My first project Touch button switch

Submitted by Nalle Berg on Sat, 01/02/2021 - 12:02

This idea I have stolen from ABTabi, more specific from this video on YouTube. This guy is clever. His ideas are good, but he have a tendency to just solder things together and then draw a wiring diagram as a scetch.

I try to do it a bit better, so you can pretty much use my instructions and his video to make this thing. I am trying to serve you the best of two worlds, so to speak. Still I am not making it too easy. You've got to think some yourself, so you learn something.

 

Now, on to the actual switch. 

This switch is not an «on/off» -switch, but a «on when touched« switch. Even if this one works just fine, I will get touch sensors from ebay for my next projects. They are inexpensive and looks and works better than what I can make myself.

Also I always try to find the lowest technology possible that can get the job done. I will not use a controller like Arduino or SMT32 (more on that waaaaaaay later, when I start using them) to do a simple task like this, even though I could probably get more functions into my projects that way. I like things that can do one ore a few things, but can do them well and integrate well into any new projects.

 

Parts:

This switch is based on the NE555P -chip. I thought that would be an easy way to ease into making my own things after only making kits so far.

I didn't have a C945 transistor, that the video says to use, but I did have a few 2N2222A -transistors, and after reading around on the internet for a few hours, I came to the conclusion that the two can be used to the same things. The 2N2222A can take stronger currents and the legs are not placed in the same order. Other than that, this one's good to go for my switch.

I blew my red led, while testing (that, I suppose's gonna happen from time to time), so now I'm using a blue one in stead, but everything else is as shown.

Oh, yeah, I almost forgot. During testing, I switched the resistors. When changing back, I didn't have more yellow 10KΩ resistors, so I ended up with blue ones. They are 10KΩ but of a different color. Just in case you should notice and wonder.

Now, as I have told you, I have bought a CNC mill with 3 axis to make PCBs, but I haven't learned how to use that yet, and also for a project this small an ordinary prototype board is just as good.

I prefer the dotted ones, and just solder from dot to dot to make traces. I will show you that further down.

 

Bought on , of cause.

 

 

Wiring diagram

To make the wiring diagram I used Circuit Maker. That's a free program that fetches the components online, so you'll always get updated component list.  You do have to register and log in to use it, even the downloaded version, but I don't mind that. If that's a problem for you, just find another program to do it with.

As you can see, there is a watermark on the wiring-diagram, but I can easily live with that too.

Now, I don't know this program at all. All I have found out about it so far, is just enough to make tha wiring diagram, something that wasn't all that hard to figure out, so I think this program will work for me in the long run.

Another thing with it is that it can produce files for my CNC mill, so I can (when I've learned as much) create those files directly and use them to actually mill out the PCB. That's a big advantage. If you (as you probably do) use another way to make it, this might not be a biggie for you. 

Now, let's have a look at our diagram.

I drew this before I started making the switch, and it helped me keeping everything in its place and with the correct polarity.

Pin 5 & 7 are not in use - it's not a fault in the diagram. What you see here, is a PrintScreen. If you ask for a print-out, it comes in black and white and as a real wiering-diagram-sheet with title, maker and all that stuff in the right lower corner. 

What you absolutely need 

This can be made with only the parts, a soldering iron and some soldering tin. I do recommend not using lead free solder, since it's hard to work with. My recommendation is using 60/40 (tin/lead) with a rosin core (flux core). 

Even if this would be enough, I also used some pins to add an extra VCC/Gnd inlet a lead-connection to a 9v battery and two small screws since that is better to touch than a wire end.

This is the finished board and I'll give you a couple of hints on how I made it.

  • I placed all parts on the lower side of the board ant the LED in the other end, It seemed natural to me.
     
  • All pieces are placed as close together as possible and I used a bit of thinking to place the parts so I didn't have to make longer traces on the back side than I needed.

    The lower right resistor is placed so its close to pin 3, where it's supposed to be attached. On the other side I placed the next component, the capacitor so close that it's easy to solder between the resistor and the capacitors positive side.

    The transistor, however needed place to let me connect all tree legs, so it had to be a bit further away.
     

  • I started by putting the NE555P chip with plenty of rooms on all sides, so I could attach components on all sides.

 

This is the back side of the switch.

At the top, you can see that my solder lines close to the LED looks terrible - even worse than the rest. Boards like this work fine for prototyping, but they are not made to look good.

Two places I had to cross the lines. On a single side board, I would usually do that by crossing with a piece of copper string (coated/insulated) from the other side, but the crossing went on the back side of the NE555P -chip, so I had to use insulated wires on the back side.

Behind the power inlet pins on the other side, I attached the wires from the 9V battery,

It takes a bit of planning not to close the trace from one thing by making a trace for one thing. Always think ahead!

 

And here it is!

As I pressed my finger on the two small screws that's playing switch, the light lit up and the darn thing actually worked!

I had to twiddle a bit with it before it worked as it should, but it's always like that and it is to be expected.

However, the switch works!

I know there's several ways to skin this particular cat, so I might make another one, when I got time and find the correct idea, but as it is now, I've got a working switch and is satisfied with that.

 

Hope you did learn something!