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Topic: modding an RC car (Read 15 times) previous topic - next topic

DuaneB

Hi Cr0sh, Destined,

I just wanted to point out to avoid confusion that while I have been asking questions in this thread, I am not the original poster. I trust this is not a problem for anyone as the questions are relevant and also relate to a radio controlled car.

Just to clarify why I am looking for an input buffer, my receiver operates on around 6v, at present I have this connected to an Arduino interrupt through a 1K resistor. It works very well, noise from the FETs and Motor is not a problem however I am concerned about putting 6V into an Arduino Pin. I did try a quick and dirty work around with a series diode to drop some of the voltage but would like a cleaner long term solution.

In looking through the 7400 Series ICs, I see many buffers, some that have protection in the form of built in voltage clamping diodes, but they all seem to be designed to buffer demanding outputs rather than buffer/protect inputs, is this because the opto-isolator is the preferred solution in this application ?

Thanks

Duane.





cr0sh


Hi Cr0sh, Destined,

I just wanted to point out to avoid confusion that while I have been asking questions in this thread, I am not the original poster. I trust this is not a problem for anyone as the questions are relevant and also relate to a radio controlled car.


Actually - a separate thread might be better for all...


Just to clarify why I am looking for an input buffer, my receiver operates on around 6v, at present I have this connected to an Arduino interrupt through a 1K resistor. It works very well, noise from the FETs and Motor is not a problem however I am concerned about putting 6V into an Arduino Pin. I did try a quick and dirty work around with a series diode to drop some of the voltage but would like a cleaner long term solution.


Hmm - did you measure this output from the receiver, and actually see that it was 6 volts? If so, no - you don't want to do that, even if it looks OK (indeed, if this has been this way for long, you may have already damaged your Arduino...). Instead, what you might try is to set up a voltage divider using a trimmer potentiometer, adjust that for 5 volts maximum on the final output (wiper is final output to Arduino; other two legs go to ground and your output from the receiver).

In looking through the 7400 Series ICs, I see many buffers, some that have protection in the form of built in voltage clamping diodes, but they all seem to be designed to buffer demanding outputs rather than buffer/protect inputs, is this because the opto-isolator is the preferred solution in this application ?


Your concern here is voltage - not current, because the Arduino will take what it takes on an input, which isn't much BTW. So - you just need something that will take at least 6 volts, but its output remain in the 5V TTL level while supplying say 10-20 mA for the Arduino's input. If there is a buffer IC that will do this, use it. If you want to use an opto-isolator, use it too (but normally, and opto-isolator is meant to isolate completely one circuit from another - especially where there is the chance of high-voltage kick-back spikes occurring; say when you are switching large inductive loads using a microcontroller or similar).
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

Destined

#22
Jan 16, 2012, 08:58 am Last Edit: Jan 16, 2012, 09:02 am by Destined Reason: 1
Hey DuaneB I don't mind at all if you post in this, but you might get better answers in your own (however you seem to of got pretty good answers in this one :) ).


I have moved through all the steps. My soldering was better than i expected :). I managed to find a black and red wire and using blue for the controls.


The car doesn't appear to have a turbo. Looking at the bottom of the board, the point doesn't appear to go anywhere so this would make sense.

Forward/back/left/right all work and the left and right flick back into position when I remove the probe.

I love the idea of labelling the wires, i haven't done it but I am going to buy some stickers to fold around them because it will really suit my purposes in the long run!


So what should I (we) do next? (by the way I almost have my arduino running with a wifi shield, so looking forward to controlling it from my phone!).



kind of an aside cause we aren't there yet.
Will it be possible to run the motors slower? Will it be possible to turn the wheels in increments rather than just left or right? (I am guessing the answer to the second is definitly no). Will I be able to power the arduino from the cars battery?

What sort of things should I be looking for to be able to do those things? (i bought the cheapest truck i could find in order to test, but if this works out I plan to spend more to get one which can do those things).

Again thank you for your time and patience. You are giving me way more help than I ever expected to get.


DuaneB

Hi,
   To get back on topic, you should be able to control the speed of the motor with the Arduino. Here is a nice set of experiments that Oomlout.co.uk provide with their Arduino Starter Kit, it also has a servo which would give you the proportional steering.

http://oomlout.com/products/ARDX/ARDX-experimenters-guide-WEB.pdf

See page 12 for controlling a toy motor of the type in your car and page 14 for controlling a servo which would give you the proportional steering. I am assuming your car doesn't have proportional steering so you would need to buy a small servo from somewhere.

Duane B

http://rcarduino.blogspot.com/





Destined

Thanks for the link. I am hoping to find an RC car which does this I can mod so I use the base of car (and build a fibreglass covering to make it look like what i want).


Is the next step to take the move/turn wires and put them into the digital outs of the arduino and set them high and low to switch them on and off? Or will that blow up my arduino?

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