I have designed this PCB for my project and when i connect ESP8266 NodeMcu along with LM35 temperature sensor and check the output on the serial terminal the output drops to 0 v. I have checked the schematic and found no short. and connected the esp along with LM35on breadboard with the same code and found the circuit to be working correctly. kindly help me to find the bugs in this.

 

Would you please post the schematic?

 

Would you please post the schematic?

i have attached the schematic below

 

Hi jenish, I see from the data sheet specs that the operating voltage of the LM35 is 4-30V.. so you are maybe not supplying enough at only 3.3

 

Hi jenish, I see from the data sheet specs that the operating voltage of the LM35 is 4-30V.. so you are maybe not supplying enough at only 3.3

I have thought of that too but mine woeks perfectly on breadboard with 3.3 volts as VCC but when the same connected to PCB gives 0 temperature output

 

I had a look at your PCB.. can you verify that the LM35 is actually the correct way around. It appears that the GND and vs+ could be reversed?

 

hi jenish,
If you break the PCB track from LM35 to the MCU input pin, does the LM35 then work OK.?
E

 

I had a look at your PCB.. can you verify that the LM35 is actually the correct way around. It appears that the GND and vs+ could be reversed?

Yes it is soldered correct .

 

hi jenish,
If you break the PCB track from LM35 to the MCU input pin, does the LM35 then work OK.?
E

Didn't got exactly what you are saying you mean if I isolate the sensor and check if it is faulty or not?

 

hi,
Yes, isolate the LM35 from the MCU input pin.
Are you sure the Input pin is configured as ADC in and not an Output pin [ thats a common problem]
E

 

hi,
Yes, isolate the LM35 from the MCU input pin.
Are you sure the Input pin is configured as ADC in and not an Output pin [ thats a common problem]
E

Yes I have checked that too and about the sensor I have first checked all the sensors on breadboard and then mounted them to the PCB . Also I have ordered a batch of 10 PCB and all are having the same issue . I think not sure how but their might be some sort of shorting happening in the PCB as I power it up. Could you suggest meways to debug this.

 

hi,
Can you cut that LM35 output track for testing, so that it can be reconnected later.?
If yes, do so, power up the PCB, use a 10k resistor to +3.3V and the MCU input pin, it should pull the pin upto 3.3v, try it.
E

 

hi,
Can you cut that LM35 output track for testing, so that it can be reconnected later.?
If yes, do so, power up the PCB, use a 10k resistor to +3.3V and the MCU input pin, it should pull the pin upto 3.3v, try it.
E

Ok will tell you the results.

 

If you select the X1 input (Marked "DUST OUT") on the 4051 does that work correctly ?
Have you measured the voltage at pins 13 & 3 on the 4051 and on AD0 pin on the ESP to see if the problem is the actual voltage getting to AD0 or just the reporting of the voltage ?

Les.

 

I

If you select the X1 input (Marked "DUST OUT") on the 4051 does that work correctly ?
Have you measured the voltage at pins 13 & 3 on the 4051 and on AD0 pin on the ESP to see if the problem is the actual voltage getting to AD0 or just the reporting of the voltage ?

Les.

Since I have sensed their is some sort of shorting happening I have not connected the sensor to dust out pin as I have fried one earlier. And regarding 4051 too yes I have checked it and it was working perfectly fine on the breadboard and will tell you the outcomes of voltage after noting them on pin 13&3 too.

 

If you select the X1 input (Marked "DUST OUT") on the 4051 does that work correctly ?
Have you measured the voltage at pins 13 & 3 on the 4051 and on AD0 pin on the ESP to see if the problem is the actual voltage getting to AD0 or just the reporting of the voltage ?

Les.

the voltages are for 0.33V for v_out of lm35 and 0.1 or 0 volts for A0 of esp and output of 4051.

 

It looks like something is shorted to the track between A0 and pin 3 of the 4051 or A0 is configured as an output or the wrong input of the 4051 is being selected. Check that pins 9, 10, 11 and 6 of the 4051 are at zero volts.

Les.

 

Hello,

Did you read the datasheet of the LM35?
In there this is given:
Features
Calibrated directly in ̊ Celsius (Centigrade)
Linear + 10.0 mV/ ̊C scale factor
0.5 ̊C accuracy guaranteeable (at +25 ̊C)
Rated for full −55 ̊ to +150 ̊C range
Suitable for remote applications
Low cost due to wafer-level trimming
Operates from 4 to 30 volts
Less than 60 μA current drain
Low self-heating, 0.08 ̊C in still air
Nonlinearity only ± 1⁄4 ̊C typical
Low impedance output, 0.1 Ω for 1 mA load

3.3 Volts is to low for power supply.

Bertus

 

From your post #5.

I have thought of that too but mine woeks perfectly on breadboard with 3.3 volts as VCC but when the same connected to PCB gives 0 temperature output

Hi,
I would agree with post#18 ie:the LM35 is operating outside the specified voltage range.
What is the input voltage to S1117 voltage regulator, perhaps you could use the Vref input voltage to power the LM35.??

E

 

Hello,

@ericgibbs , @jenish looking at the posted schematic, the input of the S1117 is 5 Volts, wich is also used for the esp-kit.
Using the 5 Volts for the LM35 would be a good idea.
I would also power the 4051 with the 5 Volts, as it is controlled by the 5 Volts of the ESP.
Perhaps the 4051 is toast already by this.



Bertus