Re: Help with 12 volt rocket igniter

ULB wrote:
Hi all,

I was looking into building a simple (but hopefully cool) model rocket
igniter. Yeah I'm bored, but stupid as a brick. About the only thing
I know about electricity is 110 volt hurts when you touch it. :)
Luckily this is only 12 volts. ;)

You can view the plans here: http://home.earthlink.net/~rbogerjr/index.html

If you scroll down and hit "contents directory" it will show you the
"how it works".

How does the lightbulb limit the current that is going through the
circuit without igniting the engine igniter? I am assuming from what
I have read is anything above 6 volts, ignites it like a fuse blowing.

I would love to build this unit, only I would like to change the
incandescent bulb to an LED in addition, add a piezo for an audible
sound as well. Where should the piezo be added in the diagram?

Can anyone shed some light for me on this? Thank you for any replies
and have a great night.


If the referenced plans are correct, then the lamp they
use draws 150 mA when lit, and around 500 mA when cold.
It would be wise to reduce that current.

When you use the LED as you plan to do, it will draw
*way* less, and that is safer. Modifying the diagram
at the site to include the led and piezo:

/
+---[igniter]---o o---+---[330R]---[LED]---+
| SW1 | |
| | |
| +------[Piezo]-------+
[Batt] 6V | |
| | / |
| +--------o o--------+
| SW2 |
| |
+-------------------------------------------+

Use a piezo that draws 10 mA or less, such as CAT# SBZ-365
from AllElectronics, and the total draw for the LED and
piezo will be under 20 mA. You can go to a 12 volt battery
if you want, and change the resistor to 1K.

See and follow all the safety points Tim mentioned.

Ed
.

Relevant Pages

  • Re: Transistor circuit what works when it shouldnt? Why?
    ... The 5 volt on -off thing is a commercially available lost plane finder. ... It works well and also alerts you to low battery voltage etc. ... power the little piezo to switch on a much bigger noise maker. ... My intention was to use the switching transistor as a relay. ...
    (sci.electronics.basics)
  • Help with 12 volt rocket igniter
    ... but stupid as a brick. ... circuit without igniting the engine igniter? ... I have read is anything above 6 volts, ignites it like a fuse blowing. ... Where should the piezo be added in the diagram? ...
    (sci.electronics.basics)