Hello.

I would like to make a circuit to scale down voltage from 24v to 5v dc , I need to read the High/low status of a industrial sensor that uses 24v logic,

I need to feed the output of sensor to microcontroller input pin, two resistor divider circuit can be use with an input pin




I heard about opt-coupler can be used,

what are the other way to read the High/low status of a industrial sensor that uses 24v logic ?

thanks for help.

 

Lookup voltage divider.

 

Lookup voltage divider.

Is it compatible to read sensor that use 24 V logic ?

 

Is it compatible to read sensor that use 24 V logic ?

What???

You have 1 sensor that outputs 24 volts right? Your MCU can only handle 5V right? You need to divide the voltage down to 5V from 24V.

 

What you have is as efficient as you can get.

The only other option is to use 24VDC controller, that way you can get rid of the voltage divider that you have. The only 24VDC controllers I am familiar with are the 24VDC PLC, this way you wire 24VDC sensor directly to 24VDC PLC. And this is where the problem rises. PLC are not cheap. Two resistor voltage divider is VERY cheap. So. You are balancing efficiency vs. cost.

 

What you have is as efficient as you can get.

The only other option is to use 24VDC controller, that way you can get rid of the voltage divider that you have. The only 24VDC controllers I am familiar with are the 24VDC PLC, this way you wire 24VDC sensor directly to 24VDC PLC. And this is where the problem rises. PLC are not cheap. Two resistor voltage divider is VERY cheap. So. You are balancing efficiency vs. cost.

Oh, that R1/R2 block IS a voltage divider? You are more aware than me.

 

Oh, that R1/R@ block IS a voltage divider? You are more aware than me.

I got "spanked" in his other thread because I missed it.

 

Use a coupler if you are looking for galvanic isolation, otherwise the divider
perfectly suitable. Use values in divider nominal in the 1 - 10 K range, ones
that are too high will subject the node to noise pickup and offset due to leakage.

Ones too low will burn unnecessary power.

Regards, Dana.

 

Use a coupler if you are looking for galvanic isolation, otherwise the divider
perfectly suitable. Use values in divider nominal in the 1 - 10 K range, ones
that are too high will subject the node to noise pickup and offset due to leakage.

Ones too low will burn unnecessary power.

Regards, Dana.

let's take the example

I have a pressure sensor which is a digital switch. It works on 24V power and if it exceeds a certain limit, It will stop motor.




I know this will work fine My question is related to optocoupler ic

should i need to use optocoupler ic in place of divider and relay to switch and drive 24 v DC signal?

I wish to drive an output say 24V device from my 5V controller output.In another case my reed switch signal ( 24V) needs to fed to the controller having 5V input.

 

hi champ1,
Is that AT89 MCU just being used to drive a relay.??
E

BTW: why have you created a new thread for a related topic in your other Thread.?
https://forum.allaboutcircuits.com/threads/digital-pressure-sensor-need-help.157120/

 

Just use a MOSFET and a clamp diode to drive your relay. MOSFET
must be a logic level MOSFET, meaning it turns on hard when gate is driven
to the high V the UP outputs when at logic 1.



The 10K is used to insure MOSFET is off when UP output is tristated, typically
when UP powers up. Diode is to clamp turn off transient from relay inductance.

You can get optocouplers for this as well, benefit is galvanic isolation from
relay power supply if it does not share a common ground with UP.

Note IRF610 is a poor choice for this application as it has a required high
V gate drive to fully turn on. Just go to digikey or Vishay website and use
searchable parameter tool to pick on that turns on adequately at the logic
1 level the UP can put out for its power supply V rating.


Regards, Dana.

 

Just for the original question, I would use a resistor + zener diode, rather than a 2 resistor potential divider. You dont have to faff around finding strange values of resistors, but also you are not affected by any voltage fluctuations, should they occur.