On March 28, 2007 at 19:20, johnsfine said...
Edit: I originally posted some fairly stupid comments
about directly connecting the minus side of the IR LED
to the micro, because the I/O pin can pull low more current
than high. Generally it is better to switch the minus
side of the LED and use constant connection to power on
the plus side, rather than switch the plus side. But
after giving it more thought, I think leaving out that
transistor is a lame idea. I expect the designs that
do so limit the range seriously.
You'll find that good designs use more than a single transistor. They use multiple transistors, configured to provide a constant current source, that will drive the IR LED at the full rated power over the entire voltage range of the cells.
Don't. Who said all universal remotes need learning.
Get the codes online or through some other IR capture
device and program them into the remote via the PC interface.
A proprietary universal remote, like what is being proposed with a need for an external capture device doesn't make the remote any easier to design, because now a capture device must be designed. And a proprietary remote design that requires finding codes online will be a real pain. I couldn't find codes for at least 10% of the items I have, and suspect many people would find even higher incidence.
Yes. Trivial electrical design. The rest is mechanical
and soldering.
Trivial, just like hooking up the IR LED. Wait a second, you didn't do too well on that one...
But most low cost universal remotes on the market run
the micro and the IR LED directly off batteries with just
a cap. It works. Just select one of the same micros
they use, such as the Freescale one I mentioned.
Which Freescale micro is that? (You don't actually give a part number for the micro, you give the part number for the remote.) The Freescale micros that I know of, fall into two categories. (Limiting this to Flash Based, as ROM based is worthless for this purpose.) The first category includes several micros that include a voltage regulator on the IC. This is not running the micro directly off the battery. The second category consists of a number of micros with narrow input voltage ranges, or varying voltages. Any of which that I'm aware of would require an external voltage regulator IC.
I was assuming a lot of cut corners, especially on the
mechanicals. I didn't mean to say you could duplicate
a low cost universal remote for parts cost less than that
remote. I meant you could duplicate the basic electronic
parts (micro, LED, etc. ) assuming you kludge the mechanicals.
Let me be even clearer, I'll take a bet, that you can't produce a working electrical design (without mechanicals) for less than the cost of a low cost universal remote. I think I'll win this handily, as any design will need a printed circuit board, and even if you etch your own, you'll spend more on the chemicals and photoresist, than the money for the JP-1's you point out.
