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[on:]

I want to build a estes rocket count down and launch system with my arduino but the problem is that the arduino only gives off 5v. To light the estes rocket i need at least 6v. Is There any way that i could build a circuit so that when i hit launch on the arduino. the arduino charges the circuit and releases 6v?

Also, is there a way that it could charge then maybe an LED would come on to signal that it was charged. Then you would press a button or flip a switch to light it?

[Reply #1 on:]

Forget the voltage, it's the current you should be worrying about. And the Arduino isn't going to give you nearly enough current for ignition. Here's a really good article that actually measured these ignitor currents. A "standard" Estes ignitor (Figure 11 in the document) needs a burst of current well over 10A to do its job, and that's just not coming from an Arduino.

http://www.gwiz-partners.com/igniters.pdf

Now, you can use the Arduino to switch a relay or MOSFET that in turn conducts current from a battery pack that can source that instantaneous current. Then you can easily have your 6V too.

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

[Reply #2 on:]

Actually I don't think that is such a great article, because he makes the incorrect assumption (or at least invites the reader to incorrectly assume) that the current required by the igniter is the current consumed when a practically unlimited supply is available.  He measures the latter, but most people need to know the former.

To the original poster, you're just switching a large load, like a motor or a relay coil. Look for typical arduino circuits that use a transistor to switch a larger current.  I'd design it to switch at least a few (2 to 4) amps.

An automated launcher doesn't really meet the NAR safety code, unless it operates with a deadman switch or override switch to keep it from firing if it becomes unsafe to launch. Think about what happens if the dog knocks the pad over after the countdown has been initiated...

-j

[Reply #3 on:]

http://www.adafruit.com/blog/2010/07/08/arduino-rocket-launcher/

+1 for dead man's switch. 

I'm making one with a key switch launch enabler and a momentary button that connects the ignition supply to the relay.  For safety, I'm using the button with the strongest spring I have, and it's heavily recessed to boot.