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Resource: the "Woah Nelly!" Turbo....

Posted: Mon Apr 19, 2004 6:07 am
by ph2t
I'm just sick and tired of frying my fet stacks.

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So I decided to make an external turbo. I wanted to make something
worthwhile in the performance side so I looked for the lowest resistance
MOSFETs I could find.

I ended up with two candidates:

NTD110N02R - N Chan MOSFET - www.onsemi.com
IRF7425 - P Chan MOSFET - www.irf.com

Search those websites to get their respecte datasheets.

These two 'lil buggers put the "Woah" in my "Woah Nelly" turbo. The all
important on resistance is mega low.

To put this into perspective you need to understand the amount of resistance in the normal IRF7389 MOSFETs that are used when "stacking" MOSFETs. Below are the values that I pulled from the datasheets for all the MOSFETs involved.

You need to add up the total resistance (less motor resistance) in the path that the motor current travels in. You then have the following values.

IRF7389 MOSFET

nchan 30 Ohm + pchan 75 Ohm = 105 Ohm

Woah Nelly MOSFETS

nchan 5.0Ohm + pchan 6.0Ohm = 11 Ohm

That's a ratio of over 9:1! This means (theoretically) that these MOSFETS will have the performance of a 9 stack of IRF7389 MOSFETs. That's nuts!


Woah Nelly v1

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Woah Nelly v1 hooked up to the RX pcb

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NOTE:You need to remove the drive train MOSFETS (be them stock or otherwise) for this turbo to work. This is the same in principle to Neurokinetik's xmod turbo over at t.i.n.y.r.c.com. As you can see in the pic above, the four grey wires connect to the RX PCB to get the control logic. I'm waiting to get my hands on some "normal" mini-z turbo's to understand how they can work from just the motor terminals.

The Test

I'm hesitant when modding my madforce's PCB these days(lol, you wouldn't think it though). I've brought it back from the dead too many times to be lucky.

I've connected my DMM (Digi Multi Meter) inline with the motor to measure the current that is going though the motor.

I've also connected (see insert top right) a temperature probe onto Woah Nelly to measure how hot the turbo gets.

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The motor I'm using consists of the following:

Plasma Dash Armature (not modified, 27 turns?)
Tamyia magnets
Yeah Racing ball bearing can
Yeah Racing carbon brushes

If there was ever a motor to fry some MOSFETS, it would be this baby :). This is my fastest motor I have.

So there it all is, a mess of cables sitting on my desk. I then went and turned it on.......

Nothing, no fssst, no pop, no crack, no smell!!! hooray! It didn't blow up!
Well, that's the first test passed....

I then opened up the throttle and all was looking good. I put it though it's paces, fwd for 3 minutes, rev for 3 mintues, bracking etc, etc... Everything was great!

The current going though the motor at top speed is 1.5A, now that's toasty considering the motor is under bugger all load (free spinning). When changing in between fwd and rev the motor current would peak as high as > 5A ! Now imagine what sort of current will be going though when the car is on the ground....

Woah Nelly didn't even get warm! She never broke the 26 degree (celsius) barrier.

Here's some video on the test bench showing the current load and the turbo's temperature. You gotta listen to the high pitched whine coming from the motor, keep in mind this is a horribly geared down Madforce!

http://users.tpg.com.au/ph2t/turbo/woah_nelly_proto.avi

DivX, 1.6MB

You need to see this vid! See how the current changes so quickly...

Sadly, all my front damper mounts are busted at the mo so I don't have any video of the Madforce flying around, but I will soon!

ph2t.

Posted: Wed Apr 21, 2004 6:46 pm
by Son_Gokou
:eek:

Wow, ph2t, another miracle.

But, I'm just curious how you knew the pattern to connect those FETs together, and how to link them into the circuit system.

But....WOW!

Posted: Wed Apr 21, 2004 7:59 pm
by betty.k
Son_Gokou wrote:But, I'm just curious how you knew the pattern to connect those FETs together, and how to link them into the circuit system.


6 years doing an electrical engineering degree probably had something to do with that :???:

Posted: Thu Apr 29, 2004 11:17 am
by payaso
I can't decide if I should get the "nelly" or multi fet the board. I want this PN-Racing S03 Pro Modified Motor, but you need multi fets, or a turbo..

my X speed motor jams.. It's a freakin flyer, but I want more.. What do you suggest?



silla :D

Posted: Thu Apr 29, 2004 5:51 pm
by ph2t
what chassis do you have man? mr01, mr02, ol, madforce?

If you're looking for a better motor than the S03 go and buy a plasma dash motor.

http://www.rcmart.com/catalog/product_i ... ts_id=1216

You can run this as it is or put it(the armature) in a ball bearing motor can and add carbon brushes. The magnets from the plasma would also go into the can. This setup is the fastest motor I have. She's a hot motor so you definately need a turbo/stack.

The advantage of a mosfet stack is that it's compact and it doesn't (usually) require any structural/cosmetic changes. You can fit up to a 4 stack without modding the chassis (for the madforce anyway, dunno about the mr-0x models).

Nelly is way more powerfull that a quad stack though. Even when the batteries are almost gone I can still pop wheelies with the 12 tooth pinion. The bitch screams torque. I have nelly handle a 12 turn motor no sweats...

ph2t.

Posted: Thu Apr 29, 2004 8:01 pm
by crazydave
betty.k wrote:
Son_Gokou wrote:But, I'm just curious how you knew the pattern to connect those FETs together, and how to link them into the circuit system.


6 years doing an electrical engineering degree probably had something to do with that :???:
Nah, it couldn't possibly be that. Everyone said degrees were worthless. :lol:



So ph2t, this should work with the Xmod, huh?

Posted: Thu Apr 29, 2004 9:41 pm
by ph2t
yes mate, I believe it will work with the xmod. The reason I say this is because they both run off 4.8V stock and neurokinetic did a similar thing over in the xmods forum and tinyrc.com.
NOTE: the original mosfets still need to be removed as I have done on my Z.

I'm working on a version that will not need the mosfets removed from the drivetrain h-bridge. The end effect will be that you just wire Nelly to the motor terminals instead. There are issues with this though, design issues that may limit how well the mosfets are turned on (it's the zzse problem all over again!). As I said, I'm working on that.

With all that said,there's nothing stopping you from trying it, lol, look at me! Half the things I've tried don't ever work, but you'd never know without trying. Even with the best theory under yer belt, it means shit it you cannot prove it!

ph2t.

Posted: Fri Apr 30, 2004 11:57 am
by payaso
Doh..... For got to say I wanted it for my OL.. Got an X speed in it now..



silla :D

Posted: Wed Jun 30, 2004 8:04 pm
by sg219
How's "Nelly" doin'? :???:

Its almost time for one, maybe another week or two till I get myXmod to where I want it.

Can you throw an update up as it would apply to an Xmod and iWaver?

Will it operate on 6 cells/7 cells?

Which motor would be the most efficent to use with it and get the most out of "Nelly"?

Thanks :-)

Posted: Wed Jun 30, 2004 8:24 pm
by Bird
http://www.ausmicro.com/topic.asp?TOPIC ... hichpage=4

Scroll down to br2ces post... it's the last one.

Posted: Sat Jul 03, 2004 9:10 am
by ph2t
sg219 wrote:How's "Nelly" doin'? :???:

Its almost time for one, maybe another week or two till I get myXmod to where I want it.

Can you throw an update up as it would apply to an Xmod and iWaver?

Will it operate on 6 cells/7 cells?

Which motor would be the most efficent to use with it and get the most out of "Nelly"?

Thanks :-)


Sorry about the late reply, been sick the last few days. Apart from work it's been food/sleep/food/sleep.....

Well Nelly is good to go into production basically. She works on all models of miniz and also iwaver. Yet to be tested on the xmod but I will know by early next week on this. I'm confident it will work.

Nelly will operate on 5/6/7 cells, no sweats. I'd worry more about the main rx PCB than nelly, lol....

A motor in the 27 - 35 turn range works the best IMHO. Get the plasma dash motor OR get the www.minizworkshop.com 35 turn motor. Both of these are great and the offer different torque/high speed characteristics....

Ultimately though I reccomened you screw around with your own motor winding combo's. You'll find one motor works well for one application, yet another motor works better for another. It's your call in the end.

AS Bird said, check out the link to the main dev thread at brucemicro.com:
http://www.ausmicro.com/link.asp?TOPIC_ ... =lasttopic

I have two current versions of nelly, 1.0 & 1.1. The performance of both differ. See the comparison graphs in the thread linked above. I'm also working on the PCB design for nelly 1.2, this bugger will have the power of an equivalent 16 stack of mosfets! yeah baby!

Cheers,

ph2t.

Posted: Sat Jul 03, 2004 9:49 am
by crazydave
Keep us updated on the Xmod situation. I just may be into that.

Realquickslightlyofftopicquestion, Does the Plasma Dash have bearings in it? For some reason I was under the impression it was a bushing motor.

Posted: Sat Jul 03, 2004 7:50 pm
by ph2t
You're right mate, the plasma is a bushing only motor. All the tamiya mini4wd motors are bushing only. You'll need to buy a ball bearing can and put the armature/magnets from the dash into there. That's what I've done. Serious high speed motor.

ph2t.

Posted: Sat Jul 03, 2004 9:41 pm
by Son_Gokou
ph2t wrote:You're right mate, the plasma is a bushing only motor. All the tamiya mini4wd motors are bushing only. You'll need to buy a ball bearing can and put the armature/magnets from the dash into there. That's what I've done. Serious high speed motor.

ph2t.


ph2t, I was talking to some guy in chat (pomme de terre) and he says that he once owned a plasma dash motor, which he did not appeal to. he says the speed and torque was just O.K.....I hear you have a plasma dash in your Madforce. Tell me, is it fast, or just torquey, or both?

In about 5 days or less, I'll be getting 4 SI4562DY FETs, a GPM alloy motor mount, A GPM Delrin and Alloy Motor Gear (11T) and a CF Midship conversion X plate from www.mini-zracer.com 's shop....one day, however, I'll get the plasma dash, put it in a BB can with neo mags and carbon brushes, build your woah nelly (or buy it from ya...still debating :-) ) and pop it in and see how it goes. One day....man, I can't wait to turn 16 and get a job.

Oh, and good luck on Nelly 1.2! Can't wait to see it...

Posted: Sat Aug 21, 2004 12:05 pm
by cj
ph2t at MRCCI have also reverse engineered two of the most popular turbo's on the market, TLP Twin and GPM v2 turbo and Nelly is way better than both.

The graph compares the the performance of nelly vs. the traditional IRF7389 mosfet stack, but I guess you just don't read titles......

Any other questions? I'm more than happy to answer.

ph2t.


How exactly does the Nelly 1.2 compair to the GPM v2 turbo?