Is the Transmitter Circuit Drawn Correctly?

[diegovishnu]

i am trying to do the circuit "www.electronicsforu.com/efylinux/circuit/.../aug99_IRcordless.pdf"[/URL]
the phototransistor showed in the circuit has only 2 leads but the 1 i brought has 3 leads with a number 1838 written on the top..
please help me what to do. even if i brought a new 2 lead phototransistor, how to find the emitter and collector?

also please help me with the audio output transformer. I am not getting it anywhere in the shops

 

[vk6kro]

That link doesn't seem to work.

However the device you have may be a TSOP1838
Here is a data sheet for it:

http://pdf1.alldatasheet.net/datasheet-pdf/view/26604/VISHAY/TSOP1838.html

If it is that one, it needs a pulsed signal at 38 KHz to work. Almost any domestic remote control should give some results with it.

That data sheet does not give the pin connections, but the following image is better.

 

[diegovishnu]

http://www.electro-tech-online.com/...931-infrared-cordless-headphone-ir_audio2.gif

this is the circuit I am using..
it will not work?

 

[vk6kro]

No, if this device you have is the TSOP1838, then you can't really use it as an optical audio receiver. They are meant for remote controls.

If possible, take it back and exchange it for a proper photo-transistor.

Be careful also not to get a light dependent resistor. These are Cadmium Sulfide cells and have a very poor frequency response.

 

[diegovishnu]

i brought 1 phototransistor.but its not semicylindrical as the circuit say..its a blue 1 which looks similar to an LED.
you told the circuit may not work. can you clarify on that?
thankyou in advance

 

[Fish4Fun]

it will not work?

No, your first link did not work. Next, No, the part you bought is an integrated circuit not a "straight" IR photo transistor. The part you bought includes a circuit to make it easy to use as an IR detector for a remote control, which uses a pulsed IR signal, and decodes it. (Changes the pulsed signal to data bits).

You will need a different part like:

http://www.fairchildsemi.com/ds/QS/QSC112.pdf

Fish

 

[diegovishnu]

thankyou...

if the link will not work (but the ckt is one whch came on e4u magazine!) i'll be glad if you could refer some similar circuit..

 

[vk6kro]

If it looks like a LED, then it might be OK. Remote control receivers usually look like the picture above, that is fairly flat with a window on one side.

Try testing it as a transistor but with the top of the device covered over to stop light getting in.
A digital multimeter will usually be able to test transistors in the Hfe setting.

If it tests OK as a transistor, disconnect the base connection and expose the device to light and see if you get a variation in meter reading.


if the link will not work (but the ckt is one whch came on e4u magazine!) i'll be glad if you could refer some similar circuit..
"the link will not work" means that if we click on the link we get no picture, not that the circuit in the link won't work.

 

[diegovishnu]

this is the reciever circuit.
and here is the transmitter

 

[Adjuster]

this is the reciever circuit.
and here is the transmitter

In the transmitter circuit, T1 base appears to fed with a relatively large audio signal without any added DC bias. I believe that this is likely to give a grossly distorted result - are you certain that this has been drawn correctly?