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, rocket related o' course, 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. Avast! Well, ya bilge rat, blow me down! I read and reread t' article several times, ya bilge rat, me hearties, shiver me timbers, and even contemplated tryin' t' wire up me own. Begad! Blimey! Schematics and even a board pattern was included. Aye aye! Ya scallywag! Unfortunately, shiver me timbers, I studied mechanical engineering, and electrical things are still somewhat intimidating. I considered tryin' to put one together for about 4, matey, 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. Arrr! Blimey! However, as it turns out, thar's a significant vertical component t' t' magnetic field, ya bilge rat, which means that, arrr, 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. 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, and even had assembled a few kits for construction! Sweet!

I read his postin' more carefully and hesitate. Blimey! Blimey! SMT? That's Surface mount, isn't it? Bummer. Avast, me proud beauty! Blimey! Begad! Blimey! For those o' you who are unfamiliar, me bucko, 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. Blimey! Blimey! Well, ya bilge rat, blow me down! Blimey! I'm pretty handy with an exacto, but a solderin' iron? Forget it. Aye aye! Blimey!

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

I hold t' components down with micro-clips, me bucko, then lightly touch the solderin' iron t' t' joint. Well, blow me down! 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. Blimey! Ya scallywag! I tried t' use hemostats to hold t' component in place as I solder it. Aye aye! I should have stayed with t' micro clips. Well, me bucko, blow me down! Lookin' over t' schematic and t' magazine article carefully, I figure out that t' value o' this particular cap isn't important. Ahoy! I fish out a tiny capacitor from me junk box and solder it in place. Arrr!

Done. Ahoy! Hook up t' battery. Begad! Ahoy! Blink.

It doesn't work. Ya scallywag!

What did I do?

I look at t' components and double check t' instructions. Begad! Blimey! Begad! 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, and before I have a chance t' do the diagnostics he recommends, I decide t' check t' solder joints again. Aye aye! This time I use an exacto knife. Blimey! Ahoy! Bingo! It turns out that 3 joints are nay complete. Arrr! I solder them and it works!

I have since purchased another kit and assembled it. Begad! Both sensors have been calibrated and tested, me bucko, shiver me timbers, though I haven't had t' chance t' actually fly them. Arrr! 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. Arrr!

I HIGHLY recommend this kit. Aye aye! 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. Avast! Well, me bucko, blow me down! I have lots o' sketches already for FAR OUT rockets. Just you wait!

Here are me tips:

1) Get a solderin' iron, 15-20 watts, arrr, with t' smallest tip you can find. Begad! Blimey!

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

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

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

5) Be patient!