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13756  Forum 2005-2010 (read only) / Troubleshooting / Re: Powering LED's from external source? on: April 18, 2009, 09:17:29 pm
You are missing a series base resistor for the switching transistor. Otherwise it should work if you've tied the ground together as you have shown. If it switches with +5vdc but not with +9vdc then there has to be something wrong with the +9vdc source or wiring to the source.

Good luck

Lefty
13757  Forum 2005-2010 (read only) / Troubleshooting / Re: Powering LED's from external source? on: April 18, 2009, 08:27:54 pm
Is there a question in there somewhere?  smiley-wink

Using an external DC voltage is no problem, just remember to wire the ground side of the external voltage source to the Arduino ground. Also you will have to recalculate the series current limiting resistors for each LED string.

Depending on how many LEDs you are going to drive and how many Arduino output pins you are going to use you might consider using a logic level N channel MOSFET transistor for switching the LED's on and off instead of a NPN transistor. A mosfet requires no continous DC current for it's gate drive and the active 40ma source and sink capablitly of an Arduino output pin will work well drive most MOSFETS gate well.

Lefty
13758  Forum 2005-2010 (read only) / Troubleshooting / Re: Is my arduino dead ? can't upload sketches on: April 16, 2009, 08:06:05 pm
Quote
You might also want to do as LadyAda suggests and put little rubber feet on the bottom of your Arduino to keep it off the table.

What I did is hand screw in 4 #6 nylon machine screws into the bottom of the board. This keeps it up off any surface and gives it a little support, looks cool also  smiley-wink

Lefty
13759  Forum 2005-2010 (read only) / Troubleshooting / Re: Create a emergency stop!! on: March 29, 2009, 11:51:57 pm
That all can be accomblished with code within your existing sketch. Remember you can have program loops inside of the main sketch loop that just wait for something to happen before returning to the main loop.

Lefty

13760  Forum 2005-2010 (read only) / Troubleshooting / Re: Create a emergency stop!! on: March 28, 2009, 12:58:16 pm
Using one of the two external interrupt input pins is one way to 'take over' a running sketch. You don't say exactly what must happen in your sketch to perform an emergency stop. If this is for personal safety features one should always at least consider external hardwired interlock wiring, etc over software safety generated functions.

Lefty
13761  Forum 2005-2010 (read only) / Troubleshooting / Re: USB at 4 volts on: April 10, 2009, 03:14:28 am
Yes that is too much current to draw from the Arduino when using USB power. It is also right at the limit of external power current I would think.

may have to use a seperate +5vdc power supply to power the LCD display if it indeeds needs 1+ amps of current. It must be the backlighting that sucks that much current.

Lefty
13762  Forum 2005-2010 (read only) / Troubleshooting / Re: USB at 4 volts on: April 09, 2009, 11:11:38 pm
You should measure the +5vdc pin with the LCD display disconnected. If it then reads the proper value then you know that the display is drawing too much current from the USB port. There is a limitied amount of current you can use externally to the Arduino board. Possibly you have it wired improperly causing too much current draw?

You can also try powering the Arduino board via the external power jack via a wall wart DC power module and see what the +5vdc terminal reads with the LCD connected. There can be more +5vdc current made available when you use the external power input.

 Do you know what the current requirement specification for your display is?

Lefty
13763  Forum 2005-2010 (read only) / Troubleshooting / Re: Lot of noise on my encoder on: April 06, 2009, 01:02:19 pm
My guess is you have a mechanical encoder. The one (from china) I tried had contact bounce problems and the mechanical detents did not always seem to be spaced properly to switching transistion points. Anyway you might see if you can add some contact debouncing code, see the Arduino reference and playground for information on that topic.

I solved my problems with finding some affordable optical encoders that do not exibit any contact bounce problems at all.

Good luck
Lefty
13764  Forum 2005-2010 (read only) / Troubleshooting / Re: Pins reading "HIGH" with no input on: April 08, 2009, 01:59:36 am
A digital input pin that is wired to a normally open switch contact will cause a floating or non-defined input state. One should use an external pull-down or pull-up resistors, or enable the internal optional software pull up resistor to force the input value to a known state.

The easiest way is to enable the internal pull-up resistor and wire the other end of the switch to ground. This will require you to reverse your 'logic' on what value a 'pushed' switch is. There is much posted on this subject and in the reference documents.

Lefty
13765  Forum 2005-2010 (read only) / Troubleshooting / Re: URGENT please help!!! on: April 03, 2009, 06:05:04 am
If time is a big factor just buy a preprogrammed chip. Maybe buy two as you really don't know what caused it so it might happen again. If you have the time then having a programmer will allow you to be a bit more self reliant.

Lefty
13766  Forum 2005-2010 (read only) / Troubleshooting / Re: Bootloader hosed? Serial.println() still works.... on: April 02, 2009, 03:23:54 am
I think your guess about having a hosed bootloader is the most likely cause. Why and how did it get hosed, who knows.

It's a good excuse to get a USBtinyISB programmer kit from Adafruit. It will burn a fresh copy of the bootloader from the Arduino IDE and if your running windows there is now a GUI wrapper for AVRDUDE avalible so you don't have to learn all the command line options and variables to utilize AVRDUDE. This would also allow you to burn in a sketch without having a bootloader resident in memory so you can reclaim that extra memory space for your application.

See, every cloud has a silver lining  smiley-wink

Lefty
13767  Forum 2005-2010 (read only) / Troubleshooting / Re: Gah! Arduino troubles. on: March 29, 2009, 05:19:16 pm
Quote
I don't think (by looking at the price) the atmega 328 from sparkfun comes with the bootloader on it.
(In the description there is also no reference to a bootloader.)

They seem to sell them in both flavors, with and without bootloader:

http://www.sparkfun.com/commerce/product_info.php?products_id=8846

http://www.sparkfun.com/commerce/product_info.php?products_id=7957

Lefty
13768  Forum 2005-2010 (read only) / Troubleshooting / Re: What was your biggest struggle or revelation? on: March 14, 2009, 10:01:21 pm
Keeping the Arduino IDE from writing all that red sh*t in the bottom window when I try to compile or upload. It sure is fussy about details  smiley-wink

Lefty

13769  Forum 2005-2010 (read only) / Troubleshooting / Re: arduino with sharp IR sensors on: March 23, 2009, 03:31:55 am
Sorry Brad, I have no experiance with that type of sensor. Seems like does output a analog voltage. Perhaps you could use a digital volt meter to see if there is valid voltage coming out of the sensor(s).

Lefty

13770  Forum 2005-2010 (read only) / Troubleshooting / Re: arduino with sharp IR sensors on: March 23, 2009, 02:36:23 am
Can you provide the part number of your sensors or a link to a data sheet for them? The 3 terminal IR receiver devices I am familiar with output a digital signal not a analog signal. Here is a project using such a sensor from the playground.

http://www.arduino.cc/playground/Code/InfraredReceivers

Lefty
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