Doug Self Preamp from Linear Audio #5

[Carl_Huff]

Yup,

I agree. Simple is the right answer.

[dine1967]

Finally, I have a working micro-controller doing all the remote duties - channel selection, mute, volume (motor pot) and a 3 second delay at startup. For mute and delay startup, I didn't populate any of the circuit on the selector board. I added a wire from the collector of the bottom transistor to the unused pin (#7) on the selector PCB. This is the ground of the output relays which the microcontroller would do the delay startup and mute tasks. For the channel relays, I had a problem since we are switching +12v on the selector PCB. I ended up building a transistor invertor (NOT gate) using NPN followed by a PNP transistor to give full +12v to the relay. If the selector PCB were switching grounds, one transistor or even a ULN2003 could have been used. The mute circuit is a standard NPN transistor driver as we are only switching grounds. For the volume pot, I used a h-bridge to drive it. The microcontroller will be using a separate 5V power.

The source code I modified can be found at : GitHub - gkiranps/gArduinoRemote
The program can be modified to be used with any remote you have lying around.
I still need to add either a encoder or switches on the panel for source selection.
I almost forgot, the preamp sounds great ! Thanks to Doug and Carl for making available such a beautiful design.


Thanks,
Dinesh

[fvzeppelin]

Hi Dinesh,


thank you for sharing your approach with us!
I am sure that both, wiring and the repo will be helpful for many people


Some thoughts (please keep in mind that I'm not a pro):

• I don't know how you provide the supply for the Arduino. But I guess that if you could hook the Arduino's ground to the 12V (not the 15V line!) line of the input pcb, you would get along with just one transistor per relay.
• Another approach would be to use optocouplers instead of transistors.
• Maybe you could use that jumper named "12V SW" on the input pcb for your mute switching. You wouldn't need to solder the jumper wire that you use for the mute control. But this line has 15V, so saving the jumper wire would cost 2 more transistors - maybe not such a good idea On the other hand, if you decide to use an ULN2003, because you hooked up on the 12V line with Arduino GND, then you have one of the Darlington's left over, anyway...

I guess, I would go for the optos. Or maybe Carl would be willing to provide a modder-friendly update of the input pcb which switches the ground lines of the relays...

[oodi]

Are boards available for this?

[Carl_Huff]

oodi said "Are boards available for this?"

oodi,

Please check your personal messages. I just sent you one.

[Preben]

Bummer.... I was eagerly awating your answer to oodi's question..... ;-)

[Carl_Huff]

"Bummer.... I was eagerly awaiting your answer to oodi's question..... "

Ha, ha ...

I still have a few. Personal message me if you want the details