How to Build a PC Controlled RC Car
Update August 2012:
See the Programmable RC Car article for an updated version of this project.
This project article was originally written in 2004 when most computers had parallel ports. This is no longer the case, so much of this information is now outdated.
The Mini RC Car Project has been one of my favorites to do. If you haven't checked that project out, please read through that one before starting on your own. I've gotten a few e-mails requesting a guide and since the software is done, all that is required is to construct the hardware. This is the second time I've done this project, using totally two completely different cars. The remote PCBs (electronics) were almost identical in both, so I'm assuming most all mini rc remotes are very similar, so this guide should be able to apply to all makes and models.
Tools and Materials Required
|- Mini RC Car & Remote
- (5) Wires 1-2ft long (or 1 cat5 network cable)
- Misc. small wires
- Wire Stripper (or knife)
-Scissors or Wire Cutters
-Small piece of plastic or plexi-glass
- *Some basic soldering skills
|- Soldering Iron
- (4) 2N3904 NPN Transistors
- (1) Small solder board
- Male Parallel Port Connector
- Digitial Multimeter if Avaliable
Total Cost: (not including tools)
Approx - $20.00 cdn
(Most of the tools required, all laid out)
(Retract-a-bit Mini Screw Driver. Very Useful)
Transistors and Solder Board
Step One: Open Remote and Expose PCB
With the antena unscrewed, remove the 3 screws from the back of the remote. You will need a fairly small screwdriver.
1 - Screw Hole Locations
2 - Buttons and Screw
3 - Attached still
4 - The PCB is free
The following corresponds to the pictures
1 - Screw Hole Locations
Remove the screws and the remote face should come off easily.
2- Take note of the button locations and remove the bottom right screw holding the PCB in place.
3- The PCB is still attached. Snip the wires close to the circuit board, but leave enough of the wire to identify the colour, for when re-attaching later.
4- The PCB should now be free, making it easier to work on.
Step Two: Drilling the Remote Case
Step Three: Soldering to the Board
|Strip the ends of the wires. Five wires, about 1-2 ft in length are needed. I used a Cat-5 network cable that has 8 wires in it, but only 5 are required.|
Step Four: Build the PC Interface
This is the most callenging part of
Before you start building the cable, feed the wires you soldered, through the hole you drilled earlier. This will allow you to put it all back together again at the end.
The rest consists on building a circuit, using the schematic (diagram) I have made up. For this you need, a bunch of small wires, solder board, (4) 2N3904 NPN Transistors. Print out the schematic below and build the circuit. (Note: the ground is the Parallel Port Pin 23 and Remote Negative Terminal connected together, there is no 'third' ground.)
(Click for a Larger Image)
Pictures of Circuit Construction:
Follow the schematic, but these may help you out. These pics do not show full construction.
If you've followed the schematic and completed the following steps properly, all we have left to do is re-attach the wires cut at the beginning and put everything back together.
Step Five: Reattaching the Wires
In the first step, you cut some wires. Those will now need to be re-attached. I would suggest replacing them with your own wires and use longer ones. The factory wires are very cheap and it's a lot easier just to use wires double as long, so you have enough room to solder them to where the old wires use to be. You can always just strip the old wires are re-attach using electrical tape, but I think my way is easier. The choice is up to you.
Step Six: Reassembly
|After the remote is put back together, the hardware aspect of the project is complete!|
Making it Look Nice
|To make it easier to plug in, it's best to have a solid unit to plug into the back of the computer. I took a small piece of plexi-glass and glued all the components to it to make it sturdier, easier to handle and it makes it look a whole lot better.|
The remote will still function normally if you use it just by pressing the buttons, but to control it with the computer, software is needed. For my grade 11 final computer science project, I built this hardware and wrote the software to control it. To control what you've just constructed, you will need the software as well. It is avaliable here. To make the software work, you need to know the port address of your parallel port. In the documention included (documention.doc, in the zip file), there are clear instructions how to find this address. The most common address (888) is the default. The software was written in Visual Basic 6, and was recently updated to run on all windows operating systems.
Source code for a similar, but simpler example program can be found here (also written in VB6).
Quick Lesson: How it Works
With the software, the computer sends a signal from the parallel port to the transistor. The transistor closes the circuit between the ground and the positive side of the button switch. This is the exact same thing that happens when you press the button manually. So essentially, the computer is pressing the buttons for you. Because we can control the computer, it means we can make the car programmable and other neat stuff like that.
I hope you've enjoyed this guide and learned something along the way. If you do construct your own Computer Controlled RC Car, and send me a pic I will post in on the site. If you have any feedback or questions let me know and I'll be glad to help. If you have any difficulties along the way, let me know and I'll try to help you out. Controlling the parallel port is quite easy and it opens to door to a whole lot of PC-Hardware interfacing. With transistors, you can control motors or other electronics. My latest pc interfacing project was my grade 12 computer science project, which was to control an LED matrix of 140 LEDs, with just the handful out outputs of the parallel port (some additional electronics were required). That project will soon be posted in the projects section.
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