8/9/2019 final yr project on door bell

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I built it on Perfboard, cut to fit a Radio Shack project box. I didn't have connectors or headers

on-hand so I used some machine-pin sockets. They're in five groups. P2 is where the internal 9Vbattery plugs in, if I'm powering it from an internal 9V battery. P1+P3+P4 connects to the

external power binding posts, the on-off switch, and the power-on LED. P5+P7+P10 and

P6+P8+P11 connect to the switched binding posts, the indicator LEDs, and the momentarycontact test switches. P9 is the Basic Stamp serial programming interface.

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step 2Soldering

There are plenty of instructables explaining how to solder, so I won't recap.

I built this on perfboard in a Radio Shack project box.

My usual technique for through-hole perf-board soldering is to use wire-wrap to make the

connections, then to solder the wire-wrapped connections. The thick black wire wrapping aroundthe board is the antenna.

The first picture shows the back of the board, where the connections are made. The second

shows the front of the board, inserted into the box with the connections to the off-board devices(switches, LED, and binding posts) made.

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step 3The code

The code is pretty simple - Basic Stamps are programmed in Basic, as the name would suggest.

The program has buttons 1&3 switch one relay, buttons 2&4 switch the other relay, and button 5starts switching the relays randomly, between five and fifteen minutes apart.

You'll notice two commented-out sections. I used to have buttons 3&4 latch the relays - press

them once and they'd close, press them again and they'd open. That's not appropriate for adoorbell, but I left the code in the file in case I use the box for something else.

step 4Installed

When I went to install this, I found that the doorbell wiring was a tangled rats nest that wasimpossible to work with. So I made a little junction panel out of a piece of basswood and somescrew-down junctions. Two wires from the transformer, two wires from each of the two doorbell

buttons, three wires from each of the two doorbell ringers, all come into separate screwdowns onthe outside rows of the junction panel, and are connected using short patch wires between the

inside rows. The panel is screwed into the wall with 1/4" standoffs.

The project box is mounted using velcro against the wall, sitting on the top edge of the junction

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panel.

Rather than relying on a battery, I added a the smaller project box on top. This contains a bridgerectifier, a 1000 uF 35V capacitor, an LM7809 voltage regulator on a small heat sink, and the

7809's ripple caps. This converts the doorbell circuit's 16VAC into 9VDC, which is acceptable as

input to both the 7805 and the BS2's onboard voltage regulator.

You can see the transmitter hanging on a nail.