[mythtv-users] IR Tranmitter

William william_munson at comcast.net
Sun Sep 27 11:52:22 UTC 2009


Colin McGregor wrote:
> On 9/27/09, Bert Van Kets <mythtv-users at vankets.com> 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.
>>     
>
> If you are after a high power transmitter you might want to have a look at:
>
>    http://iguanaworks.net/product2.psp
>
> Schematics and PCB layout are available on the website. My problem has
> been to find a local source for the 0.33 F capacitor (yes, 1/3 of one
> farad...).
>
>   

Try putting 3 x 0.1uF in parallel. If you feel a need to get even closer 
to the value, add a 0.047uF in parallel. They make a 0.033uF but it hard 
to find. These values should be available at any electronics parts counter.

>> 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.
>>     
>
> As a rule if you have two identical devices with identical remotes you
> will need two independent transmitters. There are a SMALL number of
> exceptions out there. I have a JVC VHS VCR that is one of the few
> exceptions. The JVC was designed so that you could set-up the VCR / IR
> remote so you could have two of that model VCR in the same room
> controlled independently. That VCR is very much the exception to the
> rule.
>
> Sounds like you may want to go with one of the short range
> transmitters and then tape the IR transmit LED right over the device
> sensor.
>
>   
>> Thanks
>>
>> Bert
>>     
>
> Colin McGregor
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>   



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