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Object avoiding robot question

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Krumlink

New Member
That will be difficult, you better get started.
 

birdman0_o

Active Member
Schematic***
Your going to need to do better than that if you want it to work, perhaps invest in Sharp digital IR sensors, which send a positive pulse when something is within about 80cm (perhaps too far?) and then you can use this signal to drive two transistors.
Btw: transistors need a resistor at the base, also you probably need a protection diode across the motor
 

shimniok

Member
If you want to make it super simple you could just use an IR pair... won't be perfect, won't be totally reliable ... that is how one of my kit robots works. My scratch bot uses the Sharp sensors. Those come in a variety of distance ranges as well as digital vs. analog types (ie, on/off versus voltage corresponding to distance).

I'm pretty sure your design will not work at all.

First, you should describe exactly how the robot should behave. (Requirements) Is the robot always moving forward straight? What does it do when there's an object? Stop and turn? Steer while moving? Back up and point 90° left or right? If you don't know what you're trying to accomplish, you can't build the circuit. You have to define the problem before you can solve it.

Once you have your requirements, then break the problem down further. Learn how to build a circuit to detect an object and send a logic high signal (or select a pre-made device to do this). Learn how to properly control motors using transistors -- depending on your requirements your motors may be in only two states: off or forward, in which case one transistor is needed versus an H-bridge if the motors need to reverse.

Michael
 

fredy

New Member
It keeps going forward untill there is a object than turns left when a object in front of it is detected:)
 
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shimniok

Member
ok, cool.

So basically you just need to have one detector in front, two motors, and control the left motor whenever there is something in front. That way it will steer left until there is no longer something in front...

This actually shouldn't be too hard to do. It's nice and simple.

1. Look up how to detect an object in front of you-- I think your easiest approach will be to use an IR LED and IR remote control receiver (usually in a 3 pin package). Usually pages that talk about this describe how to modulate the IR LED at 40khz. I've prototyped this approach and it works pretty well.

2. Figure out how to use a single transistor to turn a motor on and off.

3. Figure out how to turn the transistor on/off based on output from the IR circuit. Hint: the IR receiver outputs pulses when something is detected, so you will need to use a capacitor, I suspect, drained through a resistor, to ensure when something is detected the voltage remains constant and high and when something isn't detected the voltage drops pretty fast.

Ok, do some research and see what you find...

Btw, logic chips to do all this is kind of overkill I think since you should be able to do it all with a few discrete components.
 

fredy

New Member
The robot is spose to be really small and simple. I don't really know wahat type of transistor i need or if ill need resistors and diodes, I'm not electricall enginer lol:D
 

fredy

New Member
The robot only uses a not gate so when the signal comes from the sensor the gates output will turn of which will be connected to a transistor acting as a switch to turn the left motor off
 
IMHO Swordfish BASIC is far superior the the PICAxe, an initial cost of a PIC 18F programmer and you're in business.
Quite agree!! as picaxe as a very limited no. of lines available on the chips.But for simple programming (no programmer required) and resource available a good start as the op. seems to avoiding microchips even though it the sensible option and the beneficial one (in either direction).

I suppose it's down to choice on where to start.

Google and see where it leads!!

W.
 

shimniok

Member
The robot is spose to be really small and simple. I don't really know wahat type of transistor i need or if ill need resistors and diodes, I'm not electricall enginer lol:D
Choose the size and motors / wheels, then we can figure out transistors.

You don't need a not gate. Or any gate.

A transistor will (generally speaking) pass current depending on whether the signal going into it is high voltage or ground.

I am wildly oversimplifying.

Two types of transistors worth considering, I think. BJT (Bipolar Junction Transistors) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Two types of each. BJT has NPN and PNP which describe the types of materials sandwiched together. It has three pins: Base, Collector, Emitter. The Base is the 'input' that turns it on or off. The current flows through the Collector and Emitter pins. MOSFET has n-channel and p-channel and has Gate which is the input that turns it on/off and Drain and Source which the current flows through. The idea is that your detection sensor circuit would send the appropriate signal to either the gate or base of the transistor permitting one motor to run or not.

There's more detail but research some more, pick your size/motors, and can go from there. For motors on a small bot I would think some kind of servo modified for use as a motor would be a good choice.

Michael
 
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