Hello,
I have been working my own scratch built r/c system from quiet some time now and it is almost complete. The progress has been very slow due to a number of reasons. The system is a 3 channel proportional system that will have a frequency of 27mhz (legal) and a range of about 500m. The picture below shows the working encoder and decoder. The system works but needs some refinement, if successful then it could drastically bring down the cost of a complete rtf r/c model and make it available to the masses ! I am also planning to add features like transmitter battery indicator, and failsafe for the receiver I have built several r/c gadgets like esc's and v-tail mixers... etc before. I plan to build a complete scratch built r/c airplane (even servos) !!!


regards

Cool... Now, I see some real intersting stuff in the forum. I am hooked to this thread.

Could you please post more information on your design?

-Ismail

Great work buzz.
Keep it up .
We need DIYer like u.
Keep us posted on the
progress ..

Are some LHS's listening?

Keep the good work going.. Why don't you check out some of the opensource projects like arduino.cc for control logic, pwm control and transmitter integration?

Quote from: izmile on January 13, 2010, 06:32:52 PM
Cool... Now, I see some real intersting stuff in the forum. I am hooked to this thread.

Could you please post more information on your design?

-Ismail

thank you  , what sort of information would you like to know?

Quote from: antojk on January 13, 2010, 07:03:30 PM
Are some LHS's listening?

Keep the good work going.. Why don't you check out some of the opensource projects like arduino.cc for control logic, pwm control and transmitter integration?

i have seen many of the open source designs, but for some reason i wanted to put my own knowledge to the test and make something and since i love this hobby, i decided to build a complete r/c system.

Preferably the circuit diagram showing the ICs used would be better. However, its upto you to disclose the level of details.

-Ismail

Kudos     

Quote from: buzz_rc on January 13, 2010, 05:55:32 PM
The system is a 3 channel proportional system that will have a frequency of 27mhz (legal) and a range of about 500m.

The transmission part would be pretty challenging, especially supporting multiple channels etc.  Not sure how much can be done without access to spectrum analyzers and so forth. 

Here is a link
http://home.nordnet.fr/~fthobois/anglais/engl-index.htm

This is a DIY project though the TX is more complicated, the different RX's are worth a look at.

They have documentation and schematics. The best part, the  Motorolla MC3362DW  FM receivers chips are available in the surplus market from vendors like futurelec and chinese suppliers. You can also use MC13135.

Could be used for your reference build.

Quote from: izmile on January 13, 2010, 09:46:22 PM
Preferably the circuit diagram showing the ICs used would be better. However, its upto you to disclose the level of details.

-Ismail

I have used the 12Fxxx and 16Fxx series of microcontrollers from microchip, the code is written in pic basic, sorry I would not like to disclose the ckt diagrams, but more technical details will be posted soon.

what coding protocol are you using ? PCM/PPM/BCD or your own ? sounds intersting! are you using 3rd arty RF modules as the board in the pic more seems to be the Codec modules.

Great Job!! so planning to hook up with a 'force feedback' Game pad ?

Quote from: anwar on January 13, 2010, 10:01:53 PM
The transmission part would be pretty challenging, especially supporting multiple channels etc.  Not sure how much can be done without access to spectrum analyzers and so forth. 

The whole project is a big challenge, lack of availability of components, testing equipment, funds & time have been some of the major obstacles. the current system is for 3 channels only but will support upto 7-8 channels in the future. This is just a prototype for test purposes, I will have to find an enclosure for the whole setup which will allow me to add more channels and other features also !

Out of curiosity, how much time (in hours or days) have you spent on this so far, and across what time span (over how many weeks / months) ?

I was referring to "channels" as in multiple concurrent users without interference, did not realize that channels could mean two things generally in RC radio land

Quote from: antojk on January 13, 2010, 11:55:36 PM
Here is a link
http://home.nordnet.fr/~fthobois/anglais/engl-index.htm

This is a DIY project though the TX is more complicated, the different RX's are worth a look at.

They have documentation and schematics. The best part, the  Motorolla MC3362DW  FM receivers chips are available in the surplus market from vendors like futurelec and chinese suppliers. You can also use MC13135.

Could be used for your reference build.

As I am building the entire system from scratch, I would prefer to stick to the basics. The current system uses amplitude modulation. Frequency modulation is a bit advanced, I will be building a system that uses FM but that would be for later. As I am a student, I cannot afford to buy the IC's you've mentioned in surplus quantities. I do have a pair of the MC3361 NBFM chips though which i got from an old cordless telephone. Most of the components that go into the construction of RF systems like tunable inductors are really hard to find in the market. Moreover I have limited access to equipment like oscilloscopes, LC meters and spectrum analyzers.

Quote from: ujjwaana on January 14, 2010, 12:17:35 AM
what coding protocol are you using ? PCM/PPM/BCD or your own ? sounds intersting! are you using 3rd arty RF modules as the board in the pic more seems to be the Codec modules.

Great Job!! so planning to hook up with a 'force feedback' Game pad ?

I am using ppm. No,I have made the rf modules on my own, the picture is of the encoder and decoder only. I will be posting some more pictures of the boards in some time. I am planning to make an enclosure for the system. I will start work on that as soon as I manage to find joysticks .

Quote from: anwar on January 14, 2010, 12:31:57 AM
Out of curiosity, how much time (in hours or days) have you spent on this so far, and across what time span (over how many weeks / months) ?

I was referring to "channels" as in multiple concurrent users without interference, did not realize that channels could mean two things generally in RC radio land

On average I have spent about an hour every day for the past year to make this system......
I thought you were referring to no. of channels the system will support  well after I finish building the complete system, I will work on the different frequencies the system can use (27,35,40 and 49 Mhz). The prototype uses 27Mhz.   

I was thinking about handling 27.010 and 27.060 (just sample values) as channels where multiple transmitters (all in 27Mhz) can co-exist.  Then you begin to run into adjacent channel interference and so on, and more and more sophisticated testing instruments are called for.

Here are some more pictures
in sequence:
1.Encoder (old)
2.RF module
3.Encoder (new)
4.Decoder

Man, You got patience  I mean it

Some more........
In sequence
1.Some of the previous failed attempts.
2.Servo tester
3.lithium polymer charger
4.Photo of my home made PCB (encoder) with my name etched on it    !

  . Ujjwal, You got a brother. 

Awesome work! We need more guys like you in this hobby.

BTW, your RF module seems to use a simple TO-92 package transistor. I doubt if that would be adequate meet the power levels. May be the transistor is running warm. If you need a good RF power amp transistor, then try a 2N3866. Its very good for RF amplification and can dissipate up to 4W of power!!  . Thatz hell a lot of power for RC use.

-Ismail

Quote from: izmile on January 14, 2010, 02:35:15 AM
Awesome work! We need more guys like you in this hobby.

BTW, your RF module seems to use a simple TO-92 package transistor. I doubt if that would be adequate meet the power levels. May be the transistor is running warm. If you need a good RF power amp transistor, then try a 2N3866. Its very good for RF amplification and can dissipate up to 4W of power!!  . Thatz hell a lot of power for RC use.

-Ismail

This is just a preliminary version of the prototype, will use the 2sc2314 with a heat sink in the final design!

Good. That should work as well.

Quote from: buzz_rc on January 14, 2010, 12:39:04 AM
As I am building the entire system from scratch, I would prefer to stick to the basics. The current system uses amplitude modulation. Frequency modulation is a bit advanced, I will be building a system that uses FM but that would be for later. As I am a student, I cannot afford to buy the IC's you've mentioned in surplus quantities. I do have a pair of the MC3361 NBFM chips though which i got from an old cordless telephone. Most of the components that go into the construction of RF systems like tunable inductors are really hard to find in the market. Moreover I have limited access to equipment like oscilloscopes, LC meters and spectrum analyzers.

I have a bunch of these RF ICs lying around 3361 (SMD too), 3371, 3362, 3363 SMD from my abandoned projects. If you need any, it is yours.