[mythtv-users] IR Tranmitter

[William]

Bert Van Kets wrote:
> William wrote:
>   
>> Bert Van Kets wrote:
>>     
>>> I need to build an IR transmitter to set the channels on my cable box
>>> (Belgian Telenet Digibox). Anybody try the three component circuit on
>>> http://www.lirc.org/transmitters.html or is it necessary to use the
>>> higher power one further down the page.
>>>
>>> How can I find out what frequency I need to transmit? How do I set it?
>>>
>>>   
>>>       
>> The cheap one will usually work ok for one device. The output is
>> pretty weak so you need to tape it right over the sensor. The high
>> power one will allow you to control several devices from one emitter.
>>
>> To find the frequency. Find a lirc configuration for your device and
>> look at the top of the file. The frequency is shown in the info there.
>> But in actuality, it does not matter as long as you install the
>> correct conf files for your device. The config tells lirc what freq to
>> use.
>>
>> William
>>     
>
> Thanks William.
> I will need to control at least two devices, so I'll have to go with the
> transistor amplified one. It struck me that the NPN transistor is not
> specified. Anybody got any suggestions? I can convert a circuit to a PCB
> and build it, but designing a circuit is beyond my skills.
>   

The circuit will work find with any generic small signal npn transistor 
such as the venerable 2n2222. Just make sure its rated for at least 
100ma collector current and you will be fine. You are just using it as a 
current amplifier which is also known as an emitter-follower circuit.
> If I have two identical devices with identical remotes, won't I need to
> hook up two transmitters? How else will the computer be able to set the
> channels in the devices independently.
>   
Some devices such as the dishnetwork receivers allow you to setup 
multiple codes others you are stuck with a single code. In the single 
code scenario  you will need to make 2 transmitters (perfect used for 
the low powered model) and run two instances of lirc. Of course this 
will require 2 serial ports. From what I understand, you cannot use a 
USB-Serial converter. The control of individual pins is not possible 
with those.

William