I've got FETs in my SE!

Mostly dealing with electronics and pcbs and modifying them, all the things that make electrical-engineers tick and the rest of us cringe in fear.
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ph2t
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Post by ph2t »

Well I've completed the mosfet changover to the se chassis as per microsash's method and I gotta say that the car definately does perform better overall. :bs:

I've experienced a healthy amount of increased torque and the top speed has increased by approx 25% . This mod works and it does improve the performance of your car BUT it barely taps into the power of the H-Bridge mosfets unlike microamps' version of the mod. That crafty bugger has figured it out :smile: .

Still, I gotta say that my car didn't spin out under full throttle before I did the mod and now it does. I'm running a 4.2Pro in the chassis under the(possibly misguided?) belief that these motors are best suited for pulsed applications.? I will hopefully have a NX motor soon, I believe that's the best motor for zips?

Hey crazy & hog, to what extents did you fet mod your se pcbs?

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Post by ph2t »

Here's a little play by play for this mod.

Open up your SE, remove the screws, blah blah blah.

On the underside of the pcb (non expoxy side) you will
see a pair of transistors. One will be two high, the other
normal height. See below:

Image

Remove these transistors. I use a hobby knife to cut the pins
to the small black package. After you remove the old transistors
clean up the solder pads by dabbling your soldering iron onto
them remove the old solder.

I use a small drop of cantact glue to secure the new fets in place.
The fets to use here are IRLML2502.

Image

This way soldering them is piss easy!

Image

Now flip the pcb over to its topside and remove the old
pnp transistors. Again, clean the solder pads after removing the
old transistors.

Image

Here, you need to use IRLML6401 fets. Again, secure them
with glue to assist soldering.

Image

That's it. All done. Enjoy your car...

Also, if you wanted to stack the IRLML2502 fets, well you
could do that to if you wanted :suspect: .

Image

ph2t.
Last edited by ph2t on Wed Dec 17, 2003 5:27 pm, edited 1 time in total.
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Post by fook yu »

You are not misguided on the motors ph2t. The nx motors are the best with the fet modded SEs. The perfection 4.2 would probably go for my second choice.
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Post by ph2t »

from the thread:

http://bitpimps.lixlink.com/pages/phpFo ... 2921#32921

crazydave wrote:
ph2t wrote:Actually Dave the P chan fets aren't flipped mate, just replaced one-for-one from the old PNP transistors. I get 2.6V across the motor terminals when it's an open circuit but when you put a motor in there this drops to approx 1.6V instead. So it's better than stock but not to the performance of microamps version. I put 3V on the Gate pin of the nchan fet and I got 2.3V across the motor whilst in circuit! The thing flew!
Thanks for clarifying, I was a little confused, but I fugured I'd just have to stick my face in there to get it, but I get it now. :lol:

So how'd you get the 3 volts on the gate pin of the N-channel FET? DC/DC converter?

...and why 'flew' in the past tense, did something happen to it?


**Edit** Ph2t, I reviewed your PM, and saw where I got confused. You were saying something about future possibilities of useing the P-channel FETs for switching, and all Nchannel FETs in the H-bridge. That idea had appealed to me, and that's why that idea had confused me. Good thing i got that straightened before my FETs got here. :lol:



Good to know you're on top of it man. :) I soldered a wire to the 3V output from the DCDC convertor on the PCB and manually touched the Gate pin on the (rev) n-chan fet and the bugger just screemed! So there was no wizardry here, just some plain old stuffin around. It is a good example of the power you can achieve from the fets if they were to be properly turned on. Flew as in bad past tense, previously done before writing in this thread. Nothing is wrong with the motor, she's still bannanas, :).

I've got some video of this example and you can hear the pitch of the motor go through the roof when applying the 3V to it.

When I get some time I'll keep moving on it.

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Post by crazydave »

Ph2t, I hadn't seen that you'd posted your stuff in this thread. Cool, thanks for pointing that out. Pictures are definately a bonus. :grin:
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Post by ph2t »

no worries man, I'm interested to hear how you go with it all.....
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Post by hogjowlz »

so ur saying all you gota do is put fets on the bottom of the board like dave figured out a long time ago and then just put two more fets on top? no crazy jumpering?? its that simple??
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Post by ph2t »

yes and no

yes, all you do is this and you get a performance boost


no, it's still not the boost you could get if you were to turn the mosfets on fully. Microamps aint bullshitting when he says he's gotten the SE's to travel at 3 times their stock speed @ 15kph/10mph.

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Post by hogjowlz »

well get crackin and figure out what else he did!!
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Post by ph2t »

"Chill out homie, I'm on the muthafucker, I'm sending in the Wolf"

"Hell negro, that's all you had to say!"

:rockon:

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Post by hogjowlz »

thats good man cuz getting mideval on some dude who wrestles crocs all day's buttox doesnt sound very appealing.
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Post by mad_haxor »

what about a 741 op amp driving the gate?
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Post by ph2t »

you could try this but you might find the circuit would be quite complex, don't let me stop you though!

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Post by HirotoR34 »

Nice mod D. All this time I thought micro_amps was the only one doing FET mods.
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Post by ph2t »

dude, microamps is known for fet mods 'cause he sells the service to other people, that's all. he didn't come up with the mod, the krauts did!
he did invent this new SE fetmod that he won't tell us about, hence all the discussion in this thread.

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