PDA

View Full Version : help with fets


jdmgoodies
2017.01.23, 07:27 PM
can someone post links so i can read up on fets? mainly what fets do. why they are stacked in mini-z's the different types. chooseing the right ones and possibly the drawbacks of stacking fets. oh and can fets be stacked on a brushless system? my main reason for learning about fets is that i have a mb-010 and i think with the 32t pn motor im about to fry the fets and if on my brushless mb-010 if it can handle the atomic 12000kv motor or if i need to ad fets. thanks all

Traveler
2017.01.23, 07:38 PM
I can tell you there is lots of good info on the forums here about FETs. Just use the search feature. :)

EMU
2017.01.23, 08:10 PM
Can't speak for the brushless, but with a 32t on a buggy, you should definitely have stacked fets. The buggy puts more load on the motor load due to the extra weight, which I turn will draw more amperage through the fets.

To put it in basic terms... Stacking fets spreads the load through the fet. So the more fets in parallel (how they are stacked), the less load each one handles.

if you want a more in depth definition, use that search button. This topic has been explained repeatedly by more knowledgeable people than I.

http://mini-z-guide.com/mosfet.htm

jdmgoodies
2017.01.23, 09:49 PM
thanks for the info guys ill try reading a bit and using the search

Minizorro
2017.01.25, 07:16 PM
There's tons of info about fets for pre-mr03 boards.
That's when - from what I understand- installing fets did really matter.
MR03 boards can handle hotter motors but I support jdm when he's asking about brushless, I have no clue and would like to know. Is stacking fets on brushless helpful- in thinking buggy or ma020 cars.
Since I did stack a layer of fets just to try and found no difference whatsoever on a ma02 brushless... was I supposed to stack a layer onto the fets that are on the bottom side of the board as well?? I sort of guessed the fets on the underside were for reverse so I didn't bother but that might have been a mistake!

EMU
2017.01.25, 08:25 PM
Electrically, the bottom fets are stacked with the top ones. They connect to the same traces, but are on the opposite side of the board. Adding one layer to the top essentially gives you a triple stack fets. Adding another layer to the bottom will give you a quad.

Being on opposite sides of the pcb, a stock asf/ad arrangement will offer better cooling to the fet than a single sided pcb with a dual stack. It also offers a marginal decrease in resistance due to the additional fet legs contacting the pads/trace rather than all current going through one fets legs to the pads.

Minizorro
2017.01.27, 02:40 PM
Thanks for the very clear explaination!
Do you confirm that stacking fets on VE boards can be useful? As for me it made no difference. To be honest it was one of those impulse mods and i consider myself lucky I didn't ruin the board as I have no much experience in soldering!

EMU
2017.01.27, 03:40 PM
I have little to no experience with brushless technology, so I cannot be of help there.

Jshwaa
2017.01.27, 06:40 PM
Do you confirm that stacking fets on VE boards can be useful? As for me it made no difference. To be honest it was one of those impulse mods and i consider myself lucky I didn't ruin the board as I have no much experience in soldering!

Stacking probably won't do much for you with brushless. You may be able to get away with a heavier kv rated motor, but that won't change the switching speed of the inverter (controller). Stacking FET's was a big mod back in the older rev's of mini-z and when xmods were a thing. As previously mentioned, the MR-03's were impressive in how much current they could deliver. I didn't stack, but upgraded to heavier FET's and bonded a heat sink to them to draw out the heat. The benefits of stacking are limited. The circuit that turns them on and off can only provide the FET so much signal, and the more FET's you stack, the stronger the signal required to turn them all on and off.

Minizorro
2017.01.28, 05:04 AM
Very useful information many thanks!

byteme909
2017.03.26, 09:37 PM
looking for some info as well and didn't want to start a new thread. I have some stock ASF MR03 boards (RA22B w/tiki mode) and I wanted to put in a hotter motor than the X-Speed from Kyosho. Tried locating some R246 motors for NiMH to no avail. I think I saw some PN Racing S03 in stock but that is 39T motor. Do I need to have the boards FET modded to accept the motor? I saw some threads saying yes and then some websites saying the MR03 ASF boards can accept pretty much any motor.

Traveler
2017.03.27, 08:09 AM
Do I need to have the boards FET modded to accept the motor? I saw some threads saying yes and then some websites saying the MR03 ASF boards can accept pretty much any motor.

No! I've run the PN 32T on stock ASF MR-03 board with no issues, so you can run a 39T on stock ASF MR-03 board, but the S03 is a really old PN motor. I would recommend one of the newer ones. The PN 43T and 39T are good, depending on what you are looking for. I like the 35T too!

byteme909
2017.03.27, 12:31 PM
thank you for the response. if we can go down to a PN 32T on the stock board then I guess we can fit an atomic chili motor at 35T?

my objective was to fit my MR03 cars with something faster than the x speed motor but has to be ball raced and no mods to the FETS.

I also want something for a MR015 ASF I just purchased. I think its the RA18 board? Does the RA18 board need FET job to accept motors as well?

Traveler
2017.03.27, 01:15 PM
The Atomic Chili is one of my favorite motors out there for a large track and runs fine on stock ASF MR-03 board. If the F1 board has 2 pairs of FETs like the ASF 03 board, it should be fine. A 52T down to a 43T would be good for the F1 car.