*Improved* MOSFET mod…

[ph2t]

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 http://www.onsemi.com

Let s review some stats:

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.
Seems like a lot of wires but realy 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:

Here s the finished product!

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…

ph2t.

Edited by – ph2t on 16 April 2004 23:30:40

Edited by – ph2t on 16 April 2004 23:32:59

[betty.k]

impressive! definately need the external pcb, but worth it. i’ll take 2!!:8ball:

[jevries]

Looks like a killer performance! I wanna do this mod. Can you please make a bigger pic or small diagram on how to exactly hook these mosfets to the PCB? It will save a lot of time answering all kinds of questions…:D
Thanx!:)

[leonli17]

damn…u made the car look like a MiniZ wannabe. lol, but that’s a good discovery. the external turbo looks cool. so i guess a Tutorial Comin soon?

[oldtamiyaphile]

How fast is too fast? and how long until you start buring out motors in 30 seconds?

[ph2t]

Quote:

Looks like a killer performance! I wanna do this mod. Can you please make a bigger pic or small diagram on how to exactly hook these mosfets to the PCB? It will save a lot of time answering all kinds of questions…:D
Thanx!:)

Hey jevries, welcome to the boards…. 🙂

I’m not sure what you want to know exactly? Do you want the fet PCB diagram? The layout for the fet PCB? OR do you want pics of where the wires FROM the fet PCB goto on the Bit PCB….?

This is the circuit schematic, it’s an old one I made a year ago, so the fets are labled as the IRLML2502 ones, but that doesn’t matter, fets are fets… 🙂

I used CircuitMaker 2000 to make the PCB and then I printed it (in negative format) onto transparency film.

I then processed this onto pcb and etched from there.

:p

ph2t.

[ph2t]

Quote:

damn…u made the car look like a MiniZ wannabe. lol, but that’s a good discovery. the external turbo looks cool. so i guess a Tutorial Comin soon?

Tutorial? Dude, it’s pretty much just the mosfet mod using different mosfets. Since they aren’t pin for pin compatible with the original transistors I made a pcb for ’em….That’s it….

Quote:

How fast is too fast? and how long until you start buring out motors in 30 seconds?

You can never be too fast. No motors will burn out on a single cell…..

ph2t.

[merc-blue]

ph2t ur my hero 😀 bu as a single ther not as effiecent???? only once into 3-4 stack… also microamps hasnt posted yet so he may have some idea 2 whay they might not be as good for some reason

[ph2t]

A single stack is more efficient than stock BUT not as efficient as a double or triple stack of fets….. It’s all about how far you want to go.

I’ve noticed that my tri-stack car with the insanely low gearing (3.95:1) is still a great car to play with and it’s top speed is insane for a single cell.

I’ll try the single fet mod on the 3.95:1 gears today and let you know what the differences are……

ph2t.

[merc-blue]

keep us posted.. wat i meant is a single in the new fets is less efficent than a single in the old fets?.. it only when u compare a double or triple in the new with a double or tripple in the olds… if u get my drift… i would love 2 get my hands on one of these “external turbos” … in other words will u be selling them

Edited by – merc-blue on 17 April 2004 12:30:01

Edited by – merc-blue on 17 April 2004 16:15:49

[twizm]

another vote for ‘will you be selling them’

*curious what would if its compatible with already FET fitted cars*

[jevries]

Yo Donor, That’s some crazy shit man! And thanx for welcoming me to the board, I’m fairly new to all this modding and stuff and that’s why I asked for a pic on how to wire the FETS as you did on your small external turbo board leading to the Bit PCB.
I’m like a DUPLO guy you see, I can follow colored wires from the one spot to another…hehehe so when I see what wire goes where to I can do the job too.:D I think I’m not the only one..
Thanx man!:)

[betty.k]

ok gang, review number 1!:p
i got 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:
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!
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!:shock:
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! absolute killer mod, me want many more!!:p:8ball:

[jevries]

Now I mosdef wanna see a DUPLO diagram or pic of this Mosfet turbo trick!!!:D

By the way, great website you’ve got there Betty. K.!

Edited by – jevries on 17 April 2004 23:43:31

[ph2t]

Quote:

keep us posted.. wat i meant is a single in the new fets is less efficent than a single in the old fets?.. it only when u compare a double or triple in the new with a double or tripple in the olds… if u get my drift… i would love 2 get my hands on one of these “external turbos” … in other words will u be selling them

Edited by – merc-blue on 17 April 2004 12:30:01

Edited by – merc-blue on 17 April 2004 16:15:49

A single stack in the new fets is more efficient than the original fets. Theoretically it’s meant to be approx 20%. But, see betty’s comments, it is now proved to be better…..

The next “turbo” I’m making will have the performance of a tristack of fets. This PCB will be using different fets all together…

Here it is on the right of the pic. On the left is the current turbo PCB.

If all goes well I will be selling BOTH.

ph2t.

[jevries]

I think it’s about time you get some buisness going’..hehehe:D

[matic]

Quote:

PCB.

Those “big” fets on the right pcb, are they ntqd 6866r2?

[ph2t]

yup 🙂

I’ve run into a problem with the big pcb though. After putting the pcb into the circuit I only get 1.8V at the gate pin of the mosfets. This is too low to be able to turn them on properly :dead:. So unfortunately these fets won’t work. BUGGER!

I’m gonna try the large pcb on a daul cell, see if that’s enough input voltage to keep the drive on the gate pins sourced with enough current….

ph2t.

[HACHI-RYOKU]

So……..hurry up and put them up for sale………dammit!:p

[ph2t]

check the BCG for sale section, 🙂

[jevries]

I think I’m gonna check the BCG for sale section….:D

[betty.k]

well we finally got to test out a biff’ed zip zap se and the results are disappointing.:sad: pretty much halved the speed so there’s something about the se pcb that doesn’t turn the fets on properly or something like that. oh well, now that i’ve scored my new mustang and hemi cuda shells i don’t mind if it don’t go too fast now, can’t see them properly otherwise!:D:8ball:

[ph2t]

yeah, it’s a bugger that it didn’t work out, BUT we’ll wait and see. I’m waiting on some mosfet driver chips from maxim-ic that might help out in this situation…….

ph2t.

[HACHI-RYOKU]

Got the fets in the mail today. Looks good, as usual from ph2t. Any chance of getting a good picture on how to install them? I’m not sure wich wire goes where.

[HACHI-RYOKU]

That pic on page one is good, but I can’t tell what terminal some of the wires are going to. Maybe a quick drawing?

[betty.k]

ok hachi, i got some stuff that may help. here’s a biff with labelled wires

it’s important to observe the polarity of the V + and V- wires. but the gate and motor wires can go either way. just test to see if forward and reverse is correct with a tx. here’s a pic of a tomy pcb with the gate pins marked with yellow dots

you need to completely remove the transistors that have the gate pins marked. good luck!
the pics are here if they get X‘ed http://www.geocities.com/bettyksprivatestash/biff.html?1084748802175:8ball:

[HACHI-RYOKU]

Thanx betty. That was perfect.

[ph2t]

yeah sorry about being late with the doco, been pretty busy with all things “Sasser” lately, bloody viruses…..

Happy you liked the biff Hachi!

ph2t.

[HACHI-RYOKU]

No problem man. I knew where to find you. Thanx again. I’m definately gonna order some more for a couple of other operations. Do you think biff can cure my fet burning problem I recently posted about? I don’t think it will, but you don’t know untill you ask.

[merc-blue]

i got the gate pins and the motor thing worked but V+ and v- go the gnd and Vs ?? or some were else?

[betty.k]

V+ wire goes to V+ on the pcb and V- goes to GND on the pcb:8ball:

[merc-blue]

thnx betty i now have a biffed PCB

[Admin]

do you have anyclue on what happened to my bbif
ph2t?

[ph2t]

nah man, I’ve been conversing with your parents on that. I sent it off over three weeks ago now, see the email I sent your parents.

cheers,

ph2t

[zensx]

You got a customer here. I like the fact that you’ve made a “Micro Nelly” of sorts for bits. I’ll be getting of your Xmod nellys and I guess I’m gonna have to get this for a couple of my bits as well.

[Admin]

Quote:

You got a customer here. I like the fact that you’ve made a “Micro Nelly” of sorts for bits. I’ll be getting of your Xmod nellys and I guess I’m gonna have to get this for a couple of my bits as well.

I think this has been discontinued(the fets for bitcharg’s)

[merc-blue]

yeh there was a few “biff” turbos made . u can still do the origonal style fet job

[Admin]

I meant that ph2t’s bit char-g fets were discontinued:)

Edited by – Username on 02 November 2004 13:34:23

[betty.k]

well you’re both right. biff is off the market now.:8ball:

[Author]

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