Help Choosing a RC car platform

[ibm123]

Hello all, i'm new to this forum

i'm working on my final project and my idea was to have 2 rc car toys which one of them will be controlled from a rc and the second rc car toy will not be controlled by the remote controller.

the second car will use sensors , dsp maybe and data transferring  with the first car and it will have to follow the path of the first car in real time.

so now i'm looking for the platforms.. i want to buy the platform and not to make it on my own.. anyone has an idea where can i find something that is good for my project ?

i was thinking about toys with servos so i can control the speed and cornering, also i need that the platform will behave like a real car/truck and not like Tank.

thank for the help

[Razor Concepts]

How much can you spend?

[Soeren]

Hi,

If they should contain servos, they arent gonna be cheap.
Cheap RC-cars are usually made with a crude "ESC" (one or two forward speeds and one back) and a bang-bang "servo" for steering (i.e. held in neutral/straight position by springs and the motor drives the wheels fully to the side when engaged).
You have to pay up to get the real stuff.

Go for used models. A few scratches in the exterior will get the price down.

[ibm123]

i can spend around 300$ maybe 400$
maybe i can make the servo my self ? i dont know..

the problem with used cars us that i need 2 from the same model so the two car will behave the same

[Soeren]

Hi,

i can spend around 300$ maybe 400$

I'm not sure of the prices where you are. In Denmark $400 would get you 1 (one) reasonably OK RC-car.

maybe i can make the servo my self ? i dont know..

I don't think so. If the car isn't made for using real servos, you haven't got room for them.
If you really mean to make them... Forget it.

the problem with used cars us that i need 2 from the same model so the two car will behave the same

It should be the programming that make them behave alike/the same.

[ibm123]

thank for the replay..

okay so lets say i will get the cheap toys.

will i be able to make this kind of project without a servo and only by programing ?

thanks

[Soeren]

Hi,

Cheap RCs are quite sloppy in the steering, but you could put a decoder on the steering angle and use PWM to get a sort of linear steering (wheels might oscillate like crazy from side to side, but the end result could still be a certain angle).
The speed control is much easier to deal with, as it can be replaced by your own.

If you go for this alternative, inspect a number of cars and select a model that appears to have a reasonable stiff control over the wheels (some will be very "loose" when not remote controlled) and make sure it will go straight when off (some can be adjusted by a small lever underneath the car, right between the wheels).

You can do much compensation in software, but the less that needs it, the better the end result.

[ibm123]

ok.. because i cant spend 400$ on one car i think i will go on the alternative.

i did not understand the decoder part so can u please explain to me why do i need the decoder and where should i interface him

thanks

[Soeren]

Hi,

A decoder for the steering angle can be any kind of rotational decoder you can find.
Patterned disks read by IR is probably best, as it can be made flat and only the IR devices will need room in the height - could probably be mounted within the chassis and be protected from ambient light that way.

Did you consider how you want car #2 to follow the controlled one?

[ibm123]

i'm not sure about the communication protocol i will use
but i thought that the first car will have acceleration and speed sensors which will send information to the second car
the second car will get the information and will have an additional distance sensor

with all the information the control system of the second car will calculate the delay of the execute

that way the second car will hopefully behave the same as the first car

this is the big plan.. but much more details should be considered...

i need to choose sensors, controllers,car platform, communication protocol and much more..