I am Sergi and I have a project in which I need to control the resistance values of a potentiometer digitally. This potentiometer has to reach up to 1MOhm. I have found this potentiometer AD5242BRUZ1M, which meets the requirements for my project. I have also read in the datasheet that it can be controlled with software thanks to the evaluation board EVAL-AD5242DBZ.
I therefore have a number of questions:
Is the analogue output (resistance value) of the potentiometer isolated from the control board?
Is there a 1Mohm module for the evaluation board?
When I buy the board, do all the modules come with different resistance values, or do I have to buy them separately? I can’t find any 1MOhm modules.
If there are no 1MOhm modules for the evaluation board, can I still control it with the board?
Can I control it with a microcontroller via the I2C protocol?
The evaluation board is designed for interfacing to a PC running Windows.
With a device as simple as an I2C digital pot, I’d use and adapter PCB to make the raw part breadboard compatible and then wire it right up to the target microcontroller.
First, an important note about the EVAL-AD5242DBZ – it requires a control board in order to be controlled via their software on a PC. According to the User’s Guide documentation, either of the following control boards are compatible:
As of the time of this posting, only the EVAL-SDP-CS1Z is in stock.
To answer your questions directly:
No, the integrated resistor of the pot is not isolated from the control board. It might be possible to do so by using an I2C isolation chip and providing a separate isolated supply for the daughterboard.
No, the daughterboard comes populated with the 10K version of the AD5242. ADI did not produce a 1M version of the daughterboard. To use the 1M version on the available daughterboard, you would have to de-solder the 10K version and replace it with the 1M version (AD5242BRZ1M). Unfortunately, the footprint on the daughterboard is for an SOIC package, but the only version of the 1M part currently in stock is the TSSOP version (AD5242BRUZ1M).
No, only the 10k version comes with it, and no other version is made (see previous reply for options).
It might be possible to run wires from the test points on the motherboard to control an off-board device.
I don’t think you could control the module via an external microcontroller while the daughterboard is attached to the motherboard, but you should be able to control it if removed from the motherboard.
I really appreciate your help!!
Do I need one I2C isolation chip for every Potentiometer?
Because I want to control multiple Digital Potentiometers at the same time. If I need 3 variable resistors(1M), would be possible to connect 3 Potentiometers (AD5242BRZ1M) with an I2C isolation chip to one Microcontroller via I2C(for example an Arduino)? Of course with a separated isolated supply.
Yes, you should be able to communicate with up to four AD5242BRZ1M devices with a single I2C isolation chip by configuring the address pins of each chip (AD0 and AD1) to different values.
Upon further inspection, of the I2C isolation parts linked above, only the ISO1540QDRQ1 and the SI8600AC-B-IS are valid options. The other did not have the same capability.