Tuning up the steering

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HACHI-RYOKU
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Tuning up the steering

Post by HACHI-RYOKU »

So, I went on some advice from Aaron from Ausmicro. I replaced the steering fets in my MR-02 with IRF7317's. The steering got stronger and used less juice from the batteries.

Something else I noticed too. Before I messed with the steering I noticed one side turned better than the other and I had to tweek the steering adjust almost all the way left on my controller for normal operations. I got curious and experemented. I noticed that the steering wires attached to the output section of the steering fets were not soldered to an equal amount of pins on the fets. On one fet, the steering wire was soldered to two output pins. On the other fet the steering wire was soldered to three output pins. I took the one that was soldered to two and resoldered it to three. Now the steering doesn't need to be adjuted much on the controller and turns equally both ways. SOOO, basically make sure the wires going to the steering motor are soldered to an equal amount of output pins on each steering fet.

The Mini-Z line already has very good steering compared to other brands. These two mods just make it even better.

Now, if I could just figure out how to tweek Iwaver steering.
Cause I ride around town on my low-rider bicycle.

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Post by color0 »

That's clever... although electrically speaking, I thought it shouldn't really make a difference (the pins are all parallel...), I suppose theory isn't always right.
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Post by HACHI-RYOKU »

I was thinking maybe it has to do with extra surface area or interference from something else. Not really sure myself. It worked for me though.
Cause I ride around town on my low-rider bicycle.

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Post by LBRC »

Image
Notice that in the IRF 7317 the P and N channel outputs are not connected it’s the same with the HAT 3004.
Image
However the pad on the circuit board that all four output feet solder to is.

But for the sake of argument lets say that the N or P channel output side of a mosfet was not soldered properly what would happen? Simple the servo would only turn in one direction since it takes a P channel from one mosfet and an N channel from the other for the motor to turn, so if the car steers in both directions all the output pins are electrically connected.

Aside from a damaged mosfet the only thing that could possibly make a difference is a high resistance solder joint. For example if both N channel feet of one FET where not connected by the wire at all and poorly connected to the circuit board then the added resistance of the poor connection could cause the servo motor to be slower and possibly even weaker when turning in one direction.

But the servo motor driver H-bridge (the FETs) only supplies power to turn the servo motor so that it may turn clockwise or counterclockwise other than that it has nothing to do with centering or the amount of steering travel.

color0 wrote: I suppose theory isn't always right.

Theory as in physics is always right :-o improper interpretation through insufficient understanding is not :o

HACHI-RYOKU wrote: Now, if I could just figure out how to tweek Iwaver steering.

To fix the Iwaver steering you need to replace the puny servo motor driver IC with something a little more robust. I used an Epoch turbo on an Iwaver 04 and a friends 02 it worked great, aside from taking up space and adding more wire that is. I think the tread title was “Where’s the Beef.”

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Post by HACHI-RYOKU »

LBRC wrote:
color0 wrote: I suppose theory isn't always right.

Theory as in physics is always right :-o improper interpretation through insufficient understanding is not :o

HACHI-RYOKU wrote: Now, if I could just figure out how to tweek Iwaver steering.

To fix the Iwaver steering you need to replace the puny servo motor driver IC with something a little more robust. I used an Epoch turbo on an Iwaver 04 and a friends 02 it worked great, aside from taking up space and adding more wire that is. I think the tread title was “Where’s the Beef.”


So, in other words, even if you think you know everything, you could be wrong. Many of our greatest scientific discoveries were accidents that could only be proven with tools like physics after the fact.

Yes, I saw you work with the epoch turbo and the Iwaver PCB. Quite genious really. I was looking for something that I could swap out completely on the PCB. Component for component, without having to add another external board. If I'm gonna pay to get an external board for an IW02, then I might as well just pay for a MR-02. I know I'll probably never find a component that I can just do a swap with.

Here's a thought, Maybe the wire lets more current pass than the PCB's traces. I'm guessing of course, but it's gotta be something right?
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Post by LBRC »

HACHI-RYOKU wrote:So, in other words, even if you think you know everything, you could be wrong. Many of our greatest scientific discoveries were accidents that could only be proven with tools like physics after the fact.

That pretty much sums it up, with an exact definition of "proven" to be the key.

prov•en - adjective

proved true: shown to be true beyond any doubt

Verses a looser

tried and tested: done or used before and known to work or be satisfactory

Which is of course dependent on the number of times it is tried and how it is tested.

... I was looking for something that I could swap out completely on the PCB. Component for component, without having to add another external board. If I'm gonna pay to get an external board for an IW02, then I might as well just pay for a MR-02. I know I'll probably never find a component that I can just do a swap with.


Unlikely in the extreme to find motor driver with the same footprint, a low enough gate drive voltage, and over twice the efficiency and power handling requirements. One of the more annoying things about it is that it doesn’t even use any of the more popular layouts so even though there are better chips on the market you can’t swap them out.

BTW don’t look for the 02M to be a terrific improvement either, what it boils down to is that the Kyosho Mini-Z uses a large and powerful servo motor, strong gears, and very powerful mosfet driven servo motor driver to make up the servo. Replacing it with a micro servo that uses a smaller motor/gearing and/or anything less than dual 3004 H-bridge for a motor driver is not going to be a performance improvement, just easier to replace.

Here's a thought, Maybe the wire lets more current pass than the PCB's traces. I'm guessing of course, but it's gotta be something right?
Not with the relatively small amount of current involved you'd need upwards of 10 ohms to make a noticeable speed difference not something in the thousandths of an ohm, also the trace and feet have less resistance than the wire.

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