RF FSK system,help plz!

[triple5timer]

hi all, im to design a complete remote control system in rf freq's from 20-300MHz without using PICs this would be my graduation project, can any1 help coz i really dont know where to start! can refer me to some websites or books, i really appreciate any help.thank you

 

[Hero999]

When's it got to be finnished by?

Have you tried Google?

Do you know what radiowaves actually are?

Please provide more information.

Sorry but (judging by your post) you're very lazy and you obviously have no clue, go and fail your degree, you deserve to since I don't plan to do your work for you.

 

[docel]

555 to fskook

If you are to "design" you should first learn to google!

Anyhow, to spoon-feed you, you can try analog, Maxim, TI, for chipsets and RF monolithics etc for "ready made" spoonfed designs.

i suggest you 'buy' a ready module and "design" your application rather than try (!) to design your own circuits.
RF is Not for the Faint hearted. Not at 300MHz!

I specially like the TI stuff due to their support.

 

[triple5timer]

OK, HERO999 thats not a very nice thing to say , i really tried google yahoo altavista... u name it....2 month r gone now 1 to go and im really having bad time here.

docel : thanks dude! using ICs, thats what i concluded after 2 months of websurfing(webdrowning) . and yes the 300MHz is hard to deal with that exactly what my prof. said... im going to work on the 27MHz used widely in toy models....so is there any more help i can get here or what?? thanks anyway

 

[Hero999]

My point is if you're doing a degree you should know what you want, you should have a specification. I normally don't mind people asking dumb questions but when they're on the final year of a degree course there's no excuse.

 

[Papabravo]

If you signed up to do this project because you know something about FSK and RF design then it might be worthwhile trying to help you. On the other hand if you signed up for this project because it sounded cool, and you know nothing of either RF design or FSK, then in one month there is no hope. If your instructor knew you did not have the background to succeed, then shame on him for allowing you to waste two months, and shame on you for engaging in slow stupid failure. It should have taken no more than a week to figure out that you were in over your head. Let us be really clear on one thing, I am not attacking you personally, I am attacking your actions and your post describing the situation you find yourself in.

The final point I would like to make is that you have not articulated a set of requirements for this project. In the simplest possible terms you have not told us what "done" means. If you can't tell us what "done" means then how will you or your instructor know what "done" means.

 

[RadioRon]

While I am somewhat in sympathy with comments from Hero999 it is relatively easy to help you outline the process of designing something, so let's give it a try.

Step 1: define what the thing must do. Write down these things:
- the "functions" required. That is, what things must the remote control do? Must it turn the remotely controlled device ON/OFF? Must it cause the device to toot a horn? Must it cause a lamp to light? Must it cause the device to move forward or rotate in some way? Must it cause the device to explode (thereby rendering any other functions moot)?

Step 2: define the constraints placed on the project and write them down:
- is Radio Frequency control mandatory, or can you use light or sound instead?
- if RF, then what constraints, ie. frequency, power, modulation, industry standards, compatibility with others etc. are pre-defined?
- what control range (distance) is required?
- what reliability is required? In other words, is it the end of the world if the occasional command doesn't make it to the device, or gets misinterpreted by the device?
- must this device co-exist with other similar devices? In other words, what kind of RF interference is expected?
- what is the amount of time available to design it. How much time to build it and test it? How much time needed to write the report?
- how much money do you have to spend on it?
- can you buy a module that does almost everything already made, or must you design from scratch? What are the rules imposed by the teacher?
- what other constraints are placed on you?
- what power supply will you use?
- how large can the device be?


I think you will find that in answering all these questions, you will be in a better position to take the next step. So now you know where to start, and once you have tackled these questions, the next step is to find examples of devices with similar functions and study them for ideas on how yours could go together. This is the part that takes a fair bit of time. There is no alternative but to put that time in, by finding books, magazine articles, websites, repair manuals for similar devices, and part manufacturers application notes and studying the hell out of them. Once you have something sketched out on paper, like a schematic, you will be in a better position to ask for a bit of help here again. As a preliminary step, you might also consider drawing a detailed block diagram of the different stages of your electronic circuit and show it to us so that we might comment on it. I hope you know how to do a block diagram as this is the most common graphical form in which to share your design architecture before getting down to the nitty gritty of a detailed schematic.

 

[docel]

OK, HERO999 thats not a very nice thing to say , i really tried google yahoo altavista... u name it....2 month r gone now 1 to go and im really having bad time here.

docel : thanks dude! using ICs, thats what i concluded after 2 months of websurfing(webdrowning) . and yes the 300MHz is hard to deal with that exactly what my prof. said... im going to work on the 27MHz used widely in toy models....so is there any more help i can get here or what?? thanks anyway

After 2months of goofing you decided on ICs and your Goof. said 27MHZ??

And have you yet decided FSK or ASK will do?

If you still want ~300MHz, suggest Micrel MICRF102/ MICRF022 IC pair, but ASK....But no one will know better...
They are the easist and the simplest OOK/ASK pairs ever available in the world. For Technical/ Viva / report/ Funda, These ICs will give you enough to floor any of your examiners. Only problem: very LITTLE components!!!

Now I dont know if this is spoonfeed enough!!

 

[RadioRon]

Another example worth looking at is the family of narroband FM receiver chips from Philips. This includes SA604 and many other models, all numbered like SA6xx. These have been around for a long time and are not too difficult to apply, although certainly trickier than the Micrel suggestions. There are likely to be some single chip FSK transmitter chips around to match these, perhaps with Philips, or Freescale, or Atmel or Maxim etc. There is a distinct difference between a narrowband FM/FSK transceiver such as I'm suggesting and a wideband FSK/OOK system such as what I think the Micrel parts support. Honestly, the wideband approach is less demanding and may be a better way to go since you don't need tight frequency stability, and there are probably more chips out there designed for RFID, garage door openers and similar remote controls.

 

[docel]

I think you will find that in answering all these questions, you will be in a better position to take the next step. So now you know where to start, and once you have tackled these questions, the next step is to find examples of devices with similar functions and study them for ideas on how yours could go together. This is the part that takes a fair bit of time. There is no alternative but to put that time in, by finding books, magazine articles, websites, repair manuals for similar devices, and part manufacturers application notes and studying the hell out of them. Once you have something sketched out on paper, like a schematic, you will be in a better position to ask for a bit of help here again. As a preliminary step, you might also consider drawing a detailed block diagram of the different stages of your electronic circuit and show it to us so that we might comment on it. I hope you know how to do a block diagram as this is the most common graphical form in which to share your design architecture before getting down to the nitty gritty of a detailed schematic.

555, youll do well if you can follow the above advise, painfully and extensively chalked out by radioron. Wish HE was your mentor!

Ron, Micrel chips are PLL stabilised for narrow band ASK. They have some astonishing stability! This should fit 555s needs as the tx and rx put together is worth 9 components....with a built-in Antenna tuner, for Gods sake!

The 604 is a jewel indeed, but 555 here will die with it1

 

[RadioRon]

Hey Docel, I took a few minutes to study those Micrel parts you suggested. I must say you are right, they are simple! While still somewhat layout sensitive they are definitely less tricky than the old SA6xx family. In an attempt to one-up your suggestion, check out these ones:

http://www.integration.com/products/IA4420_ISM_band_transceiver.shtml

or

**broken link removed**

and others in the same family of parts from these manufacturers. These are all intended for low power ISM band applications such as the Micrel parts.

I'm not sure how impressed a prof might be if you copy the applications layout from the data sheet, solder down the 7 or 8 components and power it up. Doesn't seem like you worked hard enough. But isn't that just the way things are nowadays in RF. Used to be we had to really sweat to get a receiver to have stable gain with low noise. Just look at how easy it all is now!

 

[Papabravo]

At least it wil be a binary situation. If he can put it together and it works all is well. If he puts it together and it doesn't work what would his next step be if he is as unfamiliar with RF and ASK/FSK encoding as his original post suggests?

 

[RadioRon]

If he puts it together and it doesn't work what would his next step be if he is as unfamiliar with RF and ASK/FSK encoding as his original post suggests?

That's a good question. Even though I now have the instruments to help diagnose any RF problem, I can still remember muddling through with only a voltmeter and my wits. That was extremely tough, as I was somewhat witless, and even now I can remember the profound frustration that I suffered despite the many years that have passed. Learning is painful sometimes.

You can do a lot with a bit of discipline, some grounding in basic principles and determination. In his case, he is likely to not have a means to test either the transmitter or receiver until he gets both of them working. How do you know what isn't working? I'm going to guess that he might have access to instruments at school. Perhaps a spectrum analyzer? Or maybe that's expecting too much. Such a thing would be quite useful because then he can focus on getting the transmitter working first by watching its output (or lack thereof) on the analyzer. Once the transmitter is working, at least now you have the means to stimulate the prototype receiver.

Basic debug principles would normally apply if you had access to each stage, like checking DC bias, then signal tracing or signal injection. But with these chips, you can't get at those points. So, you are left with the approach when it doesn't work of simply checking carefully that every pin is connected the way the data sheet says, that bypass capacitors are surface mounted directly beside the pin they service, and that the entire thing is supported with a complete groundplane. Then you have to double check RF paths to see if the impedance matching components are what they should be, and that the transmission lines are somewhere near their correct impedances. Then you have to somehow prove that your digital control inputs are setting the chip up properly. If all else fails, I would ask for a bit of help. Perhaps here. But not before I'd really sweated over checking every detail against the manufacturers application notes.

 

[mstechca]

He will probably return and ask another question if something doesn't work.

triple5,

Docel and Hero999 gave you half of the answer to some of your question. What they mean is go to https://www.google.com and search for the information.

Also, when searching, try adding either the word primer or tutorial as part of your search. You might get better results.

and we want to know, what does "complete" mean to you?

 

[docel]

Hey Docel, I took a few minutes to study those Micrel parts you suggested. I must say you are right, they are simple! While still somewhat layout sensitive they are definitely less tricky than the old SA6xx family. In an attempt to one-up your suggestion, check out these ones:

http://www.integration.com/products/IA4420_ISM_band_transceiver.shtml or
**broken link removed**

Hi RadioRon!
Must say the MICREL chips are pretty easy to get working. We use these for simple switching for small Robots. Must have wired some 3K sets for hobby purpose alone! I have had school kids to Engg. students solder and get them working without problemss and I will swear by them!! Quite good range too! ....and cheap!
I have tried the Nordic/ Integ. chips, but they are a bit cumbersoime, not to mention the uC SW interface.

My first TX was an Audio tube 6V6. After a year, It then drove a single 807 @ 700V to get some 26W power and about 3WPM CW!!
ALL the components came out of a dead radio.

Ofcourse, I'd seen many test equipment.
The Micrel TX is about the size of the anode coupling capacitor!!

PapaBravo (Ham?) / MSTechCa.,
He might land up keying the 555 in Astable! Probably ripped the toy car apart...and the wires too/

 

[RadioRon]

Ok, you win. I should have know better than trying to compare transmitters with an old scratchbuilder like you! The attachment is my lame attempt at atonement, showing my favorite transmitting pair. I used these in surplus Motorola 43GGT Tpower VHF sets as well as my Kenwood T599. This type was also used on my first tx, a Heathkit DX60. I'm sorry to say that all my homebrew has been other than receivers and transmitters. I got plenty of receivers and transmitters at work, 8 hours a day. Plus I am too lazy to take on big ambitious projects and usually end up buying something.

Micrel is a good choice for simple FSK.

 

[triple5timer]

Hi all! 10x radioRon and docel, my design will be on paper only, 4 this semester. Lets suppose I used a holtek encoder such as the HT-12E with a micrel micrf102 in the transmitter and there counterparts in the receiver, now the only thing i need is a proper antenna matched to my Rx and Tx, I dont entend to buy an antenna as a product, i think its too easy to make one.
There is the loop antenna, the whipe antenna and others, im not so good at antennas what type should i use here to achieve the perfomance/range
I forgot to mention that i used the 300MHz carrier frequency the modulation is ASK.

 

[RadioRon]

I recommend a loop antenna. These can be kept small and will radiate adequately for short range devices. The Micrel data sheets and app notes for the MICRF series specifically advise using loop antenna since that is what the chip is set up for (balanced outputs) and in fact their data sheet provides a pcb layout that shows the size of the loop required. If you decide to use other than a loop, you will have to convert from balanced to unbalanced output using a balun, or you could build a balanced antenna other than a loop, but impedance will be lower so a transforming action or impedance changing network may be needed.

 

[triple5timer]

What about the TWS-434/RWS-434, i found them on www.rentron.com,
are they real?? i couldn't find their manufacturer, and they look kinda old and with a 1 page datasheet!

 

[Nigel Goodwin]

What about the TWS-434/RWS-434, i found them on www.rentron.com,
are they real?? i couldn't find their manufacturer, and they look kinda old and with a 1 page datasheet!

They look fine, you see a lot of RF modules that look like those - they even give you a nice diagram showing how to connect them with Holtek chips for a full remote control system.