Wireless infrared headphones

[Apparatus]

I recently designed and built myself a pair of wireless infrared
headphones. The project is documented on my website for anyone
interested. Feel free to learn from the design and to send me
questions.

http://www.its.caltech.edu/~hiszpans/wih/

Cheers,
Chris

 

[Ban]

I recently designed and built myself a pair of wireless infrared
headphones. The project is documented on my website for anyone
interested. Feel free to learn from the design and to send me
questions.

http://www.its.caltech.edu/~hiszpans/wih/

Cheers,
Chris

There are a few design flaws in your work, did you really pass that class?
Worst is the transmitter stage The current through the LEDs is only
determined by their forward voltage it can vary a lot and will degrade
performance since the max. permissable current is surpassed. Your
calculation "current sourcing" is completely wrong. The LEDs are in the
collector line and do not contribute to the Vbe calculation.
The transmitter will have big noise problems, as you amplify any ripple on
the supply voltage through your bias resistors, some of which can be
omitted...

 

[Apparatus]

There are a few design flaws in your work, did you really pass that class?

Yes, I did well. This was for an introductory class.

Worst is the transmitter stage The current through the LEDs is only
determined by their forward voltage it can vary a lot and will degrade
performance since the max. permissable current is surpassed.

The forward voltage did not vary all that much since it is set by the
current through V_cc / (R_9 + R_10). However, I have allowed ample room
for variance, taking into account the 50% duty cycle.

Your calculation "current sourcing" is completely wrong. The LEDs are in the
collector line and do not contribute to the Vbe calculation.

You are right. Should be as I stated above. Thank you for bringing the
error to my attention.

The transmitter will have big noise problems, as you amplify any ripple on
the supply voltage through your bias resistors,

The supply is quite stable, but yes I see your point. Noise could
potentially be a problem in a particularly noisy environment.

some of which can be omitted...

Yes, R10 can be omitted, and R9 doubled to have a near equivalent
effect.

Cheers,
Chris

 

[John Smith]

I recently designed and built myself a pair of wireless infrared
headphones. The project is documented on my website for anyone
interested. Feel free to learn from the design and to send me
questions.

http://www.its.caltech.edu/~hiszpans/wih/

Cheers,
Chris

I think you did quite allright. Of course there are improvements possible,
but hey, only 10 weeks for a clean working prototype with pcb etc and a
paper is not bad at all. One small point though, your paper references
several components that I could not find in the schematic drawing: D8, D9,
C17, C18, C24, R30 and there maybe others.

-- John

 

[Apparatus]

I think you did quite allright. Of course there are improvements possible,
but hey, only 10 weeks for a clean working prototype with pcb etc and a
paper is not bad at all.

Thank you John. I appreciate the support. Hopefully the improvements
will come with time.

One small point though, your paper references
several components that I could not find in the schematic drawing: D8, D9,
C17, C18, C24, R30 and there maybe others.

Ah, the PDF contained an old version of the schematic. Should be fixed
now. Thanks for bringing this to my attention.

Cheers,
Chris

 

[ehsjr]

I recently designed and built myself a pair of wireless infrared
headphones. The project is documented on my website for anyone
interested. Feel free to learn from the design and to send me
questions.

http://www.its.caltech.edu/~hiszpans/wih/

Cheers,
Chris

Haven't had a chance to read it yet - just scanned through.
But it was darn nice of you to post it! Thanks!

Ed