cals400ex

i am ready to hook up a manual fan switch. the only question i have is: i have two led's with resistors in them. when you go from the +12V source to the led, do you use the positive or negative section on the led? in the diagram it says the anode so i thought you just simply went from the +12V source to the negative wire on the led. however, the guy i talked to at radio shack said it only made sense to go to the positive wire on the led. i still say its the negative but i just wanted to make sure.

clownhair

How do you tell which side of the led is negative or positive?

shoebox

Anode to +

Cathode to -

Cathode is the shorter leg and will be on the flat side of a bare LED.

cals400ex

clownhair, i have led's with resistors in them and the led's have a red and a black wire. so for me it is easy to tell which is positive and which is negative. i guess i was right. the +12V source goes to the anode. the guy at radio shack told me the opposite.

shoebox

It would make sense, red +, black - .

clownhair

ok now that I know that I can inform you that my leds are hooked up to the positive side

cals400ex

well, now we have another problem. i have it all hooked up and the fans work fine on high and low but the led's flicker but don't stay on. i am not sure what i need to look for. i have only one wire for ground with two others tapped in to that one. i assume thats alright?? i am also using the same +12V source for the high and low fans. i assume that is ok also?? besides all that, i checked the connections and they look good. unless my ground needs to go somewhere else. any help would be great.

shoebox

The 12v power is only for the LEDs. The ground is used to operate the relay to turn the fans on. Double check your wiring.

cals400ex

so i guess what i am confused about is: right now i have led's with built in resistors and i have the +12V going to the negative part of the led(anode) and i have the positive part of the led going to the dark blue wire for the high speed and the dark green for the low speed. so what your saying, since everything works fine but the leds just flicker and then go off, i need to possibly check the +12v source?

shoebox

You're confusing me. 12v should go to the anode, but the anode is the + side of the LED. Cathode (-) should go to the green and blue wires.

scoobysnax83

are we talking about only one switch? If so maybe its defective. If you hold it up does the LED stay on? Try another switch.

clownhair

your wires are backwards. Mine did the same exact thing. put the wire you have on the negative to the positive and repeat. afterwards they will stay on.

scoobysnax83

that totally goes against every bit of advice in this thread. But I hope it works for you.

cals400ex

sorry for confusing you shoebox. i thought i was taught that the anode was negative and the cathode was positive. i guess i have them backwards then. i will try that and see what happens. thanks for the help everyone.

also, the switch works. when i turn it on low the fans come on low and when i turn it on high the fans come on high. just the leds flicker when i turn the switch on high or low but don't stay on. i will switch some wires around and see what happens.

coolgenner

been years and years since I learned it, but I thought cathodes were positive too?