EEG-SMT noise

[gustux]

Hi again,

Now i tried with the AE, using only CH1, and nothing... touching or not touching the USB case is the same. I switched to CH2 and just the same too.



I forgot to tell you that i did the same with CH2 using PE as before, and i got the same results as in CH1: touching the USB case reduced the noise.

Greetings,

Gustavo

[LubOlimex]

Hey Gustavo,

It seems that there is a hardware problem on channel 1, since when there are no electrodes you should see a flat line on the Electric Guru.

We recognized the problem. Penko - the creator of the device inspected the diagrams provided and came to the conclusion the operational amplifier on channel 1 is probably damaged! How did it happen is another question. Now you have two options either to return the device for a repair noting the warranty info below and mailing info@olimex.com; OR repair the device yourself.

A note if you try to repair it yourself (which I do NOT recommend) - before trying to change the operational amplifier U5 (INA114BU/1K) it is a good idea to shortcircuit around R36 (you place tweezers on both sides of R36) and holding them there check if the line seen on channel 1 becomes flat. It is extremely important that you are shortcircuting R36 (not something else). If the line becomes flat it is 100% the operational amplifier U5 that needs a change. If the line is still showing activity, then the problem would provide to be more difficult to solve.

Here is the warranty info:

• Warranty and returns:
  
  Our boards have lifetime warranty against manufacturing defects and components.
  
  During the development work it is not unlikely that you can burn your programmer or development board. This is normal, we also do development work and we had damaged a lot of programmers and a lot of boards during our daily job so we know how it works. If our board/programmer has worked fine then stopped, please check if you didn't apply over voltage by mistake, or shorted something in your target board where the programmer was connected etc. Sometimes boards may be damaged by ESD shock voltage or if you spill coffee on them during your work when they are powered.
  
  
  Please note that the warranty does not cover problems caused by improper use, short-circuiting, over-voltages, ESD shock etc.
  
  If the board have warranty label it should be not broken. Broken labels void the warranty, same apply on boards with intervention by customer like additional components soldered or removed components, such boards will be not subject of our warranty.
  
  If you are positive that the problem is due to manufacturing defect or component you can return the board back to us for inspection. When we receive the board we will check and if the problem is by us we will repair/replace free of charge, otherwise we can quote on the repair cost.
  
  Note that all shipping back and forth is to be covered by the customer.
  
  Before you ship anything back you need to ask for RMA.
  
  When you ship back please attach to it your shipping address, phone, e-mail, RMA# and a brief description of the problem. All boards should be sent back in antistatic package and should be well-packed to prevent damage during transportation.

I don't like the change in the channel 2 signal also, from my experience this might indicate a loose USB connector...

Also if you decide to return the device for repair inserted a printed copy of our forum discussion so we can repair the device faster.

Looking forward to your reply.

Best regards,
Lub/OLIMEX

[gustux]

Hi Lub,

I asked for the RMA, i prefer you to repair the device.

Thank you,

Gustavo

[Shizof]

Hi, the device came back from repair. I waited for 2,5 months and it is still the same. Noise, Noise, Noise!

[LubOlimex]

Hey Shizof,

With both electrodes again? Do you plug them firmly to the end? Is the DRL a passive electrode and do you hold it tight in your hand?

Are there readings when there are no electrodes put or it is a straight line?

Is there noise when performing EKG instead of EEG (electrodes placed in front of elbow area, DRL held in hand)?

Best regards,
Lub/OLIMEX

[Shizof]

Electrodes are plugged firmly. Ch1+, Ch1-, Ch2+, and Ch2- are active electrodes and DRL is a passive electrode. Same as before. When no electrodes are plugged in, it shows straight line. When I plug them in, they show constant noise. Nothing I do changes it. I hold the DRL in my hand, or leave it be, I place active electrodes on my head, or leave them be, there is always noise. I even tried them on my hands, arms and chest. I tried with all of the active electrodes and in different channels.

[LubOlimex]

Hey Shizof,

If the device was repaired then we have tested the EEG-SMT with an extra round for testing compared to rest of the EEG-SMTs. It is close to impossible for the device to be faulty again on arrival.

I am running out of ideas but:

1. Maybe some of your home equipment causes this interference. Some RF devices in close proximity might be the cause for this behavior.
2. Maybe your USB port/hub is damaged or faulty. Or your USB cable is too long and of poor quality.
3. Maybe there is some general problem in your software installation - please follow the instructions in the manual blindly.

I really have no clear idea what might cause the problem. If you wish to discuss the matter further please contact info@olimex.com .

Best regards,
Lub/OLIMEX