What component should i use to create a logic gate for my LED?

Question

We are using a bi-color SMD LED blue/red (link below) and the idea is that the LED will always light blue until a switch is thrown then the blue will cease and the LED will illuminate RED. Will a transistor do this? if so which type?

http://www.us.kingbright.com/product.asp?catalog_name=LED&product_id=APHBM2012PBASURKC
http://www.us.kingbright.com/images/catalog/SPEC/APHBM2012PBASURKC.pdf

Answer 1

I assume you have only a single throw switch, if it were double throw you could just control the LEDs directly. If there are any spare gates on any devices already in the circuit you might want tot try to use them rather than add another device. A transistor could be used, or various type of gates could be used, an inverter could work, or NAND or NOR wired as an inverter (when one LED is turned on via the switch, the other is turned off by the inverter). I think one could also take advantage of the fact that the two colors have different forward voltages to control them with no additional components, however one would have limited control of the relative brightness, if the switch were in series with the red LED, and that combination was in parallel with the blue LED, and that whole thing in series with the current limiting resistor, when the switch is open the blue LED lights, when the switch is closed the red LED lights and drops the voltage to below the voltage the blue need so it turns off. Note that the red would be considerably brighter in this case as a series resistor sized for the red LED will be larger than desirable for the blue, plus the red is brighter for a given current to start with.

Answer 2

build a one 2nd clock with the two 555 or purely use 2 logic gates to do the uncomplicated comments oscillator. Output administration a severe skill transistor or FET. Transistor output controls LED as many as you %. Clock may well be built with variable frequency. purely use a potentiometer to regulate the the comments loop.

Answer 3

Using two transistors make a simple circuit of a Bistable multivibrator .wire up with on / off status.you will get these circuits in ''electronics hobbys books'' market, try with that.best of luck.

Answer 4

maybe i don't understand, but why do you even need logic? just use the switch!

you can get AND gate and OR gates and the like from TI and a multitude of other places. Just search online.

Answer 5

I think you can use either an AND gate or an OR gate. Just wire it up to recognize the switch.