Introduction: DIY Touch-less Door Bell Without Arduino!

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About: Hello. My name's Arpan. At present, I'm an Aerospace engineering student. I love painting and making stuff.

Doorbell switches are one of the things that is most touched by strangers. And with the covid 19 pandemic becoming a serious issue, maintaining a good hygiene has become top priority these days.

So in this instructable, I will show you a simple way to upgrade your existing doorbell switch to a touch-less one without using an Arduino. Yes! No Arduino. Also it uses very few components so that it will be easy to build. Keeping in mind the current lock down in most countries, I have used limited components so that you can easily build this. I would suggest you to first watch the video where I have explained the building process clearly.

Supplies

An IR proximity sensor https://www.amazon.com/DAOKI-Infrared-Obstacle-Avo...

BC547 or any other NPN transistor https://www.amazon.com/Cher9-100pcs-Transistor-Sig...

A 5v relay https://www.amazon.com/Vithconl-PYXQ-9683-Photocou...

Some wires

A 5v battery/Power adapter (Your old smartphone charger should get the job done!)

Step 1: How the Proximity Sensor Works

For this build, you'll need to know one small thing about this sensor. There are two bulbs on the front. When an object comes in front of these, the sensor detects it and outputs a 3.3v digital signal from it's D0 pin on the back. If you want to adjust it's sensitivity, you can use a screw driver and rotate the onboard potentiometer until you get the desired range.

The plan is to use the 3.3v output signal from D0 to trigger a relay which triggers the doorbell switch.

Step 2: Relay Terminals

The relay has 5 pins. Two for input, 5v in this case. Then two more for output. The c.o.m. pin is common to the output. Then there are NC or normally closed and NO or normally open pins. Since the circuit should only trigger when the proximity sensor detects your hand, we have to connect the output between NO and COM pins.

Step 3: Transistor Pins

The transistor has 3 pins. Collector, base and emitter. Unless you want to have an electronics class here, this is all you need to know about the transistor for now.

Step 4: Making the Connections

Okay, no beating around the bush. I'll be straight forward.

5v pin of the sensor goes to positive 5v from power supply.

GND of the sensor goes to transistor's emitter.

D0 goes to transistor's base.

Transistor's collector goes to one input pin of relay.

Transistor's emitter also goes to negative terminal of power supply

The other input pin of relay goes to positive 5v from power supply.

The output of the relay (COM and NO) will be later connected to the existing door bell switch

Step 5: Making a Cardboard Base

I then stuck everything on a piece of cardboard and organized the wires with electric tape.

Then I bent the sensor bulbs to the front. So that it can be mounted easily. I cut two semicircular pieces of cardboard and stuck on the top and bottom of the base. I made a notch in one of them to pass the battery charging wire through

I cut out a piece of black chart paper and made a hole for the sensor to see through. Using double sided foam tape, I then stuck the sensor behind the hole making sure that there is enough space around the sensor bulbs so that it doesn't false trigger. I then stuck the black paper around the semicircular pieces with some adhesive. Our touchless switch is ready!

Step 6: Connecting to the Switch

Generally, Doorbells are not powered from mains, so it should be safe. But just to be safer, turn off the MCB before tampering with electric wires. Although it's safe from here, proceed at your own risk. Wear gloves, shoes and an armor if possible.

First, I pulled open the outer cover of the switchboard. I then removed the screws and took out the board. You can see two wires connected to the switch. We need to connect the two wires from the relay output to these terminals. Do not remove the existing wires or nothing will work.

Step 7: Ready to Be Touch-less!

After connecting, I attached the board back, and stuck the touchless switch beside it using double sided tape. You can use adhesive or screws if you want a more permanent mount. I then switched the MCB back on and started testing.

Now if we bring our hand close to the sensor, the doorbell rings. Great. It has a good range too. The good thing is that we can still use the existing physical switch. The design looks pretty good and modern. Hope you enjoyed the project and will enjoy more making it. Again, I would recommend you to watch the video for a clear understanding.