wireless energy transfer

[towndrowmatt]

Need a bit of help here( i'm a mech engineer so i'm right out of my depth please be gentle).
Need to find a way of turning on a LED through about 6mm of glass. was originally going to use a reed switch but that will conflict with other functions.
was thinking along the lines of some sort of induction/ transponder sort of thing. LED can have an active supply. Button cell battery would be ideal to keep size of component down.
Any ideas would be really wecome.
regards

 

[Torben]

I would probably first choose an LDR, photodiode, or phototransistor on the receiving side and an LED on the sending side. Or is the glass not transparent? You would probably have to modulate the light to keep ambient light from interfering.

Is that idea something which might work in your situation?

[Edit: Oh...by the way, a button cell puts out 1.5V when fully charged, so depending on what kind of LED you're lighting up you might want or need to use something like the Joule Thief to run the LED. The schematics for it are on the site I linked; you don't need to buy the kit. It does take up a bit of space, though not much.]


Torben

 

[Gayan Soyza]

LED can have an active supply. Button cell battery would be ideal to keep size of component down.regards

Button cell is not enough to drive the driver circuit unless you series more of them.A single transistor versions on LDR based will work but.........not long time

Mmmmm LED's as input sensors know about this but never tried yet.

Better try about this on weekend.

 

[Torben]

Button cell is not enough to drive the driver circuit unless you series more of them.A single transistor versions on LDR based will work but.........not long time

Certainly not with modulation, no. I wouldn't recommend using a button battery unless I was *really* strapped for space.


Torben

 

[ecerfoglio]

Need a bit of help here( i'm a mech engineer so i'm right out of my depth please be gentle).
Need to find a way of turning on a LED through about 6mm of glass. was originally going to use a reed switch but that will conflict with other functions.
was thinking along the lines of some sort of induction/ transponder sort of thing. LED can have an active supply. Button cell battery would be ideal to keep size of component down.
Any ideas would be really wecome.
regards

It could be as simple as a coil each side of the glass (think of them as a transformer without an iron core). Both coils wound with a rather large diameter (larger than the distance between them, try 20 to 30 mm if there is enough space) and facing each other.

The sender coil receives a high frecuency (1000 to 10000 Hz) AC - you may feed it from a simple oscilator, or even an LM 555 as there is no need of a clean sine wave.

On the receiver side just connect the led in anti-parallel (*) with a small diode (1N4001 or 1N4148) and both to the coil. There is no need of an active supply

(*) Don't pannic : anti-parallel just means that they are conected in parallel but with oposing polarities - that is led's anode (+) with diode's cathode ans led's cathode (-) with diode's anode

 

[crutschow]

On the receiver side just connect the led in anti-parallel (*) with a small diode (1N4001 or 1N4148) and both to the coil. There is no need of an active supply

Like the idea of using a coil. Simple and it saves a battery.

You could alternately connect another LED in opposite polarity and parallel with the first. That way one LED would light on 1/2 of the waveform cycle and the other on the other 1/2 cycle.