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Help to identify a symbol in schematic

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Karl_Harsfa

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Please help to identify a symbol in schematic block diagram! I know this maybe is silly question but what is this and what does it do?
Symbol U18:
symbol.jpg
 
It looks more electrical than electronic.

My guess is it's some sort of opto-isolator but without seeing the rest of the schematic, it's difficult to say.
 
Please post as much of the schematic as you can.

I've never seen the symbol before but going by its context, I'm still guessing it's an opto-isolator.
 
Last edited:
I agree with Hero, it is an opto isolator.

JimB
 
In the area of the schamatic marked D2, there seems to be 8 of them. The input sides of opto-isolators (if that's what they are) are connected connected to +12V and then ground. That would appear to turn them on and keep them on. What would be the purpose of that I wonder? What is this thing intended to do?
 
Switches from S10 to S13 on D6 activates two motors (they are connected to board D3 connector X11 pins 1,2 and 3,4) to rotate in one or second direction!
 
See my edited version of the schematic.

It works like this:

The diode side of the opto-isolator is supplied by +12v, the other end of the diode connects through a switch to an output port of a micro controller.
You will notice that each opto connects to several switches, the switches in turn connect to different output ports on the micro-controller.

The transistor side of the opto-isolator connects to an input on the micro-controller, when the opto is turned on the micro input is pulled low. From experience I expect that there are pull-ups are fitted on the micro board.

To read the state of the switches, the micro sets the outputs low, one at a time and reads the input port, so multiplexing the inputs in a similar manner to a keypad multiplexer.

JimB
 

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  • Opto Isolator Diagram - edited.JPG
    Opto Isolator Diagram - edited.JPG
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See my edited version of the schematic.

It works like this:

The diode side of the opto-isolator is supplied by +12v, the other end of the diode connects through a switch to an output port of a micro controller.
You will notice that each opto connects to several switches, the switches in turn connect to different output ports on the micro-controller.

The transistor side of the opto-isolator connects to an input on the micro-controller, when the opto is turned on the micro input is pulled low. From experience I expect that there are pull-ups are fitted on the micro board.

To read the state of the switches, the micro sets the outputs low, one at a time and reads the input port, so multiplexing the inputs in a similar manner to a keypad multiplexer.

JimB


Ahhhhhh, that makes much more sense. I wrongly assumed that the inputs were on the left and the outputs were on the right like this:

opto_wrong-png.38937


But that's not really consistent with the diagonal line in the symbol. Thanks for the explaination.
 

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  • opto_wrong.PNG
    opto_wrong.PNG
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Ahhhhhh, that makes much more sense. I wrongly assumed that the inputs were on the left and the outputs were on the right like this:

opto_wrong-png.38937


But that's not really consistent with the diagonal line in the symbol. Thanks for the explaination.

The INPUT IS on the LEFT, and the OUTPUT is on the RIGHT. If the input wire (lower left, X13-12 to 15) is externally pulled to non-isolated 0V, current flows from the non-isolated +5V through the LED and the current limiting resistor in the upper left. If the input is floating, no current flows in the LED.

If photons get to the base to of the photo-transistor, it conducts from upper right (collector) to lower right (emitter and the floating ground with the single bar), pulling the isolated logic line low, and lighting the Green indicator LED.
 
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