Answers on a postcard please...

Another weekend goes by and one of my favourite sellers at the flea market had a few items from a late tinkerer called Bob. It seemed that Bob was always playing around with electrical stuff and for just a few dollars, some oddities came into my possession, with no intended purpose besides curiosity. 

It seems that Bob liked to work with wood as well, basically "bread boards" for his electrical projects which is where a lot of circuits were tested out in the early days, then in the 1960s solderless breadboards, like the ACE 200k unit shown in the photo, became a lot more convenient for learning the hobby and testing out hair brained schemes.

A couple of DC motors, the little one has a pulley on it, the bigger one has a propeller and some good quality alligator clips. The other thing of interest is the over designed bank of resistors. It is a fact that once you start collecting resistors it becomes strangely addictive, difficult to resist. I like these ones, they will look good in the collection. I like sausages as well, although they are quite difficult to collect.

There were some other things too, a few solar panels and a nice tool box for my soldering kit, a whole bunch of things that I am hoping will keep me busy in the fall and winter, although I suppose solar panels will be of little use in the shorter days but here, now that summer has arrived, there is no urge whatsoever to sit at my bench fiddling with resistors and light bulbs, but that will change.

The sun is shining and the garden calls, I will do some painting today, and the things that once belonged to Bob will wait their turn until later in the year, although I may put some voltage on that ACE circuit to see what those three LEDs are supposed to be doing, perhaps that will be the subject of the next blog.

Another month, more multimeters

A few days into the new month and another vintage multimeter arrives on my bench, obtained from an electrician who is paring down his "collection" and on first inspection, this multimeter looks very much like the horrendous Chinese death trap that I bought a few months ago, and subsequently sold in a hobbyist kit on marketplace. The new acquisition was obtained for seven dollars and I could see my wife roll her eyes as I gladly paid for yet another multimeter, but hey, come on, seven dollars.....

Now, not to be too excited, the vintage leather case is not the case for this particular multimeter, I suspect it is a case from a 1950's analog multimeter, genuine hide leather, the way they used to make them when there were less cows on the planet, that's an interesting concept right there, nowadays there are more cows, yet inversely, less stuff made from real leather?

The great reveal, a Gardener Bender GDT-190A. I deliberately added an extra letter into Gardner there, just because I think it sounds rather rude. Anyhoo, the old 1995 multimeter resides in the older multimeter case, the unit is in like new condition, which sort of reflects on how little the seller used it as he plied his trade. It was probably "special" so he deliberately ignored it over the years...

The similarity to that cheap and not so cheerful Chinese facade of a meter is very apparent, however this meter itself is very solid, has a good, genuine weight to it, no sense of disappointment, yet it was still made in China. It could have been the unwilling prototype for all the "830" type multimeters that they flood the market with nowadays, selling exploding mousetraps to all the fledgling electricians. It is apparent that Chinese crap in 1995 was far better than present day Chinese crap.

It was little bit of a struggle to get the back off, but now I know how, but will forget before I take the back off again at a future date. The internal electrical bits and electronics gave me a warm sense of happiness, and everything seemed to be in order, except for a couple of the soldered joints which appeared to have been done blindfolded or while juggling. I ask for forgiveness in saying that, I am an old white guy and was brought up in a certain way, during my apprenticeship, juggling while welding was discouraged.

A single fuse for the 2A current check, the typical shunt and next to that, three well soldered probe connectors, very sturdy. A little spring next to the large L7106CPL L9625 chip contacts aluminum shielding tape on the back cover and it is obvious where a good portion of the extra weight comes from, more robust circuit board, case plastics are thicker and a good portion of "real" electronic components including an IC the size of a small planet. 

The manual was very informative with diagrams, industry quality text and good sized fonts, the PVC test leads are typical of the time, but felt as though they actually had some copper running through them, nowadays the manufacturers produce test leads that sell for virtually nothing, so you can understand why they would not want to include any valuable materials. 

The overall impression was that, in relation to modern day offerings of this type, this particular model is a better alternative for home use, hobby type DC use, Arduino etc. I would still be reluctant to place the probes into a high current situation or an AC receptacle without using a robotic bomb disposal vehicle, but that is just me, crazy old tech geezer who wants to be older.

Laters....

Multimeter Madness : Circuitmate DM15B

In a few weeks time there will be the big neighbourhood yard sale here, so I am looking forward to sharing some of my electrical finds here on the blog. I will admit that my last blog about the cheapo multimeter left me feeling rather sad, mainly because those dangerous Chinese multimeters have flooded the market, and will continue to as long as idiots like myself want to buy one "just to see how bad they can be" so I blame myself for all the ills of the planet, it is all my fault and I apologize.

I wanted to balance things out by buying a few vintage homegrown multimeters, they don't have to be manufactured in Canada or the USA, but some will have been designed on this continent in the last thirty or so years, perhaps even older, and some will be marketplace finds like this one :

This was a great find on marketplace last weekend, the owner sold it for two bucks and made a caveat that it "kinda" worked. It was on our route so we picked it up from his house, dropped a tooney in his postbox and made off like a thief in the night, or day as it was. It is a Beckman Industries Circuitmate DM15B, designed in San Diego, California and manufactured in Taiwan around 1985. In addition it came with some nice Pomona 3782-36 Minigrabber Test clip to stacking banana plug leads, 36" long and I'm not sure which part of the deal makes me happier, the multimeter or the leads.

Pomona Electronics was a company specializing in electronic test equipment and accessories, apparently it was acquired by Fluke Corporation, and as is the state of companies in the states, Fluke is no longer owned by Fluke. The test leads have Pomona on the wiring and possibly date back to the mid 1980s, they are, like the multimeter, in great shape.

After placing a fresh nine volt battery in it and giving the multimeter a slight clean, it kinda worked extremely well, very well in fact and my overall impression of it is it is a solid little device, same size as that abhorrent depressing thing that I reviewed in the last blog, but this one actually has a fuse and solid as a little rock, and I may be going on a bit but those test leads are a very nice addition to my collection. I did some testing, voltage is accurate, continuity buzzer a little buzzing wasp, and resistance testing as accurate as I need it :

Testing a 1k ohm resistor, 991 reported, within a percentage of actual value, I repeated the test for a whole range of resistors and accuracy was very good between 10 ohm and a million. I like the feel of these older meters, something to do with the weight I suppose, plus overall this Circuitmate appears to be very well built, and I suppose because it is almost forty years old and still working like a champ, that is proof of how well it was constructed.

I am very happy with the test leads, did I mention that?

I am therefore no longer sad, I am happy and my faith in life, the universe and everything has been restored once again. 

Comedy : The race to zero and why we should never be surprised by crap

I may have mentioned it a month ago, but to remind you, my invisible people, I ordered a quite well-researched cheapest multimeter from the far off lands, the price, including shipping, was just four dollars and seventy four cents of our Canadian money, I was curious, how bad could a multimeter that costs about the same as a deluxe coffee actually be?

I researched it, sort of, and ordered it, and waited...and waited....

It arrived, they mostly do, from the far off lands, and it weighed, well, it weighed very little. No ballast to make the thing seem real, but oddly, once a battery was inserted, which still made the thing appear to be lighter than air, the product seemed to do most things that it was supposed to do.

Most things.

No fuse, no beeps, very questionable triode detection. It was obvious when removing the back cover to place the nine volt battery that there was neither a fuse, nor a beeper unit and if you look at that ring of 8 holes for the transistor testing, well, you can understand why the three prongs of an NPN or PNP would have difficulty making contact all at the same time. However, to temper my rage I looked at the original listing and saw that neither a fuse or a buzzer were promised, the wording, the reviews, all pointed to the glaring fact that this was potentially a death trap that had no bells or whistles.

I know enough stuff about electrical things now to be dangerous, so looking at the above photo I can point out the shocking detail of the no fuse, where perhaps a fuse should be, so the question then would be, how would this little miracle react to bad things happening in the real world, and the answer perhaps does not require any training in rocket science.

The two main probe contacts, bottom left, well they are extremely close for potential arc points when high voltage AC or DC are applied and when installing the battery it actually pushes them closer, so there is one dangerous point of failure, another would be one of those many surface mount resistors, a mystical point of magic smoke when you jam one of the inadequate, poor quality, probes into an AC outlet. In essence, there is a fuse, just not one you can replace...

What do I know, what do I care, I cannot even buy a pint of beer any more for the price, and this little, lightweight, wonder can be used to check "little" things and can perhaps be used as a sacrificial multimeter when I do not wish to risk a higher price unit, after all, a replacement fuse on a good quality Fluke meter would probably cost twice what this little hampster costeded.

I will admit though, when I opened the package from the far off lands, my first reaction was to immediately send this to the e-waste depot, but you know, with a little time, you realise that you do get what you pay for, and if you pay next to nothing, you get next to nothing.  

I subsequently sold the little meter, I included it in a small toolbox of spare, useless, parts. It was interesting to hold and play with such a poor little multimeter, and in my research along the way, I have discovered that the terrible internals of this type of meter are sold in many different ways by our far off friends, perhaps it is in their interests to electrocute us all.

Ok, now I have rid my world of that sordid little thing, I should go and buy another....

Flip Flop LED breadboard

In the growing supply of kits I have waiting to hone my soldering skills, there are two very simple ones, they are what is called a "Flip Flop" circuit that utilizes two LEDs, two transisitors, two capacitors and four resistors. This is the circuit diagram :

There is a logic afoot within this circuit, and I will attempt to explain what it does, in simple terms it flashes two LED bulbs and most brainiacs will say that it is indeed a very simple circuit, but for me, it was a challenge to get my pea-sized brain around it all, mainly as you can buy flashing LEDs for pennies, however, flashing LEDs also make use of a miniature transistor circuit that is contained within the LED housing.

Here is my attempt at explaining, it might be wrong, but the idea is in my head and I may as well write it down so that in the future I can look back and scoff at how little I actually knew at this point in my education.

The circuit calls for two BC547 transistors which are NPN and the capacitors are connected to the base on each, think of the capacitors as little batteries that cycle from uncharged to charged and when "full" discharge and open the transistor switch so that the corresponding LED can receive current and lights, when the capacitor is discharged, the transistor base is not powered and that LED switches off. While all that is going on, the other capacitor has charged and then provides base current to the other transistor and the other LED lights, this backwards and forwards action continues, so the two LEDs flip flop.

Suitably vague?

I breadboarded the circuit using components out of my supplies, so the transistors used were ZN 2222A another NPN type and the capacitors were 10/35 which are 10 microfarad, as they say, who dares wins and I didn't have the correct components (a bit of a lie, I did, but they are part of the flip flop DIY kits I have purchased shown in the photo) anyhoo, that is what I used for the breadboard experiment.

The kit, shown on the left, will be the next step, cost was a dollar from the far off lands and I bought two, in case my big sausage fingers and soldering incompetence get the better of another set of components. The breadboard was set up and it was happy times as the flip flop worked with both 5V and 3.3V - as usual, I called my good lady out of her happy place and showed her my flashing lights and she said "That's nice dear" and went back to doing whatever she was doing before being summoned by her mad scientist spouse in his thousand year education towards building a hadron collidor.

It works! - Nay it disney!!!

The first soldering kit I have ever attempted, a little two dollar unit from the far off lands, I bought it a year ago, so I decided to hone my soldering "skills" for an hour, and it was an hour or more, and when all was done and dusted, the unit worked...

Keen eyes out there may notice there is a capacitor missing from the photo, more on that later.

I'm showing the best side, the soldered side is better left alone. When connected to five volts eight out of the ten LEDs did what they were supposed to do, react to sound via the onboard microphone, and two did not do anything. I saw it as a win, not a total win, but 90% success is what I call great for my first, nervous, time.

Later on in time, I noticed from the above photo that the top left pin of the circuit chip was not making contact, so 15 pins out of the 16 had good contact, this was the probable cause of the two LEDs not doing what they were supposed to, however, in between the two points in time, I screwed something else up, typical...

I was taking a look at the two LEDs that were not working, perhaps I had put them in backwards, a sound reason for LEDs not making light, but as I was checking, I cracked the smaller capacitor solder joints, and for the life of me, over the next fifteen minutes or so, I could not resolder them back, the minute tinned pads on the poor quality circuit board were gone.

I think that is a common problem with the circuit boards for these very cheap kits, but it is also a problem with people like me, who cannot solder for toffee, spending far too long with heat on the pads, basically removing any possible contact points, I will reset and learn, and order another one of these kits from distant lands.

So, it was (almost) working, and now it does not, probably a familiar tale over the next few attempts at learning to solder better. I have learned a lot from this first kit, eyesight could be better, dexterity too, patience can be improved and getting things right the first time would be a good idea.

Nothing ventured, nothing gained.

Inside a Radio Shack 22-032A battery meter

Another handy little meter that I've had for years, so I thought I would take a look at how it ticks. This follows on from my previous comments about multimeters that have battery testing capability and basically there is a difference between the two devices. Testing a battery purely by voltage is not a reflection of the battery health, so it is important to place the battery under load to check. In the case of a battery meter like this one, that is achieved by turning the dial which places an appropriate resistance in the test circuit.

Inside, no battery is needed as the unit uses the tested battery to provide current. I expected to see the calibrated, analog moving coil meter of course and a series of resistors linked to the rotary dial positions, that would be about it I would think, no fancy integrated circuits, just an application of good old fashioned V=IR in a handy little unit, so I took the back off to have a fiddle around. 

As predicted, twelve resistors (for nine dial positions) and annoyingly, some resistors are in backwards in relation to others, so it makes interpreting the bands a little difficult. I checked all the resistors with a multimeter and they were approximately what they should be, within reason. Instead of making a list of the resistors (and their variance from the stripes) I made a table of dial position and resistance recorded at the probe level for both the Neoteck and Klein Tools multimeters.

The dial position selects a resistor, or group of resistors and then the magic of V=IR comes into play for the moving coil meter and full scale deflection if the loaded battery is good, there is some other aspect coming into play for the button cells and AAA and AA cellls, but I was unwilling at this time to remove the meter label or the circuit board to see what jiggery-pokery is happening on the reverse side with the traces and perhaps a couple more resistors, or reuse of one of the twelve. I was tired and I needed a beer and there was also that chance that I would not be able to put it back together again and it would be a battery meter no more.

Suffice to say, clever, yet simple device, it is a shame that Radio Shack no longer exist in the form that they did a decade ago, but there were similar devices branded Micronta in the years that followed their closure and transition into the Source.