A twisted tale about a logarithmic relay attenuator

[Erlend Sæterdal]

I am interested in the volume control but I think the impedans is all too low for my purpose.

[Beefy]

Originally Posted by PB2

I know that this post is old but I'm looking at LOG attenuators and just wanted to offer a comment.
While the individual spec for the I/O pins above is correct, the absolute total for the PIC16F685 PIC
is 200 mA for all the ports. Your calculation:
20mA * 14 (all on) = 280mA........

So just to confirm what is being said here (and in Brian's original post three years ago), a balanced Joshua Tree would draw over 0.5A of current?

[MikeBarton]

Originally Posted by Beefy

So just to confirm what is being said here (and in Brian's original post three years ago), a balanced Joshua Tree would draw over 0.5A of current?

for the relays (there are 8 per JT and for balanced mode you will need 2JT's), the calculation would be:

5v / 237ohms = 21mA * 8 relays * 2 JT's = 0.33A

This is ofcourse a worse-case scenario, so 0.5A is in the right ball-park.

Originally Posted by sjalloq

I was planning on using my own encoder along with MCU board. If I want to integrate it with your relay driver board what do I need to know?

as mentioned, you need to drive the relays to ground using a ULN2803. This sinks all the current so your pic won't melt
Coupled to a 74HC595, the code to control a JT (using SPI) is surprisingly simple.

Mike

[BrianDonegan]

We use I2C rather than SPI, but, same difference. It's pretty simple. The trick is the hysteresis and averaging to prevent constant value changing.

[MikeBarton]

Originally Posted by BrianDonegan

We use I2C rather than SPI, but, same difference. It's pretty simple. The trick is the hysteresis and averaging to prevent constant value changing.

Brian
I would assume though that you use the hysteresis averaging because you are using an analogue pot, if sjalloq wants to use an encoder instead, then I don't believe this is an issue.
Mike

[BrianDonegan]

Originally Posted by MikeBarton

Brian
I would assume though that you use the hysteresis averaging because you are using an analogue pot, if sjalloq wants to use an encoder instead, then I don't believe this is an issue.
Mike

Correct.

[Keyoke]

Hate to revive an already lengthy post - but is there a 'fixed' schematic available? I didn't see one on the twisted pear site, and the ZIP (on page 4 or 5 i believe of this thread) is no longer a valid link...

[thor2]

Originally Posted by Hurtig

Cut the crap!! Software isn't my business! My main focus areas are:
- Digital to analog conversion (Which was my special during my education)
- Analog electronics (Also my special)

I know your special is more like this: http://web5687.web04.talkactive.net/...bforforamp.jpg

I am more into making electronics like this: http://img522.imageshack.us/img522/7730/pict2819vm3.jpg

For those who don't know Erlend Sæterdal, please feel free to ask me. His intentions isn't what they look like

But let's have some of the users of Diyaudio decide... Guess you have to make a bunch of fake profiles, to wote for you (Like all the other forums).

http://web5687.web04.talkactive.net/...bforforamp.jpg
There is no reason to laugh about this Hurtig.
Printed on the front plate is a completely full volume with the remote control: volume, phase switch, mute, four memories for volume setting , input select, max output setting, sleep timer, etc.
perhaps it is not so nice, but it is far above your level,
A closer look here:
http://tkhifi.homepage.dk/javapro/Ir_system1_3.jpg
It is built around an AVR controler.
and the sound of this preamp is fabulous

[novec]

Is the firmware posted anywhere?

[Erlend Sæterdal]

Originally Posted by Hurtig

Cut the crap!! Software isn't my business! My main focus areas are:
- Digital to analog conversion (Which was my special during my education)
- Analog electronics (Also my special)

I know your special is more like this: http://web5687.web04.talkactive.net/...bforforamp.jpg

I am more into making electronics like this: http://img522.imageshack.us/img522/7730/pict2819vm3.jpg

For those who don't know Erlend Sæterdal, please feel free to ask me. His intentions isn't what they look like

But let's have some of the users of Diyaudio decide... Guess you have to make a bunch of fake profiles, to wote for you (Like all the other forums).

????????????????????????????