Fan switch
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Fan switch
I am thinking of building a 12v 5v switch with DPDT toggle switches and was wondering how to hook a bipolar LED. The LED has three wires and I am at a loss to where they would go to make it work right.
AndrewC,
Welcome to the forum.
The 3-legged LED indicator you display has one common lead, usually the middle one and each outside one is a different colour. I.E. the "right" lead may be the "red" and the "left" lead may be the "green".
This LED can be tested with a volt-ohm-meter. This can be a digital voltohm-meter or equivalent. Set the meter to measure either diodes or low resistance scale. Take the black test lead & touch onto the middle lead. Take the red test lead & touch onto one of the outside leads. If the colour does not show up, then reverse the coloured leads on the LED leads.
Once you see the respective colours for each of the leads, you will know the LED polarity. If the midle lead is the balck test lead, then this terminal is the "cathode" or negative (-) connection. If the middle lead is the red test lead, then the middle lead will be the "anode" or the positive (+) connectio.
You will need some form of current limitation (resstor) for each LED. At 5VDC, the resistor will be 250-ohms @ 1/4-watt, at 12VDC the resistor will be 750-ohms @ 1/4-watt and at 24VDC the resistor will be 1,500-ohms @ 1/2-watt.
If a circuit diagram is required, I have seen similar drawings on the 'net. I doubt whether these will be suited for this LED, but could easily be adapted.
One thing nice about this LED: If both are on at the same time, you will get a third colour.
Good luck
TerryW
Welcome to the forum.
The 3-legged LED indicator you display has one common lead, usually the middle one and each outside one is a different colour. I.E. the "right" lead may be the "red" and the "left" lead may be the "green".
This LED can be tested with a volt-ohm-meter. This can be a digital voltohm-meter or equivalent. Set the meter to measure either diodes or low resistance scale. Take the black test lead & touch onto the middle lead. Take the red test lead & touch onto one of the outside leads. If the colour does not show up, then reverse the coloured leads on the LED leads.
Once you see the respective colours for each of the leads, you will know the LED polarity. If the midle lead is the balck test lead, then this terminal is the "cathode" or negative (-) connection. If the middle lead is the red test lead, then the middle lead will be the "anode" or the positive (+) connectio.
You will need some form of current limitation (resstor) for each LED. At 5VDC, the resistor will be 250-ohms @ 1/4-watt, at 12VDC the resistor will be 750-ohms @ 1/4-watt and at 24VDC the resistor will be 1,500-ohms @ 1/2-watt.
If a circuit diagram is required, I have seen similar drawings on the 'net. I doubt whether these will be suited for this LED, but could easily be adapted.
One thing nice about this LED: If both are on at the same time, you will get a third colour.
Good luck
TerryW
Hi all.
Gee, while I was typing my response to AndrewC, we got another reply. Wow you guys are quick, or I am just too slow on my typing skills.
In the link provided to Cliff's Fanbus site, look at the LED schematics and circuits 4 & 5. One of them should do you quite well. Review the note & introduction at the start of Ciff's website.
One thing to note on the use of the 470-ohm resistor on the fanbus link: On 12VDC, the curent will be around 22.9 milli-amperes. This doesn't sound like much current, but if your LED cannot support this current, it could prematurely burn out.
Most LED indicators today can operate up to 30-mA and 470-ohm will not be a problem. Personally, when I design LED-related circuits, I usually go for around 15mA operating current. This gives me a little "bandwidth" for voltage fluctuations.
Good luck & have fun
TerryW
Gee, while I was typing my response to AndrewC, we got another reply. Wow you guys are quick, or I am just too slow on my typing skills.
In the link provided to Cliff's Fanbus site, look at the LED schematics and circuits 4 & 5. One of them should do you quite well. Review the note & introduction at the start of Ciff's website.
One thing to note on the use of the 470-ohm resistor on the fanbus link: On 12VDC, the curent will be around 22.9 milli-amperes. This doesn't sound like much current, but if your LED cannot support this current, it could prematurely burn out.
Most LED indicators today can operate up to 30-mA and 470-ohm will not be a problem. Personally, when I design LED-related circuits, I usually go for around 15mA operating current. This gives me a little "bandwidth" for voltage fluctuations.
Good luck & have fun
TerryW
