I want to built a Transmitter and Receiver for Radio Remote controllled Airplane - Page 1
Forum section: electronics / beginners

author: Alexandros81
author_rank: Regular Contributor
timestamp: October 08, 2013, 10:18:01 am
content: Hi I m an electronic engineer and I want to re-examine my third year project. I never got to finish my project so now is a good opportunity for me to get back to it. It's about a Remote controlled model plane. In the original project i supposed to transmit data from a PIC but now I want to have a GUI on my PC to send data out via the transmitter. Consider that I have 8 years since that project so I have almost forgot all about it. and my report wasn't that good. Basically I want to built the Tx and Rx out of transistors. I don't want to buy an RF module. I want to go through the blocks that the Tx and Rx consist of, understand the theory behind it and finally built it-test it etc. I am now going to set up my own lab at home so I am checking out at EEVBlog.com all the info regarding setting up a lab and instruments that I would need.I don't have the specs for these Tx and Rx but I guess I good range would be 200m-300m.So let me know some suggestions and links to sites that might help and i'll start from there.Thnaks a lot - Alexandros

author: Paul Price
author_rank: Super Contributor
timestamp: October 08, 2013, 11:11:22 am
content: I am quite surprised you are a 3-year electrical engineering student and haven't learned how to use an internet search.You should start by looking at IC datasheets and schematics of proven Tx and Rx circuits, stuff that has been tried and works. Google it.https://www.google.dk/search?q=Remote+control+schematics&tbm=isch&tbo=u&source=univ&sa=X&ei=aupTUtWRH8f04QTHxoGwAg&ved=0CDQQsAQ&biw=1134&bih=863&dpr=1Hint: You can learn from wireless remote control circuits used for doorbells or RC control, the former cheap to buy at your local Walmart. Some operate at UHF freq using a single-transistor Osc. for RF output.If you use a single transistor to create a Xtal-controlled oscillator, then you could transmit and receive using pulse-width modulation methods.Long RF Pulse=Serial start pulse followed by "Shorter" pulses = 1 and 1/2 on time "Shorter" RF pulses =0's A single bjt RF-output stage would boost the Xtal osc. output power and provide a on/off modulation point at the same time.Transmitted serial control strings can be sent twice, first true logic data and then complemented(inverted) so this technique can knock out receive errors by comparison mentods.You could create a TRF or superhet or a superegen receiver. You can make a super-regenerative receiver using just a single transistor or a very sensitive TRF or superhet using several single transistor stages, perhaps a RF MOSFET RF-amp front end and otherwise use bjt transistor local Osc and 455KHz IF stages and just a diode detector. Then you have data to feed to a MCU. You can use 455KHz ceramic resonators for bandpass filter in the first IF stage.

author: F4CPY
author_rank: Contributor
timestamp: October 08, 2013, 11:51:19 am
content: hiFirst of all thing to consider is what you're allowed to do.Some countries (like mine) are very conservative toward the radio spectrum his use and power without a licence.For a plane project, and a link about 200-300m, your transmiter will not need a strong power, but you'll have to make a link budget (frequency, attenuation, receiver specs...).Be more precise about what datas must be exchanged, that can give indication about modulation, band width etc...

author: Paul Price
author_rank: Super Contributor
timestamp: October 08, 2013, 01:05:14 pm
content: It is quite obvious that all countries, conservative or not, have and allow RF wireless remote controls. People everywhere open and close the locks on their car doors and garage doors with them. Toy shops sell RF controlled toy cars and trucks to kids. You don't have to look very far to find allowed RF remote operated consumer equipment.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 08, 2013, 03:46:59 pm
content: The OP really should be careful not to interfere with properly licensed frequencies.35MHz and 2.4GHz are popular in the UK for model airplanes although I'd say that the latter is definitely the dominant force now. Output power is limited compared with US standards. It used to be 27MHz but unlicensed CB users dumped all over that. I think that a lot of the cheap RC toys are on 27MHz or they're very low power anyway so that isn't really an issue for serious flyers.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 08, 2013, 05:17:12 pm
content: Quote from: Paul Price on October 08, 2013, 01:05:14 pmThat's true enough, but that doesn't mean there are no rules to follow. There are certain frequency bands assigned for this type of thing, but they vary from region to region. The frequencies used for door locks and garage door openers normally have pretty heavy-handed restrictions on the duty cycle, so you can't use them for continuously sending control signals to a remote control plane, for example. The frequencies typically used for cheap toy RF cars and trucks have limits on the power that restrict the range. There are normally limits on bandwidth and spurious emissions, and it may be difficult to determine compliance with these limits unless you have some fairly sophisticated equipment. In most places, unlicensed radio transmitters must be certified by some government agency to demonstrate that they meet these regulations, though the chances of getting caught and punished for a homebuilt transmitter are low as long as the transmitter complies with all the other standards.Anyway, before choosing a frequency, power, and modulation scheme, you'll want to learn about your country's regulations. It's probably doable in most countries, but the precise details of how to do it without running into trouble with the authorities will vary somewhat.In the US (and probably in many other countries), if you want to experiment with building your own radio transmitters, I'd recommend getting an amateur radio license, learning the rules, and staying in the portions of the ham bands designated for your purpose. There are other approaches that could work, especially for low power, but this is an easy enough way to stay legal and do a lot of experimentation, perhaps including high power levels. A ham license is $15 for ten years, and anyone who has completed a course of study in EE should have no trouble passing the highest level of the test. It might require a bit of study of rules and operating practices.