# Current flow switch

Discussion in 'General Electronics Discussion' started by bonapardo, Apr 18, 2011.

1. ### bonapardo

1
0
Apr 18, 2011
I have an existing circuit which sends a current one way if one button is pressed and the opposite way when another button is pressed. There is no current if nothing is pressed. I would like this arrangement to control two switches - i.e. activate one switch if the current passes one way, another switch if the current flows in reverse.

Sounds like a simple enough task. Is there a name for such a circuit? Or a component? Something I can look up on the net?

These are the only outputs from the existing circuit I can use so I'm limited to this 'directional' solution.

2. ### Resqueline

2,848
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Jul 31, 2009
You use the term current, though I suspect voltage might be as/more correct? The solution might be very simple, but we need to know a little more about this "circuit".

3. ### shrtrnd

3,688
457
Jan 15, 2010
Look into the glass encapsulated reed switches, or hall effect switches. You might have to play with the circuitry to detect current flow in two different directions, but the
devices are simple (they work from the magnetic field). And looking them up, might
give you some ideas.

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,271
2,718
Jan 21, 2010
*IF* what you are asking is to turn on one thing when the current id flowing one way, and the other when it is flowing the other way, then diodes bay be your answer. These can be connected to relays (if the load is powered from another source) or directly after the diodes (if the load is powered by this voltage you are switching.

I understand what bonapardo is saying, but I'm not sure that's what is happening. If you can show us a diagram, that will help us somewhat.

Anyway. Here is my solution for you:

When point A is more positive than point B, diode D1 conducts, allowing lamp L1 to light. When point B is more positive than point A, diode D2 conducts, allowing lamp L2 to light.

The lamps could be replaced by motors, LEDs with resistors, or relays. If you used relays then you could switch a load from another power source.

My only concern -- as I've mentioned above -- is how you use the switches to reverse the current flow (which means reversing the voltage applied). The trap is that you want to be sure that there are no switch positions which short out your power source. It can be conveniently done with two SPDT switches, but I'm not sure how you've done it.

Here is my solution. Is it like yours?

...or am I barking up the completely wrong tree?

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5. ### poor mystic

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Apr 8, 2011
maybe you could substitute the existing switches with double-pole models