| Manufacturer: | Scratch |
This page describes t' how t' build a very small (1.5"x1.5", arrr, ~1 oz.) rocket ejection timer. Arrr! I have tired t' give as complete o' instructions as possible, shiver me timbers, matey, me hearties, but you still might encounter problems. While it is possible t' build this timer without printin' a custom circuit board, I don't recomend it. Well, blow me down! In t' past I have used t' pre-printed circuit boards that mimic t' layout o' a breadboard, matey, me bucko, and trust me, ya bilge rat, arrr, they are much more trouble than they are worth. Begad! Begad! T' ease construction o' this timer, me hearties, me bucko, ya bilge rat, I am offerin' t' followin' products:1. Begad! Pre-printed and drilled circuit board
All you need be t' components and a solderin' iron ................................................US$122. Avast! Ya scallywag! Pre-printed and drilled circuit board with all electronic components
All you need is a solderin' iron .................................................................................US$20If you are interested contact me at sspacepyro@aol.com.
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Components:
This is a very simple, yet effective timer based on a basic RC chargin' circuit. Blimey! It will time for an interval o' about 3 seconds up t' about 20 seconds based on battery voltage used and components used. Aye aye! R1 sets how long t' timer runs. Ya scallywag! For longer times, a larger capacitor can be substituted for C1. Avast, me proud beauty! Any voltage up t' about 12 volts should work fine with this circuit, although I have only tested it up t' 9 volts. Blimey! Aye aye! S1 be t' trigger for t' timer t' start. Ahoy! Well, blow me down! Blimey! T' timer will start when S1 opens (it is normally closed). Arrr! I use a reed switch on t' body o' t' rocket that matches up with a small magnet on t' launch tower/rod. Blimey! Aye aye! When t' rocket moves away, t' reed switch opens, me bucko, shiver me timbers, startin' t' timer. As long as S1 is closed, shiver me timbers, Q1 is saturated, reverse biasin' Q2 and turnin' it off. Ahoy! Avast! When S1 opens, C1 begins chargin' through R1 and Q1. Blimey! When it is fully charged, ya bilge rat, thar will be no more base-emmiter current and Q1 will turn off. Arrr! This will allow current t' flow through R2 t' t' base o' Q2, me hearties, saturatin' it and turnin' SC1 on. Begad! Begad! This fires t' ejection charge. Note that t' load out on t' PCB goes t' ground when t' circuti fires, arrr, arrr, so t' ejection charge should be hooked up t' t' positive o' t' battery and t' load output o' t' timer. Also note t' oritentaion o' C1 on t' PCB and t' orientation o' t' transistors. |
As an interestin' side note, me bucko, I have been experimentin' with low extremely lightweight ejection electronics and as such I am usin' a 3volt voltage source (as is shown in t' schematic). I have found that t' low voltage christmas tree lights, if broken open, will reliably light a BP charge on 3volts. This is how I plan t' do ejection for Flogiston due t' space and weight limitations.
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