Introduction: How to Make a Touch Switch Using One Mosfet

Picture of How to Make a Touch Switch Using One Mosfet

HOW TO MAKE A TOUCH SWITCH USING JUST ONE MOSFET TRANSISTOR

In many ways, the MOSFETs are better than regular transistors and in the today transistor project

we will show how to make a simple touch switch that will replace the normal switch with the help of

a mosfet transistor.

A touch switch is a type of switch
that only has to be touched by an object to operate. It is used in many lamps and wall switches that have a metal exterior as well as on public computer terminals. A touchscreen includes an array of touch switches on a display.

For this project you will need :

mosfet

9v battery

12v led strip or 12v bulb

wires

Step 1: Mosfet Transistor

Picture of Mosfet Transistor

The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor
(FET). It has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. A metal–insulator–semiconductor field-effect transistor or MISFET is a term almost synonymous with MOSFET. Another synonym is IGFET for insulated-gate field-effect transistor.

The basic principle of the field-effect transistor was first patented by Julius Edgar Lilienfeld in 1925.

The main advantage of a MOSFET is that it requires almost no input current
to control the load current when compared with bipolar transistors. In an "enhancement mode" MOSFET, voltage applied to the gate terminal increases the conductivity of the device. In "depletion mode" transistors, voltage applied at the gate reduces the conductivity

Step 2: Mosfet Transistor Projects

Picture of Mosfet Transistor Projects

Now we will proceed to the soldering of the wires to the 3 terminals of the mosfet just to be easy when we will make the connection to our switch and put in a small case for future projects.

The mosfet used in this project is IRF z44n a very common transistor

According to the IRFZ44 datasheet this
is a third generation Power MOSFET that provides the best combination of fast switching, ruggedized device design, low on-resistance and cost-effectiveness. The TO-220AB package is universally preferred for commercial-industrial applications at power dissipation levels to approximately 50 W. The low thermal resistance and low package cost of the TO-220AB contribute to its wide acceptance throughout the industry. Specifications: Maximum VDSS : 55VMaximum Drain current: 49A at 250CRDS(on): 17.5mOhmsMaximum power dissipation: 50WPackage: TO-220

Step 3: Mosfet Switch Diagram

Picture of Mosfet Switch Diagram

You have the diagram on how to connect the wires is very simple just connect the load (in this case the 12v bulb)

to the + terminal of the 9v battery and the -terminal of the load to the middle pin of the mosfet.The - negative terminal of the battery to the right end side terminal of the mosfet.And that's it you have an old-school touch switch.

To activate the switch you have to put your finger on the left end side terminal of the mosfet and the +terminal of the battery.

To deactivate the switch put your finger on the left end side terminal of the mosfet and the right end side terminal of the mosfet or the - terminal of the battery.

Step 4: Diy Touch Switch in a Box

Picture of Diy Touch Switch in a Box

Now just use your imagination and make a box/enclosure to put all the wires and the mosfet transistor you can use old plastic stuff that you don't use any more in the video i did use an old cheap power bank enclosure

but you can use a tic-tac case old hand creme(Nivea) and much more stuff.

Thanks all for reading and see you inside the channel

https://www.youtube.com/channel/UCPjqH3HfNA4Shttkx...

All the best and use your imagination!

Comments

Caspar (author)2017-12-06

I understand that the circuit was so simple that it could be drawn on a chalkboard.
As a retired electronics engineer of 30+ years, may I suggest that a combination of a photo of the completed assembly and a "proper" schematic circuit diagram would be very useful in educating other electronics newbies.
The photo would show all the wires clearly, and where they went to, and maybe include some little paper labels for clarity. If the construction was to be packaged, an exploded view might make for a better photo.
The schematic would show pin numbers, voltages, and useful notes for the hobbyist.
I couldn't work out how the touch switch worked, and think it was due to a capacitance effect or static electricity on the person. A data sheet showing the high insulation of the gate, and the voltage needed to turn it on would be useful. Others commented negatively about the lack of schematic, and I found myself frustrated also. Pictures and talking are ok, but "A schematic is worth a thousand words"

ps. just noticed your night-light circuit. A good way to combine a photo and schematic in one. For your next version (230V), you may want to include some notes on safety.

NoskillsrequiredN (author)Caspar2017-12-10

Thanks for the comment, constructive criticism always appreciated.I have more to learn myself i am not here to teach others in a school lecture way i just present some easy electronic projects that anybody can replicate fully functional.Behind all my projects are years of experiments, learning, self-learning and more experiments.I try to make people curious and if they want they can go in depth by themselves.And with the electronic diagrams it's 50-50 yes i can put them along the real ones, but if people reading/watching don't know the symbol for the capacitor, or what means 10k resistor, or Ohm law it's pointless.

The mosfet its a voltage driven transistor being different from a normal transistor 2n3055 that is current driven, by touching the 2 leads the human body has approx 1M resistance so with 0.00001A(and 9v the power supply) we can activate the mosfet

absproject (author)2017-12-04

Hello,

Can you send me similar project that can be used in Alternating Current for 230 volts that I can used as switch for normal ceiling lights?

thanks,

Abner

I am waiting for parts to arrive send me your email and will send all the new projects.all the best

misterxp (author)2017-12-05

Great simple and straightforward instructable. Thanks for sharing. I was after a simple project just like this thanks for sharing!

Thank you, anytime buddy No Skills required electronics projects

oldmanbreadboard (author)2017-12-04

Why are all the crybabies wanting a drawing in their choice of format. They have to have everything their way. Heck, everyone does not march to your particular drummer. As the Eagles sang, "Get Over It". The world does not revolve around your likes and dislikes. The drawing is perfectly adequate to convey a simple concept. The author was not trying to show you how to wire computer. You haters make me sick, as I am sure it does others. Excuse me while I go toss my lunch.

Thanks for the comment haters with their perfect world they don't have a place here, NO SKILLS Required will show only easy replicable stuff,true and tested projects,and some times funny projects because we must have hope,imagination and a good laf.All the best

robobot3112 (author)2017-12-04

Excellent!

Youre a saviour my friend!!

Thanks my friend i try my best to let people know easy replicable stuff that nobody instructed me how to do it even for a science project.All the best

Vortetty (author)2017-12-04

can you make a more in depth tutorial?

What do you want to know? this is the simplest mosfet effect that you will find

JasperKJones (author)2017-12-01

Be buggered with all the detractors wanting everything to be perfect!

I just learned about MOSFET and how it works without all the mumbo jumbo technical sshtuff (yes I do know ow to spell, read as written).

Thank you NoskillsrequiredN for maintaining the KISS principal, it helps the non-technichal newbies grasp the knowledge without getting bogged down in jargon and frightening me off. Keep it up!

Thanks for comment i will try to make more KISS electronics tutorials regardless of bad comm and hate.But i admit there is room for improuvement,better diagrams noted,more attention to text notted and for that i thank you all.

JoeStrout (author)2017-11-30

It's a neat effect, but it's not really a touch switch in the sense of a lamp or touch screen, because you have to be touching *two* things at once — two mosfet terminals, or a mosfet terminal and the negative side of the battery. You're just completing the circuit with your body.

A touch lamp activates with just a single touch. Can you show us how to make something like that?

arpruss (author)JoeStrout2017-12-01

It's a switch operated by touch. Seems like a true touch switch to me. It's a very nice, simple and super-cheap design (you can get 5 of the mosfets from China for $0.91 with free shipping).

One could take the two wires and glue them in a side-by-side zigzag pattern over a large surface area and then it would behave even more like the kind of touch switch some people want (though you'd still need a separate area for the off button).

banman11 (author)arpruss2017-12-02

Agreed!

You are correct its not a true touch switch is the older version with modern components and easy to do.The true touch switch i think is called capacitive touch and i think i remember some skematic for it stay tunned will be soon.all the best

AndrewR273 (author)2017-11-30

Please consider collaborating with a native English speaker to create text that is clear. The formatting, spelling, and odd grammar makes it difficult to read.

truecolor (author)AndrewR2732017-12-01

Unfortunately you will not be able to change that. Either they have no desire or because of their education is not possible to write good English.

Cliffystones (author)truecolor2017-12-02

Andrew, Truecolor,

Have you ever purchased anything, only to find what little instructions there are are printed in "Chinglish"?

While I agree with your basic premise Andrew, I believe there reason for not proofreading is that "NoskillsrequiredN" may not have access to someone who is fluent in both his/her native language and English. There's a big difference between accessibility and having "no desire" to do something. Two old sayings come into play here. Give the author "the reason of a doubt" as to their lack of editing and mostly "Never slap a gift horse in the face".

And as for the chalkboard, I LOVED it! Brought back memories of circuit analysis classes I took wayyyy back, in which the teacher would sometimes use all the chalkboards all the way around the room to solve a question, sometimes going as simple as 1+1=2 so that everyone in class would and could see WHY a certain answer was the correct one. God Bless all of those WWI and Korean war vets who chose to teach this stuff to us young bucks. And as for former East Los Angeles College Electronics Teacher Ben Mitchell, you'll always be remembered by many of us who thrived with your inspiration, RIP.

NoskillsrequiredN (author)2017-12-02

New project

https://www.instructables.com/id/Make-Automatic-Night-Light-Switch-Circuit-Using-Mo/

RaymondR6 (author)2017-11-30

I designed and built my first touch switch in 1974 as my EE project. FETs existed but MOSFETs didn't, so I used some TTL circuits to produce a clock signal that was transferred by my touch though a metal plate to the input of a J-K flip flop which triggered a NPN transistor and a incandescent bulb (only red LEDs existed but were pricey). I got an "A"!! Later I built one using a UJT clock (look it up) and an SCR for the load, and a third using a TRIAC for an AC load.

BTW, your schematic diagram is terrible! If you don't know how to use computer drafting or drawing programs, at least use hand tools and a pencil to draw one on paper then scan it in.

srg42 (author)RaymondR62017-11-30

the circuit diagram criticism is valid, but be constructive. An excellent and easy to use drawing program is fritzing.org Fritzing Fritzing

JesseG85 (author)srg422017-11-30

thank you I agree between this site and stack exchange I noticed a lot of unnecessary negative or harsh criticism without a constructive feedback potentially could scare off or discourage people that are new to this field and trying to learn

JasperKJones (author)JesseG852017-12-01

Here, here!

Thanks, I make these tutorials very simple everyone can replicate them

very easy no skills required averyone is invited

goforit2016 (author)srg422017-11-30

Try TinyCad for electronic schematics. It can be found on SourceForge

Thanks i will try it

NoskillsrequiredN (author)srg422017-11-30

looks alright i will give it a try thanks

GTO3x2 (author)RaymondR62017-11-30

I find the diagram completely adequate. I'm very surprised of such resentment over such a simple diagram.

NoskillsrequiredN (author)GTO3x22017-11-30

Thanks the commenter that was dissapointed about the diagram is an electrical engineer that was expecting textbook diagrams but not the case here this is simple for everybody to replicate if they like.

Thanks for stopping by the diagram is terrible i know but i try to make it so simple if i was to draw simbols and drain gate source and get to tech most of people will not get it but is simple tested and working this is all about NO SKILLS Required.All the best

I agree with you.

Thanks come and chech the channel got many ideeas

Cliffystones (author)2017-11-30

Way back in High School (1970s), I built one that needed line voltage and used an SCR. If I can find it, I'll post it here. But the moseft design, with a relay to switch higher voltages, is far safer. And furthermore IMHO, the chalk oard adds an air of nstalgia

FYI, youse guize needs an edit button, but I digress....

As I was saying before my oops....

And furthermore IMHO, the chalkboard adds an air of nstalgia I really miss those things, along with the Bakrey truck and icecream man from my youth. Please take another, but turn the camera vertical to get the whole picture.

Thanks,

Cliffystones

That was the whole point chalkboard brings me memory from school i was quite amazed about physics, informatics and many more the sound that chalkboard when it was something important underlining stuff and some times small squicks.Thanks a true nostalgic

you can find an scr in those dollar store night light and yes this can be scaled up with a 220v relay and instead of the led you can put other stuff alarm motor and so on.thanks for posting all the best

JohnC430 (author)2017-11-30

what transistor did you use? when u touch the gate u are putting a charge on it. charge that ur body is picking up from radiation from anything around you, e.g the ac wiring in ur house. a big transistor can gave big gate capacitance and can take the charge, however if u use a small transistor with a small gate, it will go poooffff. just another thing for newbies to know.

irf z44n MOSFET transistor a very small charge because the human body has a resistance of around 1Mohm (1.000.000ohm) so apply ohm low and you will find the voltage and amp going to mosfet

JohnC430 (author)2017-11-30

IRFZ44 has a huge gate... soitis ok for this application. dont try it with a 2N7000... 2N7002... etc.

Irfz44n is perfect for this application

JohnC430 (author)2017-11-30

well one can see by the way he is holding the wires to solder that he is quite experienced in soldering stuff... so perhaps he also knows a lot more than just that little circuit... good for you buddy... teaching the newbies a little bit of fun stuff

Thanks for the comment i like to think i know lots of stuff electronic related but most of them i learn from trial and error and watching those no sound clips on youtube and trying to figure it out what the hell is going on.all the best

the16thDoctor (author)2017-11-30

im confused... why did you need a transistor in the first place?

in this case to replace the normal contact switch and in general, you can use the mosfet in many applications audio amplifier, automatic on-off switch, sensors, inverters and many more

jimluschen (author)2017-11-30

I'd think that a cold dry day would make static a problem, where you'd potentially damage the oxide gate layer and destroy the MOSFET when you touched it (think big spark jumping from finger to doorknob).

How is your reliability?

I was thinking about that and even what if exposed to water or wet fingers.This system is by far perfect let's be realistic it has just one active component the mosfet.It is just a proof of concept and it is showing the difference between a mosfet and regular transistor.All the best

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Bio: Hello friends i show how to make stuff with no skills easy to replicate step by step from powerbanks,generator,invertors and so on thanks
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