Show Posts
Pages: [1] 2 3
1  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 14, 2014, 12:16:20 am
Seriously can't thank you enough for the reply, you guys have been extremely helpful with this project.

Just a quick question though in terms of options available:

Would it be possible to remove all the circuitry inside the RC car, leaving only the motors and rechargeable battery, then use a micro Arduino to replace what was once the circuit board? Then buy transceivers for my main Arduino and each RC cars' micro Arduino, thus allowing my primary board (a mega 2560) to communicate with each micro Arduino on the RC cars.

I opened up one of the RC controllers and the circuitry was much more complex than I had imagined. My guess is that a lot of it is filters in order to eliminate all other signals other than the desired frequency?

I would build an RC car myself, but it would be nice to take advantage of the steering linkage, axles, wheels and body of a pre-built car that I could then modify.
2  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 13, 2014, 06:07:06 pm
Ahh ok, I must have misunderstood one of the articles I read.

One thing that confuses me is despite the popularity of the 27 and 49 MHz transmitters for RC cars, I can't seem to find any transmitters for these frquencies. Is this due to, as you said, the proprietary technology the RC car manufacturers use?

Well this point it looks like I'm down to two choices.

1) Use relays soldered to the original RC controller to accomplish what I need. Similar to this method:


2) Use the Arduino Micro's/Mini's and modify the RC cars' cricuit board with them.

Which would you recommend in terms of both cost effectiveness, simplicity, and fast response to inputs?
3  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 13, 2014, 12:43:25 pm
I really appreciate your help in all this, finally starting to understand how this is going to work. And extremely sorry for this huge wall of text and questions I'm about to bombard you with.

**For this hypothetical example I'm going to use the 315 MHz transceiver, just because the math is a little easier, however when I actually attempt to build this I will use 2.4 GHz transceiver.

So I have four 49 MHz RC cars that have four different channels. I'm trying to control all of them with the computer and preferably a single Arduino. My goal is to not modify the actual cars in any way and instead simply mimic the controllers RF output by using the transceivers on the Arduino.

If I understand this correctly, and was using the 315 MHz transceiver, for one of the 49MHz cars I would need it to modulate between (315 - 49) and (315 + 49), so between 266 and 364 MHz.

For the different channels this is then modified very slightly? So maybe the first channel is 49 MHz, the second channel is 49.2 MHz, third is 49.4 MHz and the fourth is 49.6 MHz, or something along those lines?

So if I had the transceiver, in order to find these slight differences in frequency I would use the receiver capabilities of the transceiver and select channel one on the RC car controller and select any random movement (forward, reverse, left, or right) and with the right coding I could get the frequency to be picked up by the transceiver and then transferred to the Arduino? And I assume I could get this to display on the serial monitor.

Then I could do this for every channel and be able to know their assigned frequencies.

One thing I'm confused about, however, is how I would figure out the pulse sequences of each direction. I read this article about how RC controls work and just as an example they state that:

  • Forward: 16 pulses
  • Reverse: 40 pulses
  • Forward/Left: 28 pulses
  • Forward/Right: 34 pulses
  • Reverse/Left: 52 pulses
  • Reverse/Right: 46 pulses

Is this information that can be picked up by the transceiver?

Assuming it is, at this point I now have the assigned frequencies and pulses for each channel, so now it's time to program the arduino to control the cars. So I need to set up variables that say

CAR_1 = 49 MHz

CAR_2 = 49.2 MHz


But of course this is an extremely over simplified version of how this would go. In reality I have no idea how one would set the frequency.

I did, however, find this code online from a person setting up a circuit to remotely control their garage door opener and found this bit of code:

    // Set pulse length

    // NB Pulse length must be set AFTER Protocol,

    // because setProtocol(1) also sets pulse length = 350


I assume "mySwitch.setPulseLength(232)" is referring to the pulses that in my case would indicate direction? So based on the example I found for the directional communication, if I wanted the car to go forward (16 pulses) then it might looks something like this:


Thanks again for all your help!
4  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 02:41:49 am
Interesting! Wow those really are affordable!

My only concern with this approach is, would I need a separate bluetooth adapter for every board in order to communicate wirelessly with the computer?
5  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 02:29:16 am

Haha I'm definitely starting to agree with you, I think it would make everything much easier. My only concern with this method is the cost of buying 4 to 6 Arduino boards, in addition to any shield they might require. I also worry about their durability when it comes to RC car wrecks.

I'm also considering the possibility of using relays to accomplish what I hope to do and soldering the relay leads to the contacts on the controller. I found this tutorial that I think may make things easier. I would prefer to be able to use just my one Arduino Mega to control everything (to cut costs and simplify things).
6  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 01:33:40 am
Thanks for the reply, very sorry about the confusion, I'm not at all familiar with RF communication.

My mention of a 315 MHz transmitter was actually just an example, I would be ok with whichever worked best for my purposes.

That's interesting about the 433 MHz traffic, I had never thought about that before. I assume it's the same with 2.4 GHz transmitters? From what I remember, both residential internet routers and microwaves both run off of 2.4 GHz.

But I should definitely explain my idea first, I want to be able to have 4-6 RC cars that I can control via computer. Me and quite a few of my friends have Friday night RC car races and I think it would be awesome to be able to use our laptops as the controllers. It's extremely unnecessary, however it has been a dream of ours and I would love to make that dream come true.

I already have an Arduino Mega 2560, the RC cars we have are all the same, but operate on four separate channels. I'm looking into new RC cars that have a larger channel range but for now four channels is what we're limited to. So I imagine we need multiple transmitters to accomplish this task.

My assumption, however, is that this would require four separate PWM inputs in order to do this, which I also assume would require four separate Arduinos. Additionally, if I wanted to add the capability of having both steering inputs and throttle inputs triggered at the same time would I then need 8 separate Arduinos?

Thanks ahead of time, your help is greatly appreciated!
7  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 12:59:53 am

AH! That is exactly what I was confused about, so it is possible to select different channels, or frequency bands? So is this referring to the bandwidth of the signal? So four 315 MHz transmitters can transmit four completely separate signals by transmitting four separate bandwidths? If this is the case, how would one possibly adjust the bandwidth via Arduino, and would it be possible to send four separate bandwidths with just one Arduino Mega 2560?
8  Using Arduino / Project Guidance / Re: Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 12:47:01 am
Thanks for the quick replies! I really appreciate it!

Does this transmitter emit frequencies of only 2.4 GHz or is it adjustable? I tried reading the How-To pages that accompany this transmitter but didn't seem to get a definitive answer except that there's an example detailing how to "Transmit the position of a Joystick X and Y" which I assume means there must be different frequencies in order to do two things at once?

I really appreciate the link! While it was very detailed (and to be honest a bit intimidating), I'm hoping to use the stock receiver portion of the RC car, and use the arduino to mimick the output signal produced from the controller for the RC car. Maybe I'm in over my head  smiley-sweat

liudr: Interesting, although it isn't overly surprising I still wouldn't have imagine they have so much control over that. Although my use of the radio frequencies will hopefully be limited to the same bandwidth as most RC cars.

I apologize for my lack of knowledge on the matter, I thought it was a little more straightforward but I'm starting to doubt that. I read online ( that most radio frequencies for RC cars are 27 or 49 MHz.

My goal is to operate 4-6 RC cars via Arduino without any interference. However I'm struggling with understanding these transmitters that are advertised as having only one frequency.
9  Using Arduino / Project Guidance / Looking for RF transmitters, 315 or 433 MHz the only choice? on: July 11, 2014, 12:18:56 am
I'm looking for some RF transmitters compatible with Arduino and all I can seem to find is 315/433 MHz transmitters. Is this the max frequency or the only frequency? I assume it's just one constant frequency, but I wanted to ask because I find it odd that the only common transmitters are available in only 2 frequencies.

On a side note, is it possible to 'hack' a RC car controller and use it's transmitter?

To clarify, I'm looking to control multiple cars via Arduino (everything I've seen online has used an onboard Arduino, I'm looking to use an external Arduino to transmit RF frquencies, taking advantage of the circuitry already built into the RC cars).

10  Using Arduino / Displays / Re: Is anybody using the ElecFreaks TFT shield V2.2? on: February 25, 2014, 05:48:38 pm
Ok cool, I really appreciate the response. Hopefully we can figure something out, I've read about other attempts online at bending the backlight pin 90 degrees outward so that it can be individually operated, but hopefully it doesn't come down to that. As for the safety of the backlight, I believe it operates at 3.3V, and the shield uses the 3.3V pin on the Arduino. The ElecFreaks wiki for the LCD screen states the following (in very broken english): "TFT01 is work at 3.3v DC, if you need to connect the module with the 5v voltage I/O , you need to add the 30k and 20k resistors to reduce voltage." So as long as the shield is utilizing the 3.3V then I think we're in the clear.

Speaking of utilizing the voltages, does anybody know how to tap into the Arduino's voltage/ground pins once the shield is in place?
11  Using Arduino / Displays / Is anybody using the ElecFreaks TFT shield V2.2? on: February 25, 2014, 08:17:46 am
I finally broke down and purchased the shield for my Sainsmart 3.2" LCD screen after trying to wire it entirely with individual wires, which produced very poor results including inverse colors, weird lines, sd card slot didn't work and it didn't properly clear the screen. Now with the shield it works perfectly (with my MEGA 2560) and even the SD card works. My project I'm using it for is automating an aquarium as much as possible, which requires the Arduino to be running constantly (for the lights) but I don't necessarily want the screen to be on constantly. So I've been researching various options and most people seemed to be referencing a trimmer pot on the shield, which I didn't have. I have the ElecFreaks Mega Shield V2.2, which has a serious lack of information, ElecFreaks only has info for V1.2 and V2.0. So I did more research on the shields and found the following information:

LCD shield V1.0, trimmer pot circled

LCD shield V2.0, chip circled

The chip circled in the V2.0 is the same one on my V2.2 and by using a microscope it says AMS1117  3.3H327PE. Research on this chip yields the following information:

"AMS1117 series of adjustable and fixed voltage regulators are designed to provide 1A output current and to operate down to 1V input-to-output differential. The dropout voltage of the device is guaranteed maximum 1.3V at maximum output current, decreasing at lower load currents. On-chip trimming adjusts the reference voltage to 1.5%."

Which leads me to believe that the LCD (I imagine only the backlight) can be adjusted via the arduino instead of previous attempts for the V1.0 (which I found online) of removing the trimmer pot and using a transistor.

Does anyone have any experience with this particular shield (or even V2.0)?

12  Using Arduino / Project Guidance / Re: Reading CSV values from an SD Card on: January 26, 2013, 11:23:39 am
Reading csv values from an external file...I feel like I'm back in my Computational Methods class
13  Using Arduino / Displays / Strange Lines on Bitmap on: January 01, 2013, 11:10:29 pm
Hello everybody,

Currently working on my 3.2" TFT display (with SSD1289 controller) for my aquarium project.

Fortunately I got a second Mega 2560 for my paludarium tank the other day so I've been able to fiddle around on that and not have the LEDs on my tank flash every time I re-upload a program.

It has been a very steep learning curve for me but I'm starting to get the gist of it. The only software I've been able to fully compile and work is Henning Karlsens UTFT program and in that package the one that works the best that I've played around with and mostly figured out is the rotate bitmap example.

I managed to get my own pictures on it, as well as stop rotation, change size, and position of the picture. One thing I can't figure out is these annoying lines at the bottom right of each picture, assuming all the letters are their own little picture.

14  Using Arduino / Project Guidance / Re: RTC acting strange on: December 01, 2012, 03:03:49 pm
Well the RTC module has been working quite well for some time now, I've only encountered one issue: Daylight savings time. I figured I could just recompile the program on my computer and count on it working like it has in the past, grabbing the time off my computer, which does account for daylight savings time. Unfortunately though, the serial monitor displays the time an hour ahead when I try to re-upload the program.

My solution in the meantime is to change the times for 'sunrise' (dim on) and 'sunset' (dim off) accordingly, which I suppose works, however I was wondering if there was an easier way of doing this?
15  Using Arduino / Project Guidance / Re: RTC acting strange on: October 18, 2012, 12:51:18 pm
Lol I should've! Are you talking about the Phi-Connect shield and Phi-Connect breakout boards?
The Phi-2 looks like a cool shield, I would've definitely gone that route if the TFT LCD displays weren't as cheap.
Pages: [1] 2 3