CALLSPACE remote box in situ
Here is the prototype remote box with solar panel just before testing. We set it outside for 1 week with the cell phone powered for 6 days and in call mode for a full 24 hours. There were no problems whatsoever with power consumption, charging, or dropped calls. In the actual remote installation phase, we will have to install these boxes in varying angles and from different mounting apparati, thus possibly necessitating additional hardware or different enclosures.
2006.07.29 [5:03:01 PM PST]
CALLSPACE is listening...
In order to route the audio projected from the remote boxes to speakers in the installation, we needed to hack into a common handsfree adapator. This was more difficult that it seems, owing to the fact that the wires inside the adaptor do not have normal insulation. Rather, they are coated with a chemical that prevents them from shorting when touched. Unfortunately, this coating also prevents them from being soldered. We had to carefully sand the coating off and then solder the wires to a common 1/8" jack.
2006.07.13 [11:20:03 AM PST]
CALLSPACE phone box
Voila! Here is the completed working prototype for the remote phone box. Note on the lower left the dry cell battery which is charged by the solar cell, the charge regulator (the beige box just to the right), and the 12V auto cell phone power adaptor.
2006.06.11 [1:29:57 PM PST]
Redux: putting the R back in RTFM
Well, this should certainly make things a bit easier.
2006.05.13 [10:37:09 AM PST]
Answering for CALLSPACE
Finally we have the finished working model. The reed relay has now been replaced by an optocoupler (also called an optoisolator). This device uses a tiny LED and light sensor to open and close the connection. Its non-mechanical optical operation eliminated the interference problems and worked like a charm. The phone is now automatically answering itself as soon as it is called. Next we deal with the new solar panels.
2006.05.09 [12:18:56 AM PST]
CALLSPACE blue light special
With wires now connected to the vibrate motor and the answer button, we can get the auto answer functioning. Here we see the phone connected to a reed relay. This is a device that uses an electromagnet to open or close a pair of metal strips inside the blue casing. It worked, but not without problems. The electromagnetic properties of the relay made it too succeptable to radio frequencies, resulting in unpredictable behavior. (As a side note, the way the phone lights up when it's half apart makes us never want to put the front cover back on...)
2006.05.08 [11:52:03 PM PST]
The tender button of CALLSPACE
Things get a little tricky here as we have to solder wires directly on the the printed curcuit board. This is not recommended procedure should you have concerns with the longevity of your electronic components. PC boards have a coating on them that the soldering iron must burn through in order for the solder to "stick" to the copper elements etched onto the board. Heating the etched elements up in this manner risks having them pull off the board entirely, at which point the phone would have to be thrown away.

Things with rubbery buttons usually have a thin metal film just underneath the buttons which, when depressed, bridges a small gap between two copper elements on the board and closes the connection. Since we cannot manually press the button, we must solder a wire on each element on either side of the gap and close the connection btween the wires remotely, thus virtually "pressing" the answer button.
2006.05.08 [11:33:00 PM PST]
Did you ever wonder how your phone can put such a powerful jolt in your pocket when you receive a call? Well, look no further. This miniscule thing is the culprit. It's actually a tiny, tiny motor with a lopsided weight on the end that causes a wobble as it spins around. It's important to us, because it is where we are going to attach the wires that will transmit to our logic device the signal that the phone has been called.
2006.05.08 [11:23:47 PM PST]
Four Easy Pieces (CALLSPACE style)
Now that we have the charging situation sorted out, it's time to start taking the phone apart. With the help of a funky star-bit jewler driver, the phone comes apart in 4 distinct pieces: The back (which holds the battery and vibrator), the main circuit board (which contains the brains of the phone and the contacts), the contact overlay/screen piece, and the front plate with buttons.
2006.05.08 [11:07:16 PM PST]
CALLSPACE sees the light
Now this is more like it! Our new solar panels have a 1.15A capacity at 12V. More than twice the power of our first attempt. Here we see the panel attached to a voltage regulator that controls the amount of electricity going into the battery. This prevents overfilling the battery which could cause it to leak toxic lead-acid into the project box.
2006.05.05 [10:42:37 AM PST]
CALLSPACE Charger Solution
The solution ended up a being fairly simple one. We abandoned powering the phone with a 6v DC battery and switched to 12V DC battery, enabling us to use a standard auto charger. This performed famously. Assuming that we can get our hands on some solar cells that can adequately supply enough current, we are in business.
2006.04.22 [8:45:13 PM PST]
Hacking the Case for CALLSPACE
Here we are attempting to build a charger for the phones that will go from the solar-fed battery to the phones themselves. Cellular phones use Lithium - Ion batteries which have a complicated charging procedure. We tried to work around this by (quite literally) hacking into the power supply to do an end run around designing and building a charger cicuit from scratch.
2006.04.19 [9:19:56 PM PST]
Once the case is cut away we can get at the power regulatory circuitry inside. We detached this and connected it to our 6V power supply and then to the phone, with no success. According to the case, it should run from a constant 6V DC power source. When looking at other charger for the same model, however, the output specified was totally different, indicating that the specifications marked on the charger housing were no indication of the actual power flow.

But if the regulatory circuitry kept the 6V DC from the transformer at a constant current, constant voltage (CVCC) type of charging algorithm, why did it not work from our battery? Our only conclusion was that the tranformer was actually an AC step-down tranformer and not applicable to our DC wet cell battery.
2006.04.19 [10:18:24 PM PST]
Solar panels for CALLSPACE
Solar panels are essential to the project as they allow the remote cel phone stations to be independently fully functional. Unfortunately, solar power can be unpredictable. Here we are testing out our original solar panels, but they did not have enough voltage or current, so back to ALL Electronics they go!
2006.04.18 [5:19:08 PM PST]