JPDV

One option I looked into for testing our system without using the batteries is using computer power supplies. They are getting quite high power these days... also you can modify them to have a lower output voltage, with a bit of stuffing around. Also, they have +12, -12, and 5 volt outputs; if you modify it to only output the 12v (or less) you could most probably draw more current.

You could get away with a car battery btw, just make sure you never go past 75% duty cycle on your speed controllers. (75% of 12volts is 9volts). The down side to this is you loose some resolution on your speed controller.

Hope that helps,
Josh

ADI

Crac Wrote:
> Are you guys interested in exchanging our mechanical design too ? >

Yeah sure .... but there isn't too much difference here. Carbon fibre tube, carbon fibre tube and some more carbon fibre tube ... he he.

Cheers ADI

tve

I think the best way to do a step-down supply with that kind of current is a dual N-channel switching supply. Here is a part that you could probably use, you would have to find FETs that could handle the current and make the appropriate design changes following the design notes. http://www.linear.com/pc/downloadDoc...32,P2305,D3759

Probably not a trivial circuit... also switchers can be dangerous. I am mostly posting this to show that this probably is not something you can pick up the parts for at radio shack.

Another thing you might try is searching for OEM switching power supplies. here is a start
http://dir.yahoo.com/business_and_ec...es/makers/?o=a

I have a BK Precision 1692 switching power supply that works great for this kind of stuff, but it was almost 300 dollars.

tve

Well,

I bought some parts for the new frame today. I am going to wait until the new props show up before I get too serious though. It will be 3ft x 3ft aluminum strip. The outrunner motors will be bolted directly to it with the firewall adaptor. Plenty of room for the batteries and controllers. Should be a bit more sturdy than my first frame. I've been playing with motocalc some more trying different props and motors. The combo I came up with seems to be the best (by quite a bit) prediction for thrust using 3 cell batteries that I have found. (makes me wonder if it is real).

Spaceclam

well, i tried to fly it today, and it seems that one of my motors is not getting power. i have to investigate, but i am completely stumped by the behavior of this copilot thing. it will rock back and forth violently on the ground, and it will stick a prop into the ground, and the other motor will speed up and it keeps it stuck there unless i back off about 50 feet and it begins to let down a bit, and i can start the other prop and it swings it back, starting the process all over again. i think i may try again flying it with out the IR working, but i am curious. will lowering my CG really make it more stable? i have been having thoughts about this, and i hear drom the designer of the draganflyer board that a cg way above the line of thrust is supposed to be quite stable as well. i have not had the guts to try it, but do you guiys think i should put my CG at the prop line? what are your thoughts? in reality, i think i need to get some castle creations speed controllers becuase these are a bit too course for all the power i have.

tve

Kind of sounds like the gains are off. My guess would be back off quite a bit on the IR gain and play with the gyro gain. .... just a guess.

Jeremy Ng

Hello,

Danvel & all,

How much is cost for the Murata gyros ENC03M- A@B?

I still doing my PID - close loop.

Open loop mixing - done.

Will upload picture very soon.

Thanks


Regards,

Jeremy

Crac

Hy Jeremy !
I d'ont know, i use ENC03-JA : 50 euros for one piece (about 38 dollars) (http://www.farnellinone.com)

Crackmike

ADI

Jeremy Wrote:
>How much is cost for the Murata gyros ENC03M- A@B?>

Hard to get hold of and expensive if you can get them.
Alternative is Tokin CG-L43 at US$25 each.

on_newbie

Hi All,

Newbie here.

Very new, please guide in RC point of view. I have read a few of the post, 1,2,3,..... still a lot more to go ....42.
________________________________________________
Propeller guide:

http://www.toddsmodels.com/Props/propsother.htm

EEP1045

What does 10x4.5 means?

10 = length?
4.5 = ??

Please Guide...
__________________________________________________ __________________

GWS guide:

Can I use EPS-350C-CS (7.2V , propeller = 1047) with the EEP1045?

on the website: http://www.toddsmodels.com/Brushed%20Motors/EPS350C.htm

What is C-CS stand for? (EPS-350C-CS)?

Please guide

__________________________________________________ _____________________

ThankS!

Newbie

Spaceclam

ok, glad to have you here.
any propeller has a specific designation. it is always designated in **x* or in this case, 10x4.7. the first number, you were correct is the diameter, and the second number is the theoretical pitch. that means, that if you had a pitch of 10, it would theoretically travel 10 inches in one revolution, in a perfect world. obvioiusly we do not live in a perfect world, but it givies us a pretty close idea of a propeller's performance. for an application such as this, we will gain more thrust for the same amount of amp draw by increaseing propeller size and decreasing the pitch, as speed is not important here. that's where geared units come in. larger propellers turning slower produce more thrust than small props turning faster.

for a guide to GWS motors, visit this site. http://www.balsapr.com/catalog/motors/EPS350C.asp becasue you can click on any motor class, with any gear ratio, and it will give you an entire table of trust and amp draw with a veriaty of propellers and battery voltages. the todds models props are slightly thinner than the gws props they test with, but it will give you a pretty close idea as to what you are up against.

as for what thw "CS" stands for, it does not mean anything significant, but it is usually numbered something like EPS 350c-* and that * is where the gear ratio is specified. in gws they have it numbered a1, a2, a,b,c,d and sometimes e in 2.8:1, 3.2:1, 3.75:1, 4.4:1, 5.3:1, and 6.6:1 gear ratios respectively.

anything else, let me know.
-Clam

ADI

Danvel ..... this PI algorythm doesn't look much good if no floating point math is used.
Did you implement floating point math routines ?

ADI

danvel

I tried FP but the compiled code got too big and the execution too slow. However, using fixed point arithmetic doesn't mean that you'll have such a bad resolution as you show in your graph. The trick is to use double byte integers for the integrators.I'll develop a bit more on this as soon as I have some time.

ADI

Hi Danvel,

Yes of course .... remain in the same PPM timer/counter resolution for all integrator math and just use a 'binary shift right 4 places' copy of accumulated integral for each /16 data output.

Cheers ADI

strathy

Hey guys, thought i'd let you see what the craft will look like when its done!!
Having a few shipping problems just now, so are waiting on a few components, but will hopefully have the real thing to show you in about 2 weeks, and all being well a video or two as well!

Petrous

Hi!
I've finished my home-made controller, there are the pictures :
http://petrus44.free.fr/Aeromodelism...roller_top.jpg
http://petrus44.free.fr/Aeromodelism...roller_bot.jpg

And I've made a video with a 7*4 graupner prop
http://petrus44.free.fr/Aeromodelism...controller.mpg
You can read 4.93A and 10.14V on the multimeters and 242g of thrust.

ADI

Great work Petrous. I watched the video clip. C'est magnifique !
That's very ingenious idea to re-use the BA6849FP chip. Did you rewind the motor and replace with neodymium magnets ?
What is the frequency of your PWM input to LM393 ? Although, looking at your schematic, it looks like any reasonable frequency would be OK.

Your work is very encouraging. Great to see it here.

Cheers ADI

Petrous

Yes, I've rewounded the motor with 18 turns of 2*0.2mm diameter wire and replaced the rubber magnet with 12 meodym magnets.
For the PWM signal, I use 20kHz because it's high enough for the motor and because we can't hear it.
I generate it by comparing a triangle signal from a function generator so it may change for the final project while I'll use a microcontroller, maybe a 68HC908AB32

tve

strathy,
Sorry if you already mentioned it, but what materials are you building with? The 3d modeling looks good. What software did you use?

Petrous,
Nice video. Looks like you are making progress very quickly... looking forward to more!


I got my 11x4 3-bladed Zinger props. Nice craftsmanship! The AXi motor spins them like they are nothing though... I don't have any way to accurately measure thrust yet.. so can't give you the numbers, but I'm sure the thrust is enough to get this off the ground just fine. Seems like it would end up being about 2:1 Thrust to weight ratio for the craft (a guess). I'm just guessing, but I think this motor might do better with something larger like 15x4 4-bladed props. I am considering ordering some to try. I'll post more when I have something interesting.

btw: ADI, I am using floating-point on my project. It might not be necessary, but with the 18F458 running @ 30Mhz it is not a problem at all.

strathy

Using aluminium rod, 22mm diameter and 1~2mm thick.
The software is Pro Engineer. Using this so we can do a analysis of the loads through the structure and it also lets you extract cad drawings from the 3d model.

tve

I had a good idea today for the props I hope to have my new heli flying by next weekend! It is going to be very heavy duty and large, but still have 15-20 minutes of flying time! Now I'm excited about this project again... I will get some video of the flight this time for sure! I wish I would have got the last flight on video... oh well. More next weekend...

tve

Here is an image of my new setup. I have to order some more motors to get this thing flying again.

Spaceclam, I decided to give up on the Zinger props. They work, but not as well as I was expecting.... I'm back to the plastic props, but with 4 blades

This thing should fly for 20 minutes pretty easy!

http://www.hanfordsite.com/heavyduty.jpg

strathy

Where did you get your propellers from tve?

tve

They are the same props most are using here.... just two of them per motor. Works pretty good! I ordered the rest of the AXi motors (note: I ordered the 2820/10 instead of the 2820/12 that I currently have). If I get them before next weekend, I should have a video for you guys...

[edit]
This thing lifts off @ about 80 Watts per motor. I can put about 360 Watts to it with my current batteries (peak, 333 Watts extended) . There is almost no detectable heat generation on the motors or FETS. I love this AXi motor. With 3 cell 2600mAh Li-Polys I should get around 20 minutes of hovering I figure. I have a lot of headroom for more weight though... It would be very easy to extend the flight time to at least 45 minutes I think (correct me if I'm wrong.. I probably am).... I'm just guessing here somewhat, but I will know more when I get the thing flying.

ADI

Hey cool ..... doubling up the Todds props. I never thought of that ! What a cool idea.

Cheers ADI