Thank you Nick,

That's exactly what I need.

Thanks for helping everyone in the community. People like you make the community always better. Thanks!

Friends, I have a project already running, but I need help to improve it and would like to hear your opinions.

I have several boxes that I need to maintain the control over the inside temperature, because I have some alive samples inside.

I know that the desired inside temperature is always higher than room temperature, so I'll never have to cool the boxes, but only heat them.

The resistance used to heat each them are two incandescent bulbs in series (microwave bulbs). I used a relay to turn on the lights when the temperature drops below the minimum, and turn them off when the temperature rises above the maximum.

This was good, because I had an acceptable temperature range. But my new samples need an exact temperature, with a minimal tolerance. And turn on/off the lamps in short intervals of time is not good enough.

Using a manual potentiometer to control the intensity of the lamps is not good, because sometimes I need to stay many hours away from the boxes, and the ambience temperature reduces at night, and rises during the day.

Someone who understands of electronics know how to inform what kind of cheap component can I use to control the intensity of the lamps through my arduinos?

I need something like a relay, instead of on / off only, would have several intermediate points.

I'm talking about controlling the intensity of lamps that are like 110v-220v AC, 50-60 Hz.

I'm using some 5V DC ~400mA to ~1000mA in my arduinos...

I thank you all that give some idea, or at least suggest something...

Desde que você observe o limite de 40mA, não há problema em fazer isso.

Ok, obrigado!

Olá pessoal,
Desculpem a noobisse, sou iniciante...
Sei que isso é estranho, mas gostaria de saber se posso fazer um circuito inverso do normal com um "led" usando DigitalPin como Ground.
Com isso o LOW acenderia e o HIGH apagaria o led ou isso poderia danificar meu Arduino?
Também poderia usar seguramente resistores mais baixos que 1K, como por exemplo uns 220 ohms?

Code:

void setup() {               
  pinMode(2, OUTPUT);
}
void loop() {
  digitalWrite(2, LOW); //Acende LED
  delay(1000);
  digitalWrite(2, HIGH); //Apaga LED
  delay(1000);
}