Digital attenuator without PIC

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I could not find any relays based attenuator without using PIC microcontroller so I made one.
It's based on CMOS logic IC's and I could acheive maching between absolute dB and both channels better than 0.1 dB.
Total cost is fraction of elma/dact based attenuators which have only 24 positions.
I've used 6 DPDT relays to get 64 steps but it can be easily expanded to 7 or 8 bits (128 or 256 steps) by adding one counter, one 7-segment display and resistors/relays.
More relay boards can be added for multi-channel control.
If somebody from Dubai or UAE is interested in building one, I would be glad to hear from them so we can organise group buy for precision resistors.
 

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  • attenuator counter schematic.pdf
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  • attenuator relays schematic.pdf
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  • attenuator.jpg
    attenuator.jpg
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Pure logic is nice, but there are Arduino boards - you can easily program them without extended programming skills (no need to program like MCUs - just a few functions in main() {...}, and that's all you need.

By the way, no need to have precise resistors from E192 range - you can get precise values from paralleling/serializing E24 resistors range.
If you need some precise values, i can calculate them for you, and give them in form:
12470 = 470+12000
557 = 680|3100
I've made some simple SQL query to do such calculations, all you have to input is just required value, and preferred resistors count (could be calculated up to 3 resistors in parallel/series)
 
I still have to learn PIC programming - it's on my list amongst many other projects.
I've got small Proxxon lathe and I made the knob and the spindle which is running on 2 roller bearings.
Attached are some more photos.
 

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  • counters brd tracks.jpg
    counters brd tracks.jpg
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  • counters brd.jpg
    counters brd.jpg
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  • knob + sensors.jpg
    knob + sensors.jpg
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