I have made a couple of these and I leave them on the sofa for unsuspecting visitors.
I've been interested in touch and pressure sensors in soft toys for a while now, and this pillow is about the simplest sensor/motor combination you can do. It consists of an outer fabric shell, a battery/motor assembly, and two fabric switches that act as pressure sensors.
- Two pieces of fabric big enough for the front and back of the pillow
- pager or cell phone vibrator motor
- a battery holder for 2 AA batteries
- a piece of small scrap plastic with a convex shape, like the top of a tube of lip balm or a piece of a milk carton handle
- a couple inches of conductive fabric
- a couple feet of conductive thread
- some insulating fabric with a little thickness to it, like wool or felt
- a couple strips of scrap fabric
- a couple inches of velcro
- stuffing! you can reclaim this from a thrift-store pillow; the outside may be nasty but the inside has been protected and will usually be perfectly fine
- sewing machine
- biggish needle
- good scissors for the fabric; crappy scissors for the plastic scrap
- hot glue gun
- soldering iron
Thanks to Lea Anna Drown and Matt Ho for taking the excellent pictures, and to Jen Kwong for modelling on the kitty cat pillow.
Step 1: Cut Out the Heart
Cutting fur is best done from the back side. To avoid cutting the pile, slide the lower blade of your scissors under the backing fabric for each cutting stroke. You can't see this too well in the picture (it's the 2nd picture), unfortunately, but notice that there is a lot of fur remaining on the right edge of the cut I've done so far, sticking out under the scissors. If the pile is short you don't have to worry about this but for long pile, if you cut it off too much it will look like a bad haircut that never grows out.
Step 2: Fabric Switches, Bitches!
The fabric switch is a layer of three pieces of insulating fabric with two strips of conductive fabric in between. The middle insulating layer has a hole in it; when the switch is pressed, the two pieces of conductive fabric touch, completing the circuit. This was invented by Leah Buechley (or at least I got the technique from her), check it out at http://www.cs.colorado.edu/~buechley/diy/diy_e_sewing.html#switch
Pic 1: cut a strip of conductive fabric about a foot long and half an inch wide
Pic 2: cut the strip into quarters
Pic 3: cut a small hole from the center of one of your three insulating squares, by folding it in quarters and cutting off the appropriate corner
Pic 4: the hole! the conductive fabric strips will touch, or not touch, through this.
Pic 5 & 6: glue one conductive strip to an uncut insulating square
Pic 7 & 8: glue the insulating square with the hole on top of the conductive strip
Pic 9: glue the second conductive strip to the last insulating square
Pic 10 & 11: glue the second strip and square over the rest of the switch assembly, so that the top conductive strip's overhang is on the opposite side from the bottom strip.
Pic 12: the finished switch
Make one more of these and let them dry THOROUGHLY before testing them. If you try them out before the glue has dried, you may accidentally glue the conductive strips together which will make the switch useless. (Yes, I have done this ... several times...)
Step 3: Motor/battery Assembly
Pic 1: if your motor has a plug on the end, like this, cut it off and strip the wires. Many motors don't have wires attached, but just a pair of terminals (usually a little metal tab with a hole in it). If you have this kind, solder a little bit of wire to one of the terminals that you'll attach to the battery holder - but I'm getting ahead, that's the next step.
Pic 2: protective plastic cover. You just need something to cover the upper part of the motor shaft as the battery holder protects the lower part. I used half of the bottom of one of those round cases you get out of gumball machines. They have a cheapo ring or keychain or doll or such inside. I never have any use for the contents, but the containers I use constantly for all kinds of things. They come in 3 or 4 different sizes and cost like 50 cents. The larger sizes you can also get in drugstores, where they contain pantyhose.
Pic 3: what it will look like, pre-glue
Pic 4: hot glue the motor on
Pic 5, 6, & 7: hot glue the plastic cover on. you can be terribly sloppy about this, it does not need to be air-tight or anything. only make sure that the motor can turn under the cover, and there are no large holes near the shaft.
It's a good idea to test at this point. Put batteries in the holder and hold the two motor terminals against the two battery terminals (this may require extra wire and alligator clips depending on the configuration of your components). If the motor doesn't go around, try re-setting the covering. Other possible problems are dead battery, dead motor, or bad connections. This last is highly likely because you're only holding them together at this point, but you should be able to get a little bit of motion even if it's intermittent.
Works? Good. Take the batteries out.
Step 4: Attach One Lead
Since I had two sets of wires, I twisted a pair together, soldered them, and then hot glued for extra security.
Test the joint! Does the motor still run? Ok now take the batteries out again.
Step 5: Sew Conductive Thread Leads
First roll a bobbin with about ten feet of conductive thread. Do this by hand, as the conductive thread likes to fray. It's also thicker than normal thread, and you may want to loosen your bobbin tension (see second pic's notes). You may need to loosen your upper tension a bit, too, as you want the conductive thread to stay on one side of the fabric and not get pulled through. See the notes on pic 4.
Once you've got the bobbin in place, run two lines of stitching along your scrap fabric strips. Run one line on each side in case the fabric gets folded up inside the pillow. Leave about 6 inches of thread at each end of the seams.
Make two of these, one for each switch.
Step 6: Attach Switches
Trim the conductive thread close (we don't want any of it floating around loose causing short circuits) and hot glue it to keep it from ravelling.
Sew the other thread at the same end of the strip to the other tab, and sew the other strip and switch similarly. Test with an ohmmeter if you have one, to be sure that the thread at the other end of the strip is conducting through to the tab it's sewn to. If it doesn't, check if the thread is frayed or broken somewhere along the strip.
Step 7: Attach Switch Assemblies to Motor/battery Assembly
- the front & back of the pillow
- the motor & battery assembly, glued together, with one lead connected
- two fabric switch assemblies, with long threads off the ends opposite the switches
In order for either switch to turn on the motor, instead of both, we'll attach the switches in parallel. This basically means to treat them as one switch, attaching corresponding thread tails from each strip to the same place.
The motor/battery assembly has two remaining terminals or wires. We'll attach a pair of threads to each of these, one pair to the remaining battery terminal and one pair to the remaining motor terminal.
Attachment technique varies with what the terminals are like. If you have wire, strip as much as you reasonably can, then fold a loop back on itself, knot the conductive thread around the loop, and twist the loop around itself again.
If you have a snap terminal, wrap the conductive thread around it several times and tie a knot.
If you have a tab with a hole, thread the conductive thread through the hole and tie a knot.
Test! Put batteries into your holder and squeeze each of the switches in turn. If the motor doesn't go on, you have a loose connection somewhere. If it went on as soon as the batteries were in, you have a short circuit. If it went on after you pressed the switch and stayed on after you let go, the switch is bad. There are several ways it can be bad - glue not dry, hole too big, hole too small, conductive fabric strips touching outside the switch, etc. If it's not obvious what's wrong, simply make another switch.
Once you've verified the connections, hot glue each knot for stability. Keep tension on the thread as you glue. Test again just to be sure. You can leave the batteries in this time, as the innards of the pillow are done!
Step 8: Sew the Pillow Body
You, however, should stitch the velcro down first. Make sure you have regular thread in the bobbin again, not conductive, and that the tensions are back to normal. Choose a straight, or relatively straight, section of seam at least 6 inches long, and sew two 6" pieces of velcro to the main pieces, right up against the edge of the fabric. Sew the velcro to the front sides, so it will stick when the edges turn under.
Now, place the right sides of your pillow pieces together, matching the velcro. Pin and stitch. Backstitch at the beginning and end of the seam, as shown in pic 3. Backstitching simply means to sew forward for a half inch or so, then backwards over the same seam, then forwards again. It serves the same purpose as a knot, the seam won't unravel unless the thread breaks.
Finally, clip the concave point between the heart's ... cheeks ... close to the stitching line (last pic). This vastly improves the line when you turn it right-side out in the next step.
Step 9: Turn and Stuff
When you're halfway done, insert the motor/switch assembly. You want it to lie with the motor & battery in the middle, and each switch a third of the way across, as in the picture.
Make sure the motor assembly is padded on all sides, so it won't be noticable as a hard thing inside when you hold the pillow. Also make sure that the fabric strips aren't twisted, or they will short out. The switches should go right next to the fur, as you won't be able to feel them through the fur, but they'll be most sensitive in that location.
When you've put in all the stuffing you want - don't overstuff, you don't want a rock-hard pillow! - simply press the velcro together to close up the hole.
That's it! Hug it, squeeze it, call it George. Have your friends sit on it without telling them why. Have your dog sit on it - I haven't tried this but it should be pretty funny...
Step 10: Sources
Conductive fabric LessEMF - suppliers to the tin-foil-hat crowd! Turns out that EMF-blocking fabric does so by some kind of embedded metallic process. I use Zelt, which from my tests conducted best for the lowest price. Conductive fabric is expensive; but you usually need very little of it for any project. http://www.lessemf.com/fabric.html
Conductive thread LessEMF also sells this in very large spools, but you get about 3000 yards and it costs $60. More expensive per yard but in much smaller batches is the 200 yard spool at $15 from Lame Lifesaver - this is geared towards fencing outfits so there's not much else there that's useful if you aren't a fencer. http://members.shaw.ca/ubik/thread/thread.html
Pager motor Lots of places to get these; most of these places also sell battery holders (search for pager motor or vibrator motor):