flow chart needed!

On 29-dec-2006, at 14:00, Andre Bartetzki wrote:

> Es war der 29.12.2006 12:57 Uhr, als tobiasreber@freesurf.ch nicht
> widerstehen konnte, folgende Gedanken dem Netz anzuvertrauen:
>
>> Hi everyone,
>>
>> I am in urgent need of a flow chart for a light sensor that will
>> work with
>> the i_Cube by Infusion Systems, like the one they sell themselves
>> (http://infusionsystems.com/catalog/product_info.php/cPath/24/
>> products_id/51).
>> It just consists of a photo cell an a resistor on a small board,
>> but I don't
>> know whether they're parallel or serially connected. the three
>> cables are
>> the power, signal an ground connections.
>>
>> Any ideas how that could look when drawn schematically? I need to
>> build a
>> lot of those, in the next few days...
>> I'm not that good at analogue electronics, so I'd appreciate any
>> help, hints
>> or links to information (in english, german or french). Is there
>> some sort
>> of archive for such things, or abeginners guide to some basic
>> circuits?
>
> Hi Tobias,
>
> In the pdf there are 3 schematics. The first two are with foto
> resistors.
> In the left one, where the foto R is next to U+, the signal voltage
> gets
> higher (towards U+) when there is more light.
> In the right one, the signal voltage gets lower when there is more
> light.
> In general foto resistors are really slow so I'd recommend you to
> use foto
> transistors as shown in the third schematic (you can change R and
> FT in
> order to he inverse behavior).
> The value R depends on the Rf or FT, on U+ and the amount of light,
> I'd
> start with 1kOhm.
>
>
> Andre

one more thing: make sure that the circuit does not draw more current
that the +5V lead
can source. I would not go over 5 mA per lead, meaning that the
resistor must be 1k or higher.
for one LDR there is little risk of drawing too much current, but you
mention that you are going
to build a lot of them.
how will you connect these?
will each LDR circuit go to a separate iCube input?
or do you want to send the combined effect of all photocells to a
single input?

I am not sure if the iCube inputs are protected against overvoltage.
If not:
if you are going to use a second power supply for the photocell
networks,
(for example if you need more current)
be sure that its output voltage does not got over +5V. It may help to
clamp the iCube input
to its own +5V with a diode.

-jennek