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Opto circuit for heating purpose

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vaibhavpawar

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I am using heater circuit for bio-medical application ( to achieve 37 degree Celsius for blood samples ). I am using opto-isolator P781F to isolate control circuit ( Micro-controller I/O pins - H1G shown in schematic) and heater.

Link for opto datasheet:
https://www.farnell.com/datasheets/90914.pdf

My schematic is as shown below:
Heater.png

H1G= I/O pin from LPC2138 controller
Heater = 12V,23 Ohms Silicon Heater

But, I am little worried as I have connected controller I/O pin directly to cathode of LED of opto. So, is there any loading issue I can face, what parameter will come in picture to check I/O pin source/sink capacity with OPTO pin.

Will this cause any loading or impedance problem? Do I need any buffer circuitry from controller I/O to opto circuit.

Thank you in advance.
 

srizbf

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for the circuit attavhed , the lpc controller have to sink 10mA approx.

if you can put a buffer in between it is good.
 

schmitt trigger

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Most microcontroller will sink 10 MA of current, but I like to add a simple NPN transistor buffer.
 

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