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-   Bit Char-G Parts and Hop-Ups (http://tinyrc.com/forums/forumdisplay.php?f=11)
-   -   MOSFET mod for BCGs (http://tinyrc.com/forums/showthread.php?t=11178)

Rcmaniac246 06-09-2003 04:16 PM

ARE YOU INSULTING MY SOLDERING SKILLS YOU YOU YOU NONSOLDERING PERSON!!!!!!!!!!!!!
AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH
lol i can solder great man :)
plus im not wasteing 20 bux on this lol

so does anyone know how to hardwire this part?

micro_Amps 06-09-2003 04:26 PM

hehehe, I'm sure no offence was intended Rcmaniac.
The hardwiring instructions are in one of the links earlier in this thread.
Goodluck, let us know how you go.
:) uA

Rcmaniac246 06-09-2003 04:47 PM

yes no offense lol hahaha

Rcmaniac246 06-09-2003 04:57 PM

i cant find hardwireing on that website :confused: can you find it and give me a link ?thanks
my dream is


b3spd :bs: bg343
no body(just wings lol)4 cells and phast motor Droollllllllll
is it possible?

micro_Amps 06-09-2003 06:10 PM

Yeh sure, here is the link to the german site that published the mod, its a bit tricky to understand but all the info is here
:) uA

ph2t 06-09-2003 06:25 PM

RC, I'm the muth#$%^ solder king! hehe, lol!

That's cool dude if you can solder no sweats....But trust me, be very careful, those SMD FETs are awfully tricky......

:p

ph2t.

bdebde 06-09-2003 09:04 PM

Quote:

Originally posted by ph2t
RC, I'm the muth#$%^ solder king! hehe, lol!

That's cool dude if you can solder no sweats....But trust me, be very careful, those SMD FETs are awfully tricky......

:p

ph2t.

I second that!

Rcmaniac246 06-10-2003 05:03 PM

Quote:

Originally posted by micro_Amps
Yeh sure, here is the link to the german site that published the mod, its a bit tricky to understand but all the info is here
:) uA

i said hardwiring not replacing with other mosfets lol
never mind

bdebde 06-10-2003 08:58 PM

Quote:

Originally posted by Rcmaniac246
i said hardwiring not replacing with other mosfets lol
never mind

Dude, you can't "hardwire" the transistors. If you remove them or jumper across them, your circuit board will not work. Maybe you are thinking of the resistor jumpering mod that "some" people have had success with. The mosfet mod removes the high resistance transistors, and replaces them with low resistance mosfet transistors.

BabyKiller 06-10-2003 09:25 PM

well if you completely bypass them they would go even faster wouldnt they?

bdebde 06-10-2003 10:11 PM

Quote:

Originally posted by BabyKiller
well if you completely bypass them they would go even faster wouldnt they?
If you completely bypass them, you would be hooking the battery straight to the motor. You could only get one direction, and it would start running as soon as you start charging. You would have no control over throttle, it would always be running.

ph2t 06-10-2003 11:01 PM

BK, you need the mosfets to be able to control the motor. As bde said, bypassing them completely is the same as just hooking a motor straight to a battery, might as well through the chassis away....

The circuit that controls the direction of the motor is called a H-Bridge. It was given this name 'cause of its looks, see below.

http://www.prahranpianos.com/bit_g/h_bridge.jpg

The bottom two transistors, labeled Q4 & Q5 connect to Fwd and Rev signals on the receiver chip (which is not part of this picture).

Depending on which of these two transistors is activated, they change the direction of the current traveling through the motor.

If Fwd is on the motor turns one way. If Rev is on the current flows in the opposite direction, causing the motor to spin the other way.

This is what gives you forward and reverse!

The problem with this setup is two things:

1) The voltage is small, 1.2V.
2) The transistors drop the voltage further.

In the end (as stated in many threads here) the actual voltage that goes to the motor is nowhere near 1.2V.

Replacing the transistors Q4 -> Q7 with mosfets provides more voltage to the motor because these mosfets have very little resistance. They (the fets) also increase the current going to the motor which gives you that insane torque boost, as seen in my video posted in this thread earlier.

Using ohms law V=I/R. In this case the R hasn't changed, that's the motor. V has changed, it has increased. Re-arranging ohms law to I=V/R shows that V is getting bigger and R isn't. Given that reasoning I (current) has to increase!

Hope this helps....

ph2t.

bdebde 06-12-2003 09:29 PM

I got my new Perfection 4.2 motors the other day. They are FAST! Now I can't wait to get my mosfet modded pcb back from micro_Amps! These motors should be incredible with the mosfet mod!

micro_Amps 06-13-2003 04:51 AM

They sure are fast. I got my 4.2s in the mail this afternoon and have been screaming around the house for the last hour with a single cell fet booster and a dual cell fet booster. THEY FLY !!!
Heaps faster than a perfection 3.8
:) uA

bdebde 06-13-2003 09:22 PM

Boy, I sure wish I had a fet booster to try mine in!

micro_Amps did my booster car show up there yet?


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