Re: Re: Hmevision ir transmitter

["Ian Davidson" <ian@xxxxxxx>]

Hi

Ok if we ignore things like FET's MOSFET's etc etc then transistors come
in
two sorts.

NPN and PNP. For what you are doing it is not that important to learn
about.
The best way I can think to explain it is when transistors are used as
an
amplifier. If you try to imagine a common earth and two supplies one
say
+20V and the other -20V in relation to earth. NPN transistors would be
used
to amplify the positive half cycle of the i/p and PNP transistors the
negative. To put it simply PNP transistors operate with negative
voltages.


Now you have the circuit working and spares then use it, If others need
to
build it they could use the one transistor design and save some time.

>
> So the HV port A supplies +5v too?? This is the bit I'm really
unsure
> of... should I connect the base of the first emitter to Homevisions
A
> ports via a 10k resistor (one for each A port ie one for A1, one
for
> A2..etc)?

As I said I do not have HV so rely on others to tell me the type of o/p.
If
as said before it is open collector and uses a PNP transistor to
+5vthen...

This means that the o/p when not switched on should not have any voltage
out
and infact be high resistance to both supply rails. When switched on the
PNP
transistor would conduct and allow the 5V to reach the port pin. There
are
quite a number of different types of o/p. A quick example of some is
here

http://galeforce9.dnsalias.org/dcp_0068.jpg


> You've lost me with this. Where is this? is it that it flows (in
the
> circuit at the url above) to the second transistor via it's
emitter
> and off to the seond and then to the emitter of that and hence to
> ground?


I wish I could do ASCII art but look here for a diagram of current flow in
a
transistor, It's easier to draw than explain !!

http://galeforce9.dnsalias.org/dcp_0069.jpg


Hope that helps a bit more.

Ian D

NB I know I can't draw either but it's better than nothing !!

Yahoo! Groups Sponsor

ADVERTISEMENT

For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx 
Subscribe:  ukha_d-subscribe@xxxxxxx 
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx 
List owner:  ukha_d-owner@xxxxxxx

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.