Is it too much with 4k7 resistor?

Other Hardware General Electronics
1

I testing out DS18B20 temperature sensor and it works fine, but when i added the 4k7 resistor that everybody says you should use, my system looses almost all power.

My LCD bearly light up and when i press on reset button (EN) on my ESP32, nothing happens. When i take 4k7 resistor away, all works fine, but temperature is not showing dough.

My system uses totaly before adding DS18B20 around 200mA in peaks and around 100mA as general.

i guess i can add a smaller resistor, but why does all preferred to use 4K7?

2

Where have you put the resistor ?

Please post a schematic of your system

3

UKHeliBob:
Where have you put the resistor ?

Please post a schematic of your system

I do not have schematic for now. But i put the resistor between VCC and digital leg. It works, but i can see my LCD almost shuts off when i add resistor.

4

I do not have schematic for now

Draw it using pencil and paper and post a photo

5

PS! This is a breadboard. The ESP32 is powered by the same input via VIN pin and DSB1820 is grounded to the board.

6

The ESP32 is a 3.3volt processor.
You must power the DS18B20, and pull up the digital pin, from the 3.3volt pin of the ESP, not from 5volt.

I don't see the 4k7 resistor on that diagram.

Bjerknez:
My LCD bearly light up

When i take 4k7 resistor away, all works fine...

Are you sure it's 4k7 (4700 ohm).
Post a real picture of the setup.
Leo..

7

Wawa:
The ESP32 is a 3.3volt processor.
You must power the DS18B20, and pull up the digital pin, from the 3.3volt pin of the ESP, not from 5volt.

I don't see the 4k7 resistor on that diagram.
Leo..

Can you explain why i have to drive the sensor from the ESP32 regards to +5v and ground and not from the external power?

Sorry, i forgot to add the resistor on my bad drawing. But the 4k7 resistor is between +5v and digital on the DS18B20 sensor.

8

What is there to explain.
The ESP32, being a 3.3volt chip, is expecting 3.3volt logic.
Leo..

9

My ESP32 gets 5v from external power via VIN pin. +5v and GND from extarnal Power is connected to the board. Before VIN pin i connected the +5V and ground to DS18B20. DS18B20 shares ground with the board and gets 5V from external power.

Digital pin is connected from the board to the middle pin, with 4k7 resistor between digital and VCC.

This works and i can see temperature reading, but my display looses almost all backlight and flickering. When i remove the 4k7 resistor, my display is normal again.

10

Bjerknez:
My ESP32 gets 5v from external power via VIN pin. +5v and GND from extarnal Power is connected to the board.

I assume you don't use a bare ESP32 module, but some board with ESP32 module (metal square) on it.
If so, then that board has a voltage regulator that converts 5volt V-in into 3.3volt for the ESP module.
The DS18B20 should also be powered from that same regulator (the 3.3volt pin of that ESP board).

When the lights dim with a 4k7 resistor, then it's probably not a 4k7 resistor (yellow, violet, red, gold).
That's why I requested a real picture of the setup.
Leo..

Edit: I see that you already posted pictures of your ESP project in another thread of the forum.
Spreading your project across several threads wastes people's time, and is against forum rules.
Good luck.
I'm out.

11

Ok, so i can’t power a DS18B20 externally and same time read the sensor with ESP32?

Even when they are grounded together?

12

Regards to my other post in this forum.

I have diffente kinds of problems and or questions. I think it is better regards too Goolge Search engines etc. if posts are separated.

Or is it better if i start an own project tread and put all my question in one place?

If so, i can do that. My intension is not to waste other peoples time. :slight_smile:

13

Bjerknez:
Ok, so i can’t power a DS18B20 externally and same time read the sensor with ESP32?

Even when they are grounded together?

Of course you can, but read the previous answers you have had. The device is a 3.3V device, not a 5V device. Therefore you need to present it with 3.3V, it doesn't matter if that is an internal supply or an external supply.

14

Datasheet says 3-5v...?

15

Bjerknez:
Datasheet says 3-5v...?

...and what is the acceptable range of input voltages for the controller it is connected to?

16

That i dont understand is that the sensor is connected to power supply but grounded to the board.

Is it better to drop the external supply and power all sensors directly from board?

I do not understand why the sensor not draw current from power supply.

17

You have to connect grounds so that the two parts of the circuit have a common reference.

How do you know the sensor isn't drawing current?
How are you measuring the current?

Is it better to drop the external supply and power all sensors directly from board?

I don't understand what you are trying to say there

18

TheMemberFormerlyKnownAsAWOL:
You have to connect grounds so that the two parts of the circuit have a common reference.

Sensor and the board are connected to the same ground. I have sead that several times.

19

But you asked this

That i dont understand is that the sensor is connected to power supply but grounded to the board.

20

TheMemberFormerlyKnownAsAWOL:
But you asked this

My english is not my best side... sorry.

But the board gets power (and ground) from external power supply. Inn via VIN pin and GND on the board (ESP32)

DS18B20 is connected to Power Supply (+5v) but grounded together with the Board.