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Toggle switch without the switch?

Declan The Average

May 16, 2014
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I'm working on a project where a pre-existing button will be pressed to toggle between two circuits receiving the power. When the button is pressed, the two contacts of the button are connected, and when released the contacts are disconnected.
I'm looking for something which will act as a toggle switch, except instead of the physical movement of a knob inducing the toggle, I want the connection between two of its contacts to toggle which circuit is receiving power.
Is this a somewhat simple device? I have no idea what to search to find it.
 

Harald Kapp

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except instead of the physical movement of a knob inducing the toggle, I want the connection between two of its contacts to toggle which circuit is receiving power.
Huh?

Sorry, I don't understand this at all. Who or what is going to chnage the configuration of the "connection between two of its contacts" if not a knob?
Could it be that you mean:
  • Pressing the button once will turn on circuit 1 and turn off circuit 2.
  • Pressing the button a second time will turn of circuit 1 and turn on circuit 2?
Here would be a sample circuit (scroll for "Bistable FlipFlop"). Here's another one using only relays.
Component values may have to be adapted to your operating voltage.
 

shrtrnd

Jan 15, 2010
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It SOUNDS like you mean a 'Momentary' contact Push Button.
Depress the push-button to close the circuit, and release the push-button to open the circuit contacts.
Is that what you meant?
 

BobK

Jan 5, 2010
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Actually, I think this is what he wants:

A momentary contact switch is used to alternate power from one device to another. I.e. push button and device 1 goes on device 2 goes off. Push again and device 2 goes on and device 1 goes off.

I remember seeing a little board that drives a relay on and off from a pushbutton, but I was not able to find it.

Bob
 

Declan The Average

May 16, 2014
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I'm sorry, I didn't explain it very well. I think BobK might have it, but I am quite new to electronics and can't read circuits. I made a .gif of what I'm talking about.
32jl9IH
 

Declan The Average

May 16, 2014
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The best explanation of what I'm looking for is this gif I made:
http://imgur.com/32jl9IH
Basically I have an existing button which has two contacts. When pressed, the contacts are internally connected.
I have two USB devices that I'd like to swap between when the button is pressed. They therefore each have 4 wires. The 4 wires that leave this device will then go into the computer as an "output" USB, such that only one device at a time appears to the computer to be connected.
An easy way to do this is to have a standard 4-pole toggle switch. However, instead of moving the switch, I want to press the pre-existing button. Therefore, it is not the movement of the switch which should induce the toggle between each input, but the completion of this sub circuit.
Any ideas if this even exists, or do I need to build something? I'm VERY new to electronics and stuff.
 

davenn

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Sep 5, 2009
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Declan I moved you post to this thread
don't start new threads on the same topic ... it causes confusion for the readers and responders ;)

cheers
Dave
 

Harald Kapp

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That's a simple toggle switch or toggle momentary switch, to be precise.
See her: http://www.futureelectronics.com/en/switches/push-button-switches.aspx

For switching USB you'd need a double pole switch (you'd have to switch the data lines only, not the power supply and ground). Since your existing button has only one contact, you can use it to turn a relay on or off, where the relay has 2 contact sets (double-pole-double-throw = DPDT). Using a relay with more contacts you could also switch all 4 wires. If you release the button, the relay will fall back to the idle position, changing the connection of the USB devices back from the ON-position to the off-positio (idle).
If you want the button to switch devices with every press of the button, you will need a flipflop, see my post #2.

Be aware that momentarily switching between USB devices may produce unexpected results, though, since after toggling the USB devices the software will take some time to recognize the new USB device on the port.
 
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