Light Switch reverse engineered

Description

This commercial light switch which is super popular here (even the government uses it for city light poles) has a weird problem in its design, if you try to turn on and off a big contactor with the output, it trips all the fuses on its way.
So I wanted to improve the design and fix this.
Now I think that this problem occurs cuz it takes the circuit power input (220vAC) and connects it to the relay NO pin to use it as the output phase, and when the contactor on the output turns off, the voltage spike messes with the circuit and "something" happens that makes the fuses to trip.

So anyway, I took the circuit from the device PCB and fixed that problem to see if that helps. (I haven't received my PCBs yet to find out).

Details

Step 1:

I just took out the PCB and followed the traces and recreated the circuit.

Step 2:

Then I put everything together on a breadboard, fixed the drawn circuit problems, and tested everything.

Step 3:

Designed a new PCB with the changes needed so far.

Now I'm waiting for the PCB to arrive to see if the changes I made have done anything good.

Down below you can download the last version of the schematic and the PCB I designed. It's a working device which you can make for yourself and use it!

I will update both files as soon as I made any changes to them.

p.s: [Not recommended] in the file info means I haven't tested the PCB or schematic myself or there is a problem with it.

Files

Light switch PCB V1.3.PcbDoc

Light Switch PCB V1.3

pcbdoc - 2.01 MB - 11/27/2021 at 13:15

Download

Light Switch V1.3 Schem c.pdf

Light Switch Schematics V1.2

Adobe Portable Document Format - 113.74 kB - 11/27/2021 at 13:14

Preview

Light switch PCB V1.2.PcbDoc

Light Switch PCB V1.2 [Not recomended]

pcbdoc - 1.85 MB - 11/15/2021 at 08:20

Download

Light Switch Schematics.pdf

Light Switch Schematics V1.2

Adobe Portable Document Format - 191.47 kB - 11/15/2021 at 08:13

Preview

Components

2 × 330KΩ 1206 Resistor

1 × 330Ω 1W Resistor

1 × 4.7MΩ 1206 Resistor

1 × 100Ω 1206 Resistor

1 × 12KΩ 1206 Resistor

Project Logs

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Open Light Switch PCB V1.3
setCREATE • 11/27/2021 at 13:26 • 0 comments
Log no.2: Open Light Switch PCB V1.3

What I've done?
I edited the schematics and redesigned the PCB.

What's New?
- A fuse is added to the circuit
- PCB is designed to be able to mount on the casing
- Power, Input, and output wires are all on the bottom
- PCB is more standard, clearance between tracks is better now (still not perfect)
- PCB is a bit bigger
- It just looks way better, tracks are more organized and no jumper is needed
Where are the files?

You can download the Scheme and the PCB documents in the project files.

What's next?

I will design a casing for the PCB and 3D print it.
Open Light Switch V1.2 Prototype
setCREATE • 11/27/2021 at 13:10 • 0 comments

Log no.1: Open Light Switch V1.2 Prototype

What I've done?

I received the V1.2 PCB, soldered everything, and tested the circuit.

Images:

The Assembled PCB

This might be the worst quality you've ever seen for a PCB

Results:

Well, everything worked fine that's it.

Next Step:

I will update the PCB.

View all 2 project logs