 Piezo triggered timer
|
|
|
G^3
|
|
Thu Feb 26 2009, 03:51AM
|
|
|
Registered Member #97
Joined: Thu Feb 09 2006, 05:40PM
Location:
Posts: 61
|
I built the schematic below using a 74HCT14N and it works, but I was wondering if you guys had any better circuits. The circuit is a timer that turns on at some time after the piezo (it is marked as a crystal in the schematic) is struck. When the piezo is struck a voltage develops that is dependent on the deformation, a voltage divider lowers the voltage so that only a sufficiently strong deformation will go above the voltage threshold of the 74HCT14. The first two buffers send a positive pulse through the .01uf capacitor which permanently turns on the third and the forth buffers. The resistor R and capacitor C form an RC time circuit that determines the delay. The eventual goal is to shoot this thing out of a pneumatic potato gun and have it deploy a parachute at altitude, but that has yet to be worked out.
I am wondering if there is a better way to do this? Something simpler? A better way to distinguish between an accidental drop and the launch? Not a piezo? Any suggestions on the parachute deployment system would be welcome too.
|
|
Back to top
|
|
|
3l3ctrici7y
|
|
Registered Member #1806
Joined: Sun Nov 09 2008, 04:58AM
Location: USA
Posts: 136
|
If you're willing to use contact closure, a RC on the base of a transistor should provide the necessary delay functionality (Since bjt's have a threshold voltage).
The transistor could then be used to "power" a short piece of 0000 steel wool. Use the heating of the steel wool to ignite a very tiny charge of very fast black powder to generate some gasses to pop the chute out like is done with model rockets.
|
|
Back to top
|
|
Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob
|
|
Powered by e107 Forum System
|
