going to do anything except.. Lip Service... Much better in my way of thinking to conserve your resources for things that really matter. I purchase a pound of solder about every 5 years... and here is an example of why I consider the "Ban" to be a total waste of time for the private, non commercial "Limited" use of solder... In this world there are MANY Stained Glass windows and More being built by the day... What is done for the runoff from the lead used to create those Majestic creations to the Glory of... Were I Sony, Mitsubishi... any of the giant's it would be of some concern, Some Great Concern. However my use of solder, if continued unabated until I died of lead poisoning wouldn't be enough to make any difference whatsoever and it does make a great deal of difference to me, That ersatz stuff crystallizes and breaks where lead based solders don't. I repair equipment today as a hobby and the number one failure on most laptops is bad solder... when you finally get to the hardware level. 2. the whole movement is based on bad science distorted all out of proportion to the real effects... Yeah there is a great deal of money spent on re-mediating the "Solder (Lead)" Problem... Damn shame 10% of that money wasn't spent on dealing with Carbon Pollution... and I would be willing to bet that atmospheric warming is a whole lot more likely to be the cause of your eventual demise... than a case of lead poisoning... for that matter there is about 20% of the lead based solder used to make a  color television today... compared to even 20 years ago. I believe in Ecology with ALL my HEART, however I Believe that "Tree Huggers are getting in the way of REAL ECOLOGICAL PROGRESS... Simply by being a nuisance.
There was a man who a Very long time ago, That made one important observation... Fight the Battles you can win... Sun Tzu... The Art of War.

Doc
Let the War Begin...
1865  Using Arduino / General Electronics / Re: Wheatstone bridge? on: August 27, 2012, 01:48:27 pm
Well, Young man the knowledge was given to me for free... and the only way I can repay the patience of the people who took the time to explain things to me is to do the same for as many others as I can reasonably. You Are quite welcome and thank you for the opportunity to explain it to you...

Doc
1866  Using Arduino / General Electronics / Re: +, -, GND on: August 27, 2012, 01:41:42 pm
It Might be a bit easier to think of ground as the "return"... that removes the concept of polarity form the general discussion. Polarity is a specific term relating to a specific set of conditions, It is a lot easier to think of sources and returns rather than + - or common (Gnd). Trying to build an image from power distribution terms will always lead to confusion simply because there is no connection (pardon the pun) between ground and neutral and neutral is not necessarily the return. a 3 phase Delta connected motor or transformer.. has no neutral or ground except for safety concerns and except for dealing with fault currents needs none.

Doc
1867  Using Arduino / Sensors / Re: analogReference using a voltage higher than the Atmega 328p's power on: August 27, 2012, 02:43:22 am
or put in a bounded pot, where series resistors on each end create boundaries or limits of operation When I needed an accurate but simple circuit to use most any two resistors to set the output of an LM317 I picked the closest value less than the required one and used a 500 ohm pot to 'adjust' the voltage to the correct point... I bought 10 dual 10k digipots the other day and I am going to have fun with them and a 14 bit D/A converter I bought from Adafruit. Back in the day I might have used a DC-DC converter a buck boost device, they're not terribly efficient But can work in the middle of the battery range to put out any desired voltage... only needs to be powered op for 50 mS or so and most I worked with could be shut off- totally, the other attractive point is besides the complexity the efficiency should be slightly better than a linear doing the same work... for that matter a switcher becomes really attractive when a board can work off 3V3 because the losses become small single digit figures when the switcher is a small part of the battery load rather than the approx 50% it is now... And they can be put to sleep and the processor put to sleep with a wake up bias from the battery that switches everything on long enough for a snapshot. or at an interrupt from some external source, I did similar things to conserve batteries in my projects... turn things on briefly rather than leaving them enabled at all times.

Doc
1868  Using Arduino / General Electronics / Re: Need some help with the concepts of pull-ups/downs. on: August 27, 2012, 02:10:39 am
About 5 chapters back in this thread I mentioned that same point... when I mentioned inputs not properly dealt with in code... Also I think my comments on SPI and 2 wire are relevant as well as my $.02 on wires of more than 6 inches and the 'possible' issues and what I would do to make sure that regardless of code they can not be an issue, it's easy to make a compliable error there and spend hours trying to 'Fix' a code error electronically. Evidence my comments about the source of the random seed and what that implies for any wire digital or analog that isn't driven appropriately. Because a design works doesn't mean the design is either good or robust, All it means is that it doesn't fail under the immediate testing conditions All I can say is that when I recommend something it has either been part of a working production device I made... or it was a required 'Fix' because I took a 'shortcut' and didn't test it my self... Prior to trying to write code for it. This is the way I work and what I design usually works as well as I designed it and no more. I haven't made all the mistakes I ever will But I have learned some techniques that when followed religiously cause the devices that I design to work better... usually. That's the reason for some of my suggestions. In the end Every one has an opinion about everything they do and if it doesn't work well maybe the opinion needs some revision. The method isn't really important so much as the integrity of the whole... Sometimes a perfectly great idea can be made worthless simply because of an inappropriate method of execution, the best of course do the best with the least anywhere it needs to be done... I just wish I was that good.

Doc
1869  Using Arduino / General Electronics / Re: Resistors, many and cheap on: August 27, 2012, 01:46:43 am
I'm sorry but the place boor's me to tears... @ 9:30 every night... possibly excepting Christmas the Fireworks go off 7 days a week and I live about 1 mile east of the place... It's really a whole city unto itself and a major annoyance as the driving tourists have no idea of how to drive there... really dangerous sometimes... But it's OK really I have my memories of Disneyland and in the end they're all I need... All I really want, I went back once with the last wife and wrecked a bunch of memories because things had changed so much. So now for the past 15 - 20 years I have made it it a point not to go to the special ones, like the ones my wife and I used to go... this is really off topic...

Doc
1870  Using Arduino / Programming Questions / Re: Using arduino to read oilpressure and watertemp sensor, need help. on: August 26, 2012, 10:04:16 pm
Actually I got to thinking about the non linearity and I remembered that those sensors are tailored for a "Hot Wire Ammeter"... Sort of like a bi-metallic strip moving a pointer across a meter Face. The "meter isn't very linear and the pot's value is "spread" to "un-spread" the meter, it has a sort of logarithmic behavior as I remember. It's basically the way gasoline is measured with a float/pot combination. It is also 5% of the price of a D'Arsonval movement and about 10 times more durable so for economic as well as reliability reasons the pot's are non linear.

Doc
1871  Using Arduino / General Electronics / Re: Resistors, many and cheap on: August 26, 2012, 09:50:45 pm
Heh, heh, Heh... Truly did you get me... that time, through the eyes and mine were open when I wrote... although= I must confess some misgivings when I hit the post button and them I remembered... in reality neither will be accomplished... likely... God Willing, there's a lot of those books I have no intention of re-reading and sometimes you have to read a third to remember why you disliked it the first time. Very probably movies for you as well... I know I'd not be at all offended if no one ever asked me to watch a "Rockie" movie... The guy goes and gets his lunch eaten... Then He goes and eats the first guy's lunch and somehow his battered, Ugly face is the ... Gaaah. We Digress Again... sometime,s it is what a thread really is for. Many are for asking and answering real and many times very challenging issues come to light... And are dealt with, sometimes quickly...  There is though a certain value in some of these threads as a means of forging a continuity with those younger than us through talking about "The Day" and how much it is the same, as it is different in comparison with current times and situations... I remember liking myself, to listen to technical discussions... I didn't, when I was young necessarily understand all I heard but I forgot little of what I heard. Those things became the basis of a lifetime long search for answers to the questions left me and the challenges a day can bring.
There is a certain Zest and a Zeal in pursuing it, Life, its questions of you and of you, it.

Doc
1872  Using Arduino / General Electronics / Re: LM2917 Frequency to Voltage Converter on: August 26, 2012, 06:54:35 pm
Did you look at the data sheet I included? and see if perhaps one of the other 'suggestions' might be more applicable. What happens, If you Ground pin 1, to the current drain... as I pointed out before that is a very high impedance node... The next likelyhood in my experience is that you don't have wired what you think you do... usually when devices draw inordinate amounts of current there is a reason for the behavior... In my experience it is something Assumed or Overlooked (looked over) so many times that you simply can't see it any more... that was what my techie was for... double checking me. As much as I hate to say it I still make similar mistakes and I have to stop and think about what I had.... I once tore a circuit up and re-built it ... Three Times... The Same way. My Employer walked up behind me and asked me why did I have an output grounded... I had swapped two wires in a cable harness and had "Checked it" every time... the ground pin was adjacent the output pin and both went to a connector.

Doc
1873  Using Arduino / General Electronics / Re: 3.3v to 5V logic level shifter using transistors on: August 26, 2012, 06:38:52 pm
There is a Bi-Directional Shifter made from a pair of 2N7000's and an extra set of pull-ups (for the 3V3 side) that works Very Well, I've used it twice and had excellent results both times NXP10144 I think is the number of the app note from NXP that desccribes the interface. I made one from a pair of C945 transistors and an extra resistor for base current limiting that worked well also, that one I modeled first in MultiSim... before I used it. All worked well bi-directionally.

Doc
1874  Using Arduino / General Electronics / Re: Need some help with the concepts of pull-ups/downs. on: August 26, 2012, 06:31:12 pm
Unfortunately this thread took a left turn when I used very loosely the word Termination. What I meant was that any 'input' whether used or not should have a resistor, value as low as practible... connected from that input either to Vcc or Ground as required. a foot of wire connected to an input port with a 10K pull-down makes a formidable antenna, using large 'filter' capacitors .1uF works, But there is a finite time required for their charge, discharge and as such may well  create another problem, after fixing one... Longish runs of SPI or 2 wire can be issues for noise pickup/radiation and although a low value 'might' create a slightly larger EMI issue it is offset by the same resistor values that create it. My observations about the 'relative' impedances of I/O terminated @ 10K 4K7 and 470R and the required current for all are still to my way of thinking and experience valid, I've Been There Done that...
I once had a board where there was communication between two processors and one of them caused a relay to pull in... When that happened the Comm was lost (2 wire) and the processor WDT was the only way I found out... the device would display the initial power up message... and the transmitter was for all intent and purpose "Locked on" until I or the test tech's did a master reset.
The relay coil was powered from Raw 12Volts (about 16 - 18V and a resistor/cap Snubber and diode  clamp for back EMF. Everything else was powered from a switcher and or a linear reg connected to the switcher. The issue turned out to be a magnetic pulse induced into the 2 wire bus leads... 3 inches away. The fix was easy once the issue was determined... 1K pull-ups on either end of the 2 wire bus forcing 10 mA current instead of the Mfr's 4K7 pull-ups on the slave end of the two devices. Didn't need to move or shield the relay coil.
I used to have a mosfet with a 4" square piece of copper screening attached to the gate and a BIG Red Led/resistor in the drain circuit, connected to my main power supply on my bench and many times that warning was enough for me to prevent damage to cmos equipment being developed or repaired. When I got near my seat If it was dry that led would light and give me a chance to touch something grounded before I did anything else.
The two issues are very similar and to finally end this chapter... using the word 'connect' instead of 'terminate' seemed somehow out of place... I wanted to get across the idea of creating a real "known state" for Arduino I/O, used or unused... If the issues are interference/erratic or improper intermittent operation a "loose" port pin might well be an issue...
After All that technique provides the Seed value to "randomize" Random()... Put a 470R resistor from the Analog pin in question to ground and then note the first 10 Random() values on three runs... Bet they are all the same. In My Direct experience... not an opinion... for Me.

Doc
1875  Using Arduino / Displays / Re: Wiring up an LCD on: August 26, 2012, 05:11:38 pm
After nearly 50 years of wiring things... If I DON'T double Check things... they Will go wrong... Somehow when I get in a hurry or assume anything, I'm Wrong...
So... Double Checking is and has been a habit for many years... Somehow that old hack about "Never enough time to Do it Right, Always time to Do It Again..."
Always Fits.

Doc
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