Introduction: A 'Black Square' Door Bell
This project shows you how to build a simple yet effective door bell that is loud enough for a studio or a small apartment. (The look of the device hits at Malevich’s ‘Black Square’). That’s what you’ll need to make this bell:
fibreboard 5 mm thick
plastic 2 mm thick
a rubber band
styrofoam 10 mm thick
white paper (or white paint if you decide to paint the frame)
a mobile phone vibration motor
a step down transformer 220/120 to 6 volts
a diode type 1N4004wires
a saw for wood
a saw for metal
an exacto knife
a soldering iron with solder
a drill with drilling bits
a set of files
a pair of wire cutters
a brush (if you choose to paint the frame)
Note: the above items are for manufacturing the bell itself; you’ll determine which tools and materials you’ll need for the installation, it depends on each particular case.
Step 1: Frame
The frame is made of 5 mm thick fibreboard, its dimensions are 100 x 100 mm; I used 4 strips of fibreboard: 100 x 25 mm (2 pieces) and 50 x 25 mm (2 pieces); the strips are glued together. There are four 23 x 23 mm pads made of the same fibreboard and glued to overlap the joints of the strips; thus, the frame is reinforced. Two pads serve to fix the rubber band on them.
After the frame was assembled, I covered it with white paper on glue.
Step 2: Rubber Band
I used a rubber band from a package of some fruits; the size of its cross section is 3 x 1 mm, the diameter about 60 mm (not tensioned). You are free to use a band of any other kind; however, once installed on the frame, the band should be tight enough to ensure good elasticity for the vibrating plate.
The band passes around two pads installed in the corners of the frame, and is glued to them to prevent its displacement during the operation. The vibrating plate will be fixed to the band with 4 small plastic brackets.
Step 3: Vibrating Plate
It’s fabricated of 2 mm thick black plastic and has the size of 48 x 48 mm to ensure a gap between the edges of the plate and the opening in the frame. When installing the plate onto the rubber band, it’s important to respect this gap to avoid that the plate interferes with the frame during the operation. I used shims made of 1 mm thick cardboard to install the plate correctly (see picture).
A 0.7 mm thick steel plate is glued in a corner of the plate; the size of this steel plate is 10 x 25 mm. The eccentric cam of the motor will strike on this plate to produce noise. I think it’s possible to make the vibrating plate of a single piece of steel about 1…2 mm thick; however, the sound might be too strident in that case. I fixed the plate to the rubber band with 4 brackets made of the same 2 mm thick plastic; their size is 13 x 5 mm. There’s a groove in the middle of the bracket, the band passes through the groove. The size of the latter depends on the size of the band; in my case it was 3 x 1 mm. The groove could be cut with a narrow file. That’s how I proceeded to install the vibrating plate:
fix shims to the edges of the opening
put the plate in position
fix it to the band with pieces of isolating tape
glue the brackets with epoxy resin
Step 4: Motor
I used a mobile phone vibrating motor; such motors are available on eBay, for example. (I took mine, though, from an old not working mobile phone available at my shop.)
The motor is glued to the frame in such a manner that the eccentric cam touches the steel plate; a bracket made of fibreboard is glued over the motor to prevent its displacement during the operation. Motors of this kind need 3V for their operation; you can use a step down transformer 220/120 to 6 volts and feed the motor with half-wave current; the average output voltage would be 3 v in this case (see picture). The diode could be 1N4004 or 1N4007; it could be installed on the back of the frame. The transformer could be installed either in or outside of the junction box.
Step 5: Installation
I fixed the bell directly to the wall with 4 strips of adhesive tape; the tape is situated on 4 pads made of 10 mm thick styrofoam glued on the angle pads of the frame (see picture).
i don’t describe here how to wire the bell because you can easily find a lot of information on this subject by doing, for instance, a google search for ‘how to install a wired doorbell’.
Participated in the
Rubber Band Speed Challenge