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1846  Using Arduino / General Electronics / Re: Super cheap Arduino shield on: August 06, 2012, 03:12:24 pm
If cost is an issue, the below might be of interest. If one lives in a remote jungle, then other factors will probably interfere with even a regular arduino.
Here is one cheaper... $9.50

I like to use stackable headers on my projects and I buy the Pro mini's because they are smaller than a standard 28 pin dip... Same size as a basic stamp with 10 extra useful pins
And here is a picture on one of the breadboards W/ Uno cable connector and a plugin PSU with 3V3 or 5V on either rail or both rails... takes a USB connector (for power only) or a
2.1 mm barrel connector for an external PSU (Wall Wart) Liudr sells the cab;e/shield/breadboard header... From Either Dipmicro or Inmojo for $18.95... The PSU is $2.89 from Ebay
{Edit} The little board to the left of the Pro Mini is an USB to ttl converter also purchased from Electrodragon... I use it for a lot of different things besides the Pro Mini's.

1847  Using Arduino / General Electronics / Re: Super cheap Arduino shield on: August 06, 2012, 01:04:53 pm
I will Provide a "Photo" of My "Little Bread-board later today.... gotta find the camera... My phone camera is Very Poor But...Pics are included...

1848  Using Arduino / General Electronics / Re: atmega328 glitching on and off on: August 05, 2012, 05:09:58 pm
Calculate or Measure the current drawn and double it... Just for luck and multiply that by the voltage realizing that control/signal transformers come in standard values. A 24 V transformer, a 10 ohm resistor and a single diode with a 2200 uF - 4700 uF input filter is the simplest method to deal with 24V transformers... Because of the required high value of the input filter for a single diode (half wave) it is recommended to use a 5 to 10 ohm 'Surge' protection resistor in series with and before the diode to reduce the inrush current to the diode.
It is also recommended to use a diode of 3A forward current, typically a 1N5407 and the input filter after the diode.
This is for a supply for a 5V regulator and a low current load. This is from memory and I am certain of it's validity, It's just that right now I am too busy to go find the text and quote it here and for that I apologize...
However the loaded voltage should be about 11-13V which, while being a little high for heat considerations in the regulator should be OK.
The Best method was already mentioned and that was to use a switcher to begin with.
The methods I outlined earlier were only "Fixes" for the immediate issue which was the regulator shutting down for an over-voltage condition.
There was a comment about "Not Believing???" that a regulator would shut down... YES VERY MUCH SO...
Read the Data Sheet before you consider yourself enough an expert to quote opinions here.
The Shut down is done for several reasons primarily to control the device Power dissipation.
Ex. 1. 50 V in 5 V out @ 1 A = 5W load to the regulator and 45 Watts wasted as heat... 50W total device dissipation
Ex. 2. 35 V in 5 V out @ 1 A = 5W load to the regulator and 35 Watts wasted as heat... 40W total device dissipation
50W/40W = 1.25~ X increase in power dissipation for a 15V increase in supply voltage or simply by making the Max voltage 35 V instead of 50 V makes a 25% decrease in required power dissipation.
Under any circumstances the final shutdown is due to heat and limiting the input voltage to a 'reasonable level' increases the available current at high voltage inputs because the final control in the regulator is it's internal temperature... Not current as much as heat.
Internal to the regulator is a comparator that measures the supply voltage against a reference voltage and if high merely shuts down the drive to the pass transistor to prevent exceeding the total device dissipation.

1849  Using Arduino / General Electronics / Re: Troubleshooting 74hc595 on: August 05, 2012, 03:45:41 pm
Truly Cool DISPLAY... Terminated Properly there's no reason why the cable couldn't be 1 meter instead of 30cm. IMO... Of Course... <BG>

1850  Using Arduino / Displays / Re: Hello, need help by lcd Display issue on: August 05, 2012, 10:06:31 am
You can lead em to water and you can push their noses into the water... and in the end all you have is a dead...

1851  Using Arduino / General Electronics / Re: Troubleshooting 74hc595 on: August 05, 2012, 10:00:33 am
It is considered in the Engineering business bad practice to assume anything including code... That having been said... again and again.
Local pull-ups and local pull downs solve many mysterious problems and while I agree in theory with the comment about interleaving ground and signal lines.
"Cross-Talk" CAN be HELD to A Minimum by the proper choice of technique and actual practice.
Obviously a 1M ohm resistor is a "Token" terminator...
However since any digital output can easily supply 1/2 of the Max rated current/pin (Ipin)... A good value for a "Token" terminator.
Might well be ??? 20% ??? of that Max Current (Ipin). So MAX Ipin = 40 mA /2 = 20 mA X .2 (20%) = 4 Ma and assuming (For a WORST CASE) Vcc is = 4V ( for those who Still want to use 9V batts for an 8X8 Led Cube )
Therefore since R = E/I Rterminator = 1K ohms
and in so doing we have 90% of the Available Max Ipin available for a "Rainy Day"... In My Direct Experience.
Further the place where the Rterminator belongs is at the End of the Wire... and NOT the Driven End. IMNSHO
(It has worked well for me for well over 40 years)

1852  Using Arduino / General Electronics / Re: getting rid of re-set button. on: August 05, 2012, 09:30:32 am
Also quite required unless you are the GOD of C and C++ on the Arduino... You Know... The one who Never makes a coding mistake...
I LOVE My Reset Button...


1853  Using Arduino / General Electronics / Re: Different types of resistors on: August 05, 2012, 09:23:50 am
With a Baseball Bat... Sometimes it's the only way. One has to remember that everyone compares everything against their own set of standards...
So to a Good Person... Everyone is Good and to a ...
and this little truism applies to Every little Bitty Thing. IMNSHO

1854  Using Arduino / General Electronics / Re: relay with output pin on: August 05, 2012, 09:16:37 am
The "network" across the switch contacts was called a snubber, typically a cap between 100 -  500 nF and a 5 to 200 ohm resistor is series across the contacts. They work well at quenching the energy that causes the spark/spike to be developed across the contacts. It was used primarily to extend the contact life by reducing the "pitting" an actual ARC would be  reduces by quenching it. this pitting was the effects of the actual contact inductive switching load Currents.

1855  Using Arduino / General Electronics / Re: Do 7400 (original series) chips always run hot? on: August 05, 2012, 01:50:10 am
I know the circuit well I did several of them Many years ago... The "Clock is the rate at which the data moves through those logic IC's. They weren't static. Your '285 takes 2 4 bit binary words and "Adds them together... although it is a parallel process it Still was "Clocked Logic"... There is a specific rate at which the data moves through the adder... That is the clock rate. TTL was also famous for it's quiescent current and when you produce a chip of that complexity there's a lot of gates drawing power... They get even hotter when you run them fast... BTW LS means "Low Power Schottky" which was about as fast as "regular" 7400 series logic and drew about 1/10th the power and there were ECL logic chips that could ruin your whole day... If you touched them... kind of a circle because ECL and things like USB are Very similar in theory/technology as ECL was the fore runner of what is called LVDS or "Low Voltage Differential Signalling". The theory is that it doesn't take as much power (heat) to move a pair of wires about a common LOW center voltage as it does to take one conductor and slam it between Vcc and ground as fast as you can as for one.. the parasitic capacitance's aren't as big so it doesn't take as much energy (heat) to charge and discharge them. Does this help?

1856  Using Arduino / General Electronics / Re: Do you need to do more than ground a mint tin enclosure? on: August 05, 2012, 01:28:40 am
Try ungrounding the PCB as well. you might find the error there Ground loops and high gain amplifiers have been issues since I worked with vacuum tubes.
The comment about high level RF was not too far from the point either. Very frequently when there were "too many" grounds Local "Clear Channel' (From the conelrad (?) days remember  seeing an american AM< radio... All of them produced in the 60's had a mark at 640 and 1240 Khz and those marks were to designate the Emergency AM radio frequencies regular AM radio stations that could legally broadcast @ 50 - 100KW 24/7 all the rest had to lower power out @ 6 or 10 PM I don't now remember which and is immaterial to the topic They were the ones that you heard at night if you had built a crystal radio... I made a lot of them using Galena crystals embedded in lead (for mounting and electrical contact) A piece of pencil lead and a "Blue Blade" razor blade were also very good and very sensitive too. Gawd the old memories that get awakened here, I hadn't thought of that stuff for many years.... All of it including audio feedback and am radio's getting into PA systems... But that's where I first encountered the issue. We ised to add 1000 - 5000 pF caps on inputs to reduce the level of the offending AM signals... Sometimes the amplifiers had to "Go to the Shop" for adding capacitors to the control grids of the input stages of the amplifiers. Rf Chokes were commonly added as well to form "Low Pass" networks. Remember too that these were 50 to 200 watt tube type amplifiers with perhaps 100 ' of 600 ohm "Low Impedance" microphone cable attached to the inputs and the microphone had a switch that usually shorted the microphone to ground... So there was a "longish" Antenna connected to the Pre-amp input. This was why I didn't make too much ot the OP's comments about possible RFI. If that device works well in a plastic box then there will be a grounding issue and /  or a By-pass issue possibly both. Forget trying to insulate the jackks like you mentioned. The proper technique is to mount the connectors to a small bit of plastic and mount the plastic to the metal case. At one time (Back in the day...) there were available shoulder washers made of fiber based non conductive material commonly sold in any electronic's store just for this reason. It was Switchcraft in the US...
Well another perfectly good post shot to hell because of my reminiscing...

1857  Using Arduino / General Electronics / Re: Do 7400 (original series) chips always run hot? on: August 05, 2012, 12:48:35 am
Yes Certainly those '285 are binary multipliers and depending on clock speed some ran hotter. Remember those are "Real" TTL ic's... some ran warm enough that they were placed in Ceramic cases. even today real high speed chips run HOT not just warm. Stop the fan of your computer and see how long it takes to shut down/melt down. My CPU and GPU run about 10deg above the ambient it is 77deg in my room now and both are @ approx. 90 Deg F I have a 6 core AMD 6100 3.3 Ghz Cpu and the of the "Bridge" chips is also the GPU and I am not running a gamers box... just a reasonably fast "normal" box. Silicon will work well to 70 - 80 deg C buut for many other considerations should be kept below 50C which is about what you are measuring with your "digital" thermometer.

1858  Using Arduino / General Electronics / Re: atmega328 glitching on and off on: August 05, 2012, 12:32:07 am
It does cause more ripple that's why I pointed out that the input filter had to be bigger and in this case since there is a linear regulator the added ripple makes no difference . Even with a 470uF instead if the 2200 uF min I had mentioned the ripple could Never be big enough to cause the regulator to even be close to it's dropout voltage. You will remember that the original issue was the reg shutting down because of overvoltage... So I listed several different workable strategies to fix that problem.

1859  Using Arduino / General Electronics / Re: Ground layer on boards on: August 04, 2012, 07:32:10 pm
You must ground the cathodes... connect them all together and connect them to ground.

1860  Using Arduino / General Electronics / Re: l297 question, about chopper rate on: August 04, 2012, 07:24:57 pm
Use 3 of them in parallel If you have the parts...  That will get you close enough.

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