Touch Sensitive Switch (Take 2)

[MonkeyMera]

(EDITED SLIGHTLY AFTER SOME RESEARCH)

ive been reading this forum for a while now, and its great. Ive got loads of tips and tricks that have been very helpful. and the people on here really know what they are talking about (unlike some other froums that will go un nammed)

i dont know where else to turn for the advice i require. im not very technically minded but i am learning so please can you write any replys in simple 5yr old talk please

what im after is for my Car (Nissan 200SX S13) im making a new centre console out of smoke plastic and coating the back in vinyl with the word/symbol of what is switched on cut out in the vinyl with 2 LEDS behind Blue for off and Red for on. i want the whole face to be flat and when the car is switched off you cant see anything it just looks like a shiny piece of plastic.

this will be running on a 12V DC max 5 amp system with a negative ground.

i can solder and i can get the parts and follow instruction but i cant design the circuits, its a pain

there will be a maximum of 30+ switches in total

Now for the bit i need help with, im after some help with making some touch sensitive switches but i dont understand the what is talked about, (i have learnt and still learning about multi-vibrators/Flip Flops, transistors etc)

would i need a piece of metal on the front of the plastic spoiling the look? or could i raise the away from the front of the contact by about 4mm.

ive seen there are two types of touch sensitive switch one that that when you touch it or get close to it you stableise the "hum" ??? thus switching the item on/off. this could work as i would need the switch be 4mm away from what im touching but other iterference could cause the switchs to turn things on and off on their own or make the switches not work at all.

The other is a compacitance/resistance (i count this a 2 types but others dont) it works by detecting the difference in resistance and compacitance from a untouched state to a touched state thus switching the item on/off, the problem i find with this is has the be physically touched making to look of the finished product not what im after.

Also i have found that if i want to put 2 or more switches together in close proximity i will have to put a ground sheild round it to stop accidently switching on somethine else. is it just as simple as putting a netal strip rorund it and having a wire running to ground?

can a touch switch be adapted to make a variable switch? ie run you finger along its length to adjust the voltage of the out put (for my heater control) or is there another way using different type of switch? (the other way i was thinking was useing say 10 switches in line to give the aperance of a analogue varable switch)

Touch Switch Schematics

ive seen this is this the sort of thing i would need to create and could it be modified to run more than 16 switches?

Do i have to use a plate?? can i use a pin to create this?? how small can the switch plate be?

the other way was to use pins of some sort to and to make the circuit with the finger tip but i'd want the pins to be very small so they are almost non visible to the naked eye plus i'd put them in the midle of the light source so that the light might hide them. this is not the way i'd like to go but it seem simpler. i have found a schematic that i have attached (fINGERSW.pdf) but it is shown for a 5v system. how close can the pins be together so they dont arc and create the circuit.

the other file i have attached (GLASSSWITCH.PDF) seems a very Simple design but im not sure if i like this idea as i would have to use a special switch on the out side that i keep in my glove box and place it over what i want to switch on, but could this be adapted to give the same or similar effect? as the touch switchs as above.

or is there another way i could have really nice switches/different switches in car, im open to sujestions. im going to be using the car as a sort of show car (no stupid body kit) but for electronics etc as i feel that this has been over looked in the industry and everyone goes for big power or lairy paint/body kits and all the electronics side of this are plug and play devices.



Thanks in advance

Monkey

 

[Optikon]

(EDITED SLIGHTLY AFTER SOME RESEARCH)

ive been reading this forum for a while now, and its great. Ive got loads of tips and tricks that have been very helpful. and the people on here really know what they are talking about (unlike some other froums that will go un nammed)

i dont know where else to turn for the advice i require. im not very technically minded but i am learning so please can you write any replys in simple 5yr old talk please

what im after is for my Car (Nissan 200SX S13) im making a new centre console out of smoke plastic and coating the back in vinyl with the word/symbol of what is switched on cut out in the vinyl with 2 LEDS behind Blue for off and Red for on. i want the whole face to be flat and when the car is switched off you cant see anything it just looks like a shiny piece of plastic.

this will be running on a 12V DC max 5 amp system with a negative ground.

i can solder and i can get the parts and follow instruction but i cant design the circuits, its a pain

there will be a maximum of 30+ switches in total

Now for the bit i need help with, im after some help with making some touch sensitive switches but i dont understand the what is talked about, (i have learnt and still learning about multi-vibrators/Flip Flops, transistors etc)

would i need a piece of metal on the front of the plastic spoiling the look? or could i raise the away from the front of the contact by about 4mm.

ive seen there are two types of touch sensitive switch one that that when you touch it or get close to it you stableise the "hum" ??? thus switching the item on/off. this could work as i would need the switch be 4mm away from what im touching but other iterference could cause the switchs to turn things on and off on their own or make the switches not work at all.

The other is a compacitance/resistance (i count this a 2 types but others dont) it works by detecting the difference in resistance and compacitance from a untouched state to a touched state thus switching the item on/off, the problem i find with this is has the be physically touched making to look of the finished product not what im after.

Also i have found that if i want to put 2 or more switches together in close proximity i will have to put a ground sheild round it to stop accidently switching on somethine else. is it just as simple as putting a netal strip rorund it and having a wire running to ground?

can a touch switch be adapted to make a variable switch? ie run you finger along its length to adjust the voltage of the out put (for my heater control) or is there another way using different type of switch? (the other way i was thinking was useing say 10 switches in line to give the aperance of a analogue varable switch)

Touch Switch Schematics

ive seen this is this the sort of thing i would need to create and could it be modified to run more than 16 switches?

Do i have to use a plate?? can i use a pin to create this?? how small can the switch plate be?

the other way was to use pins of some sort to and to make the circuit with the finger tip but i'd want the pins to be very small so they are almost non visible to the naked eye plus i'd put them in the midle of the light source so that the light might hide them. this is not the way i'd like to go but it seem simpler. i have found a schematic that i have attached (fINGERSW.pdf) but it is shown for a 5v system. how close can the pins be together so they dont arc and create the circuit.

the other file i have attached (GLASSSWITCH.PDF) seems a very Simple design but im not sure if i like this idea as i would have to use a special switch on the out side that i keep in my glove box and place it over what i want to switch on, but could this be adapted to give the same or similar effect? as the touch switchs as above.

or is there another way i could have really nice switches/different switches in car, im open to sujestions. im going to be using the car as a sort of show car (no stupid body kit) but for electronics etc as i feel that this has been over looked in the industry and everyone goes for big power or lairy paint/body kits and all the electronics side of this are plug and play devices.



Thanks in advance

Monkey

This is one of the better intro/explainations I've seen in awhile. The thing about those switches that work on HUM from the 50/60Hz power line pickup is they need those to be nearby. I think when you are out in your car, you wont pickup 50/60Hz hum from power lines.

SO.. when considering methods of touchless switch, the capacitance method stands the best shot at working the way you want it to..

Also, I'm not convinced you need some metal plate to directly touch that will ruin your cosmetic appearance you're after.. All that needs to be done is sensing a change in capacitance to actuate the switch. Sensing a change in capacitance can be done through plastic.

Also consider IR sensing. If your plastic is IR transparent, you can conceivably shine an IR light out of it with a detector nearby. When a finger is near, it will reflect the IR into the detector and actuate the switch. This type of system will switch without even touching anything, your just have to be close enough to reflect IR into the detector.

In my opinion, the IR method is robably the easiest to get working.

Also look up pyroelectric detectors or PIR sensors, they work on a similar principle.

 

[MonkeyMera]

Cheers for the reply, i like to make sure that ive covered everything before posting (i hope)

yeah i agree with you on the HUM ones

i looked in to the IR switch and light atcivated switches (i cant remember the name of them but the diode things) and the praticality inside a car is not too great, as out side light/UV rays, other lights inside the car can cause interference with the light source.

he reflection of the surface and where the sensors and light sources are to be placed have to be un obstructed and there is things like gear stick, hand brake etc and no where to put the light source.

PIR sensors could work but all the switchs will be in close proximity to each other and i feel that PIR sensors would switch on other switchs i didnt mean to switch, it need to be fairly accurate but too accurate

Ive just re-read the circuit in the link provided and i think i understand it more wit hte research i have done and i think it will right up my street. if i use 2 of these that will give me a maximum of 32 switches whick is pleanty. i think the only thing to do is make a prototype and give it a try

 

[Dr.EM]

Hmm, using the capacitive switch, its only likely to work reliably if actually touch it. If you make it sensitive enough to work non-contact, you are likely to set of surrounding switches when you try and use it. It could work though, and I think you should go ahead with your prototype, keep the plate as close as possible to your finger.

You can make a simple touch switch using the 555, and I think it was debounced output too. There are 2 plates, and you finger bridges them, however, it often works by only touching the one plate. I'll draw it up if you want it.

 

[MonkeyMera]

Yeah if you could Dr M, thats one of the problems ive encountered trying to design this is the Debounce between touch and untouched, but as i said in the O/P can a ground be put around the switch to act as a force feild stopping the another switch turning on/off and localising the feild some what. if you have a look at the link at the bottom of the top diagram it says not to touch the plate directly as you will dmamge them and he shows you (a very old) a photo of the finished drum kit with the switches (6.5mm x 18mm) quite close together. i can reduce the thickness of the plastic to a min 1mm and personally with all the knowledge ive gained in the last couple of weeks i cant see this to be a problem. but will find out in the making.


can someone help with a list of parts i need as some on that diagram is listed as D1 and R3. i dont know what that means

 

[Arnak]

Finger Switch question.

Hi,

Sorry about reopening an old thread but it contained an idea that I would like to use.

In the pdf attachment called finger switch there is a load shown.

Can someone tell me if that load needs to be there, could it just be used to close the transistor and cause a path to flow?


Also does that leave the circuit in a closed configuration until the contacts are presses again or is it a momentary close?

What I am trying to do is to make an organ stop switch, well several actually and that circuit looks a good way to go.

It will be connected to a scanning board that will check for open or closed switches.

Thanks for any help,

Martin

 

[JimB]

Yes, the load needs to be there.
The load could be a relay coil or just a resistor.

The circuit is not "latching".
ie touch the pins and current flows in the FET,
take your finger off the pins and the FET and the current flow stops.

How you would use this switch depends on how your "scanning board" actually works.

JimB

 

[Arnak]

Hi,

Thanks Jim, how should I work out the required value of the resistor?

Martin

 

[swagatam]

To know more about the construction of touch sensitive switches, click on the below given link:

**broken link removed**

contact me: hitman2008@live.in

 

[killivolt]

This Thread was created 2007.

 

[Arnak]

Touch Switch.

Hi Swagatam,

Thanks very much for that it looks like just what I need.

Arnak

 

[sizala]

no friends this post is created at 1st September 2005...