Sorry, I get it now. @dendad set me straight with that last post. I apologize.

It's ok, that's what we discussion here to figure out the correct and best method.
And thanks for reminded me that to thinking some more and deep.

 

Do you ever get electrical storms near where this installation will be located? Might want to think about transient protection.

 

Do you ever get electrical storms near where this installation will be located? Might want to think about transient protection.

Yes. I was thinking of that too. We have had a number of occasions where RS485 networks have been zapped by lightning in the past. It may be a worth while option to opto-isolate the controller from the transistors, and use separate power supply. It can help a bit for a near miss but a close strike will fry it.

 

Yes. I was thinking of that too. We have had a number of occasions where RS485 networks have been zapped by lightning in the past. It may be a worth while option to opto-isolate the controller from the transistors, and use separate power supply. It can help a bit for a near miss but a close strike will fry it.

Edit: It should be limit current resistor in series with one wire of line.

 

I'm not sure but I think this will do the same truth table as your original post.

But without the transistors.

 

Just use a double pole relay (2 form C) to toggle polarity..
Relay energized = LED 1 on
Relay deenergized = LED 2 on..

same thing for forward/reverse motor control.

 

I'm pretty sure he said he wanted to do this on the cheap...so to speak.

"I do want to keep the cost to minimum, so I don't really want to use a h-bridge, relay etc"

 

Some LEDs cannot tolerate any reverse bias without suffering long term degredation. Check the datasheets for the LEDs you intend to use before you settle on a design.

Thanks for pointing this out, I will look into it!!

 

I'm not sure but I think this will do the same truth table as your original post.
But without the transistors.

Positive polarity from one transformer goes to line through winding of other transformer.

 

Do you ever get electrical storms near where this installation will be located? Might want to think about transient protection.

We are in a peaceful little islands in the southern hemisphere. I can't remember the last time we have it, so I guess I am safe.

 

Here is the updated circuit, thought?

 

Here is the updated circuit, thought?

View attachment 141122

Looks good to me.

 

Here is the updated circuit, thought?
View attachment 141122

 

Here is the updated circuit, thought?

View attachment 141122

How about the relationship between inputs and Ground, do the IO_A, IO_B has any wire connected to Ground or the inputs only have IO_A, IO_B, if you only using two wires connected to the transistor Q1 and Q2 then the Q1 and Q2 do not like two transistors to the LEDs, the transistors just like two diodes from Base to Collector and to the LEDs, it means that the two transistors don't work like the switches any more.

 

View attachment 141130

Never thought of doing a h-bridge that way, thanks for the idea! I may use this because it's more efficient.

 

How about the relationship between inputs and Ground, do the IO_A, IO_B has any wire connected to Ground...

Yes. The inputs are IO_A, IO_B, and GND. Circuit on the left (R1, R2, R5, R6, Q1 and Q2) are local. Sorry for the confusion.

 

How about the relationship between inputs and Ground, do the IO_A, IO_B has any wire connected to Ground or the inputs only have IO_A, IO_B, if you only using two wires connected to the transistor Q1 and Q2 then the Q1 and Q2 do not like two transistors to the LEDs, the transistors just like two diodes from Base to Collector and to the LEDs, it means that the two transistors don't work like the switches any more.

Never thought of doing a h-bridge that way, thanks for the idea! I may use this because it's more efficient.

Yes. The inputs are IO_A, IO_B, and GND. Circuit on the left (R1, R2, R5, R6, Q1 and Q2) are local. Sorry for the confusion.

It was idea only. Now I am working on simulation.

 

I'm not sure but I think this will do the same truth table as your original post.
But without the transistors.
View attachment 141118

If the Vf of LED is 3V, how about when the inputs voltage are different as IO_A=0V, IO_B=3.3V(or 5V), or IO_A=3.3V(or 5V), IO_B=0V, do you think will the LEDs be damaged by inputs voltage?

 

If the Vf of LED is 3V, how about when the inputs voltage are different as IO_A=0V, IO_B=3.3V(or 5V), or IO_A=3.3V(or 5V), IO_B=0V, do you think will the LEDs be damaged by inputs voltage?

Good questions. It vas idea only. Now I finished simulation. Seems R5 = 1.2 k as current limiter is too big - current is 0.7 mA only.
When resistor R5 = 100 Ohm, LED's current is 20 mA.

 

If the Vf of LED is 3V, how about when the inputs voltage are different as IO_A=0V, IO_B=3.3V(or 5V), or IO_A=3.3V(or 5V), IO_B=0V, do you think will the LEDs be damaged by inputs voltage?

Please, explain me, your questions are about post #24 or about post #33. I am confused.