Previous in Forum: RTD's   Next in Forum: MV DG Sync. Issue
Close
Close
Close
29 comments
Participant

Join Date: May 2015
Posts: 4

Transistors and Lamps

05/18/2015 4:02 PM

How can you design the control of a lamp using your fingers? Such that when two of them touch (index finger and thumb) the lamp goes on. I want to use a transistor.

Login to Reply
Pathfinder Tags: control lamps touch transistors
Interested in this discussion?
You can "subscribe" to this discussion to be notified of new comments.
Click on the Subscribe menu at the top of the page.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Nov 2007
Location: Eastern Arizona mountains on Route 666 about a mile from God's country
Posts: 1676
Good Answers: 122
#1

Re: Transistors and lamps

05/18/2015 4:09 PM

By utilizing "Hall Affect" sensors. There are many lamps, water faucets (valves) and other gadgets on the market that already use this system.

__________________
They said; "Brain size?" I heard; "Train size?" so I said: "I'll take a small one, thank you."
Login to Reply
Participant

Join Date: May 2015
Posts: 4
#2
In reply to #1

Re: Transistors and lamps

05/18/2015 4:16 PM

Isn't there a way to do this without sensors? Just something really basic to understand the uses of transistors

Login to Reply
Guru
Hobbies - DIY Welding - Don't Know What Made The Old Title Attractive... Popular Science - Weaponology - New Member United States - US - Statue of Liberty - 60 Year Member

Join Date: Apr 2009
Location: Yellowstone Valley, in Big Sky Country
Posts: 6902
Good Answers: 282
#4
In reply to #2

Re: Transistors and lamps

05/18/2015 4:46 PM

In you quest to "... understand the uses of transistors.", what has led you to believe that a transistor is the appropriate component for this proposed circuit control?

__________________
Semper Ubi Sub Ubi
Login to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 14850
Good Answers: 913
#7
In reply to #2

Re: Transistors and lamps

05/18/2015 6:02 PM

One can use a FET transistor as a sensor to trigger a power transistor circuit. However, if the person touching the FET has the slightest amount of static charge in the wrong polarity then either no switching will happen, overly sensitive switching will happen or in the worst case the static charge could destroy the FET.

One can make circuits with transistors that are so sensitive to a person that one does not have to touch the device but just carefully move in the field around the circuitry. Because of this I would not recommend trying to teach transistor circuit theory with a circuit that a person touches the circuit.

If you wish to see how sensitive to a persons movement a circuit can be, watch Pamelia Kurstin play a Theremin. The only instrument a musician does not touch to make music. I particularly love the bass solo she plays in "Falling Leaves".

__________________
"Don't disturb my circles." translation of Archimedes last words
Login to Reply
Guru
Engineering Fields - Electrical Engineering - New Member Fans of Old Computers - Commodore 64 - New Member Popular Science - Evolution - New Member United States - Member - New Member

Join Date: Oct 2013
Location: Illinois, 7 county region (The 'blue dot' that drags the rest of the 'red state' around during presidential elections.)
Posts: 3688
Good Answers: 89
#16
In reply to #2

Re: Transistors and lamps

05/19/2015 9:22 AM

"Isn't there a way to do this without sensors? Just something really basic to understand the uses of transistors"

You are looking to make a touch-operated lamp to help you understand the uses of transistors? It would appear that you are a self-directed, self-motivated learner, and that is commendable. I always encourage people to learn more.

In your case, I would recommend you start with something a little more formal. Take a basic electronics course at the local community college, that will help you get the fundamental knowledge to allow you to explore the world of transistors more easily and more effectively.

__________________
( The opinions espressed in this post may not reflect the true opinions of the poster, and may not reflect commonly accepted versions of reality. ) (If you are wondering: yes, I DO hope to live to be as old as my jokes.)
Login to Reply
Member

Join Date: Nov 2014
Posts: 6
#19
In reply to #16

Re: Transistors and lamps

05/19/2015 3:50 PM

http://www.amazon.com/Make-Electronics-Discovery-Charles-Platt/dp/0596153740

This is an awesome book. They sell complete electronics kits to go with the instruction. Very hands on.

Login to Reply Score 1 for Good Answer
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 161
#18
In reply to #2

Re: Transistors and lamps

05/19/2015 10:40 AM

Yes. It is called a lamp socket switch, and it only requires me to use two fingers - one thumb on the lamp base, the other on the switch, and it is one of the push through style, that easily turns lamp on and off. No fancy electronics to mess up in a lightning storm. These switches have apparently been around since Edison invented the light bulb.

OR - you could install an acoustically activated switch called the clapper (not the flapper), and on this one you merely clap your hands. Do not applaud your dancing girls too vigorously, or the lights will flicker on/off.

__________________
If it ain't broke, don't fix it. Just build a better one.
Login to Reply
Guru

Join Date: Nov 2007
Location: Eastern Arizona mountains on Route 666 about a mile from God's country
Posts: 1676
Good Answers: 122
#21
In reply to #2

Re: Transistors and lamps

05/20/2015 9:15 AM

Yes, but it is rather painful and I would not recommend it

No matter what type of sensor you choose there will be some transistor operation involved.

I would start here then perform more in-depth searches on the subject.

en.wikipedia.org/wiki/Field-effect_transistor

__________________
They said; "Brain size?" I heard; "Train size?" so I said: "I'll take a small one, thank you."
Login to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3231
Good Answers: 444
#5
In reply to #1

Re: Transistors and lamps

05/18/2015 5:37 PM

Hall Effect devices sense the proximity of magnetic, not electrostatic, fields. The transistor in those "touch switches" is biased to conduct when the leakage capacitance of our bodies couples with the electrical noise fields surrounding our environment. Not a lot of current, but just enough to make a neon voltage tester (remember those things?) conduct when one side is attached to the "hot" side of a circuit.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Login to Reply Score 1 for Good Answer
Guru
Hobbies - DIY Welding - Wannabeabettawelda

Join Date: May 2007
Location: Annapolis, Maryland
Posts: 6845
Good Answers: 399
#11
In reply to #5

Re: Transistors and lamps

05/18/2015 10:49 PM

GA. I remember back in the late seventies and early eighties when touch lamps were all the rage. You 'bout nailed it so I'll leave it at that. Cheers!

Login to Reply
Guru
Hobbies - CNC - New Member

Join Date: Jul 2013
Location: Lost Wages Nevada
Posts: 1578
Good Answers: 54
#3

Re: Transistors and lamps

05/18/2015 4:34 PM
__________________
Though it does seem he frequently has a Swiss Army knife or Leatherman and a roll of duct tape with him.
Login to Reply
Guru

Join Date: Oct 2008
Posts: 42259
Good Answers: 1659
#6

Re: Transistors and lamps

05/18/2015 6:02 PM

I'd let my fingers dial up a light store.

I don't think either of us is capable of doing this.

Login to Reply
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4642
Good Answers: 794
#8

Re: Transistors and lamps

05/18/2015 6:04 PM
  • Isn't there a way to do this without sensors? Just something really basic to understand the uses of transistors

Without sensors? So you want something that will read the mind of the person wanting to control the lamp when they touch their own fingers together? Are you looking for something like "the Force" from Star Wars?

"Turn on you will... or in the dark side you will stay."

Let us know when you succeed, I can think of a lot more valuable things to do with that kind of technology than controlling lamps.

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**
Login to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 29823
Good Answers: 1665
#9

Re: Transistors and lamps

05/18/2015 6:07 PM
__________________
Break a sweat everyday doing something you enjoy
Login to Reply
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 8725
Good Answers: 994
#10

Re: Transistors and lamps

05/18/2015 7:30 PM

You can use a phototransistor arranged so that when you bring your fingers together it blocks the light shining on the transistor.

A standard bipolar transistor can work as a phototransistor if light can reach the transistor base. The light releases carriers on the base-collector junction the same way that forward biasing the base-emitter junction does, turning the transistor on.

I once carefully filed the top off of a transistor in a metal can and could turn it on and off by passing my hand over it.

Phototransistor

Login to Reply
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3055
Good Answers: 140
#20
In reply to #10

Re: Transistors and lamps

05/19/2015 9:54 PM

Your image looks more like a LDR.

Light dependent resistor.

__________________
Plenty of room here
Login to Reply
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 8725
Good Answers: 994
#28
In reply to #20

Re: Transistors and lamps

05/23/2015 12:26 PM

Actually a ThorLabs FGAP71 Gallium Phosphide photodiode. I grabbed the wrong image. Sorry, good catch.

https://www.thorlabs.com/thorproduct.cfm?partnumber=FGAP71

Login to Reply
2
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 5876
Good Answers: 231
#12

Re: Transistors and Lamps

05/19/2015 12:51 AM

"How can you design the control of a lamp using your fingers?" There are numerous ways, including:

1. While doing the design work, hold a pencil or pen between those fingers. It is quite helpful to make a drawing.

2. Use those fingers to turn the pages of one or more reference books.

3. Use those fingers on a mouse or trackpad to do a series of searches on the internet.

4. Hold solder between one pair of fingers (or a finger and a thumb) and the soldering pencil between others while assembling possible circuits to test.

Sorry! I couldn't resist answering the question as posed...

__________________
Teaching is a great experience, but there is no better teacher than experience.
Login to Reply Good Answer (Score 2)
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 4019
Good Answers: 102
#13
In reply to #12

Re: Transistors and Lamps

05/19/2015 4:43 AM

That solves the 2 finger part of the problem.

Sensors can be eliminated by holding ice till your fingers lose sensation. This may have to be repeated. Burning your finger tips removes sensation for a few days, saves having to rechill, but needs to be done in advance.......

__________________
Difficulty is not an obstacle it is merely an attribute.
Login to Reply Score 1 for Good Answer
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5030
Good Answers: 272
#14

Re: Transistors and Lamps

05/19/2015 7:44 AM

A Darlington triple should do it:-

Choose the resistor depending on your power supply.

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Login to Reply Score 1 for Good Answer
Guru

Join Date: Dec 2008
Location: Cd. Juarez, Chihuahua, Mexico.
Posts: 1023
Good Answers: 69
#15

Re: Transistors and Lamps

05/19/2015 9:04 AM

This is a toggle circuit, you operate it to turn it on, and touch again to turn it off; the second circuit is a transistor touch switch.

There's an author that I like very much, Forrest M. Mims III, you can find his engineer's mini notebooks at any Radio-Shack. I have built many of his circuits and found that they always work, and that they are very tolerant when you don't have the exact component, simply put a fairly aproximate and voila !.

I got his books at home, so I couldn't pass you a couple of circuits, but the ones above should do the trick as well.

__________________
No hay conocimiento ni herramienta que sustituya al sentido comun.
Login to Reply
Power-User

Join Date: May 2007
Location: Hurst, Texas
Posts: 178
Good Answers: 4
#17

Re: Transistors and Lamps

05/19/2015 9:23 AM
__________________
Bill H.
Login to Reply
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4642
Good Answers: 794
#22

Re: Transistors and Lamps

05/21/2015 2:23 PM

You guys are reading more into the OP's statement than he said.

"...when two of them touch (index finger and thumb) the lamp goes on."

He is not describing a touch lamp circuit there. He does not say he wants to touch the LAMP, he just wants to touch his FINGER AND THUMB TOGETHER and somehow, magically, the lamp will go on or off without the use of "sensors".

FM ...

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**
Login to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 14850
Good Answers: 913
#23
In reply to #22

Re: Transistors and Lamps

05/21/2015 2:30 PM

That's why I suggested watching that TED talk where a Theremin was played. She's really good at it, too.

__________________
"Don't disturb my circles." translation of Archimedes last words
Login to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3231
Good Answers: 444
#24
In reply to #22

Re: Transistors and Lamps

05/21/2015 2:33 PM

So he wants to use a camera to capture an image of two fingers (which two?) touching each other then feed the image in realtime to a computer to decipher the information to output to a relay to close the lamp circuit...Can anybody spell "Rube Goldberg"?

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Login to Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 14850
Good Answers: 913
#25
In reply to #22

Re: Transistors and Lamps

05/21/2015 2:42 PM

Your point is made but sometimes it is better to give the customer what they need instead of what they asked for.

__________________
"Don't disturb my circles." translation of Archimedes last words
Login to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 5876
Good Answers: 231
#26
In reply to #22

Re: Transistors and Lamps

05/21/2015 2:42 PM

Correct!

Now when you touch your index finger to your thumb, you are closing a somewhat conductive, roughly circular, loop that includes a capacitance (the surfaces of the two digits separated by the dielectric of two layers of dead skin). I presume that loop would have a resonant frequency of low Q. It just might be possible to detect that loop. Of course that resonant frequency will vary from person to person, depending on such factors as orientation, size, shape, skin chemistry, recent skin history (such as wetness), etc.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Login to Reply
Guru
Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 14331
Good Answers: 161
#27
In reply to #22

Re: Transistors and Lamps

05/21/2015 2:55 PM

Why can't we all just play nice, and make the other kid's toy work?

Radio Shack has conductive thread you can sew into clothing. That might make a really nice antenna for your Theramin circuit Q-Switch where you touch index finger and thumb together. Have a wireless tuned circuit at the lamp waiting breathlessly for your every command.

__________________
If it ain't broke, don't fix it. Just build a better one.
Login to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 29931
Good Answers: 808
#29

Re: Transistors and Lamps

02/12/2021 5:02 AM
__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Login to Reply
Login to Reply 29 comments
Interested in this discussion?
You can "subscribe" to this discussion to be notified of new comments.
Click on the Subscribe menu at the top of the page.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

adreasler (1); Bill H. (1); Brave Sir Robin (1); dkwarner (2); Doorman (1); dvmdsc (1); James Stewart (2); Jeff24 (1); JRaef (2); lyn (1); Original_Macgyver (1); PWSlack (1); RAMConsult (2); Randall (1); redfred (3); Rixter (2); Sheek (1); SHOCKHISCAN (2); SolarEagle (1); Wal (1); Yahlasit (1)

Previous in Forum: RTD's   Next in Forum: MV DG Sync. Issue

Advertisement