I think either the "seek the light" or the "keep the wall on your side" technique would be fine for your purpose.
The "stay close to the wall" method is probably more versatile because it could work in any room with walls...
The "seek the light" method sounds a little cheaper and easier to implement (just a gut feeling). Just point a bunch of CDS cells around the perimeter of the car, read the values into your ADC channels and look for the one with the lowest resistance. If the lowest resistance one ISN'T at the front of the car then you need to correct the steering until is.
With the light method, you'll need to regain control before the car actually GETS to the light, or have a way to make sure it passes to one side so the car doesn't dive straight into the heart of the sun...
Decisions have been made. Avoiding the complexity of servo steering and electronic speed control drive wheels seems like a good decision. I am not comfortable with my very dated electronics (read that voltage control, FET's, current surge capacitors) memories.
I will make a fritzl-like wall hugger
(http://letsmakerobots.com/node/928)
that can also be radio controlled. I will use my toy level car much like fritsl's. I have a HiTec Ranger III RC system complete with a HiTec HFS-03MM three channel receiver.
I have Microchip's DM164120-2, a small demo board with a PIC16F887 device on board and a small surface mount prototype area. I am learning how to code it with PICbasic Pro.
All I need to finish are the SRF05 proximity sensors.
The appeal of the RC cars for hooking middle school students into technology is their near perfect miniaturization of real automobiles.
The toy grade cars just do not have that appeal. They are also too slow.
I understand and can probably duplicate the Pulse Width Modulation waves needed to control the hobby grade motors and servos. The car that I have has three channels. One is unused, it can be the signal controlling the switch from and to autonomous mode.
The idea of using velcro to attach the proto and PICkit boards has eased my mind allot. It is so obvious. Why did I not think of it?
I think, after being certain yesterday, that I have changed my mind. I shall modify my hobby level car for this project.
I am now using my hobby level RC car. I am having a Vcc problem. The RC car has a 7.2v battery pack to drive the wheels. These a big batteries, but the wheels use allot of power.
I would like to use four 1 and 1/2v AA batteries to power everything except the drive wheels. That's six volts. The PIC wants 5v. I can not find reverence to voltage regulation inside the PIC. I think I need a voltage regulator - a subject about which I know nothing. Does just inserting a 5v regulator in the Vcc line from the batteries do the job? Which 5v regulator?
Lastly the USB port supplies a pin with 5v on it. Do I just put an ON/OFF switch in the plus 6 volt battery line and turn that source off when using the USB for programming?
Is having three sources of power a blessing or a hindrance ?
If you use 4 AA rechargeable batteries then you will not need a regulator, nominal voltage is 1.2 volts each. But the PIC you are using will run on 2 volts with the 8 Mhz OSC...
So... Use any AA battery pack with a LM317 voltage regulator set to run at ~3.6 volts for the PIC. You will need three 470 ohm resistors to set the regulator. Then you should be able to fire the transistor that is triggering your relay from the PIC.
So... Use any AA battery pack with a LM317 voltage regulator set to run at ~3.6 volts for the PIC. You will need three 470 ohm resistors to set the regulator. Then you should be able to fire the transistor that is triggering your relay from the PIC.
Originally Posted by mackrackit
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