Need Help! Remote Controlled Switch

Thread Starter

kayjabbar

Joined Sep 8, 2016
50
491620F6-09DF-4170-ABCC-136269367D80.jpegThis is a micro switch which can be attached to devices on an RC car or drone which takes a UART port / PIN IO to turn on or off VTX, camera, other devices by an input by RC transmitter..
Cannot order this online so thinking to get parts and build one..
Tried searching for part numbers on internet but cannot find datasheets, can anyone help what is the big component “J27 FQT5P10” transistor i think, and the small part named LO
Can anyone help?

Mod:Lightened your image.E
491620F6-09DF-4170-ABCC-136269367D80.jpeg
 
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Thread Starter

kayjabbar

Joined Sep 8, 2016
50
Just after posting i found the datasheet, can anyone help me with understanding the function of “LO” transistor’s collector pin connected to Gate of mosfet,
Both Source and Gate of the Mosfet are connected to Input voltage Source directly while Gate via resistor
What is happening here when the transistor’s base pin gets signal from FC pad, how thr mosfet gets turned on to Drain the + batt voltage
I hope you get what am i asking
 

Thread Starter

kayjabbar

Joined Sep 8, 2016
50
There is no datasheet, i am just looking at the picture i posted in very first post of this thread, looking onto the PCB traces directly and assuming it to be one sided circuit only..
 

Thread Starter

kayjabbar

Joined Sep 8, 2016
50
yes i meant could you help me explaining the phenomenon taking the drawn schematic into consideration..
I want to know the behaviour of this circuit.
Lets say the FC pad goes high i.e. <=3.3v ,which is connecting to the base pin of the transistor, now what is happening at the MOSFET gate activating its drain pin..
My question is whether the Gate of mosfet is being grounded via collector of transistor, i mean how the circuit gets complete..
 

Thread Starter

kayjabbar

Joined Sep 8, 2016
50
hi,
So that the NPN transistor can control the Gate voltage On/Off
E
View attachment 240885
Thanks alot Eric for all your answers, i just have one confusion now..
what i understood from your reply is that VTX + would not get full 12v but still positive Batt+ voltage coming and passing through R1 is also being grounded when transistor switches on, when FC pad goes high..
Wouldn’t the heat-up in this case..
If not so what are the suggested values for this resistor, batt+ voltage can be around 5-28v
 

Thread Starter

kayjabbar

Joined Sep 8, 2016
50
hi kay,
What is your battery voltage and the drive voltage on FC and how much current does the load on VTX require.?

Update:
This should answer your query.
The VTX draws around 600mA to 1000mA and FC pad i am not sure but i guess it would be around +3.3v to toggle this switch
Battery voltage is 16.8V
 
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Thread Starter

kayjabbar

Joined Sep 8, 2016
50
hi kay,
What is your battery voltage and the drive voltage on FC and how much current does the load on VTX require.?

Update:
This should answer your query.
also in your above schematic, R4 and R2 are in series while if we look at the circuit board , Fc pad should go to R4 and R2 parallel and then from R4 to Transistor and R2 to LED
 
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