Re: [beagleboard] correct connection of an opto-coupler

[Przemek Klosowski]

On Tue, Nov 8, 2016 at 10:27 AM, mzimmers  wrote:
> I apologize for the confusion...after reading the instructions for the nth
> time, I have come to realize that I'm trying to use the wrong component for
> this exercise.
Right, Derek calls for an LDR aka Light-Dependent Resistor, aka
photoresistor, that looks like this:

https://www.amazon.com/PODOY-Photoresistor-GL5537-Resistors-Light-Dependent/dp/B016D737Y4

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Re: [beagleboard] correct connection of an opto-coupler

[mzimmers]

I apologize for the confusion...after reading the instructions for the nth 
time, I have come to realize that I'm trying to use the wrong component for 
this exercise. 

Thanks to everyone who tried to help me on this.

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Re: [beagleboard] correct connection of an opto-coupler

[mzimmers]

Thanks for the replies. I should have included this picture of the diagram:




It's the opto-coupler (labelled LDR) that I'm having trouble understanding 
how to connect. 

Przemek: I haven't tried anything. I don't want to make a connection that 
could damage anything.

Thank you for any help.

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Re: [beagleboard] correct connection of an opto-coupler

[Przemek Klosowski]

On Tue, Nov 8, 2016 at 9:39 AM, mzimmers  wrote:
> Hi, all - I thought I posted something about this last week, but a search
> doesn't turn it up, so here goes again.
>
> I'm working through Molloy's book, and trying to build the opto-coupler
> circuit in chapter 6. I'm not a hardware guy, so I'm feeling my way along
> here. The diagram doesn't show specifically how to wire up the four
> connectors. I looked at the data sheet for the device, which was helpful,
> but still doesn't get me home.

OK, so what did you try? Which four connectors are you talking
about--the opto's?
As a device, opto is normally being driven by your computer (pins A
and C on your datasheet, connected to the LED) and the output
phototransistor serves as a control switch for your working circuit.
They both need current limiting, normally in the form of a series
resistor. For instance, the LED in your opto is limited to 60mA, and
probably should be driven at 10mA, so if you're driving it from 3.3V
output of your Beaglebone, you need a resistor of
R=U/I=(3.3-1.3)/.01=200 ohm. The output phototransistor is limited to
50mA, so it also should have a similar current limiting resistor
connected to it.
Of course the opto could also be used as an input circuit---the LED
driven by a voltage from the outside, and the phototransistor
connected to the input of your Beaglebone. Similar current-limiting
considerations apply.

>
> I could trial and error, but I've already fried one component, and they're
> not easy to come by in my area. Can anyone help clarify this configuration?
>
> This is the specific device: opto-coupler
>

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Re: [beagleboard] correct connection of an opto-coupler

[evilwulfie]

You cannot use that optocoupler and directly drive it with the beaglebone.
the LED in that part needs 60ma to function correctly.

you would need to add a LED driver like what gerald has used to drive
the LEDs on the beaglebone.
you also need to calculate the correct current limiting resistor for
60ma @ 1.35v


On 11/8/2016 7:39 AM, mzimmers wrote:
> Hi, all - I thought I posted something about this last week, but a
> search doesn't turn it up, so here goes again.
>
> I'm working through Molloy's book, and trying to build the
> opto-coupler circuit in chapter 6. I'm not a hardware guy, so I'm
> feeling my way along here. The diagram doesn't show specifically how
> to wire up the four connectors. I looked at the data sheet for the
> device, which was helpful, but still doesn't get me home.
>
> I could trial and error, but I've already fried one component, and
> they're not easy to come by in my area. Can anyone help clarify this
> configuration?
>
> This is the specific device: opto-coupler
> 
>
> Thanks...
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> .
> For more options, visit https://groups.google.com/d/optout.


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[beagleboard] correct connection of an opto-coupler

[mzimmers]

Hi, all - I thought I posted something about this last week, but a search 
doesn't turn it up, so here goes again.

I'm working through Molloy's book, and trying to build the opto-coupler 
circuit in chapter 6. I'm not a hardware guy, so I'm feeling my way along 
here. The diagram doesn't show specifically how to wire up the four 
connectors. I looked at the data sheet for the device, which was helpful, 
but still doesn't get me home.

I could trial and error, but I've already fried one component, and they're 
not easy to come by in my area. Can anyone help clarify this configuration?

This is the specific device: opto-coupler 


Thanks...

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