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10561  Using Arduino / General Electronics / Re: Rotary encoders, 74LS14's and 74LS74's on: May 13, 2011, 03:24:03 pm
Is this anywhere near correct?

One obvious error is you have wired both Flip-flop's Q bar signals to ground. If you don't need them just leave them disconnected. What you have is a short circuit condition for those two output pins.


10562  Using Arduino / General Electronics / Re: switch not working unless hand is near it? on: May 13, 2011, 03:11:23 pm
also, sorry, what size resistor 220ohm?

No, 10K ohms is better so as not to draw more current then needed.

when you say +5VDC you mean between the digital pin 10 and the switch right?

No, the resistor would wire between the switch input pin 10 and the +5vdc pin on the arduino shield power connector. That should be avalible on the motor shield as a 'pass through' connection?

Easier yet would just to enable the pin 10 internal pull-up resistor:


void setup()

int Switch = 10;
pinMode(Switch, INPUT);      // sets the digital pin as input
digitalWrite(Switch, HIGH);   // turn on the internal pull-up for pin 10


void loop()

10563  Using Arduino / General Electronics / Re: switch not working unless hand is near it? on: May 13, 2011, 02:58:23 pm
Well I would have to see a wiring drawing to be sure, but I suspect you have a 'floating input pin' situation. If you indeed have a switch wired between the input pin and ground, when you open the switch there is no valid voltage to read as a high input. You need to either enable the internal pull-up for that input pin, or wire an external resistor between the pin and +5vdc pin.


10564  Using Arduino / Programming Questions / Re: Having problems with creating/adding my own library on: May 13, 2011, 02:31:23 pm
Empty sketch file in the zip?

Many problems are where and how you store your library folder and files. For user libraries they need to be stored in the users sketch folder in a folder named libraries. There you store a folder with the library name and it's .h and .cpp files. Here is what my windows user library structure looks like:

C:\Documents and Settings\Primary Windows User\My Documents\Arduino\libraries

10 Folders:


0 Files:

10565  Using Arduino / Installation & Troubleshooting / Re: Auto reconnection of Serial Monitor ? on: May 13, 2011, 02:25:16 pm
Brey terminal ( works great as a serial monitor for window users. It's free and it's a small standalone EXE program that requires no installation. While it won't automatically connect and disconnect from the comm port, it does have a connect/disconnect button so the terminal application can remain opened if you need to do a upload from the arduino IDE. Lots of features too.


10566  Using Arduino / Microcontrollers / Re: [Solved] 2560 with/out crystal on: May 13, 2011, 02:18:01 pm
and small crystals with integrated capacitors.

I strongly suspect the 'small crystals with integrated caps' is really a ceramic resonator with internal caps.

10567  Community / Exhibition / Gallery / Re: Core memory shield on: May 13, 2011, 11:01:09 am
Brings back a lot of memories. I was a field service engineer in the 70s for a mini-computer manufacture (Varian Data Machines) and they were still selling core memory into the 80s for their systems, although they did also offer semiconductor memories options starting in the 70s.

 Core memories were very reliable and rarely did I see a hardware failure with them, sometimes a weak sense amp chip would need replacement. They were however quite expensive as was anything related to computer hardware in that era. I recall working on large 132 column line printers that sold for more then my 3 bedroom house cost at the time.  smiley-wink

10568  Using Arduino / Installation & Troubleshooting / Re: Can my Arduino UNO be powered from a normal 12 V (14.7 V) lead battery? on: May 13, 2011, 10:35:04 am
Too stupid! I thought 12 Volt is the upper limit to drive an Arduino, but it is only "recommended" to drive the Arduino at max. 12 Volt. I found the article "A Big Battery Adapter for Arduino".

Hmmm... What does that mean? Does that mean it  is "not recommended" to drive it at 14.7 Volts? Still a little concerned to use the big battery as power supply...

It will work. The +5vdc regulator will run hotter then if you used a +8vdc source, but the regulator has self protection and will just shutdown if you try and run it too hot or draw more current then it's rated for. I ran a serial arduino board for over a year with a regulated +15vdc laptop power pack with no problems.

If you try and power too many external componets from the arduino's +5vdc pin then the regulator will run hotter depending on the load. 

10569  General Category / General Discussion / Re: SPST switch to car battery on: May 12, 2011, 10:15:13 am
I bought a 12vdc 30a spst switch.  I'm wanting to hook it up to my car battery and use it to turn my radiator fan on and off.  Do I need something in between the switch and battery?  Thanks for your help

A fuse would be a very good idea.

Not sure what current your fan motor draws but automotive parts stores stock these kind of fuses and inline wired socket holders.

10570  Using Arduino / Programming Questions / Re: External interrupt HW and SW mismatch on: May 11, 2011, 08:25:38 am
Pins 8 and 9 (INT6 and INT7) are not connected to anything on Arduino Mega1280 or Arduino Mega2560 boards.

The Seeeduino Mega board (1280 based) does bring all I/O pins out to connector pads including chip pins 8 and 8. However I'm not sure the arduino core pin mapping includes these pins along with 14 other 'missing' pins, probably not. I don't think I will ever understand why arduino did not wire up the additional 16 I/O pins that the 1280/2560 offers?

10571  Using Arduino / Programming Questions / Re: digitalread() on ports 22 - 53 on: May 10, 2011, 08:22:49 pm
Works fine on my Seeeduino mega1280 board. Perhaps you have a damaged pin 24? Does pin 24 work OK as an output pin?

10572  Using Arduino / Motors, Mechanics, and Power / Re: Can I program Arduino digital out pin to output a particular current? on: May 10, 2011, 03:55:19 pm
An arduino output pin is a source or sink for current, but it can not directly control the amount of current, that is determined by the load resistance. A PWM output can approximate a variable voltage/current output but again the load resistance determines the maximum current that will flow when a 100% PWM output.


10573  Community / Bar Sport / Re: Thinking about starting an Arduino magazine on: May 10, 2011, 03:51:57 pm
Will you be able to use the name 'Arduino' in the title of your product, or will you have to secure permission first?


10574  Using Arduino / Programming Questions / Re: Shift register problems on: May 10, 2011, 03:32:21 pm
I wonder if you might not be exceeding the total power dissapation rating for the chip when trying to power all 12 leds on at the same time? What current value are you driving the leds at? Are you driving the leds directly from the SR output pins through a resistor or are you using transistor drivers for the leds?

What is the total max power dissapation rating for the exact SR you have (A MM74HC595 has a 600mW max power rating) ?

10575  Using Arduino / Installation & Troubleshooting / Re: Arduino Uno - 6 Unmarked Pins on: May 10, 2011, 08:51:26 am
I am trying to Identify the group of 6 Pins by the AREF pin on the Arduino UNO board.  Is this a Second set of ICSP? 

It's a set of ICSP pins for the 8u2 serial converter chip.

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