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I am needing help, how to have a remote control car follow me. RF hopefully with a voltage comparator. Iam open for new suggestions. Please help. I am goig to use a PIC16F84A for programming.
The maximum distance i would like the to be from me is 3 feet. The surface would be solid flooring. No carpeting. The speed would at maximum, be at walking speed. I would be using a PIC16F84A chip and program. If it could avoid obstacles, that would be a plus but not needed. Im hoping to use RF , to avoid signal interferance. Thank you for your responce. I hope this will help.
This looks like a tricky one. You *could* use RF but to get any meaningful direction finding over such a short distance you would have to use rather high frequencies and the associated problems dealing with these even if it only uses micropower.
This is the principle:
you have an aerial strapped to your leg that a steady low power RF signal.
The car has a rotating dipole which seeks out the null in the signal. The null (least signal strength) occurs when the dipole points end on to the transmitter - you get maximum signal with the dipole broadside to the transmitter. You use some feedback loop to keep your car on track but:
you can see that there are 2 positions with a 'null'; pointing towards and pointing 180 deg. away from the transmitter. You would have to get around that one somehow.
The above is usually used the other way round, a car with a rotating dipole on thev roof wants to find a hidden transmitter. One soon figures out if one is travelling towards or away from the source of the signal by its received strength. I don't know how you would overcome that in a remote control car.
I would give RF away as being too difficult and, perhaps, try some optical method. A bright light at your heel gets a light seeking sensor on the car to follow it. You could use a segmented sensor, as described on this forum under 'solar tracker', to determine which way the car should steer.
my roommate, a senior EET student, tried to do an RF tracking device very similar to that as a senior project.
He spent the better part of a semester on it and never got it to work. I'm talking night and day, hours upon hours of work. It can be done but it's NOT an easy task. the difference in signal strengths between two receivers that are only a few inches apart is going to be very small so getting a useful measurement out of them is hard, as is calibrating them. getting a clean, simple analog output corresponding to signal strength isn't as easy as it may sound. there's a whole lot of analog circuitry to deal with, and you need good test equipment to build and test it.
it would be FAR easier to use modulated Infrared light. MUCH easier to work with, no real fancy test equipment needed, and if you look around you can probably find sensors that can handle the demodulation and provide you with an analog output corresponding to signal strength. some of the radio shack 40kHz IR receivers can be "hacked" to provide an analog output. being modulated it will still be resistant to interference, especially indoors, and the tracking is FAR easier since it is easy to make highly directional light sensors, whereas a highly directional antenna is trickier. This is essentially the system he ended up going with for his project.
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