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Old Jun 04, 2008, 11:24 PM
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Top cover for a legitimate build thread.

Q: What's the difference between a dog?
A: The other leg is shorter.

(the build thread is in the comments)
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Old Jun 04, 2008, 11:37 PM
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Microstar 2000 build thread

Sometimes I feel the need to tinker. I like my Multiplex Evo for programming and in particular channel assignability, but I've maxed out the model memory and don't have a real backup transmitter. Long story short, I decided to try and build a Microstar for a backup TX: www.mstar2k.com. There's a great user base and lots of help, including people who support the design by providing parts and kits and services at cost. I got an encoder kit from Kees at http://www.qsl.net/k5bcq/MS2K/MS2K.html.

I'm not an electrician, but I can follow orders, so in the past if the instructions were good enough I could usually get stuff working...so on with the show.

The encoder showed up just a few days after ordering it. I took a deep breath and dove in. The instructions are geared towards those with electronics experience, so I thought I might be in trouble, but the stuff is marked well enough and there's (usually ) enough clues to keep me out of trouble. Maybe this thread will keep the next clueless newbie from making the same minor mistakes I still managed to make. Note that the most critical part, the PIC chip, came pre-soldered. It's the only surface-mount bit on the board, so my ham-handed soldering skills turned out to be up to the task.

First step was to install the resistor networks and loose resistors:

Nauga,
for whom resistance was futile
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Old Jun 04, 2008, 11:42 PM
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Capacitors and the voltage regulator came next. I always have trouble identifying film caps, but the parts list had a few clues ('markings' listed) that made it easier. Electrolytic caps positive leads were well marked on the board, so this part went well too.

Nauga,
well regulated
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Old Jun 04, 2008, 11:57 PM
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Cool little mini ("pico") fuse came next. Never seen these before, they're kind of cool being so small and all. After smoking one I also found out they're *expensive* if I buy them locally. I'm more careful with current limiters now.

Also soldered the main header, the first of several headers on the board. This one is the wiring point for all the switches, sticks, trim pots, etc.

Nauga,
who hates when it goes 'poof'
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Old Jun 05, 2008, 12:20 AM
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Buzzer and RS-232 leveller (the DIP IC) next. I am absolutely, positively 100% certain the buzzer works. A piece of tape over the element keeps me sane

Note: This is about three short evenings worth of work so far, what with digging out components, installing and soldering them, clipping leads, flipping the board several times for each step, etc...

Nauga,
who needs a buzzkill
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Old Jun 05, 2008, 12:35 AM
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Headers, jumpers, and a crystal are about all that's left. The header pins on top are for plugs for the buddy cable, charger, and serial port; the right are for battery hookup and the RF deck, and the bottom everything else.

The crystal was also installed here - I found a note buried in some of the documentation that mentioned grounding the crystal case, and the schematic showed it once I knew what I was looking for, so I crossed my fingers and grounded the case. Whaddya know, it worked.

The remaining open holes are for the ribbon connector that goes to the LCD. Other than that the board is ready to test...but that will have to wait.

Nauga,
who knows how this one ends
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Old Jun 05, 2008, 08:15 AM
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The display that came with the parts was a surplus LCD with a little info in the notes on the parts list. I couldn't find a pinout for that exact display but found a datasheet (with pinout) for one with the same basic part number with one letter different at the end. Close enough? Let's give it a try (see where this is going? ). I soldered the LCD cable directly to the board, the other end has a connector for the display. The display also got a straight headed - which will cause mounting problems and be replaced with a right angle header later but not 'til it's tested and otherwise ready to mount.

For the first powerup there are no switches or gimbals or anything connected. You're just looking for a startup message on the display. I wired it to a 12v power supply, held my breath, and hit the power switch.

Nothing happened.

Nauga,
and the sound of silence
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Old Jun 05, 2008, 08:26 AM
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...OK, maybe not exactly *nothing* happened. While the power was on and I was probing with a meter checking voltages I bumped the LCD and noticed it was *HOT*. I disconnected the LCD and powered it back up, at which point it beeped a few times at me (that's progress, right?) then went silent, and dead. A few pokes with the meter showed I had blown the pico fuse, if not more.

So into the paperwork and Yahoo group. Everyone says things *might* be OK if I can find the problem, and to really thoroughly check the LCD wiring. Another close look at the parts list and I see a note that says to reverse pins 1 and 2 from the encoder into *this particular* LCD. That doesn't match the datasheet I've got, but what the heck, I'll give it a shot. 5 minutes with the iron and a trip to the local electronics shop for fuses and I'm ready to go again. This time I wire in an ammeter and a current limiting resistor to see if I can avoid smoking stuff again.

Holding my breath, I power up again...

Nauga,
melodramatically yours
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Old Jun 05, 2008, 11:39 PM
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Now that things have all checked out at the circuit level, it's time to find a donor radio. All I need from the radio are the gimbals (stick assemblies), trim pots (not the digital trims of current stuff), and case. If there are switches and buttons that can be salvaged, all that much better.

It took several tries, but I managed to score a Proline Comp 6 on Ebay. Proline was known for the quality of the metal gimbals they provided, and the white case just looked...well, "right". So I've got the Proline, it's in good shape, but Ginger the QA dog says, "You're not going to hack up a collectors item to stuff in an encoder you're not even sure will work, are you?" Good point. The search continues. The Proline will be refit *after* everything has been checked out in a less critical application.

Nauga,
cautiously
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Old Jun 05, 2008, 11:52 PM
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One advantage to being a pack rat is you can find stuff you need, sometimes 15 years after you lose it. With a mighty crash and a cloud of dust, an old Tower Gold radio fell out of the rafters. The "Hitec" of it's day , the Gold had top-of-the-line features like 5 channels, dual rates (aileron and elevator only) and servo reversing! (on 4 channels only). Single model only. No mixing. I doubt collectors will be beating down my door for this one, so the parts pretty much pour out of the back and into the trash. I strip it down to just one stick and wire in plugs from the stick pots to the encoder. Turns out the pots are like 5 billion Ohms or something (yes, they're functional, barely), so they aren't going to work out of the gate with this board.

I picked up a couple of Rat Shack pots in the range the board expects (5K Ohms), wired them in, and was able to simulate sticks functioning, calibrate them, and check that they worked through the menus (stick motion is used to select and change many menu items in this encoder). I now know that the board is fully functional, so it I'm not able to get new pots for the Tower radio I can give the Proline a shot with some confidence. The Proline pots check for range, by the way.

Nauga,
pot shopping
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Old Jun 08, 2008, 12:07 AM
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Quote:
Originally Posted by nauga
Turns out the pots are like 5 billion Ohms or something (yes, they're functional, barely), so they aren't going to work out of the gate with this board.
Sometimes it's good to be wrong. Wrong and a pack rat. Waaay back when I bought the Tower radio I was also able to get a xerox copy of the radio schematics. I have absolutely no idea how or when I got them, but they were in the box when I found the radio last week. The pots *are* 5K, the ideal range for the M*2K encoder...at least they're supposed to be. I went back to the first pot I tested and checked again. Yup, high resistance. I pried up the tabs and pulled off the back, and blew out the crud that had accumulated over a few years of heavy use and many more of sitting. When I slapped it back together it checked on the multimeter. This time I was able to wire up two sticks (four pots) and get good numbers out of the calibraton screen of the encoder. In short, success!

Right now I'm trying to figure out where to put the new switches and junk on the Tower case. Since this is just a test run I'm not putting in switches and sliders for everything, just a few basics to fly a glider or tow to make sure it works. That's still 4 or 5 new pushbuttons and two or three switches in addition to reusing existing switches on the case. Not easy finding room.

No pictures today.

Nauga,
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Old Jun 10, 2008, 03:21 AM
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here's a lesson in shoehorning: http://www.rcgroups.com/forums/showthread.php?t=825773


and i say gut the proline and thumb your nose at the collectors...


dave
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Old Jun 10, 2008, 08:17 AM
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Quote:
Originally Posted by ZAGNUT
here's a lesson in shoehorning...
Your thread is one of a few that convinced me to try it...and thanks for the help with the display wiring. The Tower TX is almost done and another donor should be on its way. The next challenge is RF.

Nauga,
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Old Jun 11, 2008, 01:02 AM
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Two steps forward, one step back

The build thread has caught up with the build. The Tower case has all the switches mounted (not all the switches the radio can handle, but all I'm using in the checkout build). The display was (was...?) mounted in the case and I wired up the RF deck for the first time. A test flight pack would buzz and hum when the TX was powered up, but something was obviously not getting through. I started probing voltages and stuff and the board lost power. New fuse? No power (old fuse checked good). Start checking test points on the board and get really strange results. Pull the probes and check the power supply, all is OK. Reconnect PS and check at PS connection...low voltage. Huh? I pull the board out, disconnect all the switches, and pull the display out of the case for better access, and the signs are strange. I finally grab a known-good TX battery and plug that in and the board powers up. *Whew*. So the board is good, I've done something to my power supply, and I've reglued the display in the case. A little poking on the Microstar users group makes it look like I've got to adjust the TX pulse width a little more than I tried...hope that does it. I'll stuff everything back in and take pics tomorrow.

Nauga,
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Old Jun 12, 2008, 12:35 AM
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Things are starting to happen

The past few evenings have been interesting. I've been spending a lot of time on the MP8K yahoo group asking stupid questions and getting a lot of help. The initial install went fine but I ran into problems getting a synthesized RF deck to work. Seems like nothing I did made a difference - in general the encoder did everything it was supposed to do but there was no signal radiating. Finally in near-frustration I dug an old fixed-freq module out of the recesses of my shop and stuck that in (identical pinout). My first clue that someting was different was when the surfaces on my 'test model' jumped to near-neutral and firmly resisted a push. A jump every now and then has been the norm but this was different - things looked, well, 'right'.

The next project will be to fine-tune the setup for one model, finish the install, and try it out. Duty calls, so that may take a while.

Nauga,
on the road again
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