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Topic: Running small (2.5v) light bulbs through arduino? (Read 2977 times) previous topic - next topic

mktacoma

I'm trying to build something that looks a little older, so using LEDs doesn't really work well, and figured some low voltage light bulbs would work great. I grabbed some 2.5v bulbs and little mounts for them. Lighting them with 2.5-5v worked great (a bit too bright at 5v, which was understandable).

My problem is getting them to light up with the arduino (Uno, if it matters). I have a basic sketch (starting with the "blink" example in the core example set) and it doesn't light up. I put in an LED and it lights up great. I put the bulb into either the 3.3v or 5v pin directly and the bulb comes up, but not at any of the regular pins (I've tried both PWM and regular pins,with both analogWrite and digitalWrite).

Any thoughts? I assume I'm missing a simple-but-clever piece to this, but it's eluding me and there isn't much on driving small light bulbs like this from the searching I've done (or the volume on LEDs and driving full size light bulbs has buried it).

Thanks!

runaway_pancake

Bulbs need more current than an I/o pin can provide
You need a transistor, google "arduino lamp transistor" or "arduino bulb transistor" for examples
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

larryd

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Paul__B


Lighting them with 2.5-5v worked great (a bit too bright at 5v, which was understandable).


A bit too bright at 5V, and the other problem - they tend to spontaneously go out after a little while.

Amarinf

To light up a 2.5 Volts bulb using Arduino you will need following things.

1) A power Transistor(like 2N3055 or BD series) OR a Relay
2) A 5V 300mA DC power supply (If not readily available then make it using a step down transformer and diodes and filtering Capacitor)

Connect GND of arduino and GND of power supply .
Connect the power transistor base to arduino digital out pin using a appropriate series resistor.
Emitter to GND and collector to one pin of the bulb and other pin goes to DC supply +ve pin.
If bulb burns too bright... put a series resistor of say 100R or so.
OR
You can drive bulbd using relays(If you are OK with TIC TOC sound :) )
Let me know if that's clear to you.



MarkT



Lighting them with 2.5-5v worked great (a bit too bright at 5v, which was understandable).


A bit too bright at 5V, and the other problem - they tend to spontaneously go out after a little while.



An ULN2803 will drop 1.5V or so, bringing 5V down to 3.5V at the load,
but first you need to tell us the current rating of these bulbs.

Bulbs also pull much higher current briefly when switched on as tungsten has
a much lower resistance at room temperature compared to white-hot.
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