Resource: the "Woah Nelly!" Turbo....
Posted: Mon Apr 19, 2004 6:07 am
I'm just sick and tired of frying my fet stacks.
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
Woah Nelly v1 hooked up to the RX pcb
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.
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.
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
Woah Nelly v1 hooked up to the RX pcb
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.
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.