This is my first instructable, be kind =3
Now my RC CAR has a proportional acceleration system, it works for backwards and forwards. See it on Step 5
The final result is here:
Step 1: Material List
You I'll need :
- A structure (sorry, I didn't took any photos of me making it). Mine includes a steering bar in the front with 2 wheels and the car motor on the back with 1 wheel.
- 2 hobby servos, one for steering (self explanatory) and one for acceleration (you'll see the magic very soon).
- A micro switch.
- 5V regulator for the receiver.
- 3S 2200mAh LiPo
- Instant glue
- Duct tape
You will also need creativity =]
Step 2: Fixing the Structure
Since my car is 3 wheeled, its very unstable. I've glued a little wing on the bottom of the car as shown on the picture.
If you build the same way I did, you can either do this or lower the center gravity of your car by placing the battery on the bottom of the car.
Step 3: Putting Things Together
Its time to mount the battery in the car with the battery alarm and the 5v regulator .
*Note: 5v regulator circuit is 5th picture
1- tape the cables to the battery
2- plug the regulator and the alarm in the battery
3- Now, Tape the receiver (radio Rx) to the battery, don't forget to tape the antenna tube too
It should look like the 3 picture.
Now glue the steering servo in the right place. Since it's a steering system, the center of the servo arm should be placed on the same line that the front wheels are placed. You can also carve a little space on the servo arm so the steering bar pin can slide in it. This will happen mostly because the servo is not centered perfectly.
Step 4: The OLD Acceleration System, Yet Simple
So, since the signal from the Rx radio is suitable for servos and ESCs (Electronic Speed Control), if you do not have an ESC for brushed motor like me, you'll have to either buy one, make it yourself or use magic.
I prefer magic myself, so here it goes....
All you have to do is make the acceleration servo toggle the micro switch that is in series with the motor of the car. Simple and effective, but you can't proportionally control the speed, only on/off. This was the best and quickest way to control the car that I found.
* Keep in mind that this setup, besides its simplicity, is not meant to be used in big motors/rc cars . It can damage the motor for the excessive job it has to do.
Follow the schematic and you are almost done.
Here is a video of the acceleration system in action.
Step 5: The NEW Acceleration System (Electronic Speed Control)
First you have to acquire the signal, than process it and finally use it.
To acquire the signal I wrote a code for arduino (atmega8) to read the servo signal that the receiver uses. It simply counts every x seconds while the signal is on high level logic (5v). The servo signal is on fig. 2 , the on level can be from 1 ms to 2 ms every 20 ms. Now you know the values from the signal and can use it to control the motor. Fig 3 shows the acquisition process and the max and min counts values. You can download the signal_tests.pde file in this post for testing the acquisition of the signal.
The only thing left to do is to use the data to control the motor. To do this, I wrote another code and works like a charm! The electronic schematic and the arduino (atmega8) code can be downloaded here. The code is commented, but if you ever feel lost you can always ask =3 .
A video showing the new acceleration system is here:
Step 6: Almost Done
Connect the voltage regulator to the battery, to the Rx radio and to the motor plug. Then plug the servos to the Rx radio and you are good to go
Hope you all enjoy this instructable. Go see my RC car, The Little Cricket, in action.