Maker Pro
Maker Pro

identify and upgrade power transistorson toy rc car

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
It all depends on the characteristics of the existing mosfet(s) and how they're switched.

Assuming the gate voltage is above 5V, sure, I'd give that one a go.
 

Jean Perret

Jan 3, 2013
37
Joined
Jan 3, 2013
Messages
37
As the reverse motion still works, could I use a voltmeter while the truck is running backward motion and measure the voltage on the good transistors still working? As everything seems so complicated I might just end replacing the burnt transistor with a new same one and just run stock 9.6v packs..
 

jpanhalt

Nov 12, 2013
426
Joined
Nov 12, 2013
Messages
426
That is a P-channel mosfet. The gate threshold voltage (Vgs) can be just -2V (range: -2V to -4V), so with a 12V battery, he will need a gate voltage relative to ground/common of 10V or so to be sure it is off.

Also, the voltage at the transistor base is likely PWM'd, so a simple voltmeter won't give the peak value, unless it is at 100%..

John
 
Last edited:

Jean Perret

Jan 3, 2013
37
Joined
Jan 3, 2013
Messages
37
What about using those low opening voltage mosfet? and as I have currently two bipolar regular PNP and two NPN so 4 in total how many mosfet would I need P or N channel?
 

Jean Perret

Jan 3, 2013
37
Joined
Jan 3, 2013
Messages
37
fix a toy rc car

Hi folks,

I was running some tests switching the standard 9.6V battery packs to lipo 3S , Over the 5cars tested one came to a dead stop after less then 50m..leaving the car without forward motion, electronics smelled burnt. Opened the car and nothing seemed suspect despite the burnt smell. The power transistors are the square flat with 3 legs screwed on a heat sink ( and by the way I'm surprised how fast this forward transistor burnt despite the heatsink!) ,refs are : Two are C3420 031 and two others A1357 031, Could you guys help me identify those transistors and maybe tell me which ones could replace those for higher performance ?

Appreciate your help!
 

Jean Perret

Jan 3, 2013
37
Joined
Jan 3, 2013
Messages
37
Some people tell me that if the actual bard has not been designed for power mosfets then it will not work? I'm kind of lost..Or should I use just more powerful transistors, a step better then the ones I have now and go with the exact same pnp, npn?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
What about using those low opening voltage mosfet? and as I have currently two bipolar regular PNP and two NPN so 4 in total how many mosfet would I need P or N channel?

It depends on the circuit and how they're driven.

Without knowledge of both, I'd replace BJT with BJT and mosfet with mosfet.
 

Jagtech

Feb 22, 2014
43
Joined
Feb 22, 2014
Messages
43
Have you considered just replacing the transistors with OEM, but upgrading (or adding) the heat sinks ?
 

Jean Perret

Jan 3, 2013
37
Joined
Jan 3, 2013
Messages
37
yes I think I will just put regular pnp /npn transistors but at least the most powerful ones .. any precise model you guys know?? And as for heatsink, the actual ones that burnt up in no time had already good heatsinks..
 
Top