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Optocoupler swithcing 24vdc on and off.

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louarnold

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I have a 24vdc battery supply. A manual switch now provides 22v to a signal wire (using only milliamps) I need to change this to have a micro-controller do the switching. It runs at 5v taking its power from the 24vdc via a 7805 regulator.

I have chosen an optocoupler to switch the 24 v on and and off to the signal wire. Will this work, or is there a better approach?
 

Yes, that is good if you have selected correct voltage optocoupler.
Also you can use little 5V signal relays. (search for "5V signal relays" on ebay)
 
Personally I prefer this approach (If you have many MOSFETs handy, but not many optocouplers).
VIN is +24V, VOUT is your switched output, and CONTROL is connected to your microcontroller.
control.jpg
 

Re: Optocoupler switching 24vdc on and off.

sky_123 said:
Personally I prefer this approach (If you have many MOSFETs handy, but not many optocouplers).
VIN is +24V, VOUT is your switched output, and CONTROL is connected to your microcontroller.
View attachment 78650
Click to expand...
Interesting idea. I still have to design components around the Opto. I'll see which uses less real-estate. (I'm not too good at electronics, so it will take awhile.)
 

sky_123 said:
Personally I prefer this approach (If you have many MOSFETs handy, but not many optocouplers).
VIN is +24V, VOUT is your switched output, and CONTROL is connected to your microcontroller.
View attachment 78650
Click to expand...

This has a common ground for both input and output sides;
But opto-couplers and relays have completely isolated input and outputs from each other. (eg. input side is DC while output is AC)
http://www.pc-control.co.uk/relays.htm
http://www.bcae1.com/relays.htm

reladiod.gif

http://en.wikipedia.org/wiki/Opto-isolator
http://www.technogumbo.com/projects/Learning-to-Use-an-Optocoupler-or-OptoIsolator/

220px-Optoisolator_Pinout.svg.png
 

This has a common ground for both input and output sides;
But opto-couplers and relays have completely isolated input and outputs from each other.
Click to expand...
I am aware of the function of optocouplers and relays.
If your microcontroller is being powered from the 24V supply via a 7805 (as mentioned in the original post), I think you'll find you already have a common ground.
 

sky_123 said:
I am aware of the function of optocouplers and relays.
If your microcontroller is being powered from the 24V supply via a 7805 (as mentioned in the original post), I think you'll find you already have a common ground.
Click to expand...
Hmmm, yes, that's a good point. I had thought of using the mcu on a separate proto board at first with a separate power supply. The Opto would have been good then, but once finished, the subsystem gets powered from the battery, and so has the same ground.
 

sky_123 said:
I am aware of the function of optocouplers and relays.
If your microcontroller is being powered from the 24V supply via a 7805 (as mentioned in the original post), I think you'll find you already have a common ground.
Click to expand...

Not meant only for you. Noted to distinguish both method for everyone. We see louarnold has got the advantage of everything posted here; and has made the decision based on it.
 

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