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Vitamin J
Aug 16, 2006

God, just tell me to shut up already. I have a clear anti-domestic bias and a lack of facts.


I remember dreaming about FPV RC flight while walking to elementary school. It may have taken awhile, but I finally got in the air!

I've had a few of the Blade series of helis starting with the MCX, then MSR, and now the 120 SR. They are durable and parts are cheap and they don't fly half bad either.

Here is my 120 SR set up for FPV flying. I split a 7.4v 900mah lipo pack to get two 3.7v 900mah flight packs and they let me fly for about 10 mins each.



I've modified the 120 a bit to make it more stable and more powerful. I've extended the tailboom by a few cm and used a solid carbon rod for increased stiffness over the hollow stock boom and also added a horizontal stabilizer. I glued some carbon rod into the flybar to stiffen it up and make it more precise. I've also replaced the motor and battery wires with bigger gauge, eliminated the connectors to the motor, and replaced the JST battery connectors with micro-deans for less resistance. I'm also using a DX6i controller.



I made a balsa frame to hold the video gear. I'm using a KX-1 micro camera along with a 200mw 5.8ghz vtx and a micro-microphone all from fpvhobby.com (they're located in Turkey so shipping takes awhile but it's totally worth it as they have the best 5.8ghz gear; built in filters and voltage regulators). I want to eventually run the video off the flight pack, but it will need a filter cuz I get interference when running the motor, a stock MSR lipo runs the vtx and camera.

IMO this is the cheapest route to get into FPV heli flying, although by far not the most stable. I am anxiously awaiting a 120 sized CP heli from Blade.

Here is my first video which shows my ground station setup and some funny crashes:
https://www.youtube.com/watch?v=cukkPQEGOgw

And here is my 2nd which is much better I think, it involves lots of fast forward flight, dives, and turns....and a goose:
https://www.youtube.com/watch?v=ieteE1doS-s

Here's another, it features really high altitude flying and flying through trees. Also features my flybar breaking a few hundred feet up!
https://www.youtube.com/watch?v=8DotKbtJVPk


Here's my latest video. Flying over (and in) a lake!
https://www.youtube.com/watch?v=RHi3MEM6jHw


You guys should check out https://fpvlab.com/forums/forum.php, it is a new site that is run by people who love to FPV. It's not stuck in some back corner of another site or plagued by terrible old people drama (rcgroups anyone?) and it's growing and growing.

Vitamin J fucked around with this message at 19:36 on May 16, 2011

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helno
Jun 19, 2003
hmm now were did I leave that plane

DeNofa posted:

I know I'm taking a risk here, which thankfully is a fairly inexpensive risk The local HF has the replacement wing sets on clearance for $3, so if I have fun this weekend I'll be sure to pick up a few. Worst case scenario: I pull a "what do you mean I can't return it, I just bought it!" Best case scenario: I love it, return it, and buy the one you suggested Thanks again for the advice, I'll be sure to keep an eye on this thread and hopefully be able to contribute more-so in the future.

Those differential thrust airplanes are pretty tough to fly well so don't be discouraged by it. Getting into R/C takes a bit of capital investment what with radio and battery charging gear but if you stick to the lightweight foamy end of the R/C spectrum it is a pretty cheap hobby once you get going.

I am about to drop the hammer on a CNC router for making foam aircraft and balsa wing ribs. It does feel a bit odd paying nearly $1500 to get a tool to make $5 airplanes.
http://www.phlatboyz.com/Phlatprinter-3-Kit_p_9.html

DeNofa
Aug 25, 2009

WILL AMOUNT TO NOTHING IN LIFE.

helno posted:

Those differential thrust airplanes are pretty tough to fly well so don't be discouraged by it. Getting into R/C takes a bit of capital investment what with radio and battery charging gear but if you stick to the lightweight foamy end of the R/C spectrum it is a pretty cheap hobby once you get going.

I am about to drop the hammer on a CNC router for making foam aircraft and balsa wing ribs. It does feel a bit odd paying nearly $1500 to get a tool to make $5 airplanes.
http://www.phlatboyz.com/Phlatprinter-3-Kit_p_9.html

Yeah, hopefully I'll get out tomorrow after the gym and love it. Unfortunately it might be a little windy, but it's going to be raining for the next week (Upstate NY) and I'm antsy.

Giblet Plus!
Sep 14, 2004


I'm thinking of building a clancy aviation lazy bee from scratch, and powering it with a brushless outrunner. I found the plans online and I'm going to print them out on the plotter at work.

When I was a kid I built a herr engineering cub and had crazy fun flying it, crashing it, and rebuilding it. I always wanted a lazy bee but i never had time to build another plane.

elektroboot
Nov 7, 2004



jagdtiger00 posted:

7. gently caress this kid- http://www.youtube.com/watch?v=JHJs...feature=related

jesus loving what

That level of wankery aside though, I keep seeing helicopters flying inverted, how is that possible? I understand that higher end helis allow you to change rotor blade pitch, but can they actually be reversed? It looks like the kid was twisting his control sticks to adjust something, is that the rotor pitch?

I've kind of just recently discovered how cheap this stuff has gotten, and it is awesome. It's like all of my childhood dreams are coming true for a couple hundred dollars.

Since there was some talk of ethics in here, should I feel bad about attempting to mount the innards of an airsoft gun in an RC plane? I have to admit the thought of FPV dogfights make me more than a little giddy...

IsaacNewton
Jun 18, 2005



Schottingham posted:


That level of wankery aside though, I keep seeing helicopters flying inverted, how is that possible? I understand that higher end helis allow you to change rotor blade pitch, but can they actually be reversed? It looks like the kid was twisting his control sticks to adjust something, is that the rotor pitch?


The 'higher end' helis you are speaking of are collective pitch helicopter.

http://www.rcheliwiki.com/Collective_pitch

helno
Jun 19, 2003
hmm now were did I leave that plane

The left hand stick controls rotor pitch/throttle. Most helis have mixing between the throttle and pitch and in some modes the throttle is kept high and the stick controls the pitch so if the stick is centered pitch is neutral, if you move it up the pitch increases and if you move it down pitch goes negative.

2ndclasscitizen
Jan 2, 2009

by Y Kant Ozma Post


So I've changed my mind. I no longer care about learning to fly R/C for video.

I want to fly to R/C to kill.

http://www.youtube.com/watch?v=bZCH1492CzA

Giblet Plus!
Sep 14, 2004


Giblet Plus! posted:

I'm thinking of building a clancy aviation lazy bee from scratch, and powering it with a brushless outrunner. I found the plans online and I'm going to print them out on the plotter at work.

When I was a kid I built a herr engineering cub and had crazy fun flying it, crashing it, and rebuilding it. I always wanted a lazy bee but i never had time to build another plane.

here we go:

flick3r
Apr 22, 2011


Schottingham posted:


Since there was some talk of ethics in here, should I feel bad about attempting to mount the innards of an airsoft gun in an RC plane? I have to admit the thought of FPV dogfights make me more than a little giddy...

Pretty much I've been thinking the same thing, but instead of airsoft using real BB's. I did some research and then started thinking about drilling out an aluminum tube, mounting it to the sides of the helicopters like real military heli's, and putting bottle rockets in the tubes with some form of igniter attached to the fuses in the back.. I did some research and there are actually people that battle little remote control warships from WW2 and WW1 in lakes... They do not use BB's or Airsoft pellets, they use bigger ball bearings for shot. (dang.)

Manny
Jun 14, 2001

Like fruitcake!

Giblet Plus! posted:

here we go:



I remember ARTF variants of this being really gentle and lovely to fly - should be a nice summer plane!

flick3r posted:

Pretty much I've been thinking the same thing, but instead of airsoft using real BB's. I did some research and then started thinking about drilling out an aluminum tube, mounting it to the sides of the helicopters like real military heli's, and putting bottle rockets in the tubes with some form of igniter attached to the fuses in the back.. I did some research and there are actually people that battle little remote control warships from WW2 and WW1 in lakes... They do not use BB's or Airsoft pellets, they use bigger ball bearings for shot. (dang.)

A while ago a company made something called a sonic combat module and you could plug it into a special port for their planes and allowed you to have combat sessions. I think if you hunt around you can see mods to enable it to work with any plane - not as exciting as real projectiles I know but an option.

flick3r
Apr 22, 2011


Manny posted:

I remember ARTF variants of this being really gentle and lovely to fly - should be a nice summer plane!


A while ago a company made something called a sonic combat module and you could plug it into a special port for their planes and allowed you to have combat sessions. I think if you hunt around you can see mods to enable it to work with any plane - not as exciting as real projectiles I know but an option.

Thanks Manny, I've heard about those I think but I will do some more research. When I start anything I'll make sure to post pics and info like this thread.

helno
Jun 19, 2003
hmm now were did I leave that plane

There is a whole class of planes dedicated to combat. They don't bother with pussy sonic modules they just try to knock each other out of the sky.

elektroboot
Nov 7, 2004



I had some circuit boards printed for the airsoft trigger circuits, but just before they arrived, I crashed both of my jets pretty much beyond repair. They were just foamies so it's not a big deal, but now I won't have anything to fly the gun on for a while Because of the weight I'm not sure I could fly metal BBs, but I'm sure they'd have more energy downrange than plastic. Since I'm not really familiar with airsoft, does anyone know if there are magazines more reliable than gravity feed that have a fairly high capacity? Do they make spring loaded helical ones?

I had considered rockets too, but I think without any sort of guidance, all I would accomplish is starting brush fires in unpredictable locations. Just for the hell of it, I even put some thought into what it would take to build a guided missile--I figure you'd have to track acoustically, meaning a microprocessor, multiple microphones, power source and tiny servos... a major engineering project on its own. Would be loving awesome though, even if it just tracked and didn't explode.

Anyway on the less destructive side, I've got a bunch of ideas for autopilot systems using GPS, gyros, accelerometers and such. I'm thinking functions like automatically holding altitude/heading, flying between waypoints, circling a location, maybe surveying an area for girls with a downward-pointed camera. What would be especially cool is to combine all that stuff with an FPV on-screen display for pretty much a full instrument readout. I figure this has been done already, but like half the fun for me is designing and building it on my own.

Now that the semester's ending, I might finally have time to try some of this stuff.

helno
Jun 19, 2003
hmm now were did I leave that plane

Schottingham posted:

Anyway on the less destructive side, I've got a bunch of ideas for autopilot systems using GPS, gyros, accelerometers and such. I'm thinking functions like automatically holding altitude/heading, flying between waypoints, circling a location, maybe surveying an area for girls with a downward-pointed camera. What would be especially cool is to combine all that stuff with an FPV on-screen display for pretty much a full instrument readout. I figure this has been done already, but like half the fun for me is designing and building it on my own.

Before you run with this idea you might want to look into some of the off the shelf solutions that already have mature code and hardware.

http://diydrones.com is home to the ardupilot which seems to be a very good all around solution.

There are tons of autpilot hardware makers out there but alot of them are quite pricey and not much better than the ardupilot.

kafkasgoldfish
Jan 25, 2006

God is the sweat running down his back...

Schottingham posted:

Since I'm not really familiar with airsoft, does anyone know if there are magazines more reliable than gravity feed that have a fairly high capacity? Do they make spring loaded helical ones?

~100 round spring loaded magazines are really common/popular in airsoft. Unlike the higher capacity ones they don't require occasional (or any) winding. I'v never tried cutting one open so who knows if it's feasible to cut out the guts but it's probably just a spring loaded tube. You could probably condense the design a lot as they're usually designed to match the dimensions of M4/M16 rifles mags which is a lot larger than they need to be.

How much weight could you handle? Airsoft BB's are typically .2g each up to .28-.3g for the heavy stuff.

S w a y z e
Mar 19, 2007

f l a p



2ndclasscitizen posted:

So I've changed my mind. I no longer care about learning to fly R/C for video.

I want to fly to R/C to kill.

http://www.youtube.com/watch?v=bZCH1492CzA

This is the worst idea, for so many reasons...

flick3r
Apr 22, 2011


helno posted:

Before you run with this idea you might want to look into some of the off the shelf solutions that already have mature code and hardware.

http://diydrones.com is home to the ardupilot which seems to be a very good all around solution.

There are tons of autpilot hardware makers out there but alot of them are quite pricey and not much better than the ardupilot.

So much useful information on here was totally worth the 10$ to get access to. Some of the ideas on this thread if they were taken to full fruit would probably get the attention of some DoD guys or something I'm sure.. Anyway responding more to what has been said The aircraft wouldnt need to hold many bb's, just like the original fighters planes they had a shot cap, doesn't need to shoot a million bb's a second so I was thinking it would only need maybe 100 or some modest amount at least to start. As for the bottle rocket missile launcher things, it wasn't really so much for use as it was a cool idea that I kicked around and drew some plans out, like Schottingham said the fun is in designing and building it yourself. Even if I shoot just one bottle rocket at a concrete wall and it works successfully it would be so cool to actually have accomplished it. It will be interesting to see at least.

elektroboot
Nov 7, 2004



Reliable feeding is definitely a priority over high capacity, so if 100 rounds is all I get, it'll have to do. Older planes did have unguided rockets (as do modern helicopters, which someone mentioned), so it's not that far-fetched.

I just had another idea: what if you could integrate a gun sight into an on-screen display? One that would compensate for target lead time and gravity based on your own speed and orientation, and possibly with a convergence setting if you have multiple guns. Screw historical accuracy, I think that would rule (though to be fair you can't really have tracer BBs unless you get glow in the dark ones, and fight at night)

Vitamin J
Aug 16, 2006

God, just tell me to shut up already. I have a clear anti-domestic bias and a lack of facts.


Less childish fantasies, more flying!

https://www.youtube.com/watch?v=NaFH9ia6rec

elektroboot
Nov 7, 2004



What is RC for if not acting out my childish fantasies?

Okay, so I consider myself a decent EE, but RF consistently blows my loving mind. I was reading a bit about that skew-plane wheel antenna--is it omni in a sphere pattern or just a hemisphere? My FPV gear just came in, and I'm going to be mounting it on an airplane rather than a helicopter, so if I could still do loops and barrel rolls and stuff without losing reception, that would be rad. What exactly is the benefit of that over a straight antenna?

Vitamin J
Aug 16, 2006

God, just tell me to shut up already. I have a clear anti-domestic bias and a lack of facts.


I guess you got me there.

It's Omni, it's pattern is like a donut. I don't really know much about it except for it's the poo poo. It blows away the 2db rubber ducky that came with the stock kit. Better range, better picture quality, and better behind objects. With a cloverleaf circular polarized antenna on the vtx it's supposed to be unbeatable and really wake up 2.4ghz and 5.8ghz. This is just for short-medium range though, I don't know anything about long range antennas.

With circularly polarized antennas like the SPW and CL you can flip, roll, turn, whatever and it doesn't matter.

Check out:
http://videoaerialsystems.com/produ...itter-antennas/

It's run by a guy named Alex who's a genius and flying further with less tx power.

flick3r
Apr 22, 2011


Schottingham posted:

Reliable feeding is definitely a priority over high capacity, so if 100 rounds is all I get, it'll have to do. Older planes did have unguided rockets (as do modern helicopters, which someone mentioned), so it's not that far-fetched.

I just had another idea: what if you could integrate a gun sight into an on-screen display? One that would compensate for target lead time and gravity based on your own speed and orientation, and possibly with a convergence setting if you have multiple guns. Screw historical accuracy, I think that would rule (though to be fair you can't really have tracer BBs unless you get glow in the dark ones, and fight at night)

It's not and I know it's possible with current technology, there are drones flying around killing people with real bullets, so why can't we make a mini version that just fires a couple of BBs?!

If you wanted to get that far into it ( I have thought about that as well) the size and scale of the package would be (I think) A bit too large to pack onto a small RC. But would be a better size package to pack on a small to mid size robot chasis (Are there any robotics threads in this forum? I tried to search, but this is all I could find) If you're going to go that far into development, I think you'd have to custom make your own RC, which then you could build to your specific payload package then you could store however many shots you wanted.



Schottingham posted:

What is RC for if not acting out my childish fantasies?

Okay, so I consider myself a decent EE, but RF consistently blows my loving mind. I was reading a bit about that skew-plane wheel antenna--is it omni in a sphere pattern or just a hemisphere? My FPV gear just came in, and I'm going to be mounting it on an airplane rather than a helicopter, so if I could still do loops and barrel rolls and stuff without losing reception, that would be rad. What exactly is the benefit of that over a straight antenna?

Haha true, or it could be a catalyst for DIY amature development!

elektroboot
Nov 7, 2004



This RF stuff is finally starting to make a bit more sense, thanks for that link Vitamin J. This video helped a lot, too (holy poo poo that guy is a CAD wizard).

Just for the hell of it, I decided to try my hand at making a couple of these antennas:

Skew-plane wheel at 2.4 GHz - With this on my 1W transmitter and an 11dBi rubber duck on the receiver, I got out to about 300m in my apartment complex, which is full of trees and hills and wifi. At some point I'll test it at the field where there will be less of all of those.


5-turn helical at 2.4 GHz (work in progress) - was reading about antenna trackers, and now I have this compulsion to build one.


Speaking of transmitters, does anyone know anything about this transmitter from hobbyking? Given the channels in the "tx spec" section, I'm worried some channels might be outside the 2.4G band, and I don't want any black trucks pulling up at my field...


flick3r posted:

the size and scale of the package would be (I think) A bit too large to pack onto a small RC. But would be a better size package to pack on a small to mid size robot chasis

But the point is for it to fly! I may have forgotten to mention that I'm talking about taking the guts out of an airsoft gun, not mounting a whole gun on the plane. The motor + gearbox I have weighs only 130g, and the barrel is a thin aluminum tube which could probably be cut down. Getting everything to fit together without the full gun housing might require some custom parts, so I'm looking into that as well. I'm willing to bet the whole thing would fly on a larger parkflyer without much trouble, maybe at the cost of a smaller battery.

But yeah, if modifying a stock plane doesn't work so well, I could definitely look into making a custom airframe. Is it possible to buy big solid blocks of EPS/EPO/some other kind of foam that I could cut?

flick3r
Apr 22, 2011


Schottingham posted:

But the point is for it to fly! I may have forgotten to mention that I'm talking about taking the guts out of an airsoft gun, not mounting a whole gun on the plane. The motor + gearbox I have weighs only 130g, and the barrel is a thin aluminum tube which could probably be cut down. Getting everything to fit together without the full gun housing might require some custom parts, so I'm looking into that as well. I'm willing to bet the whole thing would fly on a larger parkflyer without much trouble, maybe at the cost of a smaller battery.

But yeah, if modifying a stock plane doesn't work so well, I could definitely look into making a custom airframe. Is it possible to buy big solid blocks of EPS/EPO/some other kind of foam that I could cut?

Ok ok ok, true. True true. You didn't forget to mention, I had the same idea! Of course you'd take the gun apart and just use the necessary parts to keep the basic function in tact(Though cutting down the barrel might be necessary as well, but wouldn't hinder the operation too much) But the targeting program is more of what I was talking about when figuring in the heavier part of the package. I don't exactly know how much more gear you'd need to put on the airplane to allow for all of that, but I know it would be considerably more than just the gun part. (Not saying it's not a badass idea that I'd love to try too) Just saying it's more complex and heavier for a small plane to handle once packed with the guns/missiles? If you do take some steps in this direction I'm sure most of us on here would love to see your progress.

Helldesk
Jan 6, 2007

Hands of my ~*Space Waifu*~ planet-huggers! *tips space-fedora*

Schottingham posted:

Speaking of transmitters, does anyone know anything about this transmitter from hobbyking? Given the channels in the "tx spec" section, I'm worried some channels might be outside the 2.4G band, and I don't want any black trucks pulling up at my field...

With 1000 mW (a whole freaking watt!) of radiated power from that puppy you probably need a license anyway. Unlicensed ISM band use is limited to 100 mW EIRP in most countries (but just 10 mW in the UK, for example). Check your country's regulations before operating such hardware.

elektroboot
Nov 7, 2004



flick3r posted:

But the targeting program is more of what I was talking about when figuring in the heavier part of the package. I don't exactly know how much more gear you'd need to put on the airplane to allow for all of that, but I know it would be considerably more than just the gun part.

The microprocessor and accelerometer breakout that I was planning to use are really tiny--I just measured 7 grams combined--and can run on the plane's main battery. From what I've read, I might need another processor entirely dedicated to generating the OSD signal, maybe a gyro or two as well, but in general I'm considering that stuff to be negligible compared to the gun and FPV weight. And while it might be an interesting additional step to take, I wasn't planning to put the gun on a pan/tilt mount or anything.


Helldesk posted:

With 1000 mW (a whole freaking watt!) of radiated power from that puppy you probably need a license anyway. Unlicensed ISM band use is limited to 100 mW EIRP in most countries (but just 10 mW in the UK, for example). Check your country's regulations before operating such hardware.

1 watt is a lot of RF power? I'm in the US, and most of the information I can find about the 2.4 GHz band pertains to wireless networking (obviously). I came across these tables in a few different places, but I'm not sure I understand the difference between "point to multipoint" and "point to point". Either way, it looks like I'm okay up to 4 watts radiated isotropically; help me out if I'm misunderstanding that.

Also, is it really that as bad as I'm hearing to operate both your control and FPV systems in the same frequency band? It seems like as long as they're in different channels it should be fine--they work simultaneously for me at close range, but I guess I could see the out-of-channel noise being a problem if your control signal is already weak at some distance.

Helldesk
Jan 6, 2007

Hands of my ~*Space Waifu*~ planet-huggers! *tips space-fedora*

Schottingham posted:

1 watt is a lot of RF power? I'm in the US, and most of the information I can find about the 2.4 GHz band pertains to wireless networking (obviously). I came across these tables in a few different places, but I'm not sure I understand the difference between "point to multipoint" and "point to point". Either way, it looks like I'm okay up to 4 watts radiated isotropically; help me out if I'm misunderstanding that.
For unlicensed use it is. Sure, I have no idea about US regulations, so if 4 watts is A-OK then more power to you! I can only dream of having the options you guys have, since over here pretty much everything new gets jammed into the 2.4 GHz band. Thankfully at least 802.11n is getting some breathing room with 5GHz. If I wanted to use a live video link, I would probably have to consider moving the radio control from 2.4 GHz to 35 MHz. 900 MHz for video is off limits here, for example.

Of course radio amateurs everywhere have totally different rules, so if I went ahead and got a ham licence, it would open up plenty of options.

Schottingham posted:

Also, is it really that as bad as I'm hearing to operate both your control and FPV systems in the same frequency band? It seems like as long as they're in different channels it should be fine--they work simultaneously for me at close range, but I guess I could see the out-of-channel noise being a problem if your control signal is already weak at some distance.

Yeah, I've heard the same. I haven't tested it in practice, but if you could be absolutely sure your FPV Tx stays clear of the R/C channels it would work. In practice though, when you look at the the spectrum it isn't as clean as in theory, and even a little out-of-channel leakage from your video Tx system right next to the R/C Rx antenna would drown out your (relatively puny) signal from the R/C Tx in the distance. And especially if your FPV or R/C equipment, or both, do frequency hopping all over the 2.4 GHz band, it just might guarantee you get interference some of the time.

I'm still going to go ahead and test if I could luck out and find some stuff that works together. For example I can try and set the 802.15.4 2.4GHz Zigbee radio for telemetry to use channels 15, 20, 25, and 26 that my RC perhaps isn't using. (Or at least try and not use the most crowded 802.11 channels, like 1, 6, and 11.)

Helldesk fucked around with this message at 22:01 on May 9, 2011

elektroboot
Nov 7, 2004



So I may have misunderstood something about servo control signals--I had thought it was an analog voltage, just based on my multimeter, but I've read a couple of places that it's actually PWM, is that right? Is there a standard mapping between pulse width and servo position? Would it suffice just to throw an RC filter on that line to turn it into an analog voltage? Even so, the voltage is really low (a couple hundred millivolts) and is below the dropout voltage of the op amp I had planned to use; I may have to buy some rail-to-rail op amps to make the gun trigger work.

In the meantime, a couple things I feel like sharing for no good reason:

I got this pan/tilt mount in from servocity.com which seems pretty solid, but standard servos are waaay larger than I expected. I don't know if I'll be able to fly it on either of my planes at the moment due to the weight. Anyway this was my first order with them and I just want to say what a great company - not only did they give me better servos than I ordered for free, they sent candy in the package too


And I found that I had the parts laying around to give my little AT-6 some navigation lights (the diffusers are nylon bolts and nuts), which may or may not help me keep from losing track of the plane's orientation at a distance - probably the biggest cause of crashes for me so far. At the very least it'll look neat when I fly at dusk.


Edit: Also some old HAM dude was telling me that RF can damage your eyes at a certain power level, even if it's not ionizing radiation. Is this guy loving crazy or should I actually be careful? I was under the impression that unless the radiation is ionizing, the only danger is from heat.

ante
Apr 9, 2005

No... Not without incident.

Schottingham posted:

So I may have misunderstood something about servo control signals--I had thought it was an analog voltage, just based on my multimeter, but I've read a couple of places that it's actually PWM, is that right? Is there a standard mapping between pulse width and servo position? Would it suffice just to throw an RC filter on that line to turn it into an analog voltage? Even so, the voltage is really low (a couple hundred millivolts) and is below the dropout voltage of the op amp I had planned to use; I may have to buy some rail-to-rail op amps to make the gun trigger work.

Servos are just DC motors with negative feedback to make the motor go to a certain position as fast as possible with critical damping (as little slow-down or overshoot as possible). Basically the motor feeds positional and velocity feedback into its input, and you don't want to mess with that if you don't know what you're doing. The term PWM doesn't apply here.

edit: PWM can be used with a filter to make a DAC, so that might have been what the guy was talking about


quote:

Edit: Also some old HAM dude was telling me that RF can damage your eyes at a certain power level, even if it's not ionizing radiation. Is this guy loving crazy or should I actually be careful? I was under the impression that unless the radiation is ionizing, the only danger is from heat.

RF with enough power is literally a microwave oven. Your eyes tend to cook first. If you're using power levels that don't require a license, you really don't have anything to worry about.

elektroboot
Nov 7, 2004



ante posted:

Servos are just DC motors with negative feedback to make the motor go to a certain position as fast as possible with critical damping (as little slow-down or overshoot as possible). Basically the motor feeds positional and velocity feedback into its input, and you don't want to mess with that if you don't know what you're doing. The term PWM doesn't apply here.

I didn't mean the feedback internal to the servo, I'm pretty familiar with how that works. I mean the position command sent from the receiver. This page for example describes a pulse width of 1500us representing neutral, while 600us is -90 and 2400us is +90. Is something like that fairly standard?

ante
Apr 9, 2005

No... Not without incident.

Schottingham posted:

I didn't mean the feedback internal to the servo, I'm pretty familiar with how that works. I mean the position command sent from the receiver. This page for example describes a pulse width of 1500us representing neutral, while 600us is -90 and 2400us is +90. Is something like that fairly standard?

Oh, sorry.

So no, a smoothing filter won't work because it takes a digital signal, not an analog one, yes that's common, and I don't understand quite how you're doing this, from reading your post history.

Are you making an antenna to send a separate signal to your own plane-mounted gun to actuate a servo that physically pulls a nerf gun's trigger?

elektroboot
Nov 7, 2004



Ah, no, I'm sort of doing multiple things at once here. The antenna is for the FPV feed and has nothing to do with control.

I'm sure I haven't been clear about it; I have a bad habit of doing things first and trying to document them later. What I've got is the gearbox and DC motor from an automatic airsoft rifle, and my plan was to hijack a spare tx/rx channel to send the on/off command to a power MOSFET to drive the motor.

On the transmitter end, I'd wire up a momentary button and some resistors to send one of two position commands (doesn't really matter which, but they should be well separated) to represent "fire gun" or "don't fire". On the receiving end, I've built a circuit to try to interpret the signal on that channel, originally intended for a servo, and turn it into the gate drive signal for the FET. I'm not trying to PWM that transistor or anything, solid on/off is fine, but I think I've misunderstood what the signal coming off of my receiver looks like. I designed the circuit for an analog voltage, I think 150-300mV, but it looks like it's a variable-width digital pulse instead.

I've opened up a couple of analog servos and I think they just lowpass filter that signal before feeding it to the controller IC for the position command, but I might be wrong. Digital servos would measure the width of the pulse directly, I guess? That would certainly make them more noise immune.


Edit: Okay I was lazy before but I finally just scoped it - my receiver puts out a 3.6v digital signal at 45.5 Hz, with pulse widths varying from about 1-2ms. RC lowpass should do what I want it to.

elektroboot fucked around with this message at 06:46 on May 13, 2011

helno
Jun 19, 2003
hmm now were did I leave that plane

If you really want to just activate a switch via a reciever channel use one of these. http://www.hobbyking.com/hobbyking/...?idProduct=8833

Here is a great description of how the PPM used to drive servos works. http://www.brookshiresoftware.com/r...servos_work.htm

IsaacNewton
Jun 18, 2005



Finally fixed my 450, ended up being a lovely motor. (Don't build an heli with the Mystery motors.. It's crap.) The shaft was bent from what I assume to be the beginning since it always did that.

Welp so my 450 pro clone flies like heaven, my 450 SE V2 doesn't fly nearly as well but the servos on it aren't very good either.

Problem is.. I have the urge to build a cheap 500 clone. Someone stop me.

Snapshot
Oct 21, 2004

damnit Matt get in the boat

Schottingham posted:

Edit: Also some old HAM dude was telling me that RF can damage your eyes at a certain power level, even if it's not ionizing radiation. Is this guy loving crazy or should I actually be careful? I was under the impression that unless the radiation is ionizing, the only danger is from heat.

Yeah, however, the "sweet spot" for EM radiation absorption is near 400 MHz. You're well above it if you're working in the 2.4 GHz range. However, your duty cycle is much higher than the usual ham's. If you want a little more info, here's the US ham society's info on RF safety. I'll explain more later if you like, but my battery's toast.
EDIT: I forgot the bloody link: http://www.arrl.org/rf-radiation-an...ic-field-safety

Snapshot fucked around with this message at 19:08 on May 16, 2011

helno
Jun 19, 2003
hmm now were did I leave that plane

http://vimeo.com/22280110

I just got my KKmulticopter board today and this video makes me glad I ordered it. I am still waiting on my phlatprinter so I have a few weeks to design the frame.

elektroboot
Nov 7, 2004



helno posted:

http://vimeo.com/22280110

I just got my KKmulticopter board today and this video makes me glad I ordered it. I am still waiting on my phlatprinter so I have a few weeks to design the frame.


Man, that's pretty rad. What is the kk board, some kind of controller for stability? Is it even possible to fly a quadcopter without a controller like that?

helno
Jun 19, 2003
hmm now were did I leave that plane

The KK board is a combined mixer/stabilizer. Before these boards people would use a bunch of Vtail mixers and gyros but that is a pain to setup. These boards also have handy features like arming the ESC's which can be difficult without one.

I flew my Grifter glider the other day. 3.2m wingspan so it is the biggest model that I have ever flown. Very graceful in the air but it flys way faster than it looks.

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phpro
Jun 22, 2010


My long running Aeroquad project made it's first flight a few days ago.. Today, I was dropping stuff at altitude with an improvised quick release.

One thing I am having issues with is vibration, not really sure what to do about it other than balancing the props...

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