Re: Re: Hmevision ir transmitter

["Ian Davidson" <ian@xxxxxxx>]

Hi Ian B

If you wish to do it the way you suggest an easier circuit would be

http://galeforce9.dnsalias.org/dsc0_0069.jpg

A few less components and current draw off the ports of HV still well
within
the limits.

As I've said I don't have HV (maybe one day!) but if the members that
do
have it and require the IR say which port they would prefer to use and
the
maximum ratings they would want to control then I'm sure we could design
a
circuit with minimum components that most people even with minimum
electronics experience could build.

At the moment things keep changing so I think any designs should be
shelved
until a common goal is reached as to what is required, if not the poor
people trying to understand basic electronics from that last batch of
messages will be frightened off for life !!!

Ian D

----- Original Message -----
From: "Ian B" <Ian@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Saturday, June 01, 2002 12:46 AM
Subject: RE: [ukha_d] Re: Hmevision ir transmitter


> Your circuit looks like I had in mind back in year dot. I have sat
down
and
> had a think about this and we have been leading you up the garden path
a
> bit. Fun trip though wasn't it. Anyway, here are my
thoughts..........
>
> I have attached (for my sins) a very small pdf with the circuit
(not
quite)
> as I saw it in my minds eye.  Things have changed a bit and the
TR1 codes
> etc. no longer refer to the same transistors so pay attention. After
some
> (considerable) thought I figure the best way to do this is use Port C
in
> OUTPUT mode. According to the specs it can drive TTL and CMOS. This
means
> LED's so enough current for us.
>
> In off state PortC must be all zeros and we don't care what the IR out
is
> doing. In this state TR2 is not conducting so the LED's are never
on.
>
> Right, from the left ($^%!) we have a pull up resistor connecting to
a
> tranny TR1. When HV transmits IR the base is pulled low and the
tranny
stops
> conducting. I assume here that HV switches the ground. This in turn
sends
> the voltage through TR2 high. This is where the clever zoning bit is.
If
> PortC pin x is high it drives the tranny TR2 base and the voltage
reaches
> TR3 - zone ON. If however the PortC pin x was low the voltage would
never
> reach TR3 and nothing happens. As soon as the voltage reaches TR3
it
> conducts and the LED's come on! Voila...... Obviously the LED's on
the
right
> would be as many as you want i.e. 8 in your case.
>
> Well, that's the theory anyway.
>
> There may be a better way round this but it is late and I am tired
(excuses
> excuses).
>
> I hope this is helpful and that I have got it somewhere near
correct.
>
> Off for a midnight snack, have fun. Let me know if the diagram and
text
are
> rubbish.
>
> Ian B
>
> p.s. you owe me one for making me think!! ;-))
>
> >-----Original Message-----
> >From: andy_powell_is [mailto:ukha@xxxxxxx]
> >Sent: 31 May 2002 20:25
> >To: ukha_d@xxxxxxx
> >Subject: [ukha_d] Re: Hmevision ir transmitter
> >
> >
> >
> >Ok, I'll try again.... (this is an abridged version!)
> >
> >I've got the original circuit working.. it was the 2N2222 that
was..
> >err dead.. replaced it and it's all ok now...
> >
> >The circuit now consists of the diagram at
> >http://www.automated.it/homevision/HVIR2.jpg
but with the bit that
> >says Homevision port removed...
> >
> >
> >> I think I've read the relevant messages. IF I've read them
right
> >
> >There was a sudden rush of them, mainly due to my lack of
> >intelligence :P
> >
> >> port a o/p is via a PNP which means it will source the o/p
and give
> >a +volts
> >> supply.
> >
> >I've used the phrase before, and I'm going to use it again,
err,
> >chicken soup...
> >
> >> This lunch I built up a simple circuit details are here:
> >> http://galeforce9.dnsalias.org/dsc0_0064.jpg
> >
> >Thanks, I've saved them for reference...
> >
> >> You only need the one transistor. It is ZTX651 I had on the
bench
> >at work.
> >
> >Awwww, I have a big bag of 2N2222's and BC182's :(
> >
> >
> >> It will handling up to 2A and does not require any form
of
> >heatsink. It is
> >
> >I've put a 1k resistor in from the power supply to the collector
of
> >the first transistor and according to the Circuit maker I'm
pulling
> >2.995ma (the 1k resistor appears to drop the current from 32.5ma
to
> >2.995ma, apparently)... is that a problem? am I going to upset
> >homevision by putting that resistor in there? it still works on
the
> >breadboard...
> >
> >Bearing in mind that this is only 1/8 of the circuit, if I add 7
more
> >am I going to pull too much current?
> >
> >> an e-line transistor and has a very low on resistance. It
will only
> >take
> >> about 1mA of current to drive it from homevision. If the
led's you
> >use are
> >> 20mA devices then each transistor will drive 100 of them. If
this
> >is OTT
> >
> >Phoaaaarrrrr!! 8 zones of 100 emitters :P
> >
> >> The circuit is wired just to show it working ie the 10K
resistor to
> >the base
> >> is connected to the 5V rail to simulate a 5v o/p from HV.
> >
> >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)?
> >
> >
> >> If you drop me your address Andy I'll stick it in the post
and you
> >can
> >> experiment with it. (It is no good to me !)
> >
> >I'll email it privately... :D
> >
> >
> >>
> >> In answer to an earlier question you are correct that for
current
> >to flow it
> >> needs to complete a circuit. When voltage is applied to the
base of
> >a
> >> transistor it flows through the base emitter junction of
the
> >transistor to
> >> ground.
> >
> >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 hope I've explained things ok, I'm not the best teacher,
but if
> >you are
> >> unsure just ask.
> >
> >You're doing pretty well if you ask me...
> >
> >> Again so as not to offend the list if ANYONE wants this topic
off
> >list just
> >> say and it will be.
> >
> >I did ask and the suggestion was that quite a few people are
> >interested, not only that but that this was one of the few on
topic
> >threads... :O
> >
> >Thanks for all your help
> >
> >
> >Andy
> >
> >
> >
> >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 http://docs.yahoo.com/info/terms/
> >
> >
> >
>
>
> For more information: http://www.automatedhome.co.uk
> Post message: ukha_d@xxxxxxx
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