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. Begad! Blimey! Lots o' issues are filled with vaguely interestin' articles, ya bilge rat, rocket related o' course, but t' one thin' that caught my eye immediately was t' Magnetic Apogee Sensor! Blimey! Written by Robert Galejs, the article went into detail on his development o' a concept into a working device! Blimey! This was really fascinating. Aye aye! Blimey! I read and reread t' article several times, and even contemplated tryin' t' wire up me own. Blimey! Ya scallywag! Blimey! Schematics and even a board pattern was included. Avast, me proud beauty! Aye aye! Blimey! Unfortunately, ya bilge rat, I studied mechanical engineering, and electrical things are still somewhat intimidating. Blimey! I considered tryin' to put one together for about 4, matey, maybe 5 seconds. Ya scallywag! Well, blow me down! Blimey!

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. Well, blow me down! Blimey! However, as it turns out, thar's a significant vertical component t' t' magnetic field, which means that, matey, 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. Arrr! Aye aye! 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, arrr, and even had assembled a few kits for construction! Sweet!

I read his postin' more carefully and hesitate. Begad! SMT? That's Surface mount, isn't it? Bummer. Aye aye! For those o' you who are unfamiliar, arrr, 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. I'm pretty handy with an exacto, but a solderin' iron? Forget it.

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

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

Done. Begad! Blimey! Begad! Blimey! Hook up t' battery. Ahoy! Blimey! Blink. Aye aye! Blimey!

It doesn't work.

What did I do?

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

After much inspection and fiddling, ya bilge rat, I decide t' send a note t' Rob and go to bed. Begad! Avast, ya bilge rat, me proud beauty! 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. This time I use an exacto knife. Avast, me proud beauty! Bingo! It turns out that 3 joints are nay complete. I solder them and it works!

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

I HIGHLY recommend this kit. Blimey! 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. Begad! 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, with t' smallest tip you can find. Blimey!

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

3) Use tape, me hearties, glue, micro clips, etc. Well, ya bilge rat, blow me down! t' hold t' components in place while you're soldering. 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. Ya scallywag!

5) Be patient!