Urban Ministry Live And Unplugged: Simplest Metal Detector

Tuesday, March 1, 2016

Simplest Metal Detector

I was reminded this week how I was challenged to design one of my best known metal detectors. Rachel and Steve Hageman of Hewlett-Packard had designed a self-contained metal detector which (when built) would have just twenty-six PCB-mounted components. This was radically simple. Intuitively, I thought that I could beat that. I simplified, and I simplified, and I reduced a self-contained metal detector to one single PCB-mounted component (see the image). And its performance was better than twice that of the Hageman design. My design was published in Australia and in the UK. It was called the Poor Man's Metal Locator.

2 comments:

Anonymous said...: good afternoon. Mr.
what would be the E1 B1 and e2 b2 that go to the coil ?

LA 3220 can be used in BFO ( 2008 ) ?
grateful for the attention.; June 4, 2016 at 9:59 PM
Thomas O. Scarborough said...: Thank you Anon. e = the end of the wire, and b = the beginning of the wire. In other words, it matters which way up each coil is. I would suggest that you simply try the LA3220 and see. This circuit is beyond all simulations and calculations. Incidentally I think that my 7556 metal detector on this blog is the best embodiment of this idea: https://thomasscarborough.blogspot.co.za/2013/06/bb-metal-detector.html; June 7, 2016 at 1:43 PM

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About This Blog

I have spent ten years in suburban ministry, twenty-two years (total) in urban ministry, and seven years in country ministry. My involvements in ministry continue, now reduced.

There are a few reasons for this blog: 1. To help people form a picture of what ministry is about -- in particular urban ministry -- not least seminary students who may be destined for urban ministry. I have found that the image and the reality may be far apart in academia. 2. My experience in ministry may be (and, in fact, often has been) an encouragement to other ministers -- alternatively, a cautionary tale, as the case may be! Many notes of thanks have been recorded on this blog. And 3. Friends have simply told me how interesting reports of ministry are.

This is not a "parochial" blog. Only a tenth or so of readers are local (in South Africa). Outside of my home country, this blog is most read in Europe and North America. Russia is no. 4 on the list, and there is some interest in Muslim nations. At one point, this was the most authoritative Religion blog in Southern Africa (I now do not know how it is ranked).

With all of the above in mind, the purpose of this blog is simply to record urban ministry "live and unplugged", in the form of accounts. This blog is not a "church blog", but a "ministry blog". For the most part, I don't intend to share my views. The emphasis is the experience of ministry and the various events that surround it.

A definition of “live” is “actually being performed at the time of viewing”. A definition of “unplugged” is “without amplification or modification”. However, see my Posting Policy below.

Posting Policy

This blog may be unique with regard to its degree of transparency about urban ministry. Many people have written to me to say how they cherish the help they have received through this. However, this means that special attention needs to be given to confidentiality in particular. I use the following guidelines for posting on this blog:

I apply the following questions to posts: Are they posted in good faith? Are they balanced? Are they compassionate? Are they informative about ministry? Do they help one better understand a problem or issue?

I consider a post to be unproblematic if a person's identity is unknowable in the post, if the facts are public knowledge, or if a change of particulars (name, place, date, and so on) will truly protect privacy. If I consider that anyone who was not involved in an incident would recognise those who were, then I do not post. If a post could compromise the safety of those I blog about, then I make a post safe, or I do not post.

I believe that these measures should enable me to continue to be "open" about urban ministry while not compromising privacy.

In 2013, ninety percent of the posts on this blog were removed. I then put the question of the freedom of the blog to the South African Human Rights Commission. The position is this: if a post is legal, it is legal. Essentially, all of my posts were OK. There is freedom of expression in South Africa.

Having said this, if any post should even cause discomfort, it will be removed from this blog immediately. This has always been the position. One does need to contact me for that, best through an e-mail or a blog comment, and I prefer to see a name on it. The post will be put back up only if there would seem to be compelling reason for it. It is hoped that there will be the assumption that I wish to address any discomfort satisfactorily, compassionately, and efficiently.