2002.08.04, 11:24 PM
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#1
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Registered User
Join Date: Jul 2002
Location: Ottawa, Ontario
Posts: 889
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Simple FET Question
I need full specs on the stock FETs, and the upgraded FETs... (/me is going on a FET hunt)
__________________
-Scott
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2002.08.05, 12:52 AM
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#2
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Mini-Z Pro
Join Date: Jul 2002
Location: Hong Kong
Posts: 100
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2002.08.05, 01:43 AM
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#3
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Registered User
Join Date: Dec 2001
Location: Helsinki, Finland
Posts: 624
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__________________
W-t
"Jazz is not dead, it just smells funny..."
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2002.08.05, 08:22 PM
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#4
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Registered User
Join Date: Dec 2001
Location: Toronto ON Canada
Posts: 2,006
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where can i buy these? and how much?
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2002.08.07, 05:56 PM
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#5
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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Hmmm... That's all very nice, but I have no idea what I'm actually looking at here...
Is the Continuous N-Channel Drain Current rating what we're looking for to avoid frying the ESC's? If so, I see:
3004: 5.5 A
IRf7389: 7.3 A
What is the key parameter here?
ianc
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2002.08.07, 06:13 PM
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#6
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Same same, but different.
Join Date: Dec 2001
Location: Sweden
Posts: 822
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Is 3004 not the one pre-installed in the mini-z? Would I gain anything double it with another one then?
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2002.08.07, 06:22 PM
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#7
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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Hi Ultrawide,
Yes, the 3004 is factory installed in the Z.
I believe the purpose of the turbo is two fold:
1) To lower the internal resistance of the FET's so that a higher voltage reaches the motor, giving better performance, and
2) To increase the current rating of the ESC so that hotter motors can be used.
I think both of these objectives would be met by piggybacking an additonal 3004 on top of the originals, but the IRF7389 has both less resistance and a higher current rating than the original 3004, so this would be preferred...
ianc
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2002.08.07, 06:26 PM
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#8
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Same same, but different.
Join Date: Dec 2001
Location: Sweden
Posts: 822
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ianc
Any idea if it will work with 3006 instead in the piggyback, above the 3004?
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2002.08.08, 04:39 AM
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#9
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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Hi Ultrawide,
I have no idea whether a 3006 will work I'm afraid. I don't know whether it's pin-compatible, or any of the specifications. I'm quite light on electrical engineering. I was a mechanical engineering major in college ten years ago and regarded the few EE courses they made us take as voodoo... Forgot just about all of what little I knew...
ianc
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2002.08.08, 06:03 AM
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#10
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Mini-Z Novice
Join Date: Jun 2002
Posts: 24
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Hey ultrawide,
The IRf7389 can be bought at Elfa.se, just do a search for IRf7389 and you will find it. If you do this mod you'll have to get at least four, preferably eight FET's so it isn't economicaly defendable to get an internal turbo, at least not in Sweden
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2002.08.08, 06:16 AM
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#11
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Registered User
Join Date: Dec 2001
Location: Helsinki, Finland
Posts: 624
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I do not know how much a turbo costs in sweden but my mod of 4 irf7389 cost me approx 25e and is well worth it. If Elfa is expensive try your local RS distributor.
HAT3006r is a pin compatible replacement and seems like a good upgrade to the 3004.
The IRF part is marginally better.
Key parameters are the Rds(on) resistance and max current capacity, smaller of the two values(P or N channel) is to be considered the limit.
__________________
W-t
"Jazz is not dead, it just smells funny..."
Last edited by W-tone; 2002.08.08 at 06:25 AM.
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2002.08.08, 07:02 AM
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#12
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Registered User
Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
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Quote:
Key parameters are the Rds(on) resistance and max current capacity, smaller of the two values(P or N channel) is to be considered the limit.
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Thanks W-Tone! Then we can say for max current capability:
3004 (stock): 3.5 A
3006: 4.5 A
IRF7389: 5.3 A
If two FET's were piggybacked, would that result in a theoretical doubling of the current capacity?
I forget the relation for two resistances in parallel. Isn't it:
Rtot = (R1 + R2)/(R1 * R2)?
ianc
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2002.08.08, 07:51 AM
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#13
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Registered User
Join Date: Dec 2001
Location: Helsinki, Finland
Posts: 624
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The notation I'm accustomed to is:
1/Rtot=(1/R1)+(1/R2)
Effectively the resitance is halved when connecting identical resistances in parallel. Also the max current is doubled. Well.. in theory it is doubled, there may be some deviation if the FETs are not identical.
Within normal tolerances I think the devation can be ignored.
__________________
W-t
"Jazz is not dead, it just smells funny..."
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2002.08.08, 11:40 AM
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#14
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Mini-Z Pro
Join Date: Jul 2002
Location: Hong Kong
Posts: 100
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Dear all,
I'm from HK. I want to ask is their any R/C shop/Technical people to install the FET or Change the FET DIY?
Regards,
TungFai
from Hong Kong
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2002.08.23, 03:16 AM
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#15
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Registered User
Join Date: Nov 2001
Location: makati, philippines
Posts: 8,702
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greetings bjs-tf...
not many people know how to changes fets over here... i had somebody do mine... it works fine... can you please teach us?
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