Simple digital camera I used a Digital Concepts 3. 1
megapixel camera, about $30, but any similar,
simple digital camera should work. It should have
a fixed or auto focus and zoom, so that it doesn’t
need to be adjusted when it’s first turned on.
Inexpensive FRS radios ( 2) I used the Kenwood
Free Talk EL, but I’ve tried to write the instructions
so you can use any FRS (Family Radio Service
band) radio. Cobra makes a nice inexpensive
model that runs about $25/pair. You’ll only need
to modify 1 radio to interface with the controller,
but you’ll need a second one to trigger it. If you’re
careful, you’ll still be able to use the radio for
standard communication even after you mod it.
1" stereo panel-mount audio jacks ( 2)
RadioShack part #274-249
Mini SPST momentary switches ( 2)
One switch is used for the camera’s power and
the other for the shutter. I had 2 different ones
lying around, but you could use 2 from the same
RadioShack 4-pack, #275-1547.
Sheet metal such as aluminum flashing, or
0.016"× 4"× 10" aluminum, Hobbylinc, part
6"× 4"× 2" project enclosure RadioShack #270-1806
Mini project board RadioShack #276-148
Stereo plugs with wires ( 2) cut from dollar-store
BASIC Stamp 1 microcontroller $29, Parallax part
16-pin SIP socket Parallax #450-01601
9-volt battery connector RadioShack #270-324
DPDT submini toggle switch RadioShack #275-614
SPDT and SPST submini toggle switch (optional)
RadioShack #275-613 and #275-612
3-pin header Parallax #451-00303
Compact 5V DC/1A SPST reed relays ( 2)
2N2222 switching transistor RadioShack #276-1617
10kΩ resistor RadioShack #271-1335
Assorted jumper wires
Adhesive rubber feet
Scrap of foam block
Paper for making enclosure mock-up
Wire stripper and wire cutters
BASIC Stamp 1 serial adapter Parallax #27111, $5
Hot glue gun
Serial cable Parallax #800-00003
152 Make: Volume 15
2. Test the camera buttons.
The camera’s circuit uses pull-down type buttons.
When the button is not being pushed, the contact
is kept high internally; when the button is pushed,
the contact is shorted to ground. This may sound
backward, but it makes the camera’s circuit more
efficient and less susceptible to stray signals.
Set up the multimeter as a continuity tester, and
connect one lead to the camera’s ground. Then use
the other lead to test the button’s inner disk and
outer ring. For this camera, the meter shows continuity between the inner disk and ground (Figure B).
This indicates that connecting the outer ring to
ground signals a button push.
3. Mod the camera buttons.
Solder a wire to the outer ring (Figure C). Now the
camera will register the on/off button as being
pushed when this wire is grounded. Do the same
to the shutter button. Put hot glue on each contact
to secure the wire.
Finally, solder a third lead to the ground side of
the battery pack. Now you can take a picture by
shorting the shutter lead to ground (Figure D)!
Discard the on/off and shutter buttons, and
reassemble the camera with the 3 leads extending
through the shutter button’s original hole (Figure E).
4. Add the control jack and
new push buttons.
Solder the 3 leads to a stereo jack so that the
camera’s buttons can be hooked to the controller
using a stereo plug. Then solder momentary push
buttons between each button lead (on/off and
shutter) and ground, so that the camera can still
be used by hand (Figure F).
Make a paper mock-up of the custom enclosure,
then cut and bend the metal sheet to create the
enclosure (Figure G). Cut holes in the enclosure,
mount the buttons and jack, and hot-glue the
assembly to the camera body (Figure H).
5. Mod the radio’s call button with
new leads and jack.
The radio mod is similar, but you’ll tie in to different
parts of the circuit. Remove the cover and find convenient contacts for ground and for the speaker’s
signal wire, which is usually red (Figure I, page 154).
If it’s not, just use a continuity tester to find the
speaker wire that’s not grounded.