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. Ya scallywag! Aye aye! Lots o' issues are filled with vaguely interestin' articles, rocket related o' course, me bucko, but t' one thin' that caught my eye immediately was t' Magnetic Apogee Sensor! Written by Robert Galejs, the article went into detail on his development o' a concept into a working device! This be really fascinating. Aye aye! Aye aye! I read and reread t' article several times, ya bilge rat, shiver me timbers, and even contemplated tryin' t' wire up me own. Schematics and even a board pattern was included. Ya scallywag! Unfortunately, me hearties, shiver me timbers, arrr, I studied mechanical engineering, and electrical things are still somewhat intimidating. Aye aye! 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. Avast! However, as it turns out, me hearties, thar's a significant vertical component t' t' magnetic field, which means that, me hearties, ya bilge rat, 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. Begad! It's late at night and I'm pokin' through RMR when I see a postin' by none other than Robert Galejs himself! 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, matey, and even had assembled a few kits for construction! Sweet!

I read his postin' more carefully and hesitate. SMT? That's Surface mount, isn't it? Bummer. Arrr! 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. Avast, me proud beauty! I'm pretty handy with an exacto, but a solderin' iron? Forget it. Avast! Begad!

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

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

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

Done. Blimey! Arrr! Hook up t' battery. Begad! Blink. Avast!

It doesn't work. Begad!

What did I do?

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

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

I have since purchased another kit and assembled it. Avast, me proud beauty! Well, shiver me timbers, blow me down! Both sensors have been calibrated and tested, matey, though I haven't had t' chance t' actually fly them. Begad! 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. Avast!

I HIGHLY recommend this kit. Ya scallywag! 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. Well, blow me down! Just you wait!

Here are me tips:

1) Get a solderin' iron, 15-20 watts, matey, with t' smallest tip you can find. Ya scallywag!

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

3) Use tape, glue, me bucko, micro clips, etc. Well, blow me down! t' hold t' components in place while you're soldering. Ya scallywag! Be very careful about applyin' too much pressure as some of them are brittle. Ya scallywag!

4) Test all your solder joints t' make sure they are tacked down properly. Aye aye!

5) Be patient!