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Step 3: Intercept the Keypad

The most critical part of this hack is to intercept the keypad. Thankfully the phones use a conventional 8pin-keypad-style circuit, which makes this extremely easy :)

Pull out the keypad and start taking apart each layer. The only layer that is challenging is the plastic tan-colored enclosure. It is snap fit so you have to grab a flat-head screw driver and use brute force to detach it.

Just like the last part you can cut all the free wires. We don't need them.

** Remember to cut the grey ribbon cable or the keypad will not work as expected. **

Solder 8 wires to the pins on the keypad circuit.

Every phone has the same pinout on the keypad (numbered left to right).

1 – ROW 1
2 –
ROW 2
3 –
ROW 3
4 –
COLUMN 0
5 –
COLUMN 1
6 –
COLUMN 2
7 –
ROW 0
8 –
NA

All the keypad code has been beautifully packaged into an Arduino Keypad Library. So all we need to do is connect pins to our Arduino. Specify the pins in the code. And the keypad should be working!

For our code we are using pins 30-36 of the Arduino Mega.

COLUMN 0 – pin30
COLUMN 1 – pin31
COLUMN 2 – pin32
ROW 0 – pin33
ROW 1 – pin34
ROW 2 – pin35
ROW 3 – pin36
NA – GND

<p>Fuzzy, how are you connecting power to your amplifier? I've looked through all the photos and cannot see any power connections. Any guidance?</p>
<p>&quot;If using the 20W speaker it is important to have 12V and &gt;1.5A.&quot; <br>Just running that directly into the AMP DC INPUT.</p>
<p>I apologize, I think I phrased my question incorrectly. Both the amp and the Mega need power, so I'm curious if there's two power supplies needed, or if one piece is pulling power from the other piece. Thank you for your reply!</p>
<p>Hmm i think I actually just sent the power directly to the Mega, then used the Vout/GND pins to power to the amp (or visa versa). I definitely only used ONE power cable from the AC socket. </p>
<p>Fuzzy... what was your total cost for this hack build?</p>
<p>The phone was free and the Arduino was free so quite cheap for me. <br>I think typically it would be around 300$ to 400$. </p>
<p>Fuzzy, thanks for posting your payphone hack, very neat creation out of some old technology. </p><p>I am newer electronics but I thought I'd try to &quot;hack&quot; using an old payphone I had. When I opened the keypad and used my multimeter against the circuit board, I could not get a reading on a continuity test. It's probably just me (not knowing what I am doing). The keypad on my Western Electronics looks a little newer than the phone you hacked. I am unsure on where to go to next. Would you be able to take a look at these pics and point me in the right direction? Thanks!</p>
<p>cool! did you try the 'procedure' explained here: <a href="http://playground.arduino.cc/Main/KeypadTutorial">http://playground.arduino.cc/Main/KeypadTutorial </a> ?<br>(it was a bit confusing to me)</p><p>here is what i did. examined the traces to try and guess which ones are rows and which ones are columns. used my silicone-membrane-button-thingys to close one button at a time while getting the readout from the multimeter on the pins. within no time I knew the association between each pin and each row/column.</p><p>the thing is, that grey ribbon cable i you see in the diagram HAD to be sliced for it to work correctly. somehow the circuit on the other side of the ribbon cable was messing up the readings :( i am hoping that circuit on the backside of the PCB is not doing the same. if it is, you will have to get REALLY creative by starting to cut traces on the backside of your PCB. </p><p>can you please share a photo of the front of your phone?</p>
I read through the tutorial and followed the steps. it dixnt work at the pins, and there isn't the same grey cable to cut. I did remove the extra board, but connected and took a picture of it to show that in addition to the phone. I did some more searching, mine looks like this phone, he/she provided a short explanation on how the keypad pcb could be modified. https://www.dnalounge.com/backstage/src/phonebooth/index2.html I may try that unless you have any suggestions.
<p>If you can't get it to work just call payphone.com and request an older keypad (should be around 25$). Your phone guts look super modern compared to the ones I opened up.</p>
Thanks for the direction. I worked on it this weekend and now have the keypad working. I also started on the other steps and will post when finished. Thanks again!
Congratulations Fuzzy, inspired project that truly deserves winning the 'grand prize'. I would have voted for it if I wasn't also a competitor!
<p>Thanks pricklysauce !</p>
<p>This is brilliant.</p>
It's great but just too expensive! I wish I could build one
love this idea! you got my mind rolling over old school payphone hacks and some new ideas for projects. thank you
I also have some old torque Motors that would work real well for a moving wall that could attach to the keypad
<p>Yeah I think there is lots of potential to use the mic/mic-in on that MP3 shield. Get some speech-to-text software going :) Put an amazon echo inside :) You know where this is going...</p>
<p>The most unique build I've seen, definitely got my vote! Gotta have one!</p>
<p>ლ(́⚈‿⚈‵ლ THANKS ლ(́⚈‿⚈‵ლ</p>
<p>Ah hA nice to see it finished and hung! Will try it next time we there </p>
<p> ̄ڡ ̄</p>
<p>the picture of your payphone in the garage gave me another idea. it would make an ideal safe since no one would think to look inside it and it could actually hold quite a bit of valuables or someting as large as a handgun.</p>
<p>Yeah the safe went totally unused in this hack. It is quite secure because the key needed to get it open is bizarre. </p>
<p>DAMMIT I LOVE THIS!!!!</p>
<p>◑‿◑ THANKS ◑‿◑</p>
<p>OMG so awessssooome! *in a valley girl voice* ;D</p>
<p>haiiiiiiiiiiiiii</p>
​Its not the same model of phone, but if you want to hack a millennium payphone, check this out: http://jim.akesons.com/projects/payphone-conversi...<br><br>It works if you want to also reuse the parts inside it the phone. I made my son a piggy bank that tells him how much money he has. Otherwise it works like a regular analog phone.
<p>For some reason your link got cut off for me. I'm re pasting it here: <a href="http://jim.akesons.com/projects/payphone-conversion" rel="nofollow">http://jim.akesons.com/projects/payphone-conversio...</a></p><p>http://jim.akesons.com/projects/payphone-conversion</p>
<p>Awesome! You may already know about these, but this would allow you to keep (and ring) the existing bell - <a href="http://www.silvertel.com/products/telecom.html" rel="nofollow">http://www.silvertel.com/products/telecom.html</a></p><p>I used the AG1171, I believe, in a bluetooth antique phone conversion a while back, ran with an Arduino.</p>
<p>This is amazing! You could have 90 from the 90's, 80 from the 80's.. etc. etc... </p>
<p>Ow yeah</p><p>You also askt for sharing payphone hacks, I got one we used al the time.</p><p>What do you call that thing again, that red thing, hmmm.</p><p>O YEAH we used THE CROWBAR HACK.</p><p>WannaDuino!!!</p>
<p>WannaDuino!!!! Likes iT!!!</p><p>That will be a big shipping bill to let is ship to the Netherlands.</p><p>Pitty, because i realy want to make it myself, And Use It Myself.</p><p>And also the Coin returner, as mutch as possible.</p><p>WannaDuino!!!</p>
<p>Brilliant!</p>
I would so totally just use this to rick roll people
<p>Also where did you get those giant scissors?</p>
<p>I have a crosley 50's working payphone, much lighter plastic, would this work?</p>

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More by Fuzzy-Wobble:'90s Payphone Boombox Hack Teensy Monster v1.0 // DIY MIDI Controller Prototyping Wizardry With SPACEBREW 
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