# two leds switching from one 5v supply (2 wires)

#### Toxicvenom

Joined Apr 19, 2016
11
I have an Iron man helmet with 2 colour led eye that switch from a single button,
the leds are linked together with no other parts just connected to a 5v red / black wire
supply on a small pcb, there are parts in the switch that do it, I have seen the posts on using a 555 timer
or a npn transistor but looking at the circuits there would still be 3 wires, anyone know
what parts in the switch would do this , hold off one led press switch to the other and
so on....

Joined Apr 30, 2011
1,569
Some bicolor LEDs are selectable by polarity. Red/green is a typical example. It would be easy to determine if your device operates this way by use of a multimeter or a single LED and resistor used as a test light.

#### eetech00

Joined Jun 8, 2013
1,967
I have an Iron man helmet with 2 colour led eye that switch from a single button,
the leds are linked together with no other parts just connected to a 5v red / black wire
supply on a small pcb, there are parts in the switch that do it, I have seen the posts on using a 555 timer
or a npn transistor but looking at the circuits there would still be 3 wires, anyone know
what parts in the switch would do this , hold off one led press` switch to the other and
so on....
So...you want to know how to "toggle" the LEDs?

That is, let's say one led is green and the other red, if the green led is on,
when you press the button, the green led turns off and the red led turns on.
Likewise, the reverse happens with each press of the button.

#### Toxicvenom

Joined Apr 19, 2016
11
So...you want to know how to "toggle" the LEDs?

That is, let's say one led is green and the other red, if the green led is on,
when you press the button, the green led turns off and the red led turns on.
Likewise, the reverse happens with each press of the button.

Yes... but the one I have only has 2 wires going to the led"s
and both led"s are linked with nothing else..

#### GopherT

Joined Nov 23, 2012
8,012
Yes... but the one I have only has 2 wires going to the led"s
and both led"s are linked with nothing else..
If the two LEDs are in series, I have no answer. If the two LEDs are parallel on the two wires, it would work something like this.

#### eetech00

Joined Jun 8, 2013
1,967
Yes... but the one I have only has 2 wires going to the led"s
and both led"s are linked with nothing else..
What is the power requirements? Is this powered by batteries? If so, how many? What type?
Otherwise, what is the supply voltage?
Is the input a momentary push button?

#### eetech00

Joined Jun 8, 2013
1,967
Here is a BJT version of a bicolor LED toggle.
Since the CD4013B is a dual FF package, I use one FF for a switch debouncer.
Supply is 9v.

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#### Toxicvenom

Joined Apr 19, 2016
11
What is the power requirements? Is this powered by batteries? If so, how many? What type?
Otherwise, what is the supply voltage?
Is the input a momentary push button?
The leds look like they are in parallel. And
Running off a 3v button cell.
The switch is momentary and the electronic are in the swtich it's only about 15mm sqaure so must be smd. Forgive me but I have basic electronics and the other post the plan is confusing me.

#### eetech00

Joined Jun 8, 2013
1,967
How many LEDs per eye?
How many button cells?

#### Toxicvenom

Joined Apr 19, 2016
11
How many LEDs per eye?
How many button cells?
2 leds one white one red nothing else in the eye 1 x 3v supply, sorry it was 2 x aa not button cell ,only batteries in the box 2 wires to the switch and 2 wires each to each eye

#### hp1729

Joined Nov 23, 2015
2,304
Here is a BJT version of a bicolor LED toggle.
Since the CD4013B is a dual FF package, I use one FF for a switch debouncer.
Supply is 9v.
Your transistor on the right can never come on. The input of the base resistor is grounded. Only one LED will blink. Build it, don't just simulate it.

Is the helmet one LED that blinks red or green or two LEDs that blink. together or alternating?
Maybe LEDs with a built-in blinker?
What parts are actually on the switch?
Looking at the picture there may be circuitry inside the LED assembly. Interesting, 3 V yet a white LED???
RBG LED, red on all the time. Blue and green on makes white? Only 3 V required.

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#### Toxicvenom

Joined Apr 19, 2016
11
Your transistor on the right can never come on. The input of the base resistor is grounded. Only one LED will blink. Build it, don't just simulate it.

Is the helmet one LED that blinks red or green or two LEDs that blink. together or alternating?
Maybe LEDs with a built-in blinker?
What parts are actually on the switch?
Looking at the picture there may be circuitry inside the LED assembly. Interesting, 3 yet a white LED???
RBG LED, red on all the time. Blue and green on makes white? Only 3 V required.
They are static just switch from one to the other white on press red on , there is nothing in the eye just smd leds connected to the 3v supply on a small board with traces connecting both together

#### eetech00

Joined Jun 8, 2013
1,967
Your transistor on the right can never come on. The input of the base resistor is grounded. Only one LED will blink. Build it, don't just simulate it.
I think you need to think about that a little.

#### GopherT

Joined Nov 23, 2012
8,012
2 leds one white one red nothing else in the eye 1 x 3v supply, sorry it was 2 x aa not button cell ,only batteries in the box 2 wires to the switch and 2 wires each to each eyeView attachment 104679
Can you read a part number off of the side of that switch? It may be a latching momentary switch. If it is, I am impressed at the small size. Most are larger.

It looks too simple to have any circuitry in the little switch other than a switch. Therefore, since you now mention RED and WHITE and operated by a coin cell, Ii would assume that the White LED is always connected. Once the switch is turned ON, the Red LED connects and, since the RED LED has a lower forward voltage (Vf) than the white LED, all the current will flow through the RED LED. turn it on and leave nothing for the white LED.

Since it is only a button cell with high internal resistance, I am guessing there is no current limiting resistor in this setup.

Good luck.

#### Toxicvenom

Joined Apr 19, 2016
11
Can you read a part number off of the side of that switch? It may be a latching momentary switch. If it is, I am impressed at the small size. Most are larger.

It looks too simple to have any circuitry in the little switch other than a switch. Therefore, since you now mention RED and WHITE and operated by a coin cell, Ii would assume that the White LED is always connected. Once the switch is turned ON, the Red LED connects and, since the RED LED has a lower forward voltage (Vf) than the white LED, all the current will flow through the RED LED. turn it on and leave nothing for the white LED.

Since it is only a button cell with high internal resistance, I am guessing there is no current limiting resistor in this setup.

Good luck.[/QUOTE

There seems to be no resisters. And yes the white turns on first power up then press red press white...there is no markings on the switch been rubbed off

#### hp1729

Joined Nov 23, 2015
2,304
I think you need to think about that a little.
Sorry. You are right. I mistook crossing wires for connected wires.

#### GopherT

Joined Nov 23, 2012
8,012
The 10 ohm resistor is the internal resistance of your battery. Closing the switch turns off the blue (white) LED with 3V forward voltage and turns on the red LED with 2V forward voltage.

#### Toxicvenom

Joined Apr 19, 2016
11
The 10 ohm resistor is the internal resistance of your battery. Closing the switch turns off the blue (white) LED with 3V forward voltage and turns on the red LED with 2V forward voltage.

View attachment 104689
I still can't work out only 2 wires going to the leds in you diagram looks like 3 could you simplify the diagram ..sorry new to this.

#### GopherT

Joined Nov 23, 2012
8,012
@Toxicvenom

Hopefully, this is more clear. Look at your switch carefully. 2 wires from battery, 2 wires to red LED, 2 wires to white LED.