School Book Advice

A friend asked me some advice on what books to get for school. Here is my school book advice:

I have thought a lot about books and tried various things. Here’s what I do these days.

I buy all the required reading at the very beginning of the semester from Amazon. I figure that I can sell it back on Amazon if I want to keep it and only lose a little bit. That strategy has worked out well… low stress and generally inexpensive. Only a few times have I been stuck with a book that has a new edition, thus devaluing my book greatly. I figure that if I am trying to save $100 by not getting a book, and that is getting in the way of a $70,000/year job, my priorities are in the wrong place!

To sell on Amazon: I generally match the lowest price and it usually sells within 2 weeks. I ship USPS “Media Mail” which is usually about $3-4 instead of $8-15 for Priority Mail. Pay for shipping online, wrap the package, then walk into the post office, CUT IN LINE, set the package on the counter and say “my package is all set. Thanks.”

After I’ve bought the book, I find a PDF version as a personal backup. I leave this on my computer, this has been very useful for me as I study during my long commute. There is some question as to the legality of having the paper book and a PDF backup but this definitely isn’t a settled matter.

Looking for a VHS player

Looking to use your VHS player. I’ve got some tapes but don’t know what’s on them. Could I come over and take a peek? Message me.

Protecting Children from Leaded Solder

In August, 2015, I wrote this policy for keeping children safe from lead poisoning in the electronics lab at The Crucible in Oakland, CA. It is a description of the problem, a well researched discussion, and a solution.

————–

 

Protecting Children from Leaded Solder at The Crucible

Policy Statement:

Due to the potential of lead intoxication, it is the policy of The Crucible to not allow persons under age 18 to use solder that contains lead for electrical connections. Lead-free solder performs acceptably with far less possibility of toxicity.

 

Background:

This document is directed at multiple audiences:

– to the organization so they understand the additional expenses of maintaining a lead-free environment.

– to faculty so they understand the reasons for the shift away from an easier-to-work-with material.

– to parents so they understand how we are acting to protect children.

 

Solder is used with soldering irons in the Kinetics and Electronics department to make electrical connections. Solder composed of tin and lead is long established as a well performing product, but the dangers of working with lead are also well known. Even small amounts of ingested lead can cause irreversible neurological damage, especially in children. Large international efforts have been implemented to reduce human exposure to lead. Notably, leaded paint and gasoline were banned in the U.S. in the 1970’s, the European Union banned lead in all electronics in the 2000’s, and California’s Electronic Waste Recycling Act of 2003 bans lead in some electronics.

 

Leaded solder remains legal and commonly used for electronics in the United States. It is generally understood that when leaded solder is used with proper precautions, it does not constitute a danger to the user. However, younger students may have trouble following these precautions and may put themselves at risk.

Important dangers for children using lead solder are:

– The difficulty of enforcing strict hand washing policies in a classroom environment with children

– The relatively high incidence of pica (habitual eating of non-foods) among children and the difficulty of recognizing this practice in the classroom

– The possibility of careless handling of solder by children

– The extremely long-term toxic effects of lead poisoning

– The low dose needed to reach toxic levels

Alternatives:

Lead-free solder is slightly harder to work with but the safety concerns far outweigh the time spent learning how to use the new material. Solder that is made with 96.5% tin, 3% silver, 0.5% copper is a popular substitute for leaded solder. Here is one vendor’s product: http://www.all-spec.com/products/KWLF27500.html and another http://www.techni-tool.com/488SO7871.  Solder made from 99.4% tin, 0.6% copper works almost as well as the tin-silver-copper solder and is less expensive. Other types of lead-free solder are also available.

Costs of switching:  

Tin/lead solder costs about $25/lb, tin-silver-copper solder costs about $50/lb, tin-copper solder costs about $35/lb. Both lead-free solders wear out the tip of a soldering iron in 1/3 the time as with tin-lead solder. A new tip costs about $2-10.

A summer of classes typically goes through 1.5 lb of solder and 5 soldering tips. So switching to lead-free solder might cost an extra $50 in solder and $50 in tips.

Research on Leaded Solder:

“Lead poisoning has been reported in children after a single ingestion… Pica is a very well identified risk factor of lead intoxication in children.”

– Sabouraud, S et al. Lead poisoning following ingestion of pieces of lead roofing plates: pica-like behavior in an adult., 46 Clinical toxicology (Philadelphia, Pa.) 267–269 (2008). http://doi.org/10.1080/15563650701639014

In the Sabouraud et al. article above, a case study described a woman with a single 6mm bullet lodged in her body. Her blood lead level climbed to dangerous levels over a few months. This implies that if piece of lead-solder was lodged in a student’s stomach, the negative consequences could be dramatic.

 

(paraphrased) A 45 year-old woman had lead shot pellet lodged in her stomach, probably from eating a hunted animal. Her blood lead level climbed to 550 μg/L before she excreted the pellet. There are several similar medical case studies described in this article.

– “Intoxication from an Accidentally Ingested Lead Shot Retained in the Gastrointestinal Tract” Environ Health Perspect. 2005 Apr; 113(4): 491–493. Per Gustavsson and Lars Gerhardsson. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1278491/#!po=25.4717

“one study showed that about 10% of children older than 12 years engage in pica”

http://www.academia.edu/202338/Pica_An_Update

“Pica is observed most commonly in areas of low socioeconomic status and is more common in women (especially pregnant women) and in children. To our knowledge, the prevalence of pica is not known. Numerous complications of the disorder have been described, including iron-deficiency anemia, lead poisoning, and helminthic infestations.”

– “Pica: Common but Commonly Missed” http://www.medscape.com/viewarticle/405804_1

The CDC recognizes that “[n]o safe blood lead level in children has been identified” and that a blood lead level above 5 micrograms per deciliter (µg/dL) should be treated.

http://www.cdc.gov/nceh/lead/

“…the average blood lead levels from 4 to 10 years had the strongest association with the adult full-scale IQ. For each 1 µg/dL average blood lead levels, the adult full-scale IQ deficit was about two IQ points.”

http://www.environmentalhealthnews.org/ehs/newscience/iq-effects-childhood-lead-exposure-persist-in-adults/

 

“Lead in the body comprises 2% in the blood (t1/2 35 days) and 95% in bone and dentine (t1/2 20–30 years). Blood lead may remain elevated for years after cessation from long exposure, due to redistribution from bone.”

– Gordon, J. N., Taylor, a., & Bennett, P. N. (2002). Lead poisoning: Case studies. British Journal of Clinical Pharmacology, 53(5), 451–458. http://doi.org/10.1046/j.1365-2125.2002.01580.x

“Early symptoms of lead neurotoxicity in both adults and children include irritability, headache, decreased attention span, memory loss, and low-level cognitive impairment… As childhood exposure increases, behavioral symptoms of impulsiveness, inability to follow sequences or directions, decreased play activity, lowered IQ. and poor attentiveness are seen at PbBs of 10-35 µg/dL. …  Recent studies evaluating the relationship between blood lead levels and neurobehavioral performance have shown evidence of effect at levels below 10 µg/dL -the current level considered excessive for pediatric exposure… [In one study] a significant inverse relationship was observed between blood lead levels and reading and math test scores and comprehension testing. The correlation was noted at levels as low as 2.5 µg/dL.”

– Patrick, L. (2006). Lead Toxicity, A Review of the Literature. Part I: Exposure, Evaluation, and Treatment. Alternative Medicine Review, 11(1), 2-22. http://europepmc.org/abstract/med/16597190

 

A cursory review demonstrates that ingestion (accidental or otherwise) of even a single grain-of-rice sized piece of lead solder could be dangerous for a child. A grain of rice weighs about 0.01 grams. A 0.01 gram piece of 60/40 Tin/Lead solder has about 0.004 grams of lead. That could raise the blood lead level of a 50 kg child by 8 µg/dL, higher than the current proposed actionable level of 5 µg/dL. Accidental ingestion of piece of solder the size of a grain of rice is extremely plausible when a child eats their lunch in the same clothes they solder in.

Concerning the Dangers of Solder Flux:

Another potential danger to soldering are the fumes from the flux. People exposed to flux fumes for multiple years in the workplace have developed asthma-like symptoms. The danger to students appears to be very small owing to the short duration of exposure. Additionally, research on this topic continues to be inconclusive, even for people that have worked for many years with solder. No particular flux has been singled out as more toxic than another. As more research is found on this subject, the policy will be reviewed.

 

Research on Solder Flux:

 

“Research on the respiratory effect of exposure to solder fumes in electronics workers has been conducted since the 1970s, but has yielded inconsistent results. The aim of this meta-analysis was to clarify the potential association… Soldering may be a risk factor for wheeze, but may not be associated with a clinically significant impairment of lung function among electronics workers.”

– Mendy, A, et al (2011). Work-related respiratory symptoms and lung function among solderers in the electronics industry: a meta-analysis, http://doi.org/10.1007/s12199-011-0236-8

 

“A cross-sectional study was conducted in four medium-sized electronics firms in which control measures to capture solder flux fume were absent or visibly ineffective… The odds ratios for ‘all wheeze’, shortness of breath, and work-related eye, nose and chest symptoms were all significantly greater (raised about 4-5 fold) in women who soldered > or = 37 h/wk when compared with those soldering < or = 20 h/wk.”

– Palmer, K. (1997). Respiratory disease in workers exposed to colophony solder flux fumes: continuing health concerns. http://www.ncbi.nlm.nih.gov/pubmed/9604483

 

Tips on Using Lead-free Solder in Place of Leaded Solder

Be sure to leave a small blob of solder on the tip when putting it down. Leaded solder only needs the tiniest bit on the tip to keep going, lead-free needs a larger blob, lest it oxidize fully.

Lead-free solder needs a higher temperature than leaded, typically 700-750F instead of 600-650F. A temperature-controlled iron works better than a cheaper current-controlled iron put to a higher setting. The higher setting will contribute to the tip wearing out faster, especially so with a current-controlled iron. Common tip failures include the tip becoming uncleanable after fully oxidizing, and the tip gradually being melted away.

Leaded flux-core solder adheres to dirty metal better than lead-free solder. Cleaning your piece with 98% isopropyl alcohol or other chemical wipes can help with adhesion.

Using finer gauge wire for lead-free may help. 0.031″ is popular for thru-hole and 0.023″ for surface mount.

Using deionized water in the cleaning sponge may help.

Lead-free solder wears out tips about 3 times faster than leaded solder. Be sure to have spare tips on hand.

Here is a guide to lead-free soldering from a major solder manufacturer: http://www.kester.com/kester-content/uploads/2013/06/Lead-free-Handsoldering.Final_.4.19.06.pdf

The New UAV Fireworks

See a wonderful new drone firework artform!

With all this talk about drones being scary, here is a glimpse at the future of art!

Skip to 43 seconds
http://www.huffingtonpost.com/entry/drones-beethoven-intel-world-record_5693ae9de4b0a2b6fb70b843

.
.

Why Sauron Is Secretly The Good Guy In ‘Lord Of The Rings’

Why Sauron Is Secretly The Good Guy In ‘Lord Of The Rings’

I’m a big fan of Cracked After Hours videos. At first I thought this would be their standard “pretty funny” but they really knocked it out of the park with this one. Come be a fan with me:

Steep Streets In San Francisco

Steep Streets in San Francisco

I came across a blog post mentioning the steepest streets in San Francisco. When Charlotte and I lived there, there was one favorite steep street that I loved to drive down… I’d pull up to the corner of 22nd and Vicksburg in my Sebring, put down the top (drizzle or shine!) and look at the magnificent view. Then I’d slowly pull the car up the edge of the cliff; you couldn’t see any ground in front of the car any more. We’d pause there, on the precipice and I’d ask, “Ready? Set… Go!” I’d give it just a bit too much gas and we’d lurch over the edge! For a second you weren’t sure if we were flying or falling. It was wonderful!

I looked at the list and can say that the street I found was one of two contenders for “best drivable hill” in the city.

Filbert between Hyde and Leavenworth ties our favorite street in steepness (31.5 degrees) and has a pretty darn good view. See it here!
Ripley and Peralta has the same steepness but the view is meh.
Baden above Mangels is steeper but it’s just a driveway. Disqualified!
Nevada above Chapman is another driveway with no view.
Prentiss between Chapman and Powhattan is another driveway!

Here is our view at 22nd and Vicksburg.

Just over the edge.

Here are the two blog posts I saw with all the hill info.

And just so it doesn’t get lost, here are the contenders:

The Steepest Streets In San Francisco, For Real
1. Prentiss between Chapman and Powhattan (37% grade)
2. Nevada above Chapman (36% grade)
3. Baden above Mangels (34% grade) *
4. Ripley between Peralta and Alabama (31.5% grade)
5. Filbert between Hyde and Leavenworth (31.5% grade)
6. 22nd between Vicksburg and Church (31.5% grade)
7. 24th between Grand View and Fountain (30% grade)
8. Kearny above Broadway (30% grade) **
9. Holyoke between Karen and Woolsey (30% grade)
10. 25th above Grand View (30% grade)
11. Jones between Union and Filbert (29% grade)
12. Dwight above Goettingen (29% grade)
13. Folsom between Chapman and Powhattan (29% grade)
Source: Stephen Von Worley.
Notes: Ties are broken by the length of maximum slope.
* Crude, single lane pseudo-street, ** Grade unconfirmed.