# Looking for an RC Transmitter & Receiver

#### xxJaRxx

Oct 16, 2011
34
So I want to make a really basic remote control car, one that goes forwards & backwards, left & right, and making some kind of braking system if I manage to get the first two working. I don't want it to be anything fancy at all, I'm just interested to see if I can do it . I'd like to do as much of the building and programming myself so I don't really want to buy stuff specifically make for RC cars if that makes sense (as in my mind that's cheating)..

Right so when I first started thinking about this I imagined that I could head on down to http://uk.rs-online.com & http://uk.farnell.com where I get most of my stuff and buy 'some kind of' chip that transmitted RF and chip that received RF and then I could work around that and investigate how to get it all working. Unfortunately I can't seem to find anything like this and would appreciate being pointed in the right direction of anything that might resemble what I've mentioned in the previous sentence!

#### Externet

Aug 24, 2009
839
Just swallow the pill.

Buy a RC toy that suits your wishes; dismantle it to pieces while making a schematic of everything.

Now you have ALL the parts needed for your project at an unbeatable price and no need to spend a year looking/gathering for parts vendors or unobtanium. Ahh... Will be good proven tested parts and a printed circuit board bonus !

Then put it together/modify it the way you want.

Last edited:

Oct 16, 2011
34

#### Externet

Aug 24, 2009
839
It is gone since unobtanium parts took root.
You will come to the same deduction in a few years

And there is no flaw in having ALL your parts instantly for an unbeatable price

#### davelectronic

Dec 13, 2010
1,087
RC car

Hi xxJaRxx.
These circuits can be built using discrete components on copper strip board, in my younger days i really enjoyed RC boats, i still do.

Any way i happened upon an RC petrol driven retro speed boat, expecting to find a receiver and servos inside on opening the deck was an eye opener, all there was there a mechanical linkage and small motors, little dc ones, and a piece of copper strip board, and a battery pack.

I went out got some decent battery's, fueled it up and it run really nice, even the transceiver was home made out of aluminum sheet, cut out for the controls and switches.

As this was a 60's boat i dont think futaba excisted then, so yes a circuit build for the transceiver and receiver is possible, but not in one IC and a couple of components, i think its more involved than that.

With patience and time its possible to build a one off custom RC car and control system.
Ive never built one, well only the quick futaba route.
Searching and old library books from some decades ago, plus older web articles will produce some good finds, i have no doubt.

I can fully understand your first reply on your question, lots of ironing out to do and hurdles to over come, determination and patience will be key.

So i will leave you with a link i enjoy, good author of the site, scroll down and there is some RC circuits, and lots more, good luck with it.
Dave.

http://www.sentex.net/~mec1995/circ/circuits.htm

http://jap.hu/electronic/rf.html

#### xxJaRxx

Oct 16, 2011
34
Cheers Dave! Had a quick look at the first link, saw a page on building a cheap RF transmitter, not too keen on building my own using capacitors and inductors etc but will have a proper look after work tomorrow!

Would prefer to find a 3 or more channel RF transmitter that I need to build a circuit etc for. Found this page on Farnell, the transmitters and receivers seem to be only one channel, although I'm sure I saw a four channel one somewhere but I think it was too expensive. What is a transceiver, a transmitter and receiver in one module, that would be no good to me I assume..!

#### davelectronic

Dec 13, 2010
1,087
RC Car

Yes sorry, transmitter and receiver, i am sure your find the schematic your looking for, or a combo to make the necessary channels you need four as you said, it can be done, but as i said patience and determination, and a far bit.
Dave.

#### xxJaRxx

Oct 16, 2011
34
What did you mean by a combo to make the necessary channels?

I just had a thought.. If I got a cheap single channel transmitter and receiver, would writing, say, 2V to the input of the transmitter output 2V at the output of the receiver? If so, I could use a microcontroller to take the input and have a lookup table saying;
2.0V = Forward
2.5V = Reverse
3.0V = Left
3.5V = Right.. etc

This would solve the need to me to find the all illusive 2 or more channel transmitter and receiver!

#### davelectronic

Dec 13, 2010
1,087
Hi there xxJaRxx.
I meant a circuit thats split if it was needed in two sections for different functions, my main interest is boring to most, its putting together psu's of different kinds, i understand digital and logic ttl circuits, but find gadget electronics boring, for me its got to have a purpose, your circuit does for the application your using it for, but flashing led's and some other pointless circuits to me are a waste of time.

Some off the currents i play about with could be classed as electrical as opposed to electronics, control circuits, CCTV, sensors, are interesting enough, i just dont do the whole switching led's on of on of, as i said pointless to me.

Oh repairing and fault finding in consumer electricals as well is ok.
Any way good luck with the logic control of the RC car, i would opt for the ready built module receiver transmitter option, but each to there own, thats just me.
Dave.

#### davenn

Moderator
Sep 5, 2009
14,081
What did you mean by a combo to make the necessary channels?

I just had a thought.. If I got a cheap single channel transmitter and receiver, would writing, say, 2V to the input of the transmitter output 2V at the output of the receiver? If so, I could use a microcontroller to take the input and have a lookup table saying;
2.0V = Forward
2.5V = Reverse
3.0V = Left
3.5V = Right.. etc

This would solve the need to me to find the all illusive 2 or more channel transmitter and receiver!

sorry it doesnt work like that because the signal strength of the radio signal varies with position and distance you cant use voltage related "coding". You will need to use either time spaced pulse strings or freqency variations.

You words of "really basic" and "multi channel" are a contradiction and dont go together.
as Externet said, buy a cheap multi channel system and refashion it into your own RC vehicle.

cheers
Dave

#### xxJaRxx

Oct 16, 2011
34
Hmm yeah I am still starting out in electronics really, so I've only just got past the whole flashing of LEDs thing

Don't suppose you know if what I said in my previous post would work? If I feed a voltage into the transmitter, will I get that exact (give or take a bit) voltage out of the receiver?

#### xxJaRxx

Oct 16, 2011
34
Ah I knew it couldn't be that easy :\ Is it not possible to buy a multi-channel transmitter and receiver without buying an RC car and taking it apart?

Hmm frequency variations sounds interesting, any chance you could expand on that?

#### davelectronic

Dec 13, 2010
1,087
Not entirely sure, does that not make it a digital transmitter / receiver, Sorry for the abrupt led thing, yes i know we all have to start some where, you would be better off asking a member thats into logic ttl circuits, i dont think it would be analogue.
Dave.
PS, your find what your main interest in electronics is, then although i understand most concepts in electronics, i only put time in to what i like doing, my slight downfall i dont mind admitting is my maths, but i know enough to do whats needed, i am more practical than theory, if i see a circuit i will build it, not talk about it for months or years, not saying you are.

I have to contend with life long illness, my resources are not that of a fit well person, but thats my problem.
Having said that if i can help, or come up with what others need i will try, i dont always get it right, thats why in a thread, the OP of the thread will i have no doubt take the most useful advice.
Dave.

#### davenn

Moderator
Sep 5, 2009
14,081
Ah I knew it couldn't be that easy :\ Is it not possible to buy a multi-channel transmitter and receiver without buying an RC car and taking it apart?

yes of course you can buy multichannel systems without them already being built into a car, plane boat etc. any hobby shop that deals in RC systems can sell that. maybe for ~ AU or US$100 - 200 at a guestimate. BUT its probably the more expensive way, rather than buying an el cheapo system off ebay etc I pickd up 4 RC helicopters for Australian$10 each a couple of yrs back.
thats $10 for a 4 channel RC TX/RX system x four!! ($40 total) cant get any cheaper

the secret with all things electronic is you dig around look over different www sites, shops where-ever. There are always bargins to be had.

Hmm frequency variations sounds interesting, any chance you could expand on that?

not much point going the construction route unless you are quite proficient at electronics
it would be a really serious undertaking for some one new to the game.

cheers
Dave

#### xxJaRxx

Oct 16, 2011
34
I've decided to try and send pulses of information and programme the receiver micro to interpret them as bits.

Can anyone tell me if the pic16f648a from microchip can be programmed in C code? Or where in the datasheet is says if it can or not? I've just ordered two and just assumed they were compatable!

#### davelectronic

Dec 13, 2010
1,087
RC car control

I know you have whats seems this burning desire to build the total RC circuit from scratch, which as i said can be done, but as you said your not much further on past the led stage, get your car up and running with moduler control, then study RC, RF systems to learn the concepts of use, and limits of these types of circuit design. By all means you can attempt to build a transmiter reciever from descreate components, but it might be like trying to run before you've learned to walk.
Dave.

#### davelectronic

Dec 13, 2010
1,087
RC car control

Not trying to put out your flame, ive got stuff i want to build, but i also have more study to do to achieve my goals, but i will get there in the end, going to complex to soon can end in failure, thats depressing when that happens, i know ive done it, and all the pit falls, try a couple or more of confiendence building circuits first, just to get some excperiance built up, then tackle the bigger, or more complex circuits.
Dave.

#### xxJaRxx

Oct 16, 2011
34
Right so I've got my components, I've wired up the transmitter (correctly) and the receiver (correctly) and wired a momentry push button to the input of the transmitter, so that when pressed, it inputs Vcc (4.5V) into the transmitter. I have also wired an LED to the output of the receiver.

I figured that if I pressed the switch, 4.5V would be transmitted to the receiver and the LED would turn on (and off when not pressed).

This doesn't happen! The LED is just constantly on and I can't seem to logically figure out why! I don't yet have a multi meter as it's in the post so can't look at different voltage levels..

Anyone have any advice on what could be wrong? Or are my assumptions on how the system should work wrong?

#### davelectronic

Dec 13, 2010
1,087
As already stated by Dave, a voltage TTL logic type circuit wont work for your RC application, unless you have done an about turn and opted for an analouge circuit, with no multi meter, you might as well be circuit building in the dark.
Dave.
PS, Pictures of where you are so far can help a lot.

#### davenn

Moderator
Sep 5, 2009
14,081
Right so I've got my components, I've wired up the transmitter (correctly) and the receiver (correctly) and wired a momentry push button to the input of the transmitter, so that when pressed, it inputs Vcc (4.5V) into the transmitter. I have also wired an LED to the output of the receiver.
I figured that if I pressed the switch, 4.5V would be transmitted to the receiver and the LED would turn on (and off when not pressed).
This doesn't happen! The LED is just constantly on and I can't seem to logically figure out why! I don't yet have a multi meter as it's in the post so can't look at different voltage levels..
Anyone have any advice on what could be wrong? Or are my assumptions on how the system should work wrong?

I figured that if I pressed the switch, 4.5V would be transmitted to the receiver and the LED would turn on (and off when not pressed).

read again what I said some posts ago you dont transmit a voltage in that way.

what sort of TX and RX are you using ? as Davelectronic said some pics would help
or circuit diagrams
The best you can achieve by just turning the transmitter on and off will be that the receiver detects a carrier signal from the transmitter and produces a small voltage that
may be used to turn on a transistor which can turn on a LED or other device.
when the TX stops transmitting the carrier signal is dropped to the RX and that small voltage disappears thereby turning off the transistor and LED. That is, in this situation
the LED will only light whilst the TX is transmitting.
To switch and keep the LED circuit on with just a pulse of TX then you need a latching circuit between the output of the receiver and the LED driver transistor. So with alternate pulses it turns on or off.

Anything more complex and you need to transmit data ... strings of pulses that the receiver will decode and act on accordingly in response to what those strings of pulses represent ...
for that you will be getting into things like a PIC processor. it will be programmed such that for example ...
when it sees strings of dual pulses it would turn on output A ... that will lead to one function happening
when it sees strings of triple pulses it would turn on output B ... that will lead to one function happening
when it sees strings of quad pulses it would turn on output C ... that will lead to one function happening

etc etc

cheers
Dave

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