iwaver pcb in a zz mt, the cheats method!

ph2t · Post by **ph2t** » Sat Dec 25, 2004 8:33 pm

crazydave wrote:Alright, you cheater, betty, I want to know why this works and how you figured it out.

OK so a potentiometer, or pot for short is a like a variable resistor, and you're just replacing that with a constant resistance. So is it resistance from the pot that determines how far it turns? And I also got confused when I thought about it, because the only pots I know are the ones you turn by hand, like a volume knob. So how does the pot work in a servo?

I'm confused.

potentiometer = variable resistor = pot = trimpot (small version)

these are all the same thing, just different labels. A trimpot is short for "trimmer potentiometer" ie: a small pot that used to tweak a setting and left alone. not to be used frequenly. hence the name "trimmer", ie: to tweak....

By default the steering circuit is like the drive circuit. The one major difference is the steering circuit has a feedback loop. This is a general electronics statement, what the feedback look consists of varies. But the bottom line is that the feedback loop lets the circuit know what is actually happening in the real world.

ie: you bash your head against a wall, the feedback loop is the nerves in your forehead saying "you fucking idiot, that hurt!!!".

So the potentiometer in the steering servo tells the circuit where in relation to centre the little servo knob thingy is. IF you remove this little potentiometer from the servo case now the motor will just turn freeley in either direction, never stopping.

This is what betty was getting at. Turn left slight, causes the motor to spin to the left, slowly. Turn left hard, causes the motor to spin to the left very fast!!!

This sounds just like the motor drive circuit.

Now with the potentiometer IN the circuit it now changes it's resistance depending on its POSISTION.

You will notice that the steering pot has 2 of it's 3 tags soldered together. The usual setup is the OUTER 2 tags are the resistor, the inner tag is the one that moves along the resistor's body.

So, at halfway (for a 5K pot) the resistance from the inner tag to either outer tag is 2.5K.

Given that on the z's and xmod's theone of the outer and the centre tag is soldered together this means that full left will be 0K and full right will be 5K. So, betty choose a value to represent centre, this cas it was 2.5K, or it's closes cousin.....

buit of a rant I know, dunno if I even answered your question...

crazydave · Post by **crazydave** » Sat Dec 25, 2004 10:05 pm

Thanks dude, I know that took some typeing, but that's what I need, I need the long answer.

You did answer my question(s), from what I was reading this is the generalization I've adapted to my understanding, that the trim pot is being moved along with the steering motor, and the position of that pot is directly related to the position of the wheels. This feedback loop thingy, this is what holds the wheels in one place?

Am I keeping up?

Think I need to go do research on feedback loops.

ph2t · Post by **ph2t** » Sat Dec 25, 2004 10:55 pm

spot on man.

the resistor corellates it's value to a position on the servo. The circuit translates this into positional data and governs the motor to suit.

feedback loop is a general term in electronics, a lot of things use this principle and apply it in many different ways.

cheers,

ph2t.

backdrift · Post by **backdrift** » Sat Dec 25, 2004 11:00 pm

so do u think i can do this to a super slick? a epoch for not much would be kinda cool....

ph2t · Post by **ph2t** » Sat Dec 25, 2004 11:02 pm

I have no idea dude, we don't have SS in aus.....

betty.k · Post by **betty.k** » Sat Dec 25, 2004 11:45 pm

basically if your chassis has motor driven steering with a centering spring then this mod will work. just so long as you realise this gives you non propo steering you'll love it

thanks ph2t, i still dunno what i wrote back there!

crazydave · Post by **crazydave** » Sun Dec 26, 2004 8:07 am

Just to fill the upside down people in, Superslicks are basically 1/43rd scale versions of Zip Zaps, but have larger motors and motor driven steering, similar to the MT. They are sold at Toys R Us with all the hop ups available.
http://www1.toysrus.com/superslicks/index.cfm

I'd say if you can cram the iWaver board in the car, then I don't see why not. Being that I haven't looked at the Iwaver board in person yet, that would be a guess at this point.

Damn you know if that worked, I'd be wanting to shove iWaver boards in everything. Already thinking about my Xmods.

ph2t wrote:The circuit translates this into positional data and governs the motor to suit.

Oh yeah, digital. OK, now I think I'm really starting to get it.