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May 27, 2007, 04:33 AM
Registered User
Discussion

Sub gram solar plane


Hello,

I analyzed a model based on the TASC solar cells from Spectrolab. In order to meet the sub gram goal 2 cells will be used. They cover an area of 1.55x 3.18 cm and can generate 30mA at 4.4V if connected in series. I assumed sommer as flight time at high noon and latitudes up to 50 degrees. Besides the motor the other consumers will be limited to 3mA. In order to achieve this all consumers besides the motor will be fed via a voltage controller operating at 1.8V (or similar value, tbd).
The motor design point will be 4.4V and 24mA. It will be a brushless single phase motor operated by a PWM signal via a SC70 FET and the Hall-bridge chip 1441 from Allegro. Both units are in series and have a resistance of 7Ohms.
The magnet is 2.5mmODx1mmIDx1.5mm made by grinding from 3x1x2mm. The coil has 320windings from 0.05mm wire fitting as close as possible to the magnet. The motor will be 170mg excluding the Hall bridge. It has a very high efficiency: up to 68%! The output power is 69mW at 27300rpm.
The prop will be similar to the 30mm prop we built and measured, but shrunk to 22mm OD at 4mm width. Its efficiency is close to 30% if well manufactured.
The maximum thrust will be 0.68g which is sufficient for a 0.8g model.
I made a small study with different motors. There is a definite advantage to go to heavier motors. We get more thrust margin at a modest weight increase.
The electronics (70mg) and an airframe with 80mg are state of the art. The cells weigh 468mg. Thus 800mg seems to be feasable.
I will built a motor to these specs within the next days (weeks) and test it.

Now, the only components I need are the cells.

Angry monk,

I proposed to pay for all the cells not distributed to other users. I just need somebody to GET the cells.

Helmut
Last edited by Helmut-Schweig; May 27, 2007 at 04:35 AM. Reason: typing error
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May 27, 2007, 11:20 AM
Your ruler, in part...
Angry_Monk's Avatar
Quote:
Originally Posted by Helmut-Schweig
Angry monk,

I proposed to pay for all the cells not distributed to other users. I just need somebody to GET the cells.

Helmut
that works.

i was looking at the order form and noticed something about these cells being federally regulated when it comes to shipment overseas. its on the last page of the order form ( http://www.spectrolab.com/prd/terres...ndividuals.pdf ). this concerns me because i do not want to get into trouble for shipping these to Germany. but its Germany, not Iran or some nation that isnt on good terms with the US... what should i do about this...?
May 27, 2007, 11:34 AM
Registered User
Hallo Angry Monk,

I dont want you to get into trouble. Its a real pity that these tiny cells fall under federal regulation. I used to work with Spectrolab during my work on solar panels for satellites. We got thousands of all kinds of cells. But federal regulation is federal regulation.
Well, the next time I come over to the US I will find a way to get a few cells. Thanks for your help.
Anyway I will built and test suitable motors. I can send you a motor and you built a model, if you find a sponsor for the cells. Try to address Spectrolab. They might give you a few cells (samples) for testing.

Helmut
May 27, 2007, 01:20 PM
Your ruler, in part...
Angry_Monk's Avatar
i just emailed the company. basically i asked what it would take to get a license to export these cells (or if one is even necessary). if its not too complicated or costly i can try to get the license so i can send you the cells. im not ready to give up just yet. i'll let you know how things turn out. if worst comes to worst i can order the cells and hold them for you until your next US trip. i bet i can recover some cost by selling some of the cells.
May 27, 2007, 08:21 PM
Registered User
I'd be interested in a few of those cells if someone were selling them in small quantities. Spectrolab's minimum order is $1000...a bit steep for tinkering around.

tk
May 27, 2007, 11:44 PM
Your ruler, in part...
Angry_Monk's Avatar
Quote:
Originally Posted by tskunka
I'd be interested in a few of those cells if someone were selling them in small quantities. Spectrolab's minimum order is $1000...a bit steep for tinkering around.

tk
two points:

1) AHHHHH!!! $1000!?!? i hope thats a mistake. it also says on there site that there is a 100 piece min order for the cells at 2.5$ each. oh man, i hope there isnt a 1000$ min order on top of that... crap

2) if i order them i will sell them in small quantities (min order of 1). so no worries there.
May 28, 2007, 02:57 AM
Registered User
Quote:
Originally Posted by Angry_Monk
two points:

1) AHHHHH!!! $1000!?!? i hope thats a mistake. it also says on there site that there is a 100 piece min order for the cells at 2.5$ each. oh man, i hope there isnt a 1000$ min order on top of that... crap

2) if i order them i will sell them in small quantities (min order of 1). so no worries there.
Please put me on your waiting list.

Regards,
May 28, 2007, 03:18 AM
My member is not
Zlatko's Avatar
Angry,

I'll be happy with 12@$5 +P&P to Oz .... I've paid more for lesser quality ones :I

Cheers
May 28, 2007, 06:05 PM
Your ruler, in part...
Angry_Monk's Avatar
thanks for your support. i am waiting for a reply from spectrolabs about ordering the cells. if the min order is 1000$ then this order is too big for most of us and i will try to find a small company to help out. either way the one thing i need is a list of people willing to buy cells (quantity you are willing to buy helps greatly too!). that way any sponsor i contact can be assured they will not be left with 1000$ worth of solar cells...
May 29, 2007, 12:41 AM
Registered User
Did it specifically say the cells were subject to ITAR restrictions, or did it say that any technology that IS subject to ITAR will not be exported....
May 29, 2007, 01:08 AM
My member is not
Zlatko's Avatar
Quote:
Originally Posted by ZXLNT
Did it specifically say the cells were subject to ITAR restrictions, or did it say that any technology that IS subject to ITAR will not be exported....
I don't think it is an issue.

I had to sign and fax similar looking documents to Digikey and Mouser when I purchased micro processors from them.

Australia is okay, so I guess Germany, Europe ... etc would be too.

Cheers
May 29, 2007, 01:21 AM
is it supposed to smoke??
3dFlyer88's Avatar
what about canada? i would like some of these
May 29, 2007, 06:57 AM
Registered User
Can you pls repeat/or give a link of full details for the cells we are talking about.
Thks and rgds,
May 29, 2007, 07:51 PM
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Angry_Monk's Avatar
i just got an email. seems Germany is exempt from the export license requirement. i would think it is like this for most countries. im checking if i can just order a box of 100 cells for 250$ or if i need to order 1000$ worth. im also checking about Australia's exemption status.

UPDATE;

good news, Australia is good as far as shipping goes. and better yet the min order price for these cells is 250$ not 1000$. this means that the next step is ordering the cells. i already have names of people that want cells, so if anyone else wants some them speak up. you still have plenty of time. when i actually get the cells i will start figuring out how many cells everyone wants. my main goal will be to supply cells to everyone that wants them.

btw, if anyone wants to buy the cell separately for any reason i recommend doing it shortly, i was told that the company is trying to increase the minimum order which means that $250 will only go up.
Last edited by Angry_Monk; May 29, 2007 at 09:23 PM.


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