R/C toy car transmitter circuit - Electronic Circuits Projects Diagrams Free

cyberquest · 12th April 2005, 05:45 AM

Hi All: Can anybody help. Who knows about R/C electronics.I'm new to r/c electronic transmitters,I purchase a radio control toy car kit to build,and it came with the schemayic for the TX and the RX.The car has a range of 40 to 50ft. I would like to increase that range to the max 1000FT. that is the max set by the FCC-PART-15. THEY STATED to me 1300ft =1/4 mile. BUT I don't need to go that far. A i know its more than 50 and 300ft. there are cars that can go 1000ft because i seen them and wittness this. Like the one i purchase can go 40-50ft that not far at all and has the same internal electronics as the ones that can go alot further. Can anybody tell me and explain to me. What i have to change on the circuit and which parts. Or just add to the circuit. This schematic can beseen at this website httP://www.elenco.com/manuals/rcc-7k.pdf. The manual is (rcc7k). Icould not post it my self on this forum do to i have no scanner to scan it at this time. Sorry. Thats why i inclued the website. I hope someone can help me who knows R/C Electronics. I would like to know what kind of circuit this transmitter is set up as,are the two transistors set up as a darlington pair,is it a emitter-fellower circuit.What kind of circuit is it set up as. is it a series-parallel or a series circuit. The right side of this transmitter. What i also need to know is the of this TX is how they calculated for the frequency with those parts they used,and the output amplifier is there a low-pass filter on its output stage.I know only some basic electronics and OHMS-LAWS. IF anybody could help me to understand to calculate the oscillator to set the frequency in the circuit.I would Apprecite any help and your time posted. PS the company i purchase this kit from they can not help me on this subject. I KNOW this is alot to ask. thank you for your help and any info you post. JJ..

audioguru · 12th April 2005, 05:09 PM

Hi Cyberquest,
I think I replied on another web-forum.
Your transmitter doesn't give the max allowed power probably because it gives the max allowed harmonics that cause interference on other frequencies. My son's RC car looked like yours but was bigger and was powered by a 7.2V big rechargeable battery. It went very fast and had a range of at least 400 feet. Its good range was probably because its receiver was very sensitive. It could pickup transmitters a few blocks away! Whenever my son stopped it, it would start running around by itself!

If you boost the power of your transmitter, you might be controlling RC toys all over town, causing radio and TV interference and asking for a visit from the RF cops.

mstechca · 12th April 2005, 05:18 PM

Be careful!

There are frequencies that other people use around you. If you are able to jam those frequencies, then expect some trouble. I got caught a few times by my mom for screwing her T.V. up when I wasn't intending on transmitting on that frequency, and the transmitter was powered with a 9V battery.

Your best bet is to get frequency information first. If the frequency is way up there in gigahertz where almost nobody goes, then you probably will be OK at transmitting at 1000 feet. I would suggest getting yourself licensed.

Even ham operators can't transmit on certain frequencies without a license.

and for the frequency, use the equation: 1 /(2 * pi * sqr(L * C))

sqr = square root of, L = inductor, C = capacitor, pi = your PIE button on your calculator.

cyberquest · 13th April 2005, 06:21 AM

Hi again I understand what you're saying . BUT. I Check with my local FCC AGENCY. THEY TOLD ME any RF transmitters that is 100mW power output and under is find in my frequency band and does not have to be licensed. Plus these cars work at FT-bands that are licensed through the company who apply through the FCC for that band for the public to use these cars on. And 1000ft is within and under the range the FCC STATES IN fcc part-15 by law. Thats in the states where I'm locate. maybe the laws are different in your country. Or are you from the states. 100mW HAS a range just under 1300FT, thats stated by fcc part-15reg by law.Now as for CB thats a whole other avenue. They transmitter on AM and i think FM WITH output powers in WATTS. ANYWHERE FROM 3TO400 WATTS OR MORE. THIS IS WHAT I been told through the FCC. That WHY YOU need a licensed for CBs. not for a R/C TOY CAR. THERES always going to be some interferance with some frequencies on these small bands but that does not mean i need a licensed for a R/C CAR. GO IN TO RADIO SHACK AND ASK IF YOU NEED A LICENSED FOR A R/C CAR AND THERE ANSWER I BET YOU THEY WILL SAY NO. AS for the last part of your answer can you give me an example! please explain. this is what i need for you to be more elaborent on. I thank you for your time and your help. JJ 8)

audioguru · 13th April 2005, 11:01 AM

I think that your toy car is too cheap to have more range. Maybe its transmitter isn't correctly tuned. Maybe its receiver isn't correctly tuned and doesn't have enough gain. Maybe the factory had to reduce the gain of the receiver so that it doesn't overload when close to the transmitter.

**Nigel Goodwin** · 13th April 2005, 11:23 AM

Your answer is really pretty simple! - buy a 'proper' radio control system for a model car, instead of the 'toy' you currently have.

You're not likely to find any suitable DIY designs, nor are you likely to be capable of building and aligning one (if you could, you wouldn't need to be asking here!). The reason for the lack of DIY is that it's so cheap to buy them, why pay many times the cost for an inferior DIY system?, when a commercial one is so cheaply available - plus the encoder/decoder chips aren't usually available to individuals.

cyberquest · 14th April 2005, 01:10 AM

Quote:

To Nigel If my QUESTION was that simple. I got less than a answer from this forum. on a simple electronics circuit question as stated in your answer. Some people state they know about electronics but tell you some thing else. Because they have no expertise in that feild. Any R/C electronics expert would of gave me a much much more advise or show me what parts in the output power stage of Q2 in the transmitter schematic. in the website i provided www.elenco.com.us. I didn't want to redesign the circuit just change the output stage to give me more output power and what parts to use. Or add to the circuit. This is not a complicated circuit for a experience electronics expert. it seems like everybody talks like they know it all. but i guest not. but thats your choice on this forum. its not the suitable DIY design i would fine. Its the suitable expert i will not find. And to tell me to go out and buy a proper radio control system for a model car instead. of the one i bought. Tells me my answer about these so call electronics experts on this forum. THESE R/C CAR ARE NOT CHEAP. THESE COMMERICAL PROFESSIONAL HOBBY IS NOT CHEAP. TO START a car or tuck can cost $200 and up plus battery charger,plus battery packs,plus (esc) electronic speed control circuit,plus the the radio control transmitter RX ,plus servos. ect ect. cheap one. yeh right. minimum $300-up to $1000 or more. even a used one will cost you Maybe $150. the kind i use at this is form RADIO SHACK $2O-$99. MAYBE THE JUCK ON EBAY THAT YOU DON'T know what you're get. maybe you know a soruce to get these real cheap ones as you stated for the professional r/c cars for under $99. Because I don't have your big bucks to spend on your, so call cheap ones. :cry:

audioguru · 14th April 2005, 02:23 AM

Wait a minute, Cyberquest!

The transmitter was fully assembled by the factory so its details are not shown. It uses a cheap encoder IC that operates on only 3V. Q1, the 27MHz oscillator and Q2, the RF power output stage operate from 9V to get max output. But C6 is in a capacitive voltage divider with C5, and they are required to attenuate the output of the oscillator so that the IC's output isn't damaged by overvoltage. Therefore Q2 doesn't have enough drive to give much output. Also, the schematic doesn't show a capacitor across L2 to tune it to 27MHz and therefore the output is reduced further.

You could try reducing the value of R6 in the transmitter to get more output. However it might only reduce the life of the battery.

There isn't much you can do to the receiver since it is built into an IC.
I am sorry that you have a cheap toy with only a 40 foot range. :cry:

cyberquest · 14th April 2005, 07:06 AM

to audioguru: I understand that the encoder operates on 3V. because it has a operating range of 2.2 to 5V . It uses a zener diode to regulate the 3V from the 9V power supply. the oscillator is set for the carrier band-wd of 29.9mhz but has a range of 27.0-27.9. do to the fact that the first xtal in the transmitter and not in the car. is basically solved by the wide open receiver designed. it will accept a singal around 27.9mhz ( if the car is tuned for 27) its not a specific tuned for a specific frequency. there is no xtal in the car just a crude receiver that takes in random noise from the antenna and filters out all frequency and lets throught the 27-27.9 range do to this open reciver design. if what you sad is ture in you answer. then i think mybe not to change any of the original design just add a third stage another power amplifier transistor to increase to 100mW with out over loading the power supply. 9V can handle 100mV and another stage.Can this be done. if not. explain why!. or can you gave me a circuit that would work for R/C cars. 100mW is the maximum power output that can be usedand i need. can you help.

JJ

JimB · 14th April 2005, 10:41 AM

cyberquest, I think you have just provided the answers to your problem, the quote you:

"wide open receiver", "crude receiver"

and to be perfectly honest, the transmitter is no better.

You have bought a childs toy, the radio spectrum around 27 Mhz is full of low power devices such as yours, all squirting out poor quality RF signals, there is also the CB radio stuff. Your simple receiver is taking all this and just cant decode your transmitter because of it.

OK, increase the transmitter power, add a power amplifier stage to the existing circuit.
But, to be quite honest, the best way to improve that transmitter is to start again from scratch, it was designed to provide a signal at minimal cost, to control a cheap toy car.

The advice you are getting here may not be what you were hoping for but it is the truth.

JimB

audioguru · 14th April 2005, 11:05 AM

Quote:

Originally Posted by cyberquest

just a crude receiver, can you help.

I just finished looking at toy car receivers on Google to confirm my suspicion that your "crude" receiver is just a single-transistor super-regenerative one. The IC in the receiver only decodes the demodulated pulses. Since super-regen receivers are easily overloaded, I advise you not to increase transmitter power. Sorry. :cry:

**Nigel Goodwin** · 14th April 2005, 11:52 AM

Quote:

Originally Posted by cyberquest

THESE COMMERICAL PROFESSIONAL HOBBY IS NOT CHEAP. TO START a car or tuck can cost $200 and up plus battery charger,plus battery packs,plus (esc) electronic speed control circuit,plus the the radio control transmitter RX ,plus servos. ect ect. cheap one. yeh right. minimum $300-up to $1000 or more. even a used one will cost you Maybe $150. the kind i use at this is form RADIO SHACK $2O-$99. MAYBE THE JUCK ON EBAY THAT YOU DON'T know what you're get. maybe you know a soruce to get these real cheap ones as you stated for the professional r/c cars for under $99. Because I don't have your big bucks to spend on your, so call cheap ones. :cry:

I don't know where you're making your prices up?, but a two channel radio control transmitter, receiver, with two servos, only costs £50 in the UK - and I'm sure you could get it for less if you looked hard!. In the USA it should be well under $100.

I wasn't suggesting you buy a new car, just some proper radio gear to fit in it, your existing gear is only a toy - which is why it doesn't have any decent range.

Roboticinfo · 15th April 2005, 07:08 AM

That car is a kit sold from elenco
it is about $26:00 dollars or in that range.
If you were to replace the electronics with the expensive rc, you would be at a total of around 75 to more for a rc car.
I think he want's a cheap way to do it and also
it still would not get a range of a 1000.
Most likely only 300.

So there is no way that he could get that range.

**Nigel Goodwin** · 15th April 2005, 08:16 AM

Quote:

Originally Posted by GTAman

That car is a kit sold from elenco
it is about $26:00 dollars or in that range.
If you were to replace the electronics with the expensive rc, you would be at a total of around 75 to more for a rc car.
I think he want's a cheap way to do it and also
it still would not get a range of a 1000.
Most likely only 300.

So there is no way that he could get that range.

But seeing as you couldn't see the car at 300 feet, does it really matter?.

Roboticinfo · 15th April 2005, 08:32 AM

True, but with a wireless camera
depending on the price, you could get one that would be capable of getting even a more greater distance then 300 feet, but would jack up the price of the little toy rc kit.

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12th April 2005, 05:45 AM	(permalink)
cyberquest	R/C toy car transmitter circuit Hi All: Can anybody help. Who knows about R/C electronics.I'm new to r/c electronic transmitters,I purchase a radio control toy car kit to build,and it came with the schemayic for the TX and the RX.The car has a range of 40 to 50ft. I would like to increase that range to the max 1000FT. that is the max set by the FCC-PART-15. THEY STATED to me 1300ft =1/4 mile. BUT I don't need to go that far. A i know its more than 50 and 300ft. there are cars that can go 1000ft because i seen them and wittness this. Like the one i purchase can go 40-50ft that not far at all and has the same internal electronics as the ones that can go alot further. Can anybody tell me and explain to me. What i have to change on the circuit and which parts. Or just add to the circuit. This schematic can beseen at this website httP://www.elenco.com/manuals/rcc-7k.pdf. The manual is (rcc7k). Icould not post it my self on this forum do to i have no scanner to scan it at this time. Sorry. Thats why i inclued the website. I hope someone can help me who knows R/C Electronics. I would like to know what kind of circuit this transmitter is set up as,are the two transistors set up as a darlington pair,is it a emitter-fellower circuit.What kind of circuit is it set up as. is it a series-parallel or a series circuit. The right side of this transmitter. What i also need to know is the of this TX is how they calculated for the frequency with those parts they used,and the output amplifier is there a low-pass filter on its output stage.I know only some basic electronics and OHMS-LAWS. IF anybody could help me to understand to calculate the oscillator to set the frequency in the circuit.I would Apprecite any help and your time posted. PS the company i purchase this kit from they can not help me on this subject. I KNOW this is alot to ask. thank you for your help and any info you post. JJ..

12th April 2005, 05:09 PM	(permalink)
audioguru	Hi Cyberquest, I think I replied on another web-forum. Your transmitter doesn't give the max allowed power probably because it gives the max allowed harmonics that cause interference on other frequencies. My son's RC car looked like yours but was bigger and was powered by a 7.2V big rechargeable battery. It went very fast and had a range of at least 400 feet. Its good range was probably because its receiver was very sensitive. It could pickup transmitters a few blocks away! Whenever my son stopped it, it would start running around by itself! If you boost the power of your transmitter, you might be controlling RC toys all over town, causing radio and TV interference and asking for a visit from the RF cops. __________________ Uncle $crooge

12th April 2005, 05:18 PM	(permalink)
mstechca	Be careful! There are frequencies that other people use around you. If you are able to jam those frequencies, then expect some trouble. I got caught a few times by my mom for screwing her T.V. up when I wasn't intending on transmitting on that frequency, and the transmitter was powered with a 9V battery. Your best bet is to get frequency information first. If the frequency is way up there in gigahertz where almost nobody goes, then you probably will be OK at transmitting at 1000 feet. I would suggest getting yourself licensed. Even ham operators can't transmit on certain frequencies without a license. and for the frequency, use the equation: 1 /(2 * pi * sqr(L * C)) sqr = square root of, L = inductor, C = capacitor, pi = your PIE button on your calculator.

13th April 2005, 06:21 AM	(permalink)
cyberquest	R/C toy car transmitter Hi again I understand what you're saying . BUT. I Check with my local FCC AGENCY. THEY TOLD ME any RF transmitters that is 100mW power output and under is find in my frequency band and does not have to be licensed. Plus these cars work at FT-bands that are licensed through the company who apply through the FCC for that band for the public to use these cars on. And 1000ft is within and under the range the FCC STATES IN fcc part-15 by law. Thats in the states where I'm locate. maybe the laws are different in your country. Or are you from the states. 100mW HAS a range just under 1300FT, thats stated by fcc part-15reg by law.Now as for CB thats a whole other avenue. They transmitter on AM and i think FM WITH output powers in WATTS. ANYWHERE FROM 3TO400 WATTS OR MORE. THIS IS WHAT I been told through the FCC. That WHY YOU need a licensed for CBs. not for a R/C TOY CAR. THERES always going to be some interferance with some frequencies on these small bands but that does not mean i need a licensed for a R/C CAR. GO IN TO RADIO SHACK AND ASK IF YOU NEED A LICENSED FOR A R/C CAR AND THERE ANSWER I BET YOU THEY WILL SAY NO. AS for the last part of your answer can you give me an example! please explain. this is what i need for you to be more elaborent on. I thank you for your time and your help. JJ 8)

13th April 2005, 11:01 AM	(permalink)
audioguru	I think that your toy car is too cheap to have more range. Maybe its transmitter isn't correctly tuned. Maybe its receiver isn't correctly tuned and doesn't have enough gain. Maybe the factory had to reduce the gain of the receiver so that it doesn't overload when close to the transmitter. __________________ Uncle $crooge

13th April 2005, 11:23 AM	(permalink)
Nigel Goodwin	Your answer is really pretty simple! - buy a 'proper' radio control system for a model car, instead of the 'toy' you currently have. You're not likely to find any suitable DIY designs, nor are you likely to be capable of building and aligning one (if you could, you wouldn't need to be asking here!). The reason for the lack of DIY is that it's so cheap to buy them, why pay many times the cost for an inferior DIY system?, when a commercial one is so cheaply available - plus the encoder/decoder chips aren't usually available to individuals. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

14th April 2005, 07:06 AM	(permalink)
cyberquest	R/C toy car transmitter to audioguru: I understand that the encoder operates on 3V. because it has a operating range of 2.2 to 5V . It uses a zener diode to regulate the 3V from the 9V power supply. the oscillator is set for the carrier band-wd of 29.9mhz but has a range of 27.0-27.9. do to the fact that the first xtal in the transmitter and not in the car. is basically solved by the wide open receiver designed. it will accept a singal around 27.9mhz ( if the car is tuned for 27) its not a specific tuned for a specific frequency. there is no xtal in the car just a crude receiver that takes in random noise from the antenna and filters out all frequency and lets throught the 27-27.9 range do to this open reciver design. if what you sad is ture in you answer. then i think mybe not to change any of the original design just add a third stage another power amplifier transistor to increase to 100mW with out over loading the power supply. 9V can handle 100mV and another stage.Can this be done. if not. explain why!. or can you gave me a circuit that would work for R/C cars. 100mW is the maximum power output that can be usedand i need. can you help. JJ

14th April 2005, 10:41 AM	(permalink)
JimB	cyberquest, I think you have just provided the answers to your problem, the quote you: "wide open receiver", "crude receiver" and to be perfectly honest, the transmitter is no better. You have bought a childs toy, the radio spectrum around 27 Mhz is full of low power devices such as yours, all squirting out poor quality RF signals, there is also the CB radio stuff. Your simple receiver is taking all this and just cant decode your transmitter because of it. OK, increase the transmitter power, add a power amplifier stage to the existing circuit. But, to be quite honest, the best way to improve that transmitter is to start again from scratch, it was designed to provide a signal at minimal cost, to control a cheap toy car. The advice you are getting here may not be what you were hoping for but it is the truth. JimB

15th April 2005, 07:08 AM	(permalink)
Roboticinfo	Reply That car is a kit sold from elenco it is about $26:00 dollars or in that range. If you were to replace the electronics with the expensive rc, you would be at a total of around 75 to more for a rc car. I think he want's a cheap way to do it and also it still would not get a range of a 1000. Most likely only 300. So there is no way that he could get that range. __________________ Robotics is heaven in my book.

15th April 2005, 08:32 AM	(permalink)
Roboticinfo	reply True, but with a wireless camera depending on the price, you could get one that would be capable of getting even a more greater distance then 300 feet, but would jack up the price of the little toy rc kit. __________________ Robotics is heaven in my book.