Wimos and FS300A

[tocks]

Hello,

I am newbee on ESPEasy, I just bought 2 mini Wemos.

I wonder if it is compatible with a FS300A?

http://fr.aliexpress.com/item/Free-Ship ... 42021.html

thanks a lot

[costo]

The hall sensor needs a voltage between 4.5 and 20 volt to work properly. When powered with 5 volt it will give output pulses of 5 volt. That is not compatible with any ESP8266. You have to use a voltage divider or level converter between the yellow output pin to the FS300A and the ESP.

[tocks]

hello, thanks for your reply.

But i don't understand. Why i do use a voltage divider or level converter ?

The wemos has a pin 5 V, it's not good for this sensor ?

Thanks

[andy]

GPIO inputs are 3.3V max, except Tout, or ADO, which is 1V max.

[tocks]

ok so I understand:

I can supply the FS300A with Wemos in 5v.

But the input pin can only support 3.3V Max. So I have to put a converter for 3.3V max . Tell me if I misunderstood

Can you recommend a converter that I can find on eBay or Alibaba to put between the input pin and the yellow cable of the sensor?

Thanks

[costo]

Just use a resistive divider to drop down the 5v output of the sensor to 3.3 volt.
You can take 3 resistors of equal value, (between 1k and 5k each) connect the resistors in series from the sensor output to ground.
You will have 1/3 of the output at the resistor closest to ground and 2/3 of the output value at the other point, that point can be connected to a ESP GPIO input.

[tocks]

thanks for your reply.

Can you post me a schema of the divisor ?

I have found this : http://fr.aliexpress.com/item/4-channel ... .18.i3mqq8

This module does it work?

if not, I have this module in my stock :





I can use in my case?

Thanks

[costo]

Sure that module of your aliexpress link will do the job.
But using a few resistors will work in this particular case as good because you dropdown the voltage.
Resistors are probably more easy to get. (some people stockpile them)

explanation:
https://en.wikipedia.org/wiki/Voltage_divider

Vin is your sensor output FS300A
Vout to the GPIO of the ESP where you count the pulses
GND common ground for all of the circuits.

Z2 is twice the value of Z1
If Z1 = 1k-ohm then Z2 = 2k-ohm
or
Z1 = 4k7 and Z2 = 10K That is exact enough.

[tocks]

thanks for your explanation.

I have in stock 10k, but not 4.7K. I can buy it.

but if :

Z1 = 4k7 and Z2 = 10K
Vin is your sensor output FS300A : 5V
Vout to the GPIO of the ESP where you count the pulses 3.3V
GND common ground for all of the circuit

Vout = (R2/(R1+R2))*Vin

Vout = (10/(10+4.7))*5
Vout = (10/14.7)*5
Vout = 0,680272109 *5
Vout = 3,401360544

the result is > 3.3V, it's not a problem ?

I have a another project with PH sensor on wemos, the output is analogic with 5V. I can use the same ?

Thanks a lot

[costo]

If you have enough 10k in stock you can use 2 * 10k in parrallel instead of 4k7.

A difference of a few tenths of a volt is usually no problem

[tocks]

thanks, but i don't understand .

I can replace 4K7 with 2*10K ?

Z1 = 2*10K and Z2 = 10K
Vin is your sensor output FS300A : 5V
Vout to the GPIO of the ESP where you count the pulses 3.3V
GND common ground for all of the circuit

Vout = (R2/(R1+R2))*Vin

Vout = (10/(10+20))*5
Vout = (10/30)*5
Vout = 0,333333333 *5
Vout = 1,666666665

My Vout is not good .

[costo]

thanks, but i don't understand .

I can replace 4K7 with 2*10K ?

You don't know what parrallel is ?

[tocks]

Ho, sorry. I understand.

Can you confirm my schema ?



Thanks

[costo]

Do the calculation yourself please.