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Old May 23, 2002, 10:16 AM
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Dave Wulff's Avatar
USA, FL, Fort Lauderdale
Joined Feb 2002
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Gordon,

Do you use the bulb by itself, or do you put in a reflector as it is in the car headlamp. I imagine by itself, or the beam would be too focused and bright. I'll bet the little bugger gets pretty warm!

Dave W.
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Old May 23, 2002, 10:36 AM
Sticky Shepherd
Graham Stabler's Avatar
Oxford/England
Joined May 2001
4,017 Posts
Not wishing to fly two far off thread but I've been thinking of making a motor test rig and thought a laser pointer and photodiode might be a nice way to do the speed sensing. I can feed it into my scope or read the frequency on my multimeter. They might even work with a std tach but theres not too much point. Just something to do with a spare pointer, don't have a lot of pointing to do these days.

Graham
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Old May 23, 2002, 11:26 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Dave,
I use the bulb by itself. Be careful nothing is near it. It can start a fire it is so hot.

Graham, sounds good if you've got the equipment. My digital tach from Hobbico generally reads bouncing between two RPM's that are 40 to 30 RPM away from each other. I figure this is acceptable given the level of precision of everything else I have and the error present in any of these tests. For example, if I run three static tests from the same battery I will get three different results within a band of 5% or so thrust. Anyway, I record the lower of the RPM's in my static tests. You probably have way more precise instruments at your disposal.
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Old May 23, 2002, 02:35 PM
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bmutlugil's Avatar
Turkey
Joined May 2002
2,178 Posts
Hi everybody,

I am a newcomer to the site, quite amazed and interested. I have a few questions on some subjects currently being discussed:

* Is the Mabuchi M20LV (HV) being mentioned frequently actually Mabuchi FF-M20VA (VK) by designation?

* If single cell Li-Poly is being used to power M20 and similar motors, what sort of RC gear is being utilized at this voltage?

* Who sells pager drives and similar micro motors?

* I have some dc motors with a company logo in the shape of a capital M, with the legs bent inside slightly at the bottom. Does anybody know which company this is? I have rewound an 8 gr. motor produced by this company, the designation was something like PM103-1. Other motors from this source have designations like PPN-13KA10C, MDN3BT3CSA, etc..

I am currently in the process of constructing an approximately 35 cm. wingspan Sperry Messenger biplane modified from MAN plans. My equipment is Sky Hooks & Rigging RX - JMP 7 ESC - 2 x Hitec HS50's. The motor will be a rewound dc motor from a CD drive, with prop reduction and probably a 5x3 prop. I hope to keep all-up weight below 100 grams, but this is not easy without a lightweight battery. My equipment will not work below 7.2V theoretically, so 2 Li cells seem to be a good solution. Don't know if this wing loading will be practical..

Living in Turkey, I have to construct everything including motor winding, prop reduction, propeller, wheels, etc. The new Li-Poly cells look interesting, but will be difficult to procure for me. The best I can find is a 7.2V 400 mAh Li battery at 32 grams - this battery is prismatic and won't even fit in the fuselage..

Life is not easy for some of us..

Keep up the good work.

Bulent
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Old May 23, 2002, 02:46 PM
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dhurd's Avatar
Buffalo, New York
Joined Jan 2002
1,024 Posts
Bulent,
A single LiPoly cell would probably most likely be used with the RFFS-100 (www.slowfly.com). Currently we are building planes that weigh less then 28g using nicad batteries (others that are more skilled at building are building planes that are lighter then this). With the LiPoly's, getting micro models to weigh less the 20grams should be fairly easy even for the worst of builders (ie me). At these weights, and according to Gordons measurements vertical performance may be attainable.

Dan
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Old May 23, 2002, 03:07 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Bulent,
Welcome to the Ezone.

Didel in Switzerland sells a variety of pager motors and gears and gearboxes for them, didel. I also started a thread here for Didel questions. Just do a search and you will find it.

I have a variety of static tests on my web site and have some information on the M20 motors on my M20 Page. If you measure the Ohms on your motor and compare to the ones I have measured that will give you an idea. I'm not an expert on Mabuchi numbering, but understand that part of what the number is is the manufacturing date or batch number, so these are difficult to compare. I'll jot down the numbers on mine and post.

Check out http://www.wildrc.com. Dan Krieg is selling Two-Cell LiPoly's that are larger than the 135's and an inexpensive charger for them. He has some weight comparisions etc. I think he will ship internationally. These may satisfy your need for volts.

What part of Turkey do you live in? I've traveled through Turkey twice and have a friend from grad school who has returned to Istanbul. Just curious.
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Old May 23, 2002, 03:40 PM
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bmutlugil's Avatar
Turkey
Joined May 2002
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Hi Gordon, Dan,

Thanks for your replies..

Dan, by your help, I have just seen the low voltage receivers and micro servos - or actuators. How do these servos work? Is the coil stationary, or the magnet?

Gordon, I live in the capital - Ankara, which is about 400 km. from Istanbul. The number of modellers in Istanbul is much higher than those in Ankara - don't know if your friend is a modeller. I have seen your web site, it is packed with useful info. I will have to study it in detail, and extrapolate for my motor size.. My rewound motor is around 7 Ohms, but remember it is for 7.2V. It drives a standard Kavan 6X3 at 0.3 A with 1:4 reduction, but the thrust is not enough, so I will wind it for slightly higher power and reduce the ratio in the coming days.. I have added cooling slots in the body to increase the cooling and to reduce the weight to 7.3 grams. I have two pager motors, but these are too small for my use - and they are for 1.3V, I guess. What is your grad speciality?
I have B.Sc, M.Sc. degrees in Electrical Eng. and Ph.D in Solid State Physics..


Your 1 ounce micro planes are a bit too much for me. Guess will stick to my 100 grams category for the time being.

Best regards,

Bulent
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Old May 23, 2002, 04:21 PM
"Simplify, then add lightness"
Raleigh,NC
Joined Nov 2000
2,701 Posts
Bulent,
Welcome to the zone. I believe the "M" with the bottoms bent in is a logo for Matsu****a, but I don't have any info on their motors.
The following page shows the Matsu****a logo along with other major electronics logos.

http://www.elektronikforum.de/ic-id/

Jeff

PS. Is the E-zone software great or what. It censors the word Matsush ita.
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Old May 24, 2002, 11:30 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
Here's what I know about the life of these. I have 7 charges and discharges (all at way more than mfg specs) on a single 135 mAh LiPoly now. So far, no degredation in performance.

I corresponded with Dan Krieg about his experiences. He has never got more than 30 cycles on his LiPoly's as someone always buys the completed plane from him and he starts again. But, the people buying them with several or more cycles are not calling back with problems.

We may have some preliminary evidence that abusing these cells won't cause us to have life expectancies of only 15 or 20 cycles. Past that, only time will tell.
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Old May 24, 2002, 03:54 PM
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USA, FL, Fort Lauderdale
Joined Feb 2002
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Gordon, Dan K., anyone?

I just got my charger from Dan Krieg (WildRC). It is made by Potensky, and is designed for both Li-metal (3.4 V) & Li-Ion (4.2 V) @ a range of 20 - 40 - 60 - 100 - 200 mah, selectable by dip switch. My 135 mah LI-Poly cell lookes like it wants 4.2 V @ a max of 1C (130 mah). 100 mah @ 4.2 looks like the conservative max, as there is nothing between 100 & 200 mah, but I wouldn't mind a bit of input. BTW, charger has an auto cutoff to triclke. Also BTW, I ordered this on Dan's website Wed. and it got here Friday. Thats CA to NY in 2 days for $5 shipping & handling....pretty good!

Gordon, what kind of currents are you drawing?

Dave W.
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Old May 24, 2002, 04:34 PM
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opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
given most of these cells are spec'd for 1/2 c charge, I wouldn't go over 1C charge, use 100ma. you want endurance under discharge stress to be tested, not a test of charging stress. charging too fast may work, but may cloud your results.
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Old May 24, 2002, 04:47 PM
"Simplify, then add lightness"
Raleigh,NC
Joined Nov 2000
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Dave,
Does it cut off completely after a while or continue to trickle charge. Continuous trickle charge is bad for Lithium Ion, and I would imagine it is the same for the Lithium Polymer. If the charger does not cut off completely after a while, make sure you don't leave the cells on trickle for too long or you will shorten their life.

Jeff
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Old May 24, 2002, 05:17 PM
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jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
954 Posts
To be precise, when the cell is held at 4.2V at the end of the charge cycle, the current goes down. Charging definitely should be cut off when the current is down to 1/10C or 1/20C (manufacturers specifications differ at this point).
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Old May 24, 2002, 06:15 PM
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bmutlugil's Avatar
Turkey
Joined May 2002
2,178 Posts
Did anybody track down the 230 mAh Li-Poly batteries yet? The attached picture (hope it is..) is available at the link previously given - the blimp page - but nothing else is. These cells are the size I need..

Jeff, thanks, the M indeed stood for Mabuchi. Data sheets are available at the web page - no weight data. Shortform at http://www.motor.panasonic.co.jp/www...AGC1000_E.html . These motors can be frequently found in old CD ROM drives, although mostly having 16mm or larger diameter. I found one 12 mm dia. one (8 gr.), which I am modifying. You can't beat the CD motors for price, as they are usually free.

Regards,

Bulent
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Old May 24, 2002, 08:11 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,430 Posts
That picture is (I think) the same one from that guy in India's site (can't remember his name right now). Apparently he and Aeronutz Mark got theirs from plantraco.com, but it's not listed on their site yet. Possibly if you email them you can get one if they have a few. Other than that, I have no idea, except it looks like a larger version of the 135 mAh, but probably from a different manufacturer as Kokam doesn't list this size. This size will fill a gap.

Sorry, I forgot to mention that Dan Krieg said his charger was from Potensky. My charger is automatic. It detects what the battery is by the 3 minute surface charge at the beginning. So, I can't tell you what charge rate, except that it takes 65-70 minutes to take if from 3.65v to 4.30v. You can guestimate from that. I think my charger may use a variable charge rate, but I'm not sure. BTW, it's made in Korea.

Here's a picture.
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