RE: Re: Hmevision ir transmitter

["Ian B" <Ian@xxxxxxx>]

Oh nuts

A small addition to the diagram. I missed the pull down resistor on the
port
output to stop it floating and TR2 maybe doing strange things. Sorry

Ian B

>-----Original Message-----
>From: Ian B [mailto:Ian@xxxxxxx]
>Sent: 01 June 2002 00:46
>To: ukha_d@xxxxxxx
>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
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>>
>>
>
>
>For more information: http://www.automatedhome.co.uk
>Post message: ukha_d@xxxxxxx
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>

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HVIR.pdf