I need to make the bulbs in a lamp pulse on and off.

April 7, 2006 10:05 PM

I need to make the bulbs in a lamp pulse on and off.

I made some lightboxes, printed some photos on silk and framed them in the lightboxes. Now I want the bulbs to pulse just like that little light on the front of a Mac laptop. I want it to slowly dim up to full power (the bulbs are only 11 watts) then slowly dim off again, then slowly go on again, etc, etc...

Is there a product I can buy and simply splice into the wires, or plug into the wall? Thanks.

posted by bkeaggy to technology (11 comments total)

I don't know the answer to your question, but the verb some folks use for this effect is "throb."
posted by scarabic at 10:41 PM on April 7, 2006

I would use a microcontroller, but you have to know how to code. Also they are expensive. I don't know of any analog way to do this (which doesn't mean there aren't any).

BX-24
Basic Stamp

ps. Have you considered using leds for this project?
posted by pg at 11:40 PM on April 7, 2006

You could put them on X10 modules and sequence with a PC.
posted by StickyCarpet at 11:56 PM on April 7, 2006

Christmas tree light flasher?
posted by fuzzy_wuzzy at 12:37 AM on April 8, 2006

It's not all that difficult to do from analog dircuitry. What you need then is a frequency tunable square wave oscillator and a triac. That's four components for a total cost of USD 2. The square wave would be used to trigger the triac, and if the oscillator fequency is slightly lower than the frequency of your power line, the lamp will successively light earlier in the power cycle. Thus, the lamp shines brighter and brighter until it reaches maximum power, whereupon the duty cycle starts to shorten again, and the light gets weker. The period is set by the oscillator frequency, and the pulsing pattern should be nice and smooth.

If you don't ususally tweak with electronics, however, you probably don't want to do this, and I wouldn't recommend you to since line-level voltage is involved. Instead, look for something like this. I googled "triac board", and saw a couple of items that may be suitable for you.
posted by springload at 4:24 AM on April 8, 2006

I would use a microcontroller, but you have to know how to code. Also they are expensive.

Well, yes if you get a Stamp or some such. The PIC on it's own is very inexpensive (~2$ for one that will handle something like this, the 12c series perhaps?). The only thing is the programming hardware (The assembler and TONS of free source/help are available) but that can be built for around ~10 (much less if you have a well stocked junk bin and don't mind take-out parts). Oh, look here's a PDF schematic, with the text here (needs tweaking to pulse on and off, it's a pushbutton dimmer). Problem is, a uC is overkill for this application, unless you want some external control over the pulsations (serial, with PC to PIC IrDa sounds like a good idea for that) and sprinload's got the simplest DIY answer nailed.

For the buy it route..... look in the novelty shops and perhaps the light section of wallmart, there should be something in there you can adapt to your needs. They regularly sell wierd pulsing lights of one kind or another, usually just a case of seperating the base from the gizmo and plugging in your own bulbs.
posted by IronLizard at 6:27 AM on April 8, 2006

You could just skip the electricity all together - Pixels for you, pixels for me.
posted by Chuckles at 8:35 AM on April 8, 2006

this is terribly low-fi, but have you considered a physical screen that rotates around the bulb? i remember seeing somewhere a setup that used the hot air rising from the bulb to rotate a suspended mask so that the intensity varied.
posted by andrew cooke at 9:00 AM on April 8, 2006

convert from 120VAC to somewhere around 5-9VDC (cell phone charger will probably do the trick)

use a square wave oscilator in series with a capacitor and a trim pot all wired in parallel with a bunch of LED's. The pot will allow you to adjust the speed of the bulbs.

i had to do almost the exact same thing on a breadboard 2 semesters ago.

you can look up rc circuits online to get an idea for the cap and pot values you need. Or email me, ill see if i can whip something up.
posted by I_am_jesus at 9:05 AM on April 8, 2006

Thanks folks. I'll dig into these suggestions and mark best answer when I figure out what worked for me.
posted by bkeaggy at 3:59 PM on April 8, 2006

So my dad figured out a solution (he always does). We used the receiver from a Casablanca ceiling fan and an Adapt-Touch remote. The remote has a button that dims the light, but if you keep the button held down the light pulses on and off just like on the front of a Mac laptop.

This is the remote and normal setup, which we obviously modified a bit (links to PDF): http://www.casablancafanco.com/services/omans/instructions-w52.pdf

I really appreciate all the suggestions.
posted by bkeaggy at 8:22 AM on April 17, 2006