*Improved* MOSFET mod...

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ph2t
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*Improved* MOSFET mod...

Post by ph2t » Fri Apr 16, 2004 8:46 am

I have found some MOSFETS that are (on paper) better performers than the IRLML2502 mosfets we have all grown to love. These MOSFETS offer 20% more performance than the IRLML2502 fets that everyone is using. They are nths5404t1 and they are available from www.onsemi.com

Let's review some stats:

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So the nths5404t1 have less resistance that the regular IRLML2502. This means more torque for the motor! This is higlighted in orange in the table above.

SNEAK PEAK!!! Also I have found some fets that when double stacked they outperform a triple stack of IRLML2502 fets(see the yellow records above), stay tuned for futher developments on this.....

The only bugger is that the package they come in (ChipFET) isn't compatible with the pin layout of the BitChar-G PCB. This means problems. So I made my own little external TURBO, lol, to accomodate these FETS.

Image

Seems like a lot of wires but really it isn't. There are two wires(white & blue) that goto the battery terminals, - and +. There are two wires(yellow & orange) that go to the motor since the motor no longer connects to the BitChar-G PCB. The last two wires(brown & dark blue) goto the PCB and solder on to the locations for the Forwards/Reverse signals. For people(techos) in the know, these two wires go to the respective Base pin of the two NPN transistors in the motor H-Bridge.

Here's an idea on it's size:

Image

Here's the finished product!

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NOW, YOU'VE GOT TO SEE THIS VIDEO!!!!

http://users.tpg.com.au/ph2t/fet/fet_comparison.avi
DivX, 900KB.

The video shows a comparison between three identical cars starting from a stop. The surface the cars are running on is a rubber mat that is incredible for its grip. After approx 1.5m there is a steep incline for the car to travel up. The car's setups are as follows:

Car 1: Stock PCB with 3.0 TOMY Motor and 12:1 gears.
Car 2: Single Fet Stack PCB with 3.0 TOMY Motor and 12:1 gears.
Car 3: Triple Fet Stack PCB with 3.0 TOMY Motor and 3.95:1 gears.

The video shows some interesting results. First the obvious, the stock car doesn't even make it all the way up the hill, both mosfet modded cars do this easily. The stock car is the last to reach the foot of the incline, both the single stack fet and tri-stack fet cars reach the incline before the stock car.

Keep in mind that what's impressive about the 3rd car is that the gearing is set to 3.95:1, vs that of 12:1 for the other cars (stock and single fet). This clearly shows the INSANE about of torque that the tri-stack of fets delivers to the motor...


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Post by crazydave » Fri Apr 16, 2004 9:22 am

That's cool, I'll have to check that out.

I remember a while back you had some better FETs on a piggyback board, but these look a lot smaller than I remember those, and that piggy back board looks a lot smaller.

You know with Cyborg Zero's little voltage bypass mod, the Zip Zap SE performs fairly well, but I've been wanting a bit more. Any idea how these FETs might work with the SE?
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Post by sg219 » Fri Apr 16, 2004 3:14 pm

Your just too damn smart for me!! That electrical mumbo jumbo is greek to me.......

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Post by TMP » Fri Apr 16, 2004 3:33 pm

whats it run like with average gearing?
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Post by ph2t » Fri Apr 16, 2004 6:23 pm

crazydave wrote:That's cool, I'll have to check that out.

I remember a while back you had some better FETs on a piggyback board, but these look a lot smaller than I remember those, and that piggy back board looks a lot smaller.

You know with Cyborg Zero's little voltage bypass mod, the Zip Zap SE performs fairly well, but I've been wanting a bit more. Any idea how these FETs might work with the SE?


I'm selling a couple of these pcb's to betty. We'll put one on his ZZSe and try it out.... did you see the video dude? The tri-stack with the 3.95:1 gears clearly whips the arse of the stock pcb with 12:1 gears and is not far behind the single fet pcb with 12:1 gears either, this really impressed me......

To beuaty of the pcb is that you just connect it to the two signal (Fwd and Rev) pins on ANY micro rc car. If you have fets installed on the car's PCB already that's ok, just solder these two wires straight on. If you have the normal NPN transistors, then you must remove these two trannies to bring the voltage back up to 3V at this pin.

I'll be selling these shortly and I'll be including instructions on how to install to.

Now, I've got to get back to working on my tri-stack TURBO, lol.....


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Post by ph2t » Fri Apr 16, 2004 6:26 pm

TMP wrote:whats it run like with average gearing?


even better!

I choose the 12:1 gears as a comparison 'cause they were the highest torque gears I had and 3 times the gearing ratio of my super fast 3.95:1 gears..... To see the 3.95:1 gear'ed car out do the stock 12:1 really shows the power of the fets.......

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Post by clxfiles » Sat Apr 17, 2004 12:30 pm

So in a drag, does the 3.95:1, tri-stack overtake the 12:1, single stack at the top end? Or do you run out of space?

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Post by ph2t » Sat Apr 17, 2004 6:52 pm

I found that at the 3 meter mark the 3.95:1 geared car overtakes the 12:1 geared car. triple and single stack respectively.

here's a shot of my next gen external TURBO pcb. the fets on this bastard are better than a tri-stack of the regular IRLML2502 fets. (This is the theoretical value, I gotta test obviously to prove!)

Image

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Post by betty.k » Sat Apr 17, 2004 8:24 pm

ok pimps, review number 1! :smile:
i gots me one of these placed in my sweaty little hands by the man himself today. he gave me a quick but thorough lesson on where each wire goes and it seemed to make sense. so i thought about installing this turbo into my slowest car, but i thought "let's go for gold! so i cracked open my fastest bit (my ferrari) and performed some minor surgery!

THE TEST SUBJECT: MY FERRARI
enertec chassis
dual 150mah nicad
lxx 2 speed pcb with IRLML2502TR fets
zz nos motor
7.1:1 gearset

installation was simple, and as this replaces the 4 drive transistors they can be completely removed. so now i can use those fets on another board or fet the steering. i checked a few things before installation for a before and after comparison.
i did the patented hold the rear wheels trick and go forward. previously the car would turn til the nose pointed straight down. after, it pointed 45 degrees further! vast torque increase! :eek:
next i took it outside and i can safely estimate a 10 - 20% increase in boosted speed and a 30 - 40% increase when unboosted. this is definately due to the massive increase in torque.
before, it was difficult to get a wheelie out of this car as it has a low centre of gravity. after it was difficult to get a wheelie out of this car as it has so much torque it just flips onto it's back when you go reverse then forward![:O]
i checked the motor temp periodically through the run and i didn't notice any increase at all, which is a good sign that motors won't die quickly.
so in summary, you're gonna hafta pry this outta my cold dead hands if you want it back ph2t! there's a noticeable increase in overall power between the ext turbo and the regular irlml fets. absolute killer mod, me want many more!! :cool:

(you see this cd? stick one of these in your pro stocker and it will go through a wall!!) :smile:
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Post by betty.k » Thu Apr 22, 2004 10:55 am

well i biff'ed a zip zap se and i'm sorry to reprt that the results were dismal! :-( pretty much halved the speed, i'm guessing the fets aren't turned on properly or something like that. oh well, since i got my hemi cuda shell i don't mind the se cruising around slowly, can't see it properly otherwise! :eek:
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