not sure what to do...

[danielsmusic]

i want to build a very simple robot it does'nt have to controlled by the pc.
but i want it to think for its self. has anybody got any ideas i have three motors i want to use for it, 2 stepper motors(powerfull) and a normal motor still powerfull. the stepper motors are different so i don't want them on each wheel stepper motor drivers are no problem i just use a 4017 and transistors. i need help on the thinking side, the only sensors on it are going to micro swiches on the front in case it crashes. what electronics would i use to make think for its self and detect and move away from a crash

 

[Someone Electro]

Microswitches are not realy good for this since the switch can only be pused a few milimeters in.The bot wod literaly ram in to the wall.(probobly leving a visible mark)

So a beter way wod be to have long rods to sense if it hits somting.The rod wod simply be bent back making contact whith a wire an that wod tell the MCU that the bot is going to hit an object if it keeps going.To preventi hiting the wall the MCU wod simply reverse one weel to thrun the bot.If it hits a wall directly so that bouth roods make contact it has to back up by truning bouth weels backwards and then thurn left or right.

Since you dont have 2 identical motors you cod do power steering like in a car.This is more complicated and it makes the harder for the robot to control

 

[danielsmusic]

im using a old model car i found. stering is not a problem because it already has a lever i turn with a motor and it turns. the same with drive it a diffs on it so driving with one motor is ok. i just need to know how it will detect a hit then revers and go forward a again im goin to trash the micro swich idea and use what u said.

 

[Someone Electro]

You dont neeed a rod,1mm or more coper wire from an monster coil wod do.

You simple mount is at 45° on each side and wen it hits somting it will bend back an make contact whith an second wire that is behind the thick one.You can make this yourself easaly. you cod melt the two wires in a pece of plastic whith a mounting hole an you have your own wall sensor made in a cuple of minutes.

If you alredy have your power steering just mount it on a board and make to other motor power it forward.You cod freely use the DC motor since who cares exsacly how fast it spins.

If the drive motor is too powerful the bot may be clumsy whithout PWM.Since whithout PWM you can only run it at full power or no power.The problem is the motor is going to fast so the power steering motor cant steer that fast and it may bang head on directly in to a wall(Ouch!).

If the motor is too powerful sliping can be a problem too and whith a diferencal makes ti even worse.I once made an simple car to see how powerful that vacum clener motor was( 11000 rpm,realy loud and powerful as hell).The thing was even i used big tires it sliped and that made it trurn up to 90° and banged right in to the hallway wall sending the batery pack flying (It was simply put in a hole and i didnt strap it in since i thorwn it togeter fast.)But it had tromendus aceleration.

So how powerful is your motor?

 

[danielsmusic]

not as powerfull as that but very powerfull it is a stepper motor run directly from a car battery.

 

[Someone Electro]

For the drive it wod be much easyer to use the DC motor since it dosnet need to spin at an exsact speed.It also makes the code simpler.

Do you also have the drive electronics for the motors?(H bridge)

How fast dose the motor go? Is it slow enugh for the power steering.Since power steering needs some time to react.

Do you hav any experiance whith microcontrolers ?(Using analong stuff your bot may be a bit stupid and react wrong)

I have 2 identical DC motors from an realy old VCR.They are small but quite strong and i run them from 20V.the first thing they ware used is to drive 1 weel each in a car.I way feeding power to each one trough an 10 m wire.I used 2 micro switces from an phone.You needed some practise to get it driving good since it was damn fast.My dad tryed it out an after about 1 minute he acsedentaly drived it right down the stairs.It needed some repair to make it going agen.It way hilarius to se it rool down the stairs that fast.

Since the wire had 1 more line free i put on an ruber band canon.(You shod see my mom wen i unexpetedly fierd it at her)

Even i am shoring the motor wen the switch is not pushed,It drives about quater of an meter forward from the point the switch is relesed.This is probobly becose of the big and heavy tires i used.

 

[danielsmusic]

it is going to be electronics 2 4017's to control each stepper i don'y have a up/down counter

i have a pic of the model.

 

[danielsmusic]

another

 

[Someone Electro]

So this is the RC car.

Dose it alredy have the motors in ?

All you need now is the control circuts.

Anyway what kind or "brains" will your robot have? Analong makes to bot much les "smart" and makes it harder to add stuff but you dont have to make an program.On the other side you can use an microcontroler.Whith good programing the bot can be prety smart and it easy to add fetures.But if you have no experience in MCUs you may have a hard time.

You can do it analong but the problem is how to make it react wen bouth rods are making contact (directly facing a wall).Whith an MCU you wod simply program it to go backwards and then left or right.This can get complicated doing analog.(But it is posible)

 

[danielsmusic]

im useing both, relays that "latch" when it hits somthing and a mix between 555's and logic chips to revers and turn.

iv mounted stepper motors because i want it to go slow like a explorer but be powerfull to go uphill(i don't want gearing i hate it :evil: ).

the "brains" will be simple, for forward run a 4017. for backward use a 4017 but connect the wirs backwards the relays will switch between 4017. and the 555 timer will "tell" how long the relay will stay on for.

ps:if you don't know a 4017 is. it is divide by 10 counter.

 

[danielsmusic]

iv had an idea about wall sensors.
you can buy "kits" from maplin, a ultrosonic parking aid one of those ones that beep as you get close to something. i could modify one.

 

[Someone Electro]

You cod.

Nigel has on his page an circuit of an ultarsonic obstacle detertor.It has 1 digital output that tells it to go left or right.


Oh an the problem whith the 555 timer wod be that wen it switches back in forward it will get in to the same wall agen and agen.You must slitly trurn it left or right so it dosent met the wall heado on agen.

 

[bryan1]

Hiya Daniel,
It's got me baffled how your going to control a stepper motor using a decade counter as stepper motors need a certain bit pattern to energise the coils. Why not just use a simple picaxe chip for your project, by using an 18x or higher you could not only drive the steppermotors but also use the spare pins for the brain (so to speak). There is a heap of info available on the net and you'll find most of the code needed will be there for you to find. The picaxe is a great for robotics as coding the chip is done in a very easy basic programmer. Alot of schools are now using the picaxe to teach students and there is a heap of info out there.

Just a Thought
Cheers Bryan

 

[danielsmusic]

Hiya Daniel,
It's got me baffled how your going to control a stepper motor using a decade counter as stepper motors need a certain bit pattern to energise the coils.

this stepper motor just need a counter to create the sequence

 

[danielsmusic]

maby i was wrong about the sequence i bult the stepper motor driver it worked but was vibrating too much for how fast it was going.
can anybody help me with this too.

 

[Someone Electro]

Meaby your making an step back someware.

Try driving it realy slow (Make the counters clock about 1-2 Hz).And watch how the motors shaft thurns.It may be sotping or thruning backwards a bit in the seqence.

 

[Nigel Goodwin]

maby i was wrong about the sequence i bult the stepper motor driver it worked but was vibrating too much for how fast it was going.
can anybody help me with this too.

As already suggested, a decade counter doesn't seem a good choice to try and do this with?.

A PIC makes it simple to do, and you can use the motor in various ways as well (full step, half step etc.), or there are specific stepper motor drive chips, which you simply tell to go forwards or backwards.

If you google for "stepper motor tutorial" there is a LOT of information available, and plenty of examples.

 

[danielsmusic]

thanks, i still mite use a 4017. only if i can't get my pic programmer to work.