Using ADS1298 with active electrodes

DBour

Other Parts Discussed in Thread: ADS1298

Hi,

I am trying to make the ads1298 evaluation board to work with active electrodes.

I try to do that for an emg application so I bypass the dummy connector and connect the 2 differential signals of the electrodes on JP33.

For the DRL I'm using a passive electrode and I connect it on JP1 on the side of DRLOUT.

I supply the buffers of the electrodes from a 5V TP and a ground TP from the board.

When I connect the board to the power supply and before connect the active electrodes to their power supply from TP there are some LEDs that turn on. When I, subsequently, connect the TPs to the electrodes' supply, the LEDs turn off and the board doesn't seem to work.

Do you see any problem with these connections?

over 10 years ago

0 Brian Pisani over 10 years ago

TI__Mastermind 38745 points

Hey Dbour,

What is the rated current consumption of the buffers you are using and how many of them are you using? It could be that you are overloading the 5 V power supply which comes from the MMB0 board.

Regards,
Brian Pisani

0 DBour over 10 years ago in reply to Brian Pisani

Prodigy 90 points

I am using two of these www.olimex.com/.../open-source-hardware for the differential signal and this www.olimex.com/.../open-source-hardware  for the DRL.

It says that the suppy current is 200uΑ.

0 DBour over 10 years ago in reply to Brian Pisani

Prodigy 90 points

I am using 2 of these www.olimex.com/.../open-source-hardware for the differential signal and this www.olimex.com/.../open-source-hardware for the DRL.
The datasheet writes that each of the 2 amplifiers has supply current of 200uA.

0 Brian Pisani over 10 years ago in reply to DBour

TI__Mastermind 38745 points

Hey DBour,

It looks like the current would only be a few milliamps. However, TI cannot support the unintended use of the evaluation board so you might be "on your own" in terms of determining what is wrong and how to fix it. My opinion is that the current draw is somehow getting too high for the board to handle and a good place to start might be measuring the current leaving the board and comparing it to a calculated value.

Regards,
Brian Pisani

0 Evert Dekker over 10 years ago

Prodigy 140 points

Don't think you need to connect the power for the active electrodes to 5V & gnd, but that depends on how you configured the analog domain of the ads1298.

Myself work with active electrodes from Plessey and using the +2.5v and -2.5v for the powering the electrodes.

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Using ADS1298 with active electrodes