Ground routing (basics)

Thread Starter

vult-r

Joined Jan 10, 2020
7
wondering too much with this..
is there maybe someone who can tell me which way is preffered and why..

im usually taking low-current 3.3v applications out of the 3.3 volts onboard regulators on some of the ESP boards out there.
then a way to route the ground , which could be 1 of 2 :

1) back to the same esp board , that provided the 3.3v
01.jpg

2) back to the more general ground of the (5V) PSU
02.jpg

Thank you
 

eetech00

Joined Jun 8, 2013
1,968
wondering too much with this..
is there maybe someone who can tell me which way is preffered and why..

im usually taking low-current 3.3v applications out of the 3.3 volts onboard regulators on some of the ESP boards out there.
then a way to route the ground , which could be 1 of 2 :

1) back to the same esp board , that provided the 3.3v
View attachment 200813
Any current drawn thru the CE of the transistor will pass thru ESP.
2) back to the more general ground of the (5V) PSU
View attachment 200814

Thank you
Any current drawn thru the CE of the transistor will not pass thru ESP.
 

dl324

Joined Mar 30, 2015
11,223
For low current applications, it doesn't matter.

For high current applications, connection 2 might be better because you can make it a lower resistance path.
 

bertus

Joined Apr 5, 2008
20,649
Hello,

What will be the load?
You will need a base resistor to limit the current from the ESP into the transistor.

Bertus
 

Lo_volt

Joined Apr 3, 2014
100
It's probably better to connect the emitter to the ground next to the 3.3v supply pin. Best practice is to route your current return alongside of your current supply, be it pcb traces or wires. This is why we twist wires together. It minimizes the space between the conductors. Minimizing that space limits the influence of external electromagnetic fields on your circuit as well as emissions your circuit may make.
 

Thread Starter

vult-r

Joined Jan 10, 2020
7
thanks ; the onboard 3.3v regulators on such boards provide up to 600mA. but usually i go for this build with 100-200mA max.

I guess reading all this , it is kinda the question between:
2. 'relieving' the ESP from the mA's, not putting that current thru the board (situation 2)
1. keeping things tidy, and from prevent (possible) interference (situation 1)

still bit confused , although it probably doesnt matter?

also wonder if the GND of the ESP32 can handle up to 600 mA's , never could find it clearly in the datasheets..


(yep , will add the base resistor)
 
Last edited:

Lo_volt

Joined Apr 3, 2014
100
2. 'relieving' the ESP from the mA's, not putting that current thru the board (situation 2)
You won't be running the return current through the board, but you'll still be running the supply current through. Subtle difference. If you are turning the transistor on and off rapidly, e.g. pwm or modulation, you could be introducing noise on the 3.3 volt rail that's not mirrored in the ground on the ESP. This will show up on parts that use the 3.3 volts on that board.
 

dl324

Joined Mar 30, 2015
11,223
still bit confused , although it probably doesnt matter?
It looks like your board has two ground connections. One of them is likely to have a resistance connection. You should use the lowest resistance connection for both:
1583528331761.png

I didn't comment on your lack of a base resistor because I thought you were just drawing cartoons of the intended circuit, not the actual circuit.
 
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