Fading LEDs – Circuit & Arduino Way

Posted by Erin, the RobotGrrl on Monday, September 7th, 2009

Someone recently commented on one of the posts and asked:

Hey Erin, I was just checking around looking for help with a project Im doing. Im not an expert by any means ,I could really use the help and expertise of somone like you. I like your robot too.
Im building a Terniator endo Bust. Its Recast vinyl kit. My …dilemma is ,…The kit came with 2 Red LEDs for the eyes,a bouble A battery pack and a switch. I want to mod this guy so the lights come on slowly,and when switched off they dim out.(3-5 sec.)
The second effect I want is to install a pulsing or vibrating motor inside the scull that comes on momentarily with the lights?
I have other Ideas too. If I can interest you ,Id be will to pay for your help.
I hope this sounds interesting to you, Thanks ,Daniel Shaffer

Sounds like a great weekend project!

There are two ways to solve this problem: with a circuit, or with a microcontroller.

I can’t exactly help out with the mathematical part of the circuit, but in order to obtain the dimming effects, you would need to first charge a capacitor up when you switch it on, that would be connected to the LEDs. As more and more voltage fills up into the capacitor, the LEDs will make a fade-in effect! When you switch off, the capacitor will have to de-charge (perhaps into a different capacitor). When it is emptying, the voltage will be going lower and lower, making a fade-out effect.

The second part of your question, how to make a vibrating motor come on with the lights… you would have to use a 555 timer IC. These also use capacitors and resistors in order to create a timed circuit. They are a really interesting concept, and I would encourage you to check out these sites about them!

Now… if you wanted to use a more extendable option with a microcontroller, that is more easier! I made a post about how to fade many LEDs here, with an Arduino. You could have the LEDs fading in and out while having the motor turning on/off. AND, you could use sensors to create specific behaviours and triggers for the Terniator.

I hope this answers your question, and I hope you will keep us posted on the status of your project! Woohoo for blinking LEDs!

Posted in: Other, Programming, Projects.
Tags: dilemma, LEDs, motor, reader question, Terniator

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