Marks256

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jpanhalt

Nice. What do you fly? John

Hank Fletcher

Lawn mowers?
http://www.youtube.com/watch?v=JdKUl...eature=related

Marks256

Thanks. I don't fly anything. I am going to use it to make random stuff remote control. My first project is a powerwheels electric car for 3 year olds. Then maybe something a bit bigger, like maybe a real car (if i can find one that both runs and moves) Next thing i will need will be a linear actuator for the breaks.

I would like to start flying model airplanes, though. I got a simple foam one for my birthday a few years back, but i crashed it (i totally forgot to put batteries in the remote ) and it never flew again...

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jpanhalt

You do have a nice set of hardware and at a good price.
You do realize it is PCM, not PPM, right? A lot of the PCM transmitters I know about can also do PPM. The difference is only important (for your uses), if you start to design receivers for it.

Also, the 72 MHz band is not approved for surface control. Probably the only risk that you run is if you go to some sort of sanctioned AMA event or similar (like organized RC clubs). You aren't going to go to jail for it; they just won't let you use it and may warn you. Almost all modern transmitters can be changed by simply getting a different frequency module for surface control.

Have fun.

John

Marks256

Yeah, i saw a list that shows frequencies and their uses. I think it was 75MHz that is for surface... Do you think the 8 channel can be changed easily? I am not worried about the 4 channel one, as that will just be used for random stuff, but the 8 will be used for some more important things (maybe some competitions if i make anything fun...)


Also, what do you think the range is (line of site, unobstructed).

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jpanhalt

You are getting a very good transmitter and receiver set. Most of the modern transmitters have a plug-in module on the back for the frequency band. You can even get a 2.4 GHz module for Futaba, so I don't think it will be a problem. I can't be sure, only because I don't own that model. Go to Tower Hobbies (towerhobbies.com), see if you can find your model, and download the manual for it.

Range is line of sight plus it will reach around reasonable obstructions for both 72 and 75 MHz. The GHz is strictly line of sight. In the air, range is at least a mile. On the ground it should be at least a few hundred yards, based on what we get with our range checks with the antenna removed. Range is definitely less on the ground, but I have no experience with surface radios to give you a better idea of what it should be.

John

Marks256

Ok. Thanks for answering some of my questions, John.

I have another question. The outputs on the receiver are for servos, but what if i wanted to simply say "on" or "off" (without hooking a servo up to a toggle switch), or what if i wanted to control something analog? Would i have to make something, or are there modules out there?


I just looked on tower hobbies. They don't have the Futuba T8UAF. I guess i will have to wait and see when i comes. I can't find the manual on google, either.

thanks

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jpanhalt

A simple on/off can be constructed from a microswitch with the servo arm actuating it. Most people I know have gone to electronic versions, however. Here are some references:

http://www.uoguelph.ca/~antoon/gadgets/rc-sw.htm
http://www.welwyn.demon.co.uk/rcsw/rcsw.htm

I have attached an image of the Guelph schematic. The Welwyn schematic is pdf and too big, but I have attached the explanation that downloads with it. It is really quite simple. You just set up your flip-flops to determine whether the pulse is longer or shorter than what you set the switch point to be.

Remember, the receiver does all of the decoding. If you have an oscilloscope, it is kind of fun to circuit trace the signals and see what the composite looks like when you wiggle the sticks. I have done that to show mixing to other fliers. Where the servos plug in, however, it is simply a single channel of PWM.

There is a variety of commercial switches made and many of the hobby sites have them. John

Oh, and thanks.

Attached Images

rc-sw.gif (11.7 KB, 14 views)

Attached Files

rcswitch.txt (4.5 KB, 2 views)

Hank Fletcher

This is the kind of project you don't want to wait on, it's just too cool. If you get a car like my P.O.S. ('93 Sable), you've got your linear actuator included. Just use the power seat adjustment and attach the seat to the brake - it's not like anyone's going to be sitting there! If you want to get more "sophisticated," you could remove the driver seat and use some power seat motors to operate both pedals with an ad hoc mechanism of your own design.

Getting an old car with a lot of former, powered comforts is a good idea, because you won't need a lot of them since there'll be no driver. Seats, mirrors, vent fans, wipers, and even lock solenoids are expendable if you have an exterior driver. Recycle! Economise!

jpanhalt

I must have been half asleep. The T8UAF is a version of the 8UAF series. Here is a link to the manual. John

http://manuals.hobbico.com/fut/8uafs-8uaps-manual.pdf

Marks256

Those are my feelings exactly. I just need a car... We have one at the moment that runs fine, but the transmission is dead. We also have one with a good transmission, but the engine has been parted out (very nice car, too...) Since we got them for junk, i don't think either would be worth putting any money into them. Although it wouldn't hurt to see what a used transmission would cost for the one that runs...
I tore an electric motor out of a power window, and that gave me some great ideas for a few projects as well.

That is what i was trying to avoid, but it may come in handy when i first get it.

Ok. That schematic looks simple enough...

So the receiver actually consists of two separate parts? The radio decoder, and then the signal from the decoder is sent to the PWM circuit? So in theory, i could just intercept the signal from the decoder before it is sent to the PWM to control my own stuff, instead of just having a PWM output?

Oh, and thanks for the link to the 8UAF manual.

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jpanhalt

I am not exactly sure what you mean by intercepting before pwm. If you are lucky, your receivers will be big enough to circuit trace and find out what is going on. Otherwise, you will just have to use the pin outs.

The Futaba color code is black-red-white. Black and red are the + and - supply; white is the signal. On the pinout from the receiver, red is center and white is on the side with the key tab. The signal pin will be the PWM to the servo. In PPM, the receiver consists of the RF section/demodulator and a PPM decoder. The latter determines to which pin (i.e., servo) each signal goes. A commonly used chip for that purpose is the HEF 4015. Each of the eight output pins goes to one channel. Here's the datasheet for that chip:

http://pdf1.alldatasheet.com/datashe...HEF4015BT.html

I have never looked at a PCM receiver that carefully. I suspect the older ones were similar, except there needed to be a decoder for the pulse code instead of position. Your receiver may be newer and more highly integrated. None of the new stuff I have uses that chip. It is all microcontroller. I keep the old receiver as an easy way to check some things on the Tx.

John

Marks256

Yay! It came today! They both work awesome. Pictures tomorrow (if i get time) The 8 channel one is really sexy! The four channel one looks like something you would find in a Happy Meal... , but it works great.

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dknguyen

What a coincidence. I just went out and bought a JR 9303 2.4GHz radio and a chopper to go with it the other day.