Re: [Openeeg-list] DRL tested and working

[Andreas R. <and...@st...>]

Hi Joerg,

that bandpass-DRL you are talking about sounds interesting, so please have a go at it! (Simulate it anyway) I assume it would make it possible to have capacitors on the inamp inputs?

> To verify this, I have just reactivated my comEEG:
> In fact the INA114AP does not have the common mode offset voltage of the AD620:
> 0 mV offset at the gain setting ports.

If you have the AP version I'm quite certain the BP version will work too, since it is the "prime-grade"(i.e more expensive). From the TI-website: INA114AP: $3.59/1000pcs, INA114BP: $5.41/1000pcs.

Your bandpass-DRL would then be suitable as an improvement for the next major revision of the amplifier - because it would lower the cost.

However, I suspect people are eager to get started here, and a new DRL would mean longer delays...what do you think?

Anyway, these are the preliminary changes for ModularEEG v0.04-RC1, based
partially on our previous discussions:

Analog part:

* Switch to INA114BP (or AP)
* Try to squeeze in a third trimpot for the DRL, just in case.
* Add a 2nd order LP-filter to second gain stage in preparation for switched-cap filters if anyone wants to add some.

Digital part:

* Remove the secondary 5V voltage regulator (IC106) to get more room for the following two changes:
* Add a schottky diode in series with the power input to prevent damage from a reversed power source.
* Add a power bleeder-resistor/LED.
* Move the two resistors needed in the programming cable, to the digital PCB.
Is there a reason for them to be in the cable and not on the PCB?

By the way, the quiescent current consumption is 70mA with the DRL patch (65 without).
A regular rechargeable 9V battery would then last 1.5 - 2 hours. I suppose if someone decides to build a 6-channel unit, they would have to run it on a 12V lead-acid battery or a wall-wart.

Regards,

Andreas