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46  Using Arduino / Motors, Mechanics, and Power / Re: Logic Level Mosfet on: February 05, 2013, 06:58:42 pm
Quote
Some surface mount packages like DPAK aren't
particularly small and can be soldered onto strip board fairly easily, note.
Good tip. I was wondering about that. thanks
47  Using Arduino / Motors, Mechanics, and Power / Re: Logic Level Mosfet on: February 05, 2013, 02:16:53 pm
Thanks Lefty.

When I search a company like Mouser or Digi Key for a logic level mosfet, what filter am I looking for?
48  Using Arduino / Motors, Mechanics, and Power / Logic Level Mosfet on: February 05, 2013, 01:49:27 pm
Is the FQP30N06L a logic level mosfet? This is from a post that is about a year old referring to the the FQP30N06L:

http://arduino.cc/forum/index.php/topic,102455.0.html

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Both those MOSFET types require 10V of gate drive, they won't work properly with 5V - they might turn on a little bit, but they won't do so reliably.

When looking for MOSFETs for direct drive from logic level (5V) signals, you must get logic-level MOSFETs.  The key spec on the datasheet is the value of Vgs at which the Rds(on) is specified.  "Rds(on) at Vgs=4.5V" is typically the specification to look for.  4.5V is used to allow for below-spec 5V supplies.  If the only Rds(on) values are given for Vgs=10V, or if Vth is specified as "2--4V" then is NOT logic level.

Vth (threshold voltage) confuses a lot of newcomers - its the voltage at which the device switches OFF.  For logic level devices it will typically be 0.5 to 1.0V or so.

I bought that mosfet from Sparkfun without looking at the data sheet because they claim that it is logic level.
https://www.sparkfun.com/products/10213

Here are some screenshots of the data sheet that I don't understand.  http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General/FQP30N06L.pdf

The first screenshot leads me to believe that is is logic level because of the R
DS
characteristics, but the second screenshot leads me to believe that it isn't logic level. Can somebody please enlighten me?
49  Using Arduino / Motors, Mechanics, and Power / Re: Wishing my Tamiya Motors Had More Drive on: February 03, 2013, 08:02:29 pm
It would be a huge help to get rid of the weight of that lantern battery and to have front wheels that can actually turn instead of dragging on a high friction surface.
50  Using Arduino / Sensors / Re: MaxSonar Noise Problem? on: February 01, 2013, 04:22:45 pm
This wiring diagram is from Maxbotix to help suppress noise.
51  Using Arduino / Sensors / Re: MaxSonar Noise Problem? on: February 01, 2013, 05:55:41 am
Can you post your code and schematic? That would be a huge help for diagnostics.
52  Using Arduino / Project Guidance / Re: FTDI Debugger on: January 30, 2013, 11:24:08 pm
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or because my custom Arduino based boards have a +5v voltage regulator.. which needs more than +5 to power it).. so I power externally.. but I still want my FTDI cable connected (RX/TX/GND) so I can see whats going on in my serial monitor.. or do serial communications..etc..
Yea that's the only reason I would like the FTDI cable connected as well, and I'll also be using a 5V regulator.  Good to know it isn't letting the smoke out. Thanks
53  Using Arduino / Project Guidance / Re: FTDI Debugger on: January 30, 2013, 07:28:13 pm
I disconnected the 5v from the FTDI cable and put the 1k ohm resistors in series with the rx-tx and tx-rx, but am still getting 1.9 V to the 5V rail. Any other ways to get rid of that? Or will it not damage my chip or components with a separate battery supply to the circuit?
54  Using Arduino / Sensors / Re: Help with the SparkFun PIR sensor on: January 30, 2013, 06:35:58 pm
double check your connections from your arduino to the breadboard. looks like you might have 5v connected to the GND rail on the breadboard. And I don't see where you have anything connected to ground on the arduino. hard to tell from that angle though
55  Using Arduino / Project Guidance / Re: FTDI Debugger on: January 29, 2013, 10:10:29 pm
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What you can do to help with conflict like when your standalone 328p and external circuitry is being powered up with a battery or other independent voltage source but the FTDI module is not plugged into the PC, is to use two series 1K ohm resistors in each of the Rx and Tx signals going to your standalone. That will prevent any 'back door' current flow in that situation.

Thanks Lefty. I previously just tried unplugging the 5v from the FTDI, but my "test power" led was still dimly lit. You say that a 1K resistor will work from RX of FTDI to TX of uC and another series 1K resistor from TX of FTDI to RX of uC while the FTDI is connected to the PC and the rest of the board is under external power? I just want to make sure I understand you.
56  Using Arduino / Project Guidance / FTDI Debugger on: January 29, 2013, 09:37:14 pm
I have set up a breadboard arduino  (ATmega 328 with Arduino Uno Optiboot) much like the picture below according to this tutorial: http://arduino.cc/en/Main/Standalone

In order to program, I wired up the FTDI Basic Breakout https://www.sparkfun.com/products/9716 like this:

ftdi                     arduino
5v         -------->      5v
GND      -------->     GND
TX         -------->     RX
RX         -------->     TX
DTR (RST)   ----->    Reset     must connect through a .1uF ceramic cap

I uploaded this code and it works fine.
Code:

int led = 9;

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);
  Serial.begin(9600);  
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  Serial.println("test");
  delay(1000);               // wait for a second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);               // wait for a second
}

For future use, I would like to use a power supply for the chip and inputs/outputs other than the USB power supplied by the FTDI breakout board, but I would like to use the FTDI breakout board connected to my computer for debugging. How can I connect the FTDI board without the conflicting power issues?
57  Using Arduino / Motors, Mechanics, and Power / Re: Unsure which motor controller to use on: January 29, 2013, 12:45:47 pm
Do your motors need to spin in both directions?
58  Using Arduino / Sensors / Re: slight change in sketch means sensor won't let servo run with the +5v connected on: January 27, 2013, 09:54:33 pm
If you look at the data sheet or the quick start guide on the Maxbotix website, I think you'll see that the minimum distance is six inches for the EZ although there are other Maxbotix sensors with different ranges.

It's almost always best to change one variable at a time. You'll save tons of debugging time that way.
59  Using Arduino / Motors, Mechanics, and Power / Re: H bridge using 4 PNP transistors. on: January 27, 2013, 08:58:22 pm
also I don't think IRF 520 is even logic level
60  Using Arduino / Sensors / Re: Extreme data variation with MaxBotix Ultrasonic Rangefinder on: January 05, 2013, 04:58:00 pm
Did you read the links that you provided?
The first line of the second link says, "Continuous free run operation will generally not work when using more than one sensor in the same system."
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