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Testing network
connections
Stepper
motor connections
Choosing a multimeter
A circuit for moving lights
NE555 article in the Midlands Meccano Guild Gazette
An extract from the SELMEC News
EiM article in the Midlands Meccano
Guild Newsletter
A letter from Mike West
Testing network
connections
March 2000
The following is an extract from a letter sent to me by my friend John Hewes:
Dear Tim,
...Incidentally, the moving lights circuit (see 'A circuit for moving lights' below) could be done with just two ICs if you use a 555 astable driving a 4017, the disadvantage is that it will only drive 10 LEDs (the 4017 being a 1-of-10 counter). I in fact recently built a circuit like this for testing 8-way computer network cables; the 8-way cable goes between the 4017 outputs and the LED's. If the cable is OK, each of the 8 LEDs should light up in the correct sequence - simple but effective and very much cheaper than professional testers.
The circuit and stripboard diagrams can be found here...
Best wishes,
John Hewes
Beckenham, Kent, England
Stepper
motor connections
June 1999
Dear Tim,
I have discovered a good source of cheap second hand stepper motors, plus a lot of other second hand electrical gear. It's the Display Electronics shop at 215 Whitehorse Lane, South Norwood, near Crystal Palace football ground.
They are selling small stepper motors at £3.80 each. They come in all shapes, sizes and voltages, some with four leads, some with six, some with eight.
The snag is that there's little or no indication on most of them about what they need to power them, and there's no indication on any of them about which leads are the common and which are the main windings (and it's no good asking the man in the shop; he says he doesn't know the first thing about steppers!)
But here's what I found in a marvelous American book by Gordon McComb, The Robot Builder's Bonanza, which I got from Maplin:
"The wiring in a two-phase stepper motor is actually easy to decode. You use a volt-ohm meter to do the job right. You can be fairly sure the motor is two-phase if it only has four wires leading to it. You can identify the phases by connecting the leads of the meter to each wire and noting the resistance. You can readily identify mating phases when there is a small resistance through the wire pair.
Four-phase stepper motors behave the same, but with a slight twist. let's say for arguments sake, that the motor has eight wires leading to it. Each winding, then, has a pair of wires. Connect your meter to each wire in turn to identify the mating pairs... No reading (infinite Ohms) signifies that the wires do not lead to the same winding; a reading indicates a winding.
If the motor has six wires, then four of the leads go to one side of the windings; the other two are commons and connect to the other side of the windings. Decoding this wiring scheme takes some patience, but it can be done. First, separate all those wires where you get an open reading. At the end of your test, there should be two three-wire sets that provide some reading among each of the leads. You should not get a reading when testing wires from each of the two sets.
Locate the common wore by following these steps. Take a measurement of each combination of the wires and note the results. You should end up with three measurements: wires 1 and 2, wires 2 and 3, and wires 1 and 3. The meter readings will be the same for two of the sets. These two wires a re the main windings. The remaining wire is the common.
Decoding a five-wire motor is the most straightforward. Measure each wire combination, noting the results of each. When testing the leads to one winding, the result will be a specified resistance (let's call it 'R'). When testing the leads to two of the windings, the resistance will be double the value of 'R'... Isolate this command wire with further testing and you've successfully decoded the wiring."
Best regards,
Mike West
Blackheath, London, England
Choosing
a Multimeter
June 1999
Dear Tim,
May I just say how much I have enjoyed reading your article "Electronics in Meccano" in the April issue or the Midlands Meccano Guild Gazette. As a beginner to electronics, I found EiM very helpful and the instructions written in a clear and non-technical manner, much easier to read than some of the electronics books I have read.
Before including electronics in my models, I would like to gain more experience by building the projects in EiM and experimenting. Can you advise about choosing a multimeter?
Albert Howe
Ripon, North Yorkshire, England
A simple, cheap multimeter should be good
enough for most hobbyists since they do not need the accuracy or
features that a professional needs. One can be brought for under
£10! Have a look at the 'low cost multimeters' on page 1332 of
the new Maplin catalogue. Some of the basic features that are
probably essential are:
A few other features on more expensive multimeters:
One thing to note is the difference between 'features' and 'ranges'. There will be more ranges than functions because most functions have several ranges. E.g., my multimeter has six ranges for resistance testing; 200W, 2kW, 20kW, 200kW, 2kW and 20kW. You choose the range depending on what you expect to measure, and the accuracy of the measurement changes accordingly.
A
circuit for moving lights
March 1999
Dear Tim,
I am interested in the design of moving light circuit in which I want to use the NE555 IC and divider IC 4520 and 2003. Could you suggest a design for the circuit?
Thank you very much,
Bassim Naom
Windsor, Canada
You were right to suggest the use of the
NE555 and a counter IC such as the 4520. The NE555 can clock the 4520 to produce a regular counting sequence. You can then feed
the lower four bits of this sequence into a decoder IC such as
the 4514 which will then provide a high output on each of it's
outputs in turn. Connecting each output to an LED (via a
resistor) will produce a 'moving light' effect. Up to sixteen
LED's can be connected to the outputs of the 4514. If you want
less, you can use one output to reset the 4520 as shown in the
circuit diagram...
Circuit diagram for the moving light circuit
The 4515 can also be used if you want inverted outputs. Please note that I have not tested these circuits!
NE555
article in the Midlands Meccano Guild Gazette
December 1998
Robert Thompson, Chairman of the Midlands Meccano Guild has asked me if I would like to write an article for the Midlands Meccano Guild Gazette which is due out in April next year.
I have started writing an article about the NE555 Timer IC for the Gazette, and this article will be also be split into three parts for Electronics in Meccano issues three to five.
An
Extract from the SELMEC News
November 1998
"During the free time in the
afternoon Tim Surtell pressed into my hand a copy of the first
issue of Electronics in Meccano, a four page magazine
written entirely by himself and selling for a modest 25p.
I know almost nothing about electronics, but Tim is obviously an
expert: he should be, he's reading the subject at university. And
it's written for the layman - well, intelligent layman!
This first edition has items
covering motor reversing switches, relays, resistors, a look at
Tim's own chocolate vending machine and tips on soldering.
Usefully, a price list is included for the various components
used.
Definitely worth buying!"
Chris Warrell
SELMEC News Editor
EiM
article in the Midlands Meccano Guild Newsletter
October 1998
The October edition of the Midlands Meccano Guild Newsletter included the 'Motor Reversing Switches' article from issue one of Electronics in Meccano. Thanks to Robert Thomson for including this article in the newsletter.
A
Letter from Mike West
October 1998
Dear Tim,
I must congratulate you on the first issue of Electronics in Meccano.
As a Meccano model builder and enthusiastic but strictly amateur dabbler in electronics, I found it really useful, well laid out, clearly explained and full of helpful advice.
Following your instructions, Ive now built a sophisticated electronic de-clutching device for the so-called Spanish Automatic Mechanical Loom that Im building and adapting.
Using a Meccano relay, a powerful 6V solenoid, plus some Maplin microswitches, it disengages the drive, thereby halting the loom mechanism, in the event of the shuttle misfiring. It replaces a fiddly mechanical de-clutching system incorporated in the original model plan which despite constant adjustments I could never get to work properly.
So, many thanks for that and I look forward to future issues of Electronics in Meccano. Details of where to get the stuff, plus practical matters like soldering and using resistors, all explained in clear, jargon-free language are right up my street. I think they will appeal to a lot of other people too, who need practical advice to help them further into the wonderful world of electronics.
Best regards,
Mike West
Blackheath, London, England
Suggestions for future articles
Below is a list of topics that readers have suggested for articles in Electronics in Meccano On-Line. If you have a topic you would like to see that is not on this list, please e-mail me or fill in the form above.
Using
the Meccano infra-red unit
Controlling a model by computer or microprocessor
Solid-state relays
Motor speed control (AC & DC motors)
Battery charging
Electrical and battery safety
Zener diodes
Flip-flops for motor reversing
Frequency control of the Meccano Infrared Kit so two can used
Fairground lights using LEDs
Switching by breaking light beams
The STAMP microcontroller
Time-lapse control - auto reversing
Bench and Model Railway power supplies
Reproducing Electrikit parts
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