Hi, I have to design a 5-button keyboard. I would like to use infrared leds and transistors to make the buttons of the keyboard. Years ago, in fact, I had a digital manometer that had 4 buttons based on that principle. Before starting the design I would like to see a couple of keyboards as an example... Can anyone address me to some product using infrared led and transistors as buttons? thanks in advance, Enrico
Using infrared leds and transistors to make a keyboard
Started by ●September 8, 2009
Reply by ●September 8, 20092009-09-08
On Sep 9, 2:11=A0am, Enrico <zig...@libero.it> wrote:> Hi, > > I have to design a 5-button keyboard. > > I would like to use infrared leds and transistors to make the buttons > of the keyboard. Years ago, in fact, I had a digital manometer that > had 4 buttons based on that principle. > > Before starting the design I would like to see a couple of keyboards > as an example... Can anyone address me to some product using infrared > led and transistors as buttons? >TV Seriously, the transmiter can be a simple PWM port pin from a micro (you are in c.a.e.) into the base of a transistor buffer. The receiver would need a few amplificating transistors feeding ito the timer input of the micro.
Reply by ●September 8, 20092009-09-08
On Sep 9, 6:11=A0am, Enrico <zig...@libero.it> wrote:> Hi, > > I have to design a 5-button keyboard. > > I would like to use infrared leds and transistors to make the buttons > of the keyboard. Years ago, in fact, I had a digital manometer that > had 4 buttons based on that principle. > > Before starting the design I would like to see a couple of keyboards > as an example... Can anyone address me to some product using infrared > led and transistors as buttons?This is a confusing question, you cannot use led/trx as buttons ? - but you can set up a light sense path, which can be either * Opto interrupter, with a beam-break button/plunger eg Digikey 425-1964-5-ND or * reflective sensor, that looks for fingers - this needs a surface above the sensor for natural operation. eg Digikey GP2S60 PHOTOINTERRUPTER REFLEC 1MM SMD 34c/100+ -jg
Reply by ●September 9, 20092009-09-09
Hi,> This is a confusing question, you cannot use led/trx as buttons ?yes, that's exactly what I would like to do.> - but you can set up a light sense path, which can be either > * Opto interrupter, with a beam-break button/plunger > eg Digikey 425-1964-5-NDI understand what you mean about, but that's not suitable for my needs.> or > * reflective sensor, that looks for fingers - this needs a surface > above the sensor > for natural operation. > > eg Digikey GP2S60 =A0PHOTOINTERRUPTER REFLEC 1MM SMD =A0 34c/100+That's interesting! Thanks a lot pal for your suggestion. Enrico
Reply by ●September 9, 20092009-09-09
In message <e3ec7faf-988d-44f4-912a-ced9db977656@z24g2000yqb.googlegroups.com>, Enrico <zigbee@libero.it> writes>Hi, > >I have to design a 5-button keyboard.OK..>Before starting the design I would like to see a couple of keyboards >as an example... Can anyone address me to some product using infrared >led and transistors as buttons?Possibly, but how about this, http://projects.dimension-x.net/technology-and-projects/ledsensors Far more interesting to use the LED as indicator and sensor.> >thanks in advance, >Enrico-- Clint Sharp
Reply by ●September 9, 20092009-09-09
On Sep 9, 3:11=A0pm, Enrico <zig...@libero.it> wrote:> Hi, > > > This is a confusing question, you cannot use led/trx as buttons ? > > yes, that's exactly what I would like to do. >I misunderstood it as well. Yes, IR detectors (look like LED, but not really emitter) can sense IR from fingers. Some come with integrated transitor pre-amp. Even so, you need additional amplifier before wiring it to your logic block, whatever that may be.
Reply by ●September 9, 20092009-09-09
Hi,> I misunderstood it as well. Yes, IR detectors (look like LED, but not > really emitter) can sense IR from fingers.Ok.> Some come with integrated > transitor pre-amp. Even so, you need additional amplifier before > wiring it to your logic block, whatever that may be.Got it, thanks. I read a bit what the literature says about IR detectors: basically they are bipolar transistors without the Base terminal: on receiving IR light they drain some current from the Collector terminal. Now, the problem is to understand whether or not, the signal shown at the Collector terminal is digital or not. My guess is: 1) If the injected IR light in the Base is intense, the transistor saturates and the voltage at the Collector terminal should goes down to 0.3 Volts. 2) If the injected IR light in the Base is NOT intense, the transistor DOESN'T saturate and the voltage at the Collector terminal is unpredictable. Enrico
Reply by ●September 9, 20092009-09-09
On Sep 8, 10:23=A0pm, -jg <jim.granvi...@gmail.com> wrote:> * reflective sensor, that looks for fingers - this needs a surface > above the sensor for natural operation.Why does it need a surface above the sensor? It can detect the difference between "nothing in proximity" and "finger in proximity".
Reply by ●September 9, 20092009-09-09
On Sep 9, 6:35=A0am, Enrico <zig...@libero.it> wrote:> I read a bit what the literature says about IR detectors: > > basically they are bipolar transistors without the Base terminal: on > receiving IR light they drain some current from the Collector > terminal.If you get an ordinary transistor in a metal case, something common like a 2n2222, and carefully cut the top of the case off, you have a phototransistor... oh course not one optimized for the task. Additionally, many LEDs are at least weakly photodiodes. Try putting an ohm meter on one and holding it close to a lightbulb, then in the dark.
Reply by ●September 9, 20092009-09-09
In article <8c1acec3-88ef-4819-a34b- 31e68498e23f@m11g2000yqf.googlegroups.com>, zwsdotcom@gmail.com says...> On Sep 8, 10:23=A0pm, -jg <jim.granvi...@gmail.com> wrote: >=20 > > * reflective sensor, that looks for fingers - this needs a surface > > above the sensor for natural operation. >=20 > Why does it need a surface above the sensor? It can detect the > difference between "nothing in proximity" and "finger in proximity".And you would never see ANY other IR source that might trigger it like the sun, fires, bodies close by........ --=20 Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny <http://www.badweb.org.uk/> For those web sites you hate
