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1  Using Arduino / Motors, Mechanics, and Power / Re: RGB LED + Servo Problem on: April 10, 2012, 11:38:24 pm
It was completed, yes. I have a problem with saving my code in an organized way so I'll try to dig up a version and debug it and get it uploaded.
2  Using Arduino / Networking, Protocols, and Devices / I2C - 3.3 or 5V? on: September 29, 2011, 02:50:30 pm
For using I2C devices with Arduino, would I want to get the 3.3V or 5V versions?

If they're digital, is there any difference besides slightly lower current requirements with the low-voltage version? Does either have some advantage?

Looking at
3  Using Arduino / General Electronics / Pin-type / Piercing Probes that fit into breadboard holes on: July 30, 2011, 09:18:08 pm
Hi. I'm not sure if the subject line is the right terminology for what I'm looking for.

My school has electronics labs with multimeter probes that actually stick into breadboard holes and are strong/sharp enough to make deep scratches in the leads on TO-220 style components.

Can anyone link me to a good product I can plug into my Extech/Amprobe? The leads they come with are a huge pain to use with breadboard work.
4  Using Arduino / Motors, Mechanics, and Power / Re: Remote Actuated Fuel Gas Valves on: July 28, 2011, 05:12:01 pm
Flow capacity should be minimum 0.5L/min, which is not hard to find.

I really like the idea of using a spring-loaded ball valve. Perhaps a linear action solenoid bolt could block the valve handle so that if it loses power, the pin/bolt is pulled back into the solenoid, releasing the handle. Might need a little lubrication so friction doesn't make the bolt stick. I like that.

Will look super hacky of course...but it would be the most effective for its real purpose.
5  Using Arduino / Motors, Mechanics, and Power / Re: Remote Actuated Fuel Gas Valves on: July 27, 2011, 07:48:24 pm
Something equivalent to this: (except we're using a metal-hydride tank). Different school though, and our hydrogen is stored at 125psi instead of generated on the spot.

Our car as-is is considered safe enough for the competition, and actually won a "Best Application of Safety Practices" award at an earlier competition. We just think hydrogen is dangerous (duh) and want to build on our no-compromises approach this year. We've already put a lot of work into making sure the car was safer than any other hydrogen-powered vehicle.

I'm building a hydrogen leak detection system with MQ-8 sensors from Hanwei Electronics. If hydrogen is detected, an arduino should cut power to a normally-closed solenoid.

The system's purpose is to impress judges (we're optimizing the engineering for a competition, after all), provide me and other students with experience designing and implementing control systems, and give me an excuse to write programs for the arduino.

We're also going to be designing/building our future cells from scratch, so a properly controlled isolation valve like this could be used to protect our investment.

Thus, the real safety considerations are: reliability of closure, tightness of closure, and compatibility with hydrogen gas.

If we could find one rated for at least "Class 1, Div 2, Group B" service, that would be great. If we could find one that's explosion-proof, that would be great. However, it has to fit in a small vehicle and be powered by a relatively low voltage DC source (maybe could go up to 24V, but would prefer <=12V DC). So far I haven't found anything at any price.
6  Using Arduino / Motors, Mechanics, and Power / Re: Remote Actuated Fuel Gas Valves on: July 26, 2011, 07:48:52 pm
Update: The following companies could not recommend any of their products currently:

Gems Sensors

The consideration was usually that they don't have experience with Hydrogen gas, it's a small molecule that can permeate some materials.

ASCO suggested U8256A002V with a Buna-N or Viton seal. I'm not a valve expert but Buna-N and Viton are pretty common, and the aforementioned companies carry very similar valves. The valve can be purchased for $35-45.

Our distributor, who looked at many company's valves for us, gave a price for that Asco valve but was unwilling to recommend it, primarily because we haven't fully established our specification. The representative wanted to know what our media temperature was, and we only knew that the tank can get below freezing when the hydrogen is being used heavily (some frost forms on the tank, but not on the fittings downstream). Until I get back to school we won't be able to measure the gas temperature at the valve position.

I'm actually pretty sure that each of these companies make valves that would be appropriate for this use (DIY hobby-scale PEM fuel cell "vehicle" - R/C car like). However, trying to hold myself to the standard of safety present in industrial applications makes the selection difficult.
7  Using Arduino / Motors, Mechanics, and Power / Remote Actuated Fuel Gas Valves on: July 11, 2011, 09:50:58 pm
This probably isn't the right site to ask about something this specific, but it is for an arduino controlled project.

Looking for tiny valves that can isolate 125psig hydrogen gas, Specifically I want to find something that can fit onto 1/8" or 1/4" NPT thread. I'd like them to be able to be remote actuated, similar to the sort of "Air-Operated Valve" (AOV) operation of valves in the chemical, oil and gas industries. Should ideally "fail-closed" in the event of power loss.

It's for a hobby-sized project, but needs to conform to reasonable standards of safety.

Obviously it's hard to find something like this, so I'm asking around.

For controlling hydrogen flow on a small vehicle maybe 16"Wx24"Lx10"H
8  Using Arduino / Motors, Mechanics, and Power / Re: RGB LED + Servo Problem on: July 11, 2011, 06:25:42 pm
Thank you mem,

That was the problem. Switching the output pins in the code solved the issue.

Incidentally the power supply of the arduino seems to work fine for running both a tiny servo and a bright RGB LED.
9  Using Arduino / Motors, Mechanics, and Power / Re: Forward and Backwards? on: July 10, 2011, 10:38:26 pm
You should look at various "linkage" designs. is an earlier, relatively simple linkage for converting rotary movement to linear movement. This one is more exact.

See this website for excellent java models (does not seem to work in Google Chrome, okay in FireFox)
10  Using Arduino / Motors, Mechanics, and Power / Re: RGB LED + Servo on: July 10, 2011, 10:22:19 pm
This is the program code, for reference:

  Cycles through the colors of a RGB LED

  Written for SparkFun Arduino Inventor's Kit CIRC-RGB


#include <Servo.h>
Servo myservo;  // create servo object to control a servo

// LED leads connected to PWM pins
const int RED_LED_PIN = 9;
const int GREEN_LED_PIN = 10;
const int BLUE_LED_PIN = 11;
int potval = 0;
int ledval = 0;
int potpin = 0;
int serval = 0;
// Used to store the current intensity level of the individual LEDs
int redIntensity = 0;
int greenIntensity = 0;
int blueIntensity = 0;

void  setup()
 //myservo.attach(3);  // attaches the servo on pin 3 to the servo object **RGB LED BREAKS IF UNCOMMENTED**

void loop() {

   potval = analogRead(potpin);            // reads the value of the potentiometer (value between 0 and 1023)
  ledval = map(potval, 0, 600, 1, 900);  
  if (ledval < 310) {
    redIntensity = map(ledval, 1, 300, 1, 255);
    greenIntensity = 0;
    blueIntensity = map(ledval, 1, 300, 255, 1);
    else if (ledval < 610 && ledval > 300) {  
    redIntensity = map(ledval, 310, 610, 255, 1);
    greenIntensity = map(ledval, 310, 610, 1, 255);
    blueIntensity = 0;
   else if (ledval > 600 && ledval < 900) {  
    redIntensity = 0;
    greenIntensity = map(ledval, 610, 910, 255, 1);
    blueIntensity = map(ledval, 610, 910, 1, 255);
  else {
    redIntensity = 0;
    blueIntensity = 0;
    greenIntensity = 0;
        analogWrite(RED_LED_PIN, redIntensity);
        analogWrite(BLUE_LED_PIN, blueIntensity);
        analogWrite(GREEN_LED_PIN, greenIntensity);
11  Using Arduino / Motors, Mechanics, and Power / RGB LED + Servo Problem on: July 10, 2011, 10:21:01 pm

I'm using the components included in the Sparkfun Inventor's Kit. I'm trying to get a demonstration working where a potentiometer knob controls both the hue of an RGB LED and the position of a small servo motor.

I've run into an issue (documented earlier here: When:
is added to the setup() section, RGB LED functionality breaks. The LED will only produce blue light.

This has nothing to do with the power requirements of the servo. Even when the servo is not plugged in, or if there is no output to the servo, the RGB LED still breaks. It seems to be the pin assignment function in servo.h that breaks the RGB LED.
12  Using Arduino / Microcontrollers / $25 computer-on-a-chip on: May 06, 2011, 11:57:17 pm
Not a microcontroller per se, but seems relevant to a lot of the Arduino community. I have seen some newbies ask "Can I run linux on an arduino?????", etc.

Mainly, we're going to see more and more of these sorts of chips come out, and their functionality will blend well with arduino's. I know a lot of people here like the simplicity/efficiency currently offered by Arduino, and are staunch supporters of its great combination of its dual digital/analog processing capabilities. That's not going anywhere, but I bet we'll start seeing projects use chips like this in the near future.

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