Beginner Electronic Engineering

[webstorms]

Hello,
I need your help to find out how to tackle this idea I have. Currently for my recent project I have one free motor port.
And I have:
- 1 Computer fan (Spins with the power of 3 AA Batteries)
- 2 normal LED's
- 1 red LED
- 1 green LED

So my idea: connecting the components above to my NXT with 1 port. So yes, I guess I'll be able to calculate the right Power output and needed resistors for the LED's. Yet here is my concern:

What happens when the power level of the NXT drops? I know the Servo motors turn slower yet will the LED's still light up and the fan still turn when the minimum power supply are 3 AA batteries?

Another question would be if I could put a wait period between every light up of the individual LEDs? Should be possible but what components would I require?

If you familiar with this, could you please tell me how you would work this out (since this is my first time developing an external device for my NXT).

Your help will (like always) be appreciated.

[mattallen37]

For the LEDs, I would use either a 470 or 1k ohm resistor. 1k5 or up to 10k would be okay as well, but the LEDs would be dim.

What type of control are you looking for? Do you want to be able to tun LEDs on and off with the program? What do you want to do with the fan?

[webstorms]

Thank you. I would want the fan to turn at a constant speed and at the same time having the LEDs flash in a certain sequence (if this is possible - requiring a certain component that I am unfamiliar with). Would these resistors work if I have a 100% power output (75%,50%) - outputting the same results?

[webstorms]

Preferably I would like a period of 1 second between every flash.

[h-g-t]

These websites will help to determine the size of the resistors you need for the LEDs.

http://www.horrorseek.com/home/hallowee ... gLEDs.html
http://led.linear1.org/led.wiz

This site has a circuit for a LED flasher but it only works with 2 LEDS at a time - not sure how you can incorporate the third.

This is another circuit, but only for a single unit so I don't see how you can synchronise it with the others.

http://www.cappels.org/dproj/simplest_L ... rcuit.html

This shows 3 LEDs but has no circuit provided.

http://www.youtube.com/watch?v=EdBbBTfWhO8

And this one is a bit more complex but has 41 LEDs, should be possible to scale it down.

http://www.instructables.com/id/41-LED- ... ng-555-IC/

You might have to use a relay on the NXT motor port to switch all this on using an external battery to avoid drawing too much power from the NXT port.

[mattallen37]

So you just want the fan to run with one speed? You just want On/Off control over it?

You could use a 555 and 4017 to control up to 10 LEDs in sequence (no need for the NXT).

I think what you want is a PCF8574 though. It has 8 GPIO's that you could use to control LEDs, motors, or whatever else. The NXT uses the I2C interface of the sensor port to communicate with it. You could have program control of the LEDs that way. It is a great IC. You can do all the timing and whatnot with the NXT program (instead of analog/logic circuits). Mindsensors sells a decent looking PCF8574 kit. I don't have it, but it looks really good. I just use the IC's themselves, on breadboards.

If you want to get even more advanced than just circuits, you could get into PICAXE's (basic programmable ICs). They can do some pretty nifty stuff with the NXT.

[nxtreme]

If you want to get even more advanced than just circuits, you could get into PICAXE's (basic programmable ICs). They can do some pretty nifty stuff with the NXT.

Yup, me and Matt are on a mission to rule the world with a NXT brick and a handful of Picaxe microcontrollers. So far we haven't even needed muntoo's help!

Seriously now, you could probably set something up using just a couple of diodes and a NXT cable cut in half. Use the information on this page. You could run the fan and switch the LEDs on and off with the setup mentioned. Or, like Matt says, you could buy a PCF8574 to get individual LED control, as well as motor control.

[webstorms]

Thanks for the advice guys - I'll be working on this one. If I need any further advice, help or I'm done I'll add a new thread to this post.