LesCir

I need to build an automobile circuit that lights LED 1 if circuit A sends it 12v; lights LED 2 if circuit B sends it 12v; or lights LED 3 (and not LED 1 or LED 2) if both circuits send it 12V. I figured it out using three relays, but I'd much prefer a non-mechanical solution for reliability on the road and mounting space considerations. Can someone give me some fairly specific pointers? I know nothing of IC's, except that I'm sure there are some that would help :-) I can read a schematic and solder on a breadboard but designing a circuit with anything beyond relays and diodes exceeds my skill level. I need some hands-on examples of how to do it. Thank, s

I need some help building a simple circuit (logic wise it's simple, that is). I can build it with three mechanical relays, but I'd prefer to do it with solid-state components. Unfortunately my electronics knowledge doesn't extend much beyond a basic understanding of simple components. Here what it needs to do: I have two switches, switch 1 & switch 2, which send 12 volts to two different automotive components. The switches are "latching", not momentary. When switch 1 is turned on I want to light LED 1. When switch 2 is on, I want to light LED 2 (I know how to do that part of the system). However, when BOTH switches are on, I want to detect the "AND" condition and light a third LED 3 while shutting off LED's 1 & 2. If switch 1 or 2 is shut off, it should fall back to lighting the proper LED 1 or 2 and drop power to LED 3. I don't need any serious power through the circuit, the main switches take care of that, I just need to light the LED's. Are there some logical components I can use to do this (and I need hand holding... my skills are more limited than you think :-) Thanks,

Thanks... you're right, even with my enclosed wiring, it looks like anything in my parts box will do it :-)

I have a circuit of relays and diodes. Total draw will be 400ma at 12 volts. (Actual PS delivery is 13.2 volts). What gauge wire do I need to safely hook this up?

Thanks boys. I'll start at 1K and see how bright they are. I only need reasonable brightness and these will probably last a lifetime with those parameters.

Whoops - typo above! I meant 470 ohms, not 470K ohms. I think the are some minor errors in my earlier calculations, but after correcting them I still end up with the same rough numbers. I'm taking the 13.2V supply voltage and subbtracting the LED's operating voltage of 2.1v. That gives me a drop of 11.2v. I then take 11.2v divided by the current draw of .2 (r = v/i) and I get 11.2/.020 or 560 ohms. It looks like you are suggesting taking the 13.2 volts and dividing by .02amps, to get 660 phms. Would that be a good starting value?

I am setting up a small circuit that will use LED's. The source power supply is marked 12volts, but actually delivers 13.2 when tested. The LED's in question are rated 2.1v adn 2.4v (red and yellow). Here's my question: how critical are the voltages in terms of reasonable LED life and proper brightness? Based on my calculations, to get the 13.2v down to 2.1 volts for the red, I need a resistor of ~ 530 ohms. To get the 13.2 down to 2.4v needs 450 ohms. OTOH, if I went with the spec on the power supply of 12v, I'd be thinking 470K and 400 ohms. Should I just put in 470K resistors and call it a day? Or do I need to carefully get as close as reasonalbly possible (+/- 10 ohms) to get proper brightness and reasonable life from the LED's ? Thanks,