Re: [ha] Re: Good ideas at work here, but...

Dan McDaid (
Mon, 23 Aug 1999 09:19:58 +0100

In message <>, writes
>On Sun, 22 Aug 1999 17:13:50 -0400 John Mullan <> wrote:
>> The whole theory here sounds like it is developing well.
>Ah, if only that were true. The list has been very quiet for months.
Good... I wondered if I was on the wrong list. I checked the
specification on the site, some of the things mentioned don't seem very
feasible. People were using lamps as examples having controllers that
controlled a bunch of lamps and the controllers could talk to one
another..... or something like that anyway.

This kind of system will shoot the price up - ok having a centralised
controller is not good if it goes down but we have to assume that the
controller is robust enough never to go down. Afterall not much can go
wrong if the program in the PIC's or whatever is left alone
... this is just my opinion.
>> I am more than willing to build some device/interface prototypes if someone
>> is willing to help design some. I imagine that powerline interfaces will
>> be a good one to try but not sure how to develop modulated carrier
>> circuits.
>Same here. I would love to have a play with some power-line modems, but
>don't feel confident designing one myself.

I am very interested in powerline communication for devices - mainly
because in many of our homes running new cables - even if it was just a
single optic fibre - would be unrealistic.

I looked into these a while back. I spoke to someone who had torn the
PLM-24 interface to pieces - they gave me lots of information on its
architecture - if I remember correctly the IC used was made by philips;
the philips data sheets were pretty simple.

I'll see if I can find out about it again
>Like John, I feel the need to get some hardware built to prove I'm
>actually getting somewhere, so I have just started on my design for
>a simple touch-sensitive wall-mounted LED control and display unit,
>even though I currently have nothing to display or control:-) So far,
>I have the touch sensor bit partly working. One of those little OPB706B
>infrared reflective proximity sensors and a 4070 hex inverter can
>reliably detect a finger from a distance of a few millimetres through
>a dark red bezel which fits the front of a standard 96x48mm DIN case.
>This needs to be generalised to several sensors mounted near each other.
>Currently, the modulated light from one sensor would trigger the others,
>so I need to add a multiplexing mechanism. I also have some cute 5 by 7
>red LED dot-matrix displays (Kingbright TA07-11) which I need to figure
>out how to drive. Does anyone have experience of this sort of thing?
>They run indefinitely on 20mA or take a maximum of 150mA at 10% duty
>cycle. The LEDs are connected by row and column pins, so they have to
>be multiplexed. How many rows can I run before the multiplex time makes
>it too dim to see? I hope to have six of the displays (and six of the
>photosensors) side-by-side, so they will be visually 7 rows by 30 columns.
>I could wire them this way too, or group them in other patterns, such as
>2*7=14 by 3*5=15, which might be easier to drive from a microcontroller
>with a limited number of ports. I'll probably use a 68HC11 for now as it
>has enough spare capability to do the sensor scanning and bus protocol
>(whatever it turns out to be). Until we get a power-line interface,
>the unit could respond to and issue IR remote control signals.
>I reckon the cost of the control/display box will be comfortably less
>than 30 GBP (50 USD), so I can afford to have a several of them dotted
>around the house. I would really like to have touch-LCD panels, or even
>LCD panels with soft buttons alongside, but the cost of pre-built units
>is prohibitive and the practicalities involved in making a home-built
>unit look nice and be visible in all light conditions are daunting (and
>it still wouldn't be cheap). The LEDs in my box are large enough and
Hmm... you can say that again... cheap.
>bright enough to be seen across the room in full sunlight.

Dan McDaid