ranjieanthony

Hi guys,

I'm not sure if there has been a topic posted regarding a similar matter, because I tried searching for one and I didn't find any, so here I am.

Anyway, as a personal project of mine,I'm planning to build my own RC off-road car (about 1/8 to 1/10 scale) from scratch and to start with, I'm about to build a 7-channel encoder and decoder manually, using these diagrams:

http://www.pm.keirle.com/1_gadgets/encoder/encoder.htm
http://www.pm.keirle.com/1_gadgets/decoder/decoder.htm

So now I'm wondering if any of you guys know of diagrams/PCB layouts for a transmitter and a receiver that are compatible with the encoder and decoder? I'd appreciate it if you could share links or images here.

Campgems

Not to try to throw cold water on your idea, but that encoder is about 1960's vintage. Ibuilt the same type in my old 1969 Royal Classic radio system. It is very difficult to keep the encoders tuned. They drift with temp and voltage changes, It was so bad that I never was able to fly with the radio after spending I don't remember how manyTens or even hundreds ofhours soldering parts in the TX, RX, and even the servos, and then bringing one of the big old Tectonics O scopes home and tuning and tuning and tuning. Take it out and try it on the plane only to find one or more channels were off or missing or responding to the wrong stick.

Unless this is a nostalgia project for just your enjoyment and not for actual use, and cost isn't a consideration, it Could be fun to do. You can buy a geometrical set much less expensive though, one that is made of current technology parts, IEsurface mount IC's and is rock solid inperformance . In fact, you may have a difficult time even finding some parts for that project. If I remember right, there were a lot of 1% and better components. Radio shack parts would not work. Ithink I had close to $300 invested in my experiment and that was in 1970 Dollars. New electronics are much cheaper, but old electronics are more expensive.

Don

ranjieanthony

Well, before I was diving into this project I was already well  aware of how much time I would have to spend on it. But yes, this is in fact some sort of nostalgic project and also for learning purposes, since I will be taking up a course on Electronics in a few months.

fizzwater2

My Feedback: (61)

too bad you couldn't find some of these old NE5044 chips around - or maybe you can.

This was an encoder that Signetics had many years back - then I think Signetics was purchased by Phillips or something like that.

Anyway - I build several encoder boards based on the Signetics part, with a linear ramp (constant current) timing generator. Had pretty good luck with them. Mine had adjustable dual rates, servo reversing, and adjustable throttle throw and centering before computer radios.

If you're interested, you ought to look (google) for the microstar encoder - it's computer based, I think you can get kits, and it's a pretty slick encoder. I believe there's a group of guys on Yahoo that build radios based on that board, you can find lots of info there.

Good luck with the project - have fun!

http://www.dzjsw.com/jcdl/n/NE5044.pdf

Campgems

Building and tuning your encoder will sure give you an understanding about how an RC system works.

"You can buy a geometrical set much less expensive though" This would make more sense if you substituted commercial for geometrical. More and more I'm finding that spell check is happy with a word that is spelled correctly, but the word fitting the statement isn't considered.Sorry for the garbled wording.

We got off on the encoder though when your question was about the transmitter and receiver. The encoder is just input, like a microphone, to the transmitter.. The receiver can be of any design that will receive the frequency and modulation of the transmitter. The catch comes in that the receiver output has to go into a decoder to break out the individual channels. It has to match the encoder scheme you use.

Don

Pete_K

Without wishing to rain on your parade, the encoder in question (albeit of vintage origin) is actually rock steady. The zener diode maintains a steady signal due to battery voltage fluctuations, and any thermal drift is compensated by modern 5% tolerence bog-standard monolithic capacitors. In fact, all the components are bog-standard and are easily available from most any component supply house. Also, any commom-or-garden PNP and NPN transistors can be substituted with those shown in the circuit diagram. The whole caboodle is a simple excerise in building your own R/C encoder/decoder, and also to glean a little knowledge of the workings of the PPM system. Many homebrew enthusiasts' are without the means of programming microprocessor chips, which is why the simple matrix version was designed.

@ranjieanthony: You might consider a ready-made and affordable 2.4GHz 'hack' transmitter and appropriate receiver - both available from GiantCod. They work perfectly with the homemade encoder/decoder circuits.

AndyKunz

USED TO WORK would be more accurate.

We all go through that stage of DIY for learning. Happy building, and retain what you learn! Keep a notebook for the project.

Andy

Campgems

Andy, tell me more. Are you saying that that the stick movement isn't converted to a pulse width and that the stick pulses are then sequenced into a chain of data that is sent to the receiver which seperates the chain into individual channels and that pulse width is sent to the servo which then reads the pulse and generates an equal width one by moving the motor in the right direction? I know the encoding has changed, 2.4 brought a lot os changes, computer radios changed the way the pulses interact with one another, but has the basic concept changed that much?

Don

Zor

Hey guys,

Not long ago we were having discussions about how the systems work.

Very little info was being contributed.
Even some comments were made that were somewhat discrediting who was looking for more knowledge.

These recent postings and links are super infomative.

With more recent computerized facility the technology has improved further but the fundamental functions remain at the base of the systems.

Thanks for these recent postings.

Zor

AndyKunz

Hi Don,

Got your PM.

In a modern computer radio, there is no more need for PPM (that chain of pulses sent to a receiver).

Stick positions are measured by a micro, mathematically manipulated, and then transmitted as digital data (similar to what PCM did). In the receiver that digital data is converted to PWM that is delivered to the servos.

Old radios were continuous wave (always generating RF). 2.4g radios speak in bursts of very short duration but with lots of data in them.

So I guess the answer is, Yup, things are very different.

Andy

Zor

Hi Andy and everyone.

Your postings are always very valuable and reflect your high knowledge level.

The transmissionof packets containing digital modulation certainly provide improved flexibility to manupulate the data.

An example of that is the possibility of simultaneous command to a servo that is a slave.

However the servos are still receiving the PWM (Pulse Width Modulation) they are and have been designed to respond to.

If I am a servo, I do not have a clue how the pulse width sent to me has been processed.
I do not know either what my colleagues in this model aircraft are doing or when in time they do it.

If I am a servo with a brain, there is one thing I do know and that is the fellow handling the transmitter stick cannot possible respond as fast as the system I am part of can.

Beside, once I move a control surface the effect of the airstream to create a rotational movement of the model or to stop it is beyond my capability as a servo.

All I can do is react to the pulse width with the strength and speed designed into me.

I am your faithful servo.

Hee Hee !!!

Zor

AndyKunz

That's true. Remember though that PPM and PWM are quite different.

Andy