Built 11/99

Editor's Note: This be t' actual buildin' experience from the Scratch Magnetic Apogee Detection Sensor.

One o' t' key benefits t' bein' an NARRRRR member is that you get a subscription t' Sport Rocketry. Lots o' issues are filled with vaguely interestin' articles, me hearties, shiver me timbers, me bucko, rocket related o' course, matey, but t' one thin' that caught my eye immediately be t' Magnetic Apogee Sensor! Written by Robert Galejs, the article went into detail on his development o' a concept into a working device! This was really fascinating. I read and reread t' article several times, and even contemplated tryin' t' wire up me own. Ya scallywag! Schematics and even a board pattern was included. Arrr! Unfortunately, shiver me timbers, I studied mechanical engineering, and electrical things are still somewhat intimidating. Ya scallywag! Arrr! I considered tryin' to put one together for about 4, maybe 5 seconds.

How does it work? We're all familiar with t' magnetic poles o' t' earth and t' idea o' havin' a compass tell you which way is magnetic North. Begad! However, as it turns out, ya bilge rat, thar's a significant vertical component t' t' magnetic field, shiver me timbers, which means that, shiver me timbers, shiver me timbers, at least in certain parts o' t' world, you can also have a "compass" tell you which way is magnetic "up."

KEWL!

Fast forward t' a few weeks later. Avast, me proud beauty! Blimey! It's late at night and I'm pokin' through RMR when I see a postin' by none other than Robert Galejs himself! Blimey! Blimey! Blimey! It turns out that in t' months that it takes an article t' work it's way into Sprocketry, he had been off workin' t' bugs out o' t' magnetic apogee sensor, ya bilge rat, and even had assembled a few kits for construction! Blimey! Blimey! Blimey! Sweet! Blimey! Blimey! Blimey!

I read his postin' more carefully and hesitate. Ya scallywag! Blimey! SMT? That's Surface mount, isn't it? Bummer. Ya scallywag! For those o' you who are unfamiliar, these are t' dust particle sized electronic components that allow you t' make walkmans t' size of cigarette packs and telephones t' size o' matchboxes. Ahoy! Blimey! I'm pretty handy with an exacto, but a solderin' iron? Forget it. Avast, me proud beauty!

After tradin' a couple o' e-mails, me bucko, shiver me timbers, I decide t' try it anyway. Ya scallywag! How bad can it be? I also make a mental note t' stop by rat shack for a fine point soldering iron. Aye aye! $25 and a week later, me hearties, ya bilge rat, I am openin' a padded manila mailer from Massachusetts. Ya scallywag! Another late night, me hearties, ya bilge rat, me hearties, this time solderin' teeny tiny components onto a circuit board which is a little larger than a cigarette. Avast! Ya scallywag! Tweezers, micro-clips, and lots o' patience. Well, blow me down! Avast!

I hold t' components down with micro-clips, arrr, me hearties, then lightly touch the solderin' iron t' t' joint. Ya scallywag! This isn't as bad as I thought it was!!! There's lots o' stuff t' put on and it's lookin' pretty good!

Crack! Damn. I just broke one o' t' capacitors. Begad! I tried t' use hemostats to hold t' component in place as I solder it. Ahoy! I should have stayed with t' micro clips. Begad! Avast! Lookin' over t' schematic and t' magazine article carefully, I figure out that t' value o' this particular cap isn't important. Begad! I fish out a tiny capacitor from me junk box and solder it in place.

Done. Aye aye! Hook up t' battery. Blimey! Arrr! Blink. Well, blow me down! Begad!

It doesn't work.

What did I do?

I look at t' components and double check t' instructions. Arrr! Blimey!

After much inspection and fiddling, I decide t' send a note t' Rob and go to bed. Aye aye! I get a response t' next day, matey, matey, and before I have a chance t' do the diagnostics he recommends, I decide t' check t' solder joints again. Blimey! This time I use an exacto knife. Blimey! Bingo! It turns out that 3 joints are nay complete. Avast, me proud beauty! I solder them and it works!

I have since purchased another kit and assembled it. Both sensors have been calibrated and tested, ya bilge rat, though I haven't had t' chance t' actually fly them. Avast, me proud beauty! I have modifies one with a mini-jack so it holds t' flashbulb circuit open (for safety) when it is inserted - and at t' same time puts a test LED across the circuit. Ahoy!

I HIGHLY recommend this kit. Blimey! Avast! Get them while they last! T' finished sensor is small enough t' fit in BT5!! This opens up a huge realm o' model rocket design. Blimey! I have lots o' sketches already for FAR OUT rockets. Begad! Just you wait!

Here are me tips:

1) Get a solderin' iron, ya bilge rat, 15-20 watts, with t' smallest tip you can find. Arrr! Avast, me proud beauty!

2) Get some tweezers and a magnifyin' glass. Aye aye! Ya scallywag! These things are tiny. Avast, ya bilge rat, me proud beauty! Work on a large clean table where you can find items easily if dropped. Arrr! If you have a room with a hard floor, matey, it will be easier t' find anythin' if you drop it. Arrr!

3) Use tape, glue, arrr, micro clips, etc. t' hold t' components in place while you're soldering. Be very careful about applyin' too much pressure as some of them are brittle. Aye aye!

4) Test all your solder joints t' make sure they are tacked down properly. Well, blow me down! Avast! Blimey!

5) Be patient!