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Old Dec 01, 2011, 08:22 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
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DOSD Text Border Update

I was doing some DOSD board modifications to improve the Text Borders and reduce smearing when the boarders are on. Jedas started some testing and I joined in to help confirm/test some other possibilities.

The first modification was adding a 100ohm resistor to the collector leg of a transistor (as shown in this post: http://www.rcgroups.com/forums/showp...ostcount=14194 ). This required physical modification of the board by cutting some tracing, repositioning the transistor, and adding the resistor. This IS NOT a mod for someone who is not well versed in surface mount soldering. It did; however, clean up the borders and made the text look 'sharper' when the borders were on.

The next test was replacing an 11ohm resistor, on the same transistor, with a different value (picture in this post: http://www.rcgroups.com/forums/showp...ostcount=14175 ). Again, this is not a mod for someone inexperienced; however it did work. I removed the 11ohm resistor and replaced it with a variable resistor then powered up the system and increased the resistance value until I saw no more improvement on the bordered text. My best results were with ~111ohms. This is an odd value so I set it for 100 ohms which worked very well. I'll post some comparison screen shots this weekend for y'all to look at.

I've talked with JMSTech about the tests. The second mod, replacing the 11ohm resistor with a 100ohm resistor, is something that could likely be incorporated in future builds IF it is determined it is a worthwhile improvement that doesn't cause any unforseen, by me, problems. I'll be leaving the 100ohm resistor in place as I like the text borders more than just pure white text (which can be difficult to see against clouds, light backgrounds, etc). I would not recommend attempting either of these mods unless you are experienced as you run a high risk of bricking something.

Lastly, I did try installing a variable resistor in series with the Video In line. All I got was a lighter or darker overall picture...no improvements on the text quality.

Again, I'll post some comparison pictures of the bordered text this weekend.
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Old Dec 01, 2011, 11:11 PM
Registered Loser :)
mark hitchman's Avatar
New Zealand
Joined Sep 2009
1,928 Posts
I have not tried GPS stabilization or RTH while inverted but it should right the plane if you are too high, if you are too low I think it will hit the ground before it rights itself.

I will try tomorrow and post the video.

Mark
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Old Dec 02, 2011, 12:48 AM
Gravity sucks
jedas's Avatar
Kaunas, Lithuania
Joined Sep 2009
92 Posts
Quote:
Originally Posted by Vantasstic View Post

Lastly, I did try installing a variable resistor in series with the Video In line. All I got was a lighter or darker overall picture...no improvements on the text quality.

Again, I'll post some comparison pictures of the bordered text this weekend.
I'm glad that you took these tests further. After last mod , I've added resistor at the input of the DOSD (as Daniel advised), and it helped to make letters to become slightly more white, while black level seemed be stay the same, which is prefered. I don't remember exact value, but I've found it with potentiometer.
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Old Dec 02, 2011, 02:14 AM
Just clumsy. Oh, forgetful too
MikeTheCrash's Avatar
undefined
Joined Jun 2008
3,198 Posts
I'm pretty sure Daniel put something in the firmware that would right the plane, as he challenged us to try it out some time back
check out this video from 3:56

Some Dragon OSD features (5 min 3 sec)


I suppose most planes won't stay inverted without a lot of down elevator anyway.
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Last edited by MikeTheCrash; Dec 02, 2011 at 02:34 AM.
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Old Dec 02, 2011, 12:58 PM
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El_Nono's Avatar
Buenos Aires
Joined Jun 2008
39 Posts
Hello Jmstech

Quote:
Originally Posted by JMSTECH View Post
Hello El Nono,

Have you tested this by getting into your OSD via this method: http://www.forum.tsebi.com/viewtopic.php?f=7&t=67

John
That method is for recording the program. I would not like to risk the integrity of my dosd with a test.

it would be possible to be tried of another way?

Tanks

El Nono
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Old Dec 02, 2011, 01:05 PM
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squishy654's Avatar
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502 Posts
Quote:
Originally Posted by Vantasstic View Post
The stock DOSD + GPS module don't know bank angle, right side up, up side down, etc. It only sees heading changes and rate of climb/dive from the GPS information (and baro sensor if you have one). You'd need an IMU for the DOSD to get bank angle information. If you have enough altitude the DOSD would likely get itself righted and come home, but it likely need some time for things to 'correct' themselves back to normal flight. Most FPV planes are 'stable' and want to fly upright...given enough time (altitude) to do so from an odd flight parameter. If you have a really unstable plane then an IMU might become a NECESSITY vs a Nicety.
This is what I was thinking, with enough time it would right itself...
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Old Dec 02, 2011, 02:43 PM
Kiwi in Germany
whakahere's Avatar
Germany
Joined Jun 2010
2,255 Posts
I am about to wire up my wing with DOSD. I am trying to cut down on the wire mess and this is my wire plan. I need some advice before I go ahead and start cutting cable. Does everything look in the right place? I am mainly concerned about the LC filter and how I have sorted out the grounds.

Does the ubec need to be after the LC filter or is it fine how I have drawn it?

Do I need a ground going from the RX to the PPM ground? Is it okay that I removed the ground from the ubec

Do I need a ground from the dosd to the video and cam .. or is the ground from the LC filter ok?

Do I just need the signal wire for the throttle on the osd correct?

Does anyone know if a 3A ubec will be enough to power everything .. servos are hitech hs 645mg
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Old Dec 02, 2011, 08:57 PM
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Joined Dec 2008
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My dragon OSD isn't RTH. It just circles over the spot the RTH is switched on?

Any one got any idea of what causes this problem
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Old Dec 02, 2011, 09:00 PM
Just trying to get a nut.
scrtsqrl's Avatar
United States, VA, McLean
Joined Oct 2006
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Quote:
Originally Posted by cody069 View Post
My dragon OSD isn't RTH. It just circles over the spot the RTH is switched on?

Any one got any idea of what causes this problem
Your plane is probably out of trim. Before fiddling with AP, fiirst try setting up your plane such that it will fly relatively hands off with neutral sticks, all servos centered.
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Old Dec 02, 2011, 09:03 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
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Quote:
Originally Posted by cody069 View Post
My dragon OSD isn't RTH. It just circles over the spot the RTH is switched on?

Any one got any idea of what causes this problem
#1. Make sure the HOME is set before flying.
#2. Make sure you waypoint mode is set to NEXT.
You may have your waypoint mode set to HOLD in which case it'll hover over the set hold position vs it HOME position.
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Old Dec 02, 2011, 09:04 PM
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Plane flys fine..Straight, just when the RTH is engaged it circles

Home is set and it's on Next..

Will double check all the settings and confirm that's it is all good
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Last edited by cody069; Dec 02, 2011 at 09:09 PM.
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Old Dec 02, 2011, 10:06 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
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Quote:
Originally Posted by cody069 View Post
Plane flys fine..Straight, just when the RTH is engaged it circles

Home is set and it's on Next..

Will double check all the settings and confirm that's it is all good
I don't ever recall hearing behavior before. Could you take some pictures of the different screen shots...maybe we can find something that looks 'off'.
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Old Dec 03, 2011, 08:44 AM
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cody069,

Make sure you have sufficient forward speed - if it's too windy such that it's actually flying backwards, the GPS gets confused and hence the autopilot gets confused. The other thing you want to do is to make sure that your aileron directions (or rudder depending on what you are using). You can do this using the surface direction test mode.

Daniel
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Old Dec 03, 2011, 02:04 PM
Kiwi in Germany
whakahere's Avatar
Germany
Joined Jun 2010
2,255 Posts
Quote:
Originally Posted by whakahere View Post
I am about to wire up my wing with DOSD. I am trying to cut down on the wire mess and this is my wire plan. I need some advice before I go ahead and start cutting cable. Does everything look in the right place? I am mainly concerned about the LC filter and how I have sorted out the grounds.

Does the ubec need to be after the LC filter or is it fine how I have drawn it?

Do I need a ground going from the RX to the PPM ground? Is it okay that I removed the ground from the ubec

Do I need a ground from the dosd to the video and cam .. or is the ground from the LC filter ok?

Do I just need the signal wire for the throttle on the osd correct?

Does anyone know if a 3A ubec will be enough to power everything .. servos are hitech hs 645mg
anyone with some advice if I am heading in the right direction? Will this work?
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Old Dec 03, 2011, 04:45 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
17,949 Posts
Quote:
Originally Posted by whakahere View Post
anyone with some advice if I am heading in the right direction? Will this work?
Just so you don't feel ignored..
1. I never used a LC filter on my setup...can't provide experienced advice. How you have it is how I'd do it...well, sorta. I'm using a separate LiPo for the video/camera system so have not power interactions with the main battery.
2. Yes you need a ground. It doesn't have to run back through the video gnd AS LONG AS the ground used ties all the other grounds together. You need a 'reference' point for the electronics to work properly. As long as all the gnds tie together you should be fine.
3. Yes, just signal from DOSD (or Rx) to the ESC is all that's needed.
4. How many servos are you talking about? Rule of thumb I've read is to plan on 1A per servo with 1.5A for digital servos. A 3A UBEC should be plenty save for a 3 servo setup...even fine for 4 servos. Me personally, I'm using a 5A UBEC with...5 analog servos (rudder, elevator, 2xAilerons, Pan). I'm thinking of adding flaps and would feel safe using the same UBEC.
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