ZEO Replacement heaband problems

I developed a replacement sensor fro my zeo that snaps in place. I originally used an old headband and added snaps to it.

I noticed that the resistance I measured from the snap to the sensor using the old headband was about 45 - 50 ohms. I figured that some of that was the plastic snap and some may have been that I was re-using some ofhte worn out fabric to conduct the signal.

So, I made up a replacement backing. The resistance from the snap to the sensor on the replacement was less than 3 ohms. I figured that this was a good thing.

BUT

When I tried the new backing, I got strange readings on the ZEO. The first night it recorded several ours of WAKE. Tehn it went to a more normal pattern. But it ended up recording 17% deep sleep. Using the old headband, I was only getting about 9 - 12% deep sleep. When I looked at the text file fro ZEO Viewer, the impedance numbers

On the second night on the new backing it recorded all night as all wake. It did not even write a record.

Here is some of the impedance data and other data on the nedw backing vs the old backing. I removed the 00000 data from when it was charging to make the data easier to read.

Record_write time: 03/22/2015 09:19 - new backing

Headband_impedance: 255 0 0 0 0 222 145 229 176 250 158 159 121 114 115 115 115 115 115 115 115 114 114 116 115 124 121 117 115 123 128 134 133 126 161 133 118 121 117 117 146 128 129 125 130 122 119 117 120 118 132 137 120 126 120 124 124 123 121 124 123 118 118
Headband_Packets: 2 0 1 0 0 4 5 4 4 3 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 4 5 5 5 5 5 5 5 5 5 5 5 5 4 5 4 4 4 5 5 4 5 5 5 5 5 5 5 5 5 4 4 4
Headband_RSSI: 18 0 0 0 0 5 5 8 10 10 10 11 11 10 6 3 0 0 10 29 30 30 24 21 17 20 10 7 3 22 29 29 29 19 18 20 21 2 246 10 18 17 10 9 7 7 4 3 7 10 3 11 1 15 14 13 13 11 5 12 14 20 12


date 03/21/2015 - old backing
Headband_impedance: 124 124 127 125 125 255 212 207 168 169 255 210 125 117 117 120 179 117 118 117 198 0 118 119 119 117 118 117 118 117 117 121 128 117 119 119 118 120 119 118 117 117 162 121 125 120 122 144 118 117 118 122 118 140 153 130 132 136 190
Headband_Packets: 4 4 5 4 6 3 5 5 5 4 1 1 4 4 4 4 4 2 5 5 4 0 4 4 4 5 4 4 4 4 4 4 4 4 4 5 5 4 4 4 4 4 4 4 5 5 5 5 5 5 5 4 5 5 4 4 4 4 6
Headband_RSSI: 4 16 16 19 252 91 8 2 19 17 15 12 253 254 252 252 18 18 17 17 18 0 5 1 244 243 253 0 244 243 243 246 0 249 252 20 20 20 3 2 3 3 12 9 12 9 4 2 247 247 246 254 16 12 252 254 247 244 10


I went back to an old headband that I had taken apart. The resistance throught the snap to a piece of protected cloth is right at 30 ohms.


For now I will continue to use the modified headband that gave reasonable readings. I may try making a new hacking with snaps, but add in a 30 ohm resistor between the snap and the sensor and see what happens. If nothing else, I am curious.

It could be that the processor was designed to expect some resistance in the headband and is trying to compensate for it.

One reason I made the backing is hat I was going to post an indestructible on how to make the replacement sensor and wanted to include how to make a new backing just in case someone did not have an old headband. I do not wantto do that until I have this figured out.

I am willing to send out the one I made to someone else to test. It will have new unused sensors. The backing will have been used twice, but it does not really touch the head.

If the person who does the testing will send me one of their used headbands, I will add snaps to it and send it back to them, then they can switch the sensors to their own backing if there is a problem.

I have had a few teething problems wit the replacement pads I made. You have to pull off the middle sensor to charge the unit. I used a double stick tape on the first ones that got gooey after a few weeks. I am testing a new sensor that uses the stitch witchery heat setting material used for sewing. So far that is working fine. But it is still the early testing days.

I ONLY HAVE ONE MADE UP.
Send me a PM if you are willing to test it for me.

THE REAL PURPOSE OF THIS POST IT TO ASK:

Has anyone else made a replacement headband and had similar problems?

It cold be that I have a bad sensor module.

Ted, using a very cheap ohmmeter, on a sensor that's been in use for several months, I get a reading of less than 10 ohms from each male snap to its corresponding cloth surface where it would be placed against the skin. My guess is that this path ideally would offer no resistance, 0 ohms.
I've seen erratic readings such as you describe when the snaps haven't been properly seated (male sensor into female transmitter).
In the past, I've been unable to use the impedance readings to determine sensor state. I've not seen an expected correlation between age of the sensor and impedance readings.

Thanks Jay.

I will try it gain tonight, I will aslo retest the readings. I have a few different meters and several headbands.

More later tonight or tomorrow.

UPDATE:

When I made the backing, I "wired" it wrong. I reversed where the center and end sensors are connected. I made a new backing (actually 2 of them, I got the second wired wrong also..... )

I will try it tonight and see how it goes.

I double checked several of the headbands that I have and none of then had a reading below 30 ohms on either of 2 meters I have. I tested between the snap and some silver material that was protected under the plastic. It may be that the snaps on my headband are all older. I am glad to hear that a newer sensor has a lower resistance reading. Maybe I can chart resistance over time and use this as an indication of wear.

On my new backing, the resistance between the snap and the sensor is 0.9, 0.5, and 1.3 ohms on a digital meter. I also got less than on ohm on an analogue meter.

I will update this tomorrow. I hope that it is as simple as me making the strap wrong......

I found a second problem with my backing that was causing intermittent connection to the sensor. The KAMSNAPS snaps that I was using were a loose fit in the sensor.

When this first started, I got several samples from 3 snap manufacturers. The ones from YKK snaps fit best into the sensor. They make a stainless steel snap with a post (vs 3 prong setting) part number 879-0-303 for the snap and 930-0-303 for the make snap fit very well in the sensor.

The only problem I have with this one is that the female snap in only available in a 3 prong ring setting. It works very well with itself, but if you use another brand snap (for example you want to use it with disposable eeg pads) it can take a set and then do not grip others well.

The YKK brand did say that they sell to a lot of eeg pad manufactrers, and when I measure their snaps, their match the dimensions from two different eeg sensors that I was trying. One a normal eeg pad and one was from a ekg pad.

For a a more robust female socket I found that the "fashin 14" snap from KAMSNAPS is the most robust. It has a female snap that can be set with a post that has an actual spring as part of the snap. Tis is more forgiving if you put different sized snaps into it. (fro an eeg sensor.... or a home made sensor).

BUT the male snap in that range is a loose fit into the sensor. I think that this was causing the connection to be ost with the sensor.

So last night I made up a new backing apad wit the YKK for the part that snaps into the sensor and the fashion 14 for the part that accepts the sensor pads. This worked well last night. The machine quickly synced, and there were no gaps in the data this morning.

I did find one last disappointing item. When I made up my last set of sensor pads, I used a heat setting tape from the fabric store. It needed a medium hot irn to set and he sensor fabric changed color. Someone else emailed me a sheet that they got with their fabric that had a do not iron warning. I got hold of the manufacturer, and they said that I probably ruined the fabric wit the heat. They said that the mad heat was 60-90 degreed C. So, I need to look for a new way to make up the sensor.

A low temp hot melt glue should be alright, or I may have to revert to sewing it. I had tried double stick tape, but it interacted with the oil from the skin and got gooey. I have some medical grade tape from 3m, some of which is approved for making medical devices for implanting. I may give it a try, but I have not seen the price for it yet. I imagine it will be expensive.

I guess the glue gun will come out this weekend and I may try sewing some up as well. If I can sew it on 1 side, and maybe zig zag right at the edge of the foam it might work.