[PLC Sample Code] - analog output 0-10volt

[batool 0]

analog output 0-10volt

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i draw analog output 0-10 volt , but now i dont know how to convert this circuit to become isolated , i need someone to help me ?

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• Submitter
  batool
• Submitted
  02/20/22
• Category
  PLC Sample Code

[panic mode 246]

please be mindful where you post. download section is meant for placing resources such as documentation, program examples etc that are likely to be useful to others. that is not a place to ask for help. that will also have an effect on how many people will find your post and how soon you may be getting any tips. 

normally when isolation is required one would simply use 3rd party signal conditioner that provides the 3-way isolation (in/out/power). for example

https://www.weidmuller.ca/en/products/electronics/analogue_signal_conditioning/index.jsp

https://www.automationdirect.com/adc/overview/catalog/process_control_-a-_measurement/signal_conditioners/dc_voltage,_current_or_potentiometer_input

https://www.redlion.net/product/isolated-universal-converter-signal-conditioning-module

etc.

not sure why are you doing DIY rather than using off the shelf components but i guess you must have a reason.

anyway, looks like you are working with own circuit that attempts to produce an analog output using very basic circuit. it does not even have an ADC or voltage reference, it is just using PWM signal into 1st order filter and buffering output to produce an analog voltage. it does not get more crude than that, so you obviously do not need great stability, accuracy etc.

in that case, consider getting cheap isolator from Amazon. if this is some school project or whatever homebrew, no point spending hundreds of $$$ on proper isolator when signal is produced by such simple circuit.

https://www.amazon.com/Isolation-S-10V10V-Quantities-Voltage-Isolating/dp/B07RGWJC26

 

but if you are planning to integrate isolation into your own circuit, you need to make some decisions. this means consider spec etc. deciding on 2way or 3way isolation, place in circuit where isolation is done etc.

at the very minimum you will want 2-way isolation. This can be done two ways, isolating analog output or isolating PWM input.

in general isolating PWM input is much simpler as long as used optocoupler can handle signal at frequency you are using. if your PWM is not more than couple of kHz this should be fine. but optocouplers are not very good for high speeds since latency becomes a factor. in case of higher frequency, distortions due propagation etc become factor which is not good for PWM where duration of the pulse is important.

there are of course other types of coupling (capacitive or inductive). so not sure what your comfort level or needs are. in case you are only using 2-way isolation, opamps would need to be powered from the target circuit, not from your MCU circuit, so your booster to produce 12V will need to be replaced.

btw. using switching supply is also not the best idea, specially since circuit is low power. also using single sided supply for your buffer is another problem as you will not be able to get close to zero even if opamp is rail-to-rail.

isolating an analog side of the circuit is also possible and several solutions exist. in your case time constant is very long (0.1sec) and your analog output would be very slow.