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16  Using Arduino / Project Guidance / Re: 24V Derivation on: April 11, 2014, 08:29:52 pm
If you use a linear regulator as was suggested above... You will need a rather large heatsink as the power Wasted is the load current multiplied by the voltage drop across the linear device... Not really a great idea unless your load current's are very low.
.1 A X (24 - 6) is 1.8 watts and 5 Led's can easily draw .1A or 100 mA.
A switching supply (regulator) is a better choice as the loss is the efficiency X the load power IE a 100 mA load @ 6V is .6W and @ 80% efficiency it would be .8(80% Eff)  X .6 watts (load ) or .48W (loss) vs 2.4 + .6 (load) or 3 watts loss of energy as heat Vs 1.48 Watts for the linear regulator and 1.8/2.4 = a 25% greater efficiency. I tend to think of switchers as Power converters rather than Voltage converters.
The immediate effect for a very light load @ 100 mA seems a small savings But at higher load currents...
EX:
1A X (24V - 6V) is 18 watts of power lost as heat in the linear device but the switcher will dissipate : (1A X 6V ) X .8 [Eff} or 4.8W and where the linear device will dissipate 24 watts of power and 24 watts/4.8watts is a great deal less wasted energy.. a 5X decrease in wasted power...
However this is Not to say that linears are bad... A Low dropout regulator does a nice job of removing switcher noise with a much smaller footprint than a Pi section filter. It is a good idea to use a small linear behind a switcher at low current for..? Measurements or Audio applications...... There is a Lot of voltage gain in a linear Reg and as long as the I/O differential is just great enough to prevent the device from "Dropping Out" or failing to regulate they can be a useful tool... but when improperly used a real headache
17  Community / Exhibition / Gallery / Re: Scrolling LED matrix display - Parola for Arduino on: April 09, 2014, 07:56:37 pm
All I can Say is Thank You both Bill and Marco... I have 8 of the original and 20 of the square Ebay modules with the SMD 7219's (Leave it to CN to Phuck things up)... I had been using a digistump USB power switch [Really Handy] to clear my original modules... BTW I had the artwork reworked to triple the bus width for the common signals, CLK... and no joy... I'm not too sure I made a wise decision in buying 20 of the Ebay modules (the SMD ones)... But so far it really looks like a slight mistake in the initialization order... with the original Parola code... I haven't done much with the MD_72XX code yet. I have a 40 year history with H'ware but pointers are just becoming clear enough to read and understand... Not yet too sure about using them... I have to say that this has been a Very interesting project, Very educational in Many aspects...
Again Thank You BOTH for your hard work.. I own a Saleae Logic... Funny thing but it never occurred to monitor each I and O Vs the clock.. The scope pictures really look like capacitive loading is the issue... A lower value pull-up or some Fast buffering might fix that. However Sharp leading edge generally means an HP filter (faster rise time, sharp trailing edges generally mean a LP filter..  I use a Buono for testing as it has a switcher for the 5V output and a 7.5V wall wart or a 5A PSU adj to 7V out. THe USB switch seems to clear things up But it might take two or three attempts and I have noticed that as the modules are handled the artifacting will re-appear and is cleared by cycling the PSU via the power switch... I've been too busy to build a wooden box to hold two rails (90 Deg angle brackets 10" long) which will with some smoke acrylic for front and rear house both a Pro-Mini and the GPS for the time data... Etc. More latter.. Off to get the latest code.. and try it out. Sure beats an HT1632 though..

Doc
18  Using Arduino / Programming Questions / Re: Need help creating an Object. on: April 09, 2014, 07:10:46 pm
@ Paul, Thank You... I am still learning and what you say makes perfect sense.

Doc
19  Using Arduino / Programming Questions / Re: Need help creating an Object. on: April 09, 2014, 06:28:38 pm
A Real n00b question but are they in scope?

Doc
20  Using Arduino / Programming Questions / Re: Simple question on arrays on: April 09, 2014, 05:31:36 pm
What is unique about the "First" measurement that validates it as a comparison standard?. Better IMO to discard the outliers and average or smooth the rest.

Doc
21  Using Arduino / Programming Questions / Re: Power LED's using RF transmitter and receiver on: April 08, 2014, 10:37:12 pm
@ OP, at least Paul can count. Apparently you can't... or for that matter read your code 'carefully' before asking for help...
Typical N00B attitude...
The Attitude and I've had my share... is meant to kick your loose and flaccid grey matter into action...
I'll warrant that you will be more careful in the future when writing code...Checking for DUMB errors SHOULD be done First....

Doc
22  Using Arduino / Programming Questions / Re: Help with extracting coordinates for usage in GPS program on: April 08, 2014, 10:29:16 pm
 There is a shorter method... Go look at the TinyGPS++ library by Mikal Hart... It is a little easier to use...  for example time doesn't require a position lock... All My GPS devices can return time as soon as they are powered up... no wait for the position lock required by TinyGPS12... I use the library and It always works well for me..

Doc
23  Using Arduino / Programming Questions / Re: Writing in ladder logic? on: April 08, 2014, 10:21:27 pm
What did you find from Mr Google?.. Always best to do your own work/research first...

Doc
24  Using Arduino / Microcontrollers / Re: AnalogRead - readings are erratic on: April 07, 2014, 11:47:37 pm
Smoothing is always in order... and the Arduino unfortunately doesn't have a separate ground plane. ?The other unfortunate thing is the fact that the LSB is not something to really count on because the ADC is a SAR? (sp?) or uses successive approximation as the conversion method..
The addition of an analog ground plane that is connected to the lowest impedance point relative to the power return connection. Or both the analog and the digital ground planes must connect at the same point and close as possible to the PSU ground terminal.

Doc
25  Using Arduino / Microcontrollers / Re: Custom board review please on: April 05, 2014, 10:31:56 pm
I see  an error in the ground net/ground plane net... there are 6 connectors at the top of the board and I notice that the ground pins are connected to the power connector - pin and D7 appears to be in series with the - pin to ground while the other grounds are to the ground plane... So the ground pin from the power connector doesn't connect directly to the ground plane... This is a real problem as noise will develop across the diode, assuming that you want the ground plane to be 1 diode drop above ground a .1 and a 220 uF cap should be across the diode. This is sometimes a valid design technique for reverse polarity protection but I believe that it is a mistake as using the 'protection' diode in the minus lead from the power supply creates a lot of other issues. If a series diode is the reverse polarity protection it should always be in the positive side of the power supply connection and both ends of the diode must be bypassed...
the method I generally use is a 1N5822 schottky diode across the power input and a .1uF cap and a 220 uF cap from pos to neg at the power connector. Series protection for reverse power protection is always a poor idea because of the voltage drop across the diode. It is worse if the device is battery powered because the internal resistance of a battery will always increase as the battery becomes depleted. Without a big bypass cap the battery cannot deliver all the usable energy contained in the battery...

Doc
26  Using Arduino / LEDs and Multiplexing / Re: Multiplex Thermocouple Input on: April 01, 2014, 04:25:05 am
If accuracy is a requirement, use a converter/cold junction compensator the each thermocouple and a member of the CD405XBE family to multiplex the data to the controller 1/2 of a CD4016BE (2 gates) will handle your issue nicely... A good rule of thumb is to use voltage followers from the thermocouple converter outputs to the multiplex inputs. THis is done to shift the output resistance down as far as possible to eliminate the small temperature variance of the on channel gate or switch.. It probably wouldn't hurt to read this on the Seebeck Effect  http://en.wikipedia.org/wiki/Seebeck_effect#Seebeck_effect.
Multiple measurements with thermocouples can be 'difficult' to do with any great accuracy and the only solution I've found so far is to measure the temperature and convert it locally to a buffered, possibly scaled value local to the thermojunction. This in order to present two or more clean (noise free) amplified and or scaled channels of analog data to the controller.

Doc








effect
27  Using Arduino / General Electronics / Re: another soldering quesition - perhaps incorrect use of flux? on: April 01, 2014, 03:28:14 am
63% Lead 37% Tin with an active rosin type flux  is the Only one I will use... I used Ersin solder for many years but it seems most scarce in the smaller sizes (still in business?)
Second best is Kester where I use .018, for small parts pins like SMT.. anything and .032 for general PCB soldering. I use a Kester flux sold at Radio Shack under the Radio Shack name. it is a "Rosin Soldering Flux" in a very useful albeit messy format as the rosin is dissolved in petroleum jelly (R.S. P/N 64-022 I've used this flux for years on all my PCB and SMT work.
No/Low clean or water wash type fluxes are aggressive organic chemicals that are removable with water and as a class are perfect for digital work and as a general purpose 'active' flux. There is a drawback to most of the water clean, No Clean and Low Clean based on the idea that the flux is both chemically active enough to ionize water and a solid slightly hygroscopic residue on the PCB that can and will cause a conductive film to form on the PCB. This 'stray' or leakage current is difficult to detect. and more so to compensate or correct for.
Finally, I use a Hakko 936 that is perhaps one of the absolute best I've ever used.The temperature control is fast and really keeps an iron tip at the setpoint.
The Digital Variable Temp device is nice but nearly useless but nice looking. I prefer to keep my iron @ 500 - 550F when using it and when not reducing the temp to 450F as this prevents or helps to prevent that really tough scale from forming on the tip. .. Great job for an ATTiny... Add digital display of temperature data and an idle power reduction mode if the iron isn't used... Although i all fairness a simple MicroSwitch and a piece of small gauge stainless steel wire used as the sensor for the presence of the iron... I have the controller circuit and I think I'll be using an ATTiny for readout and to start the 5 min wait delay to reset.. Just move the iron..
There are many tip cleaners available but remember that the ones like Sal Ammoniac can leave a residue on the tip that gets transferred...
I don't use any of those things as I have two habits in regard to tip care and cleaning, Never, Never file one unless you are doing an instructable on how to turn a soldering iron into a very expensive wood burning set. Steel Wool if used frequently is almost as bad. in particular when the iron is hot.
I remove that glaze by scraping (blade @ 90 deg to tip) gently with the iron hot... when you chip a piece away immediately tin the spot but also wipe and repeat the process.  Scrape, Tin and wipe/re-tin.. until the film is gone or nearly so.
 I usually get those films from contacting or deliberately melting plastic.. Or leaving my iron on for days at a time..

Doc
28  Using Arduino / Programming Questions / Re: 2 analog controller and a relay on: March 30, 2014, 05:50:38 pm
Not to mention the noise that results from driving a DC coil with an AC or PWM (variable pulse width) signal... Also there is the issue of the back EMF developed every time the coil is energized/de-energized. When one powers up a coil the coil makes a magnetic field, storing the electrical energy as a magnetic field. When the power is removed/de-energized the magnetic field is converted back to electrical energy or ElectroMotive Force (EMF)

Doc
29  Using Arduino / Programming Questions / Re: Simple Code on: March 30, 2014, 05:23:13 pm
Excellent thread subject... A Most  Excellent topic for "n00b's" and those of us that have been using or designing with microcontrollers for years... And, Yes I got bit with that one too.. except I made 300 copies of the mistake.. I had a deal with my employer... He or the assemblers made a mistake, they or the Boss fixed them.. I made a design mistake, I fixed it... I fixed my share... and then some...
Kinda sux BUT it does wonders for making mistakes in basic circuit design.... Especially with solar powered, Very low power devices..

Doc
30  Using Arduino / Programming Questions / Re: Understanding Serial Shift Register (74HC595) on: March 30, 2014, 04:03:23 pm
Connect Vcc to pin 16 of the SR (HC595) and ground the side that now goes to Vcc... Do the same for EVERY IC you use that is  external to the Uno or whichever board you are using as the controller.. If the power wires are more than 3 cm long a 22 - 100 uF capacitor at the place where the power leads connect to the breadboard or circuit board connected to the uController (Uno or ?) is a very good idea too... If you need to, think of the added parts as insurance against weird issues.... As has been pointed out to you before in this thread.

Doc
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