Let's Make Robots!

RC car


As some of you may already know, I'm building an RC car which will ignore user input and prevent a crash when necessary. It'll run on an arduino platform. I'm waiting for my parts ATM and doing whatever I can on the chassis I already had (making a motor mount, making a deck to put the electronics on, fitting in a battery...).

All pics can be found here.

 

UPDATE May 5th, 2011

I just finished a 5V regulator to power my Arduino UNO board. Of course I kinda forgot Arduino accepts a voltage of 6-12 V. Stupid me. Going to mount the motor the the chassis and maybe cut out the deck.

 

UPDATE May 7th, 2011

Got the motor mounted, and tested it... Boy this thing is LOUD and powerful!

My mailorder arrived, trying some things out with the arduino. Love that thing already :D I'm still waiting for my other mailorder with 20 transistors and 2mm pin sockets for my H-bridge and my 2nd xBee. Will keep you guys up to date!

PS: I know the servo doesn't work with PWM, made a mistake.

 

UPDATE May 12th, 2011

Cut out the new deck and it rocks! There's just enought space between the base and the deck to fit the battery between them. Also, I've mounted the servo and tested the steering. I'm still waiting for those transistors :( 

Update 2: mounted the Sharp IR sensors, pictures are still here.

 

UPDATE May 22nd, 2011

Got my transistors and soldered toghetter my H-bridge... Now I only need to solder a 5V regulator and som pin headers to make all the connections to my µC. I'll keep you guys updated.

 

UPDATE May 26th, 2011

I completed the PCB which holds the H-bridge and a 5V-regulator. There is a problem with the H-bridge though... I use the BD911 and BD912 transistors in my H-bridge and they are not repsonding as I expected them too. More info in the fourth vid.

Datasheets on the transistors can be found here. Can anyone confirm that I should feed 5V to the base to make these things switch on/off?

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UPDATE July 19th, 2011

Since I couldn't get the H-bridge to work, I just tested the system with one transistor and a potentiometer (see pic). I found out that I will need a transistor to drive every transistor in the H-bridge. Too bad all radioshack-like shops in the neighbourhood are closed for vacation at the moment. Seems this project will take a lot longer than expected. I was happy to see the wheels finally spinning though :)

 

UPDATE March 20th, 2012

Alright, this has been some time! I kind of lost my eye on this project for a few months, but now I'm back on it! I've just finished soldering up the motorcontroller (pic below) and am now going to start figuring out how xBees work and communicate, so that will take a while to complete. At the moment, I'm kind of doing two projects at the same time, so it can be another while before I update this.

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Searched on about the topic and it seems to be right... Damn, now I'll have to rebuilde the whole thing to make room for a darlington pair :(

I hope those values are NOT correct, otherwise I can not use my arduino to power these transistors: I can only supply 40 mA and according to that web page I would neet 60-400 mA... Seems quite a lot if you ask me.

instead of making a big mess with all these transistors, use a motordriver. I prefer the l298HN because it has everything you need to get it working, no need for extra flyback diodes and it can handle some current and voltage. STM has the IC for free sampling.

First of all, this motor draws 2.8A if it is just driving the wheels with no load. The L298H won't cut it! And motor drivers are expensive if you need to handle 20 Amps of stall current

Second, I'm a hobbyist, I like doing things by myself. I'm not going to take the easy way and buy a motordriver but I'll make this thing work and learn a lot of stuff I didn't know before ;)

Thanks anyways :)

I'll do some measurements when I have the time (exams start in a few days). About the motor I can say the following:

  • Voltage: 6-8V
  • Unloaded current: 1.5A
  • Stall Current: 15-20 A (don't know for sure, don't want to fry my multimeter)

I'll try with even lower resistor values when I get the chance...

Thanks!

If your motor needs 6V to work well, you may need a higher voltage (~12V) instead of the 7.2V racing pack. You'll see when you take your measurements and determine how much voltage you lose across the transistors.

Good luck!

how did you calculate the torque for the propultion motor?

I see no use in calculating the torque. But if you want, I think it would be something like this: power=voltage*current. 'angular velocity'=2*pi*rpm. Torque=power/(angular velocity)

That should be about right :) if you can measure your voltage, current and rotations per minute, you can calculate the torque produced using the three formulas above. I cant measure my rpm's so I have no Idea about the torque.

it's so heavy that it does not move forward very fast and check this site out it shows how to build a r/c circuit for cars http://www.botskool.com/tutorials/electronics/general-electronics/building-rf-remote-control

Do you have the car posted here on LMR or do you have a picture of the motor? It really seems not that much...