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FS: R-2R attenuator, source selector and I2C controller PCBs

OlegSh

Member
Paid Member
2010-12-01 11:00 am
Germany
Hi,

I have some leftover PCBs for R-2R attenuator, input selector and complementary I2C controller. They have been designed for the arduino controlled passive attenuator with source selector. The dedicated thread is here. All works as intended in my home audio system.

R-2R board:
The R-2R board is similar to many others. The main difference is that it has mute relay at the output which allows pop free operation via mute-before-switch sequence when many relays switch at once (e.g. 0001111 ↔ 0010000). I2C controller can be connected to the R-2R board using flat cable. If no power is provided the board is in mute state (see attached schematic for more details). The GNDs of two channels are not connected by default but the solder jumper is available near the outputs for common GND connection. All SMD resistors forming the R-2R network are 1206 size, all others are 0805. Mouser BOM for the attenuator board is here. Note that resistors are not included in the BOM since their selection depends on the desired impedance and precision.

The bare board images (top and bottom) and the example of an assembled board are attached.
Board size is ~4x10 cm. Mounting holes are on the 10 mm grid.

Input selector:
It has 4 dual inputs and can be controlled by the I2C controller board or by the mechanical rotary switch. Each input has resistor (0805 size) to GND if it is not selected. The resistor is disconnected once the input is selected. The GNDs of two channels are not connected by default but the solder jumper is available near the outputs for common GND connection. Mouser BOM for the input selector board is here.

The bare board images (top and bottom) are attached.
Board size is ~4x6 cm. Mounting holes are on the 10 mm grid.

I2C controller:
The board is built around the MCP23008 IO expander IC with the ULN2803 as the relay driver. The I2C address can be selected using three way DIP switch. Pull-up resistor pads (0805 size) on all relevant pins are provided. One board can control one R-2R attenuator or two input selectors. The board is designed to operate from 5VDC supply. Mouser BOM for the I2C controller is here.

The bare board images (top and bottom) are attached.
Board size is ~4x5 cm. Mounting holes are on the 10 mm grid.

Better quality pictures of assembled boards are in post #14.

Price: SOLD (bare board, no parts)
Payment by paypal.
Buyer pays paypal fees and shipping.

You may also be interested in Arduino Nano interface PCB designed to control the attenuator, and a small power splitter PCB to power all your peripherals.

PM if interested.

Regards,
Oleg
 

Attachments

  • R-2RAttenuator.jpg
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  • R-2RAttenuatorSch.png
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  • R-2RAttenuatorAssembled.jpg
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  • InputSelector.jpg
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  • I2Ccontroller.jpg
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Last edited:

OlegSh

Member
Paid Member
2010-12-01 11:00 am
Germany
I decided to sell one set of modules that I built. The R-2R attenuator and input selector are mildly used.

Brief description:

The R-2R attenuator uses 0.1% precision Susumu 1206 resistors and is configured for 10k constant input impedance. I skipped one relay since I realized that I did not need an extra attenuation step. In the current configuration the board provides 63 dB of attenuation in 64 steps (1dB steps using 6 relays) plus mute. It has 10k5 termination resistor which is tuned for 200k input impedance of the following stage (used it in front of B2 buffer).

The input selector is just that, an input selector (see pics).

Both R-2R attenuator and input selector are coming with the dedicated I2C controller.

Prices for assembled boards (you will get what you see on the dedicated picture):

R-2R attenuator with I2C controller: 45 Euro
Input selector with I2C controller: 25 Euro
or make me an offer.

Payment by paypal.
Shipping is around 8~16 Euro (registered). I'll provide exact shipping costs to interested buyer depending on location.

To drive the boards I can also offer an assembled Arduino Nano interface board (see the link in my signature).

Regards,
Oleg
 

Attachments

  • R-2R.Attenuator.Top.jpg
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  • R-2R.Attenuator.Bottom.jpg
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  • Selector.Top.jpg
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  • Selector.Bottom.jpg
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