• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

RC Plane, Autopilot Type Stabilizing Circuit

Status
Not open for further replies.

kirby89

New Member
I would like to create a stabilizing circuit for RC. Something comparable to the FMA Copilot that wouldn't depend on infrared signatures to track the sky. My thought is to use a board of reed switches 1 each to detect a tilt in the 4 basic directions. I've only read a brief summary of reeds. The book suggested that they are sequential level-sensors w/ as many as 4 switches. Can someone give me the lowdown on reeds? Has anyone else attempted to build this type of project?
Not sure how to mix inputs if the plane tilts in an odd direction where both the tail-tilt & left-wing-tilt reeds (for ex.) are triggered. That would engage both the rudder, aileron, & perhaps even the engine if tilt is a far nose-down move. Only want circuit to engage when radio controls go to neutral. I believe a reverse logic circuit that would register high when radio inputs go low would be adequate.
Would I need some type of EEPROM to
control this circuit? What I am missing here?
Thanks for the help. :D
 

kinjalgp

Active Member
If you use a simple logic circuit / flash microcontroller then you won't need any EPROMs.
 

lavenatti

Member
I don't think you are going to have much luck using reed switches to detect tilt. You may be thinking of mercury tilt switches.

What you are really going to need is a gyro and an accelerometer to stabilize a plane.
 

kirby89

New Member
Yeah, I took a second look at another book on robotics & found that reed switches were not what I was lead to believe originally. Boy do I feel stupid. I must ask what is an accelerarometer? Did I spell that right? I expect that when the plane accelerates it would actuate the tail-down mercury switch.
Thanks
John
 

tansis

New Member
Acclerometers are a bit of an overkill for an small R/C plane unless you plan to scale it a up a bit, that and they are expensive.
Sometimes the simplest solution is a switch , you were half right in that respect. What you are missing is a fixed reference to operate from.
A simple gyroscope mounted on the end/ tip of a joystick switch/potentiometer (have i spelt that right? I allways write "pot" in my notes ) could provide some measure of position feedback.
But not much, only say +- 30` degrees Pitch/Roll.
 

kirby89

New Member
Gyroscope on a stick. Thats a great idea, thank you. I wonder what vendor would provide an inexpensive gyroscope that might work for this application.
Regarding mercury switches (not reed switches) I would say that a merc switch uses gravity to reference 0 degree attitude. What type of sensor does a manned aircraft use to indicate attitude?
 

tansis

New Member
A rather usefull source of powered gyroscopes is a common vcr. Find an old one and open it up , what your looking for is the actual head mechanism cant miss it ,bright shiny and round, spins easy with a push from finger, (if it dont spin chuck it back on the scrap pile)

As for mercury switches these are unlikey to work well because the effect of gravity as a reference can easily be overcome by forces due to acceleration. ( the old text book demonstration is swinging a bucket of water upside down over your head, do it quick enough and you stay dry)

The artificial horizon indicator (-v-) is gyro stabilised gimbal array.

Saying that though, gravity is the operating method for the "Turn and Bank" indicator in light aircraft and many model glider designs use pendulms to maintain some measure of stability.

A great deal hinges on just how big the airframe is.
 

MichaelBurton

New Member
Acclerometers..... COOL stuff.

Kirby,
I have been playing with Accelerometers and microprocessors.
If you have any programing experience you half way there. kinda.
message me if you want to persue this.
 

Eclipsed

New Member
Analog Devices have some excellent and pretty cheap(aroung $15) accelerometers such as ADXL202.The cool thing about accelerometers is they can measure static acceleration(Tilt).They are extremely small(around 5mm by 5mm), measure on more than one axis, and are available with PWM or analog outputs.I have used them as 3D tilt sensors on several projects. www.analog.com
 

spock

New Member
Hi,

I am thinking about designing a navigation system and I thought about accelerometers.

I would like to ask you something. I was always afraid of the drift of the accelerometers in time, because for getting the position you must integrate two times and that means that a small drift in the acceleration measure will produce a big error in position as time goes on. Did you
noticed that efect as important ?

And an other question, have you tried to create a complete coordinate sytem, with (x,y,z,pich,roll,jow) ??? how many accelerometers do you need ??


thanks a lot and sorry for so many questions, but I was always wandering how it was with the accelerometers and you are the first person I see that has used some.


david
ps.- these accelerometers from Analog, are they easy to buy or you must order some million pieces direct to Analog ??
 

ivancho

New Member
I have alwyas wanted to create something similar as is being said in this thread. I believe that a combination of a gyroscope and accelerometer will give you enough sensors being Pitch and Roll the most important movements to take care of.

There is a project by a group, they are doing a system for autonomous aerial vehicles for the hobbiest.http://autopilot.sourceforge.net/

Good Luck

Ivancho
 

Eclipsed

New Member
When used to measure static acceleration(with reference to gravity) time is a non-issue(gravity doesn't change with time).I have mostly used them for pitch and roll, to measure yaw, you can no longer reference to gravity, so dynamic acceleration must be measured and time will be an issue.I am still working on yaw(not absolute yaw, but deviation from last known yaw) control, it's seems a single axis accelerometer in the tail section of the craft is a cheaper option than a gyro.As far as a absolute coordinate positioning system X,Y,Z and yaw would be nearly impossible to measure via accelerometers(since no reference exists), GPS is probably the only option here or maybe a ground based reference of your own design(not practical).I have experience with GPS,if you have any questions.And analog sells quantities of 1-999 pieces right from their site.
 

tansis

New Member
XY coordinate position could be roughly determined on the cheap with a suitable cell phone service provider, accurate to about 50meters or so.
The accelerometers are almost certainly going to be connected to a micro-computer, that in turn is connected to the servo mechinism, bolting on a cellphone to handle external telemetry is worth looking at , who knows a small ccd camera as well perhaps.....

Now there's a thought what's the phone reception like around say
Groom Lake in Nevada ????
:wink:
 

Eclipsed

New Member
Are you talking about Assisted GPS, like in modern cell phones,so emergency services can located the user?
 

tansis

New Member
Basic tracking of a cell phones location has nothing to do with Global Positioning Systems / Satellites, it is done by the network as a function of its basic operation. The signal from your handset may be picked up by more than one reciever and the system has to find the best one to route your call through based on the strength of the radio signal.Better resolution can be achieved by sending a query/handshake to the handset and measuring the minute differences in time delay between different cell transmitters.
 

falleafd

New Member
Basic tracking of a cell phones location has nothing to do with Global Positioning Systems / Satellites, it is done by the network as a function of its basic operation. The signal from your handset may be picked up by more than one reciever and the system has to find the best one to route your call through based on the strength of the radio signal.Better resolution can be achieved by sending a query/handshake to the handset and measuring the minute differences in time delay between different cell transmitters.
What do you mean Tansis? A gyro is just an sensor to measure the direction both vertical and horizontal. It works with acceleration sensor. There are many types of gyro: mechanical gyro, electrical gyro, electronical gyro and even optical gyro.

Don't know what you mean!
 

dogdens_R

New Member
actually, has anyone tried to use gyros to try to remove small signal oscillations experienced by RC helicopters (windless conditions)?
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top