Cellular Rotary Phone

Posted on Feb 6, 2014

This is a deeper look into the Port-O-Rotary phone. We stuck the GM862 cellular module into an old rotary phone enclosure, and voila, it was an instant, ridiculous, hit. Really simple - the GM862 requires 3. 8V and a Lithium Polymer outputs 3. 7-4V. No regulator needed, but we will need a charger. We currently use an external charger from a third pa

Cellular Rotary Phone
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rty company. Aubrey noted the GM862 has a built in Lithium-Ion charger that may work, we haven`t tested it yet. Ideally we would stick a barrel jack in the back of the enclosure where the RJ11 telephone jack used to reside. Anyone have any recommendations I have used the charging circuit in the GSM862 on the exact LIPO batteries you use and it works good, it takes forever to charge. NOTE: You must connect a low esr cap to the battery if you are using the internal charger. We use a 100uF 6. 3v cap in our design, Digikey part# 493-2309-1-ND. We use a PIC 16LF88 (remember we are at 3. 7V! We need a low-voltage PIC!) to read the hook and rotary. Pretty simple switch decoding routine. We just read the opening/closing of the paddles behind the rotary. There are two - one set of paddles opens and closes for each number that passes by, the other set of paddles is normally open when the rotary is in the home position and closed while the rotary dial is moving. Reading this second set of paddles will tell us when the dialing of a single number is complete. Finally, because we don`t know how long of a number the user is dialing, the PIC waits for a 4 second timeout before sending the given phone number to the GM862. This way the user can dial any type number of any length: 911, 3035551234, and 011212465748. The ringer circuit must use the 3. 7VDC nominal from the battery and output ~80VAC to get the coil to kick the hammer between the...

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