Design Con 2015
Breaking News
Comments
Newest First | Oldest First | Threaded View
Page 1 / 2   >   >>
Rocket_G
User Rank
Rookie
re: X-rays and Photovoltaics
Rocket_G   12/30/2010 1:19:49 AM
NO RATINGS
Thanks Parity, ESD-protective encapsulation sounds really interesting. At what airspeed does triboelectric charge become significant? We would need something in liquid thermoset form that doesn't darken under UV (sunlight).

parity
User Rank
Rookie
re: X-rays and Photovoltaics
parity   12/29/2010 6:00:32 AM
NO RATINGS
Rich, to break this down to a finer level, 1) Do any of your tags work reliably time after time or do they all fail intermittently? Design issue? 2) If voltage spikes are suspect, inserting a zener diode in the circuit might be an interesting design revision. 3) Going back to electrostatic discharge, if your tags are encapsulated in any non-conductive plastic package like polycarbonate, they will develop charges on the order of 3-5 KV just from air friction leading to ESD events. Using PEEK or similar conductive plastic will dissipate charge collection and ESD events.

sharps_eng
User Rank
Rookie
re: X-rays and Photovoltaics
sharps_eng   12/24/2010 10:40:09 PM
NO RATINGS
Since the tags fail during deployment could we be seeing SEU problems due to solar radiation? What altitudes are you logging among similar tags that survive? It also is possible that your stripped-down ultra-light design allows more exposure to radiation than ordinary enclosures.

Jagdish Bisawa
User Rank
Rookie
re: X-rays and Photovoltaics
Jagdish Bisawa   12/24/2010 7:21:15 AM
NO RATINGS
Glad to know that Rich ! Would you also post the results of your findings once you are through with them ? It would be an interesting lesson for the design engineers around.

Rocket_G
User Rank
Rookie
re: X-rays and Photovoltaics
Rocket_G   12/23/2010 3:10:07 AM
NO RATINGS
Actually we're hoping for some help from the TSA folks at the airport across the street :-)

Rocket_G
User Rank
Rookie
re: X-rays and Photovoltaics
Rocket_G   12/22/2010 3:51:29 PM
NO RATINGS
Thanks, zman - the output of the PV cell goes through a 3V LDO regulator before going anywhere else, to prevent overcharging the battery.

zman_tekinsil
User Rank
Rookie
re: X-rays and Photovoltaics
zman_tekinsil   12/22/2010 3:23:21 PM
NO RATINGS
The cell is loaded during transit. With X-Ray this may "perhaps" lead to permanent traps that "may affect" the light to electricity conversion efficiency. Also the 0 instead of 1 logic you mensionned may be stuck bits that can be also due to ESD damage internally in addition to the I/O. Side question since the Voc is 4V, I assume the lithium battery is at least 2 diodes voltage-drop below the cell Voc?

zeeglen
User Rank
Blogger
re: X-rays and Photovoltaics
zeeglen   12/22/2010 2:15:53 AM
NO RATINGS
"these failures are observed after they've been in use" Possibly moisture getting into them? How are they sealed? Amendment to previous test - immerse some devices in salt water while at the beach. Your downhill ski idea is also a very valid test for simulating the shock and temperature extremes of a bird in flight.

Rocket_G
User Rank
Rookie
re: X-rays and Photovoltaics
Rocket_G   12/21/2010 11:46:01 PM
NO RATINGS
The PV cell Voc is 4V, Isc is 50 microamps. The cell is loaded during transit. A diode on the output of the LDO prevents reverse current flow through it. Checking output shorts and opens postmortem is a good idea. Thanks!

zman_tekinsil
User Rank
Rookie
re: X-rays and Photovoltaics
zman_tekinsil   12/21/2010 2:40:46 AM
NO RATINGS
You may have several problems that occured durang the cicuit build-up! ESD may be one of the culprits. You maybe able to see the I/Os quality with a voltmeter. ESD may create a short (metal melt from excessive zap). If that the case your data output maybe shorted after the ESD event. As for the X-ray, silicon based PV may survive X-ray pulses if not loaded. I am not sure what you have!. I assume the PV is not loaded (to generate electricity) during transit from FedEx for instance. Finally what is the output voltage spec of the PV (Open circuit voltage Voc, and other!). That diode may act as back to back scheme limiting current flow to the LDO!

Page 1 / 2   >   >>


Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

Book Review: Deadly Odds by Allen Wyler
Max Maxfield
8 comments
Generally speaking, when it comes to settling down with a good book, I tend to gravitate towards science fiction and science fantasy. Having said this, I do spend a lot of time reading ...

Martin Rowe

No 2014 Punkin Chunkin, What Will You Do?
Martin Rowe
Post a comment
American Thanksgiving is next week, and while some people watch (American) football all day, the real competition on TV has become Punkin Chunkin. But there will be no Punkin Chunkin on TV ...

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
13 comments
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Martin Rowe

Book Review: Controlling Radiated Emissions by Design
Martin Rowe
1 Comment
Controlling Radiated Emissions by Design, Third Edition, by Michel Mardiguian. Contributions by Donald L. Sweeney and Roger Swanberg. List price: $89.99 (e-book), $119 (hardcover).