Hack Notes CVA 090616 - Revision history

SpammerHellDontDelete: /* Pillow Material Sourcing */

2009-06-17T01:04:06Z

Pillow Material Sourcing

← Older revision		Revision as of 18:04, 16 June 2009
Line 51:		Line 51:
	Eric did some searching for a suitable "velcro-compatible" pillow material. I found some great stuff called "Display Loop", it's "100% Nylon Fabric with Polyester Foam Core and Nylon Tricot Backing". It is the "hook" half of velcro. Unfortunately, I've only been able to find it in 60" bolts, minimum 5 yards - comes to about $60, plus enormous shipping no doubt.		Eric did some searching for a suitable "velcro-compatible" pillow material. I found some great stuff called "Display Loop", it's "100% Nylon Fabric with Polyester Foam Core and Nylon Tricot Backing". It is the "hook" half of velcro. Unfortunately, I've only been able to find it in 60" bolts, minimum 5 yards - comes to about $60, plus enormous shipping no doubt.

	My favorite supplier so far is ~~<a href="~~http://www.buyhookandloop.com/DisplayLoop.asp">Buy Hook and Loop~~</a>~~, but you can also get some at <http://www.levittextiles.com/veltex.html">Levitt Textiles~~</a>~~, and at ~~<a href="~~http://www.hookandloop.com/site/department.cfm?id=sewn_velcro_straps&level=14293">Hook and Loop~~</a>~~ (which by the way offers custom sewing into straps - looks familiar!). I'm going to call Buy Hook and Loop at 781-767-4511 sometime soon, and ask if we can get it in 3/4" strips/ribbons, and ask about samples.		My favorite supplier so far is [http://www.buyhookandloop.com/DisplayLoop.asp Buy Hook and Loop], but you can also get some at [http://www.levittextiles.com/veltex.html Levitt Textiles], and at [http://www.hookandloop.com/site/department.cfm?id=sewn_velcro_straps&level=14293 Hook and Loop] (which by the way offers custom sewing into straps - looks familiar!). I'm going to call Buy Hook and Loop at 781-767-4511 sometime soon, and ask if we can get it in 3/4" strips/ribbons, and ask about samples.

	[[Category:Sensebridge]]		[[Category:Sensebridge]]

SpammerHellDontDelete: /* Hack Notes, June 16th, 2009 */

2009-06-17T01:02:38Z

Hack Notes, June 16th, 2009

← Older revision		Revision as of 18:02, 16 June 2009
Line 45:		Line 45:

	The cost isn't so bad, but the total footprint for this stuff is pretty high. Also, the FTDI chip needs a pile of passives not listed here. I'm actually thinking these 3 on a sub-board would make a pretty sweet "expansion kit". But I can also make a "convenience" case for putting the charger / USB jack on the board. For 5ish bucks, people don't have to move the batteries back and forth every night, just jack it into their computer. That makes the device a lot more usable.		The cost isn't so bad, but the total footprint for this stuff is pretty high. Also, the FTDI chip needs a pile of passives not listed here. I'm actually thinking these 3 on a sub-board would make a pretty sweet "expansion kit". But I can also make a "convenience" case for putting the charger / USB jack on the board. For 5ish bucks, people don't have to move the batteries back and forth every night, just jack it into their computer. That makes the device a lot more usable.


			==Pillow Material Sourcing==

			Eric did some searching for a suitable "velcro-compatible" pillow material. I found some great stuff called "Display Loop", it's "100% Nylon Fabric with Polyester Foam Core and Nylon Tricot Backing". It is the "hook" half of velcro. Unfortunately, I've only been able to find it in 60" bolts, minimum 5 yards - comes to about $60, plus enormous shipping no doubt.

			My favorite supplier so far is <a href="http://www.buyhookandloop.com/DisplayLoop.asp">Buy Hook and Loop</a>, but you can also get some at <http://www.levittextiles.com/veltex.html">Levitt Textiles</a>, and at <a href="http://www.hookandloop.com/site/department.cfm?id=sewn_velcro_straps&level=14293">Hook and Loop</a> (which by the way offers custom sewing into straps - looks familiar!). I'm going to call Buy Hook and Loop at 781-767-4511 sometime soon, and ask if we can get it in 3/4" strips/ribbons, and ask about samples.

			[[Category:Sensebridge]]

SpammerHellDontDelete: /* Battery Messes Up Compass! */

2009-06-16T22:56:50Z

Battery Messes Up Compass!

← Older revision		Revision as of 15:56, 16 June 2009
Line 5:		Line 5:
	So apparently having AAA batteries next to the compass (we measured effects starting about 2" away) really distorts the reading.		So apparently having AAA batteries next to the compass (we measured effects starting about 2" away) really distorts the reading.

			<pre>
	reading real		reading real
	-37 135		-37 135
Line 17:		Line 18:
	323 495		323 495
	388 540		388 540
			</pre>

	Basically it imposes a ~~sinusiodal~~ distortion of about 50 degrees amplitude. But of course it's more complicated that just that. I tried to model an equation which would allow us to compensate for this distortion, but it would be very complicated. Also, we have no confidence that the distortion pattern will be constant enough for any "calibration" scheme to work well. Different battery types, different states of charge, etc will all make it read different.		Basically it imposes a sinusoidal distortion of about 50 degrees amplitude. But of course it's more complicated that just that. I tried to model an equation which would allow us to compensate for this distortion, but it would be very complicated. Also, we have no confidence that the distortion pattern will be constant enough for any "calibration" scheme to work well. Different battery types, different states of charge, etc will all make it read different. The compass chip has onboard calibration system as well, but (a) we don't have code to use it and (b) as before, calibration may not stay constant. Furthermore it would be extra work to flash the calibration unto all the compass chips before putting them in the kits...

	The ~~only solution is~~ to ~~get~~ the ~~batteries away from~~ the compass~~, or otherwise change~~ the ~~existing solution~~. ~~After some brainstorming, we settled on the idea of~~

			The only solution is to get the batteries away from the compass, or otherwise change the existing battery solution. After some brainstorming, we settled on the idea of moving the batteries to a closed enclosure on the other side of the anklet, and using barrel jack and wires to bring the power over:

			<pre>
	New battery solution:		New battery solution:
	SBH-431-1A-ND 3xAAA batt holder with cover, leads $0.75		SBH-431-1A-ND 3xAAA batt holder with cover, leads $0.75
	CP-M2509N-ND 2.5mm submini audio jack $0.38		CP-M2509N-ND 2.5mm submini audio jack $0.38
	CP3-1004-ND 2.5mm submini plug $0.76		CP3-1004-ND 2.5mm submini plug $0.76
			</pre>

	The old battery holder was $1.68, so actually this solution is only like 20 cents more.		The old battery holder was $1.68, so actually this solution is only like 20 cents more.

			An additional benefit of this is spitting up the considerable weight and bulk of this solution, balancing the armature out a little bit.

			==Onboard Charger Idea==

			<pre>
	Charger / FTDI chip:		Charger / FTDI chip:
	296-9320-5-ND 8DIP NiMH batt charger IC $2.13		296-9320-5-ND 8DIP NiMH batt charger IC $2.13
	WM17115-ND USB Mini Jack $2.19		WM17115-ND USB Mini Jack $2.19
	768-1011-1-ND FTDI programming chip $4.50		768-1011-1-ND FTDI programming chip $4.50
			</pre>

	The cost isn't so bad, but the total footprint for this stuff is pretty high. Also, the FTDI chip needs a pile of passives not listed here. I'm actually thinking these 3 on a sub-board would make a pretty sweet "expansion kit". But I can also make a "convenience" case for putting the charger / USB jack on the board. For 5ish bucks, people don't have to move the batteries back and forth every night, just jack it into their computer. That makes the device a lot more usable.		The cost isn't so bad, but the total footprint for this stuff is pretty high. Also, the FTDI chip needs a pile of passives not listed here. I'm actually thinking these 3 on a sub-board would make a pretty sweet "expansion kit". But I can also make a "convenience" case for putting the charger / USB jack on the board. For 5ish bucks, people don't have to move the batteries back and forth every night, just jack it into their computer. That makes the device a lot more usable.

SpammerHellDontDelete: New page: =Hack Notes, June 16th, 2009= ==Battery Messes Up Compass!== So apparently having AAA batteries next to the compass (we measured effects starting about 2" away) really distorts the readi...

2009-06-16T22:51:22Z

New page: =Hack Notes, June 16th, 2009= ==Battery Messes Up Compass!== So apparently having AAA batteries next to the compass (we measured effects starting about 2" away) really distorts the readi...

New page

=Hack Notes, June 16th, 2009=

==Battery Messes Up Compass!==

So apparently having AAA batteries next to the compass (we measured effects starting about 2" away) really distorts the reading.

reading real
-37 135
28 180
60 225
80 270
94 315
124 360
124 360
221 405
278 450
323 495
388 540

Basically it imposes a sinusiodal distortion of about 50 degrees amplitude. But of course it's more complicated that just that. I tried to model an equation which would allow us to compensate for this distortion, but it would be very complicated. Also, we have no confidence that the distortion pattern will be constant enough for any "calibration" scheme to work well. Different battery types, different states of charge, etc will all make it read different.

The only solution is to get the batteries away from the compass, or otherwise change the existing solution. After some brainstorming, we settled on the idea of

New battery solution:
SBH-431-1A-ND 3xAAA batt holder with cover, leads $0.75
CP-M2509N-ND 2.5mm submini audio jack $0.38
CP3-1004-ND 2.5mm submini plug $0.76

The old battery holder was $1.68, so actually this solution is only like 20 cents more.

Charger / FTDI chip:
296-9320-5-ND 8DIP NiMH batt charger IC $2.13
WM17115-ND USB Mini Jack $2.19
768-1011-1-ND FTDI programming chip $4.50

The cost isn't so bad, but the total footprint for this stuff is pretty high. Also, the FTDI chip needs a pile of passives not listed here. I'm actually thinking these 3 on a sub-board would make a pretty sweet "expansion kit". But I can also make a "convenience" case for putting the charger / USB jack on the board. For 5ish bucks, people don't have to move the batteries back and forth every night, just jack it into their computer. That makes the device a lot more usable.