Need some help with some LED Diagrams

[thejuggla1]

Looking to 'spice' up some lego models, I am wondering if you guys could help.

First off I want to make a landing pad have 4 RED flashing lights all together, pretty simple, I forget most of what I learned in school like how to make LEDs flash.

Second I just want to know the Voltage level of White LEDs(Going to make street lights) I know the formula for choosing the resistor.

Now this ones going to be a little harder, and I think would cost a lot, an estimate of the price would be nice(Not including LEDs) I want to make a 4 or 3 way stop light. Red Amber Green. Just how a normal light would work minus the sensors and pedestiran corssing button.

 

[Sceadwian]

The voltage for your LED will depend on the LED you get, it's listed in the datasheet of the LED you purchase. Typical white LED voltage drop is 3.6 volts so that's a good place to start they're actually slightly variable with each LED.

Flashing an LED is pretty simple, a basic 555 timer circuit will easily blink multiple LEDs, a good search for 555 LED blinker will provide you with MANY links to easily constructed circuits.


The stop light you want is not as complex as you might think. My first thought would be a micro controller, but if you're not ready to take that leap you can do it with a single 555 timer and a few logic gates. You would use the same type of 555 timer circut connected to perhaps a few flip flops and logic gates to sequence the lights. It'd be a good exercise in understanding basic logic to figure out exactly how to set things up, and not excessively complex.

 

[thejuggla1]

I remember a bit about the 555, I don't think it can simulate the light properly though? Like do the Yellow Pause for 5 or so seconds then turn red and turn the other side green.

 

[Sceadwian]

I didn't say a 555 could do the stop light, I said a 555 with other logic could. Such as flip flops and and and/or/not gates
The 555 itself would simply generate a constant tick/tock, feed that into the right combination of logic gates flip/flops and it will give you the desired sequencing. If someone else doesn't post the proper gates/sequence to feed it (and I hope someone does cause I hate discrete logic) I could probably work it out. The logic gates themselves are maybe a dime a piece for multiple gates.

 

[MrDEB]

A 555 and a 4017 , a few resistors, leds and your done with the stop light 3 way or 4 way.
I believe about Sept this past year a circuit was posted using just that..
will do some searching.

 

[MrDEB]

the last one looks most promising
Traffic Lights Project.
Traffic Light Project
Led circuits page

 

[thejuggla1]

Traffic Lights Project.

So this one will work? How long is a 'pulse' about a second each? Is there a way to increase the 'pulses' on this diagram? Or you think I should go with the 2nd one? It includes it's own circuit layout so I don't have to make one seems pretty nice.

 

[MrDEB]

If you want all 4 directions then Led circuits page is the circuit you want.
the Traffic Light Project is for only one direction.

 

[thejuggla1]

Alright thanks, Just to make it clear the little +9 means it runs off of 9 Volts right?

 

[thejuggla1]

One other question, the diagram uses a set of LEDs(Red Yellow Green) for both north and south and one for east and west, I can just series another 'set' of LEDs? A problem I believe the 555 only lets 200mA of current through correct? But in this case it shouldn't be a problem since at most 4 LEDs should be on at the same time?

Edit since I am adding another 2 sets of lights, should I upgrade the cap to 20uf? And the cap should be 9Vs?

Oh and since I'll be adding a second set of LEDs, I will probably use a 'gate' instead of the diodes, is one gate good for 2 sets of LEDs(N/S or E/W, 2 gates total) or should each set of leds get its own gate(N S E and W all separate, 4 gates total)?