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Member postings for Robert Atkinson 2

Here is a list of all the postings Robert Atkinson 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Mains outlets with USB sockets - safety?
06/07/2019 12:44:07
Posted by SillyOldDuffer on 06/07/2019 10:07:05:
Posted by Bazyle on 05/07/2019 23:47:58:

Bear in mind that very little electronic equipment lasts more than ten years, often less than 5. ...

Sorry, can't agree with that. True equipment based on vacuum tubes (high voltages and lots of heat), weren't reliable and early transistors were rather delicate. Three-legged fuses we called them 50 years ago.

Well-made electronics have been more reliable than mechanical items for at least 30 years. The last car I scrapped had multiple mechanical issues after 15 years - corrosion, oil-seal failures, worn-out brake disks, weeping hydraulics, leaking fuel injector, steering that clunked turning right, and a suspicion the clutch was slipping. All the electronics, and there was rather a lot, were fine.

To answer the question, I'd happily install sockets with built-in USB power supplies wherever it was worth doing. I wouldn't fit them everywhere as a matter of course. They're handy in a kitchen or bedroom for recharging mobile phones etc. The way they are designed and made makes them rather safe; very unlikely that mains voltage could appear on the output, or that enough heat would be generated by a fault to start a fire. Any trouble and they fail open circuit. The same can't be said of transformer type wall-warts; they consume power off-load, can overheat, and shorted windings can catch fire without blowing a fuse.

As always, it makes sense to avoid buying cheap and nasty.

Dave

Sorry Dave, but that's just not true. Modern electronics are not long life. The reduction ic size is the biggest problem as it causes higer power density and voltage gradients. The most common failure compnent is electrolytic capacitors.Many have specified lives (at max rating) of only a few thousand hours. Electronic failures are the most expensive repair on modern cars. This is not helped by technicians who just change boxes.
I have laptops that are twenty years old and still working fine. more modern, faster slimmer models from the same manufacturer have only lasted 3 to 5 years.
The USB outlet sockets fall between regulaton and all of them draw some stanby current. By physically having components they must be more of a fire hazard than a simple socket. They also add to the background electronic noise.

Robert G8RPI.

Thread: Phillips vs Pozidrive and portable drills
05/07/2019 22:01:18

Mick said " Maybe we should all buy a 3 foot long yankee driver and bin the Bosch lol "

About 15 years ago I used to take machines to trade shows in the USA, The machnes were shipped in crates with lots of screws to open them . Having got fed up with short battery life on the cordless drivers back then and restrictions on carrying spare bateries on aircraft, I bought a yankee. Never goes flat (but you can wear out) and has automatic increased contact pressure with increased torque so hardly ever slips. Numerous people would come over and say " that's great, I'd fogotten about those" or similar. Not cheap but a great tool.

Robert G8RPI.

05/07/2019 19:45:13
Posted by Michael Gilligan on 05/07/2019 17:27:24:
Posted by Robert Atkinson 2 on 05/07/2019 17:07:42:

As an aircraft engineer I have also had to deal with Bristol spline

.

Do you happen to know of a reasonably priced supplier [to the UK]

... I have a set of small keys, but need a couple of larger ones.

MichaelG.

I use Xcelite which are available from RS Comoponents e.g.

https://uk.rs-online.com/web/p/screwdrivers/2550519417/

but even then they are extended range.

Snap-On sell a set of L type ones but they will set you back about £150

Robert G8RPI.

05/07/2019 17:07:42

It's not just simple Phillips / Posidrive. Two fairly common variations are the Japanese JIS which is close to phillips but less pointed. Then there is Supadriv which neither Phillips or Posidriv fit properly. JIS headed screws are often identified by a dimple on the head.

More esoterically there is RIBE/Polydrive (used on FCA nd GM vehicles) and Spline which look a bit like Torx. As an aircraft engineer I have also had to deal with Bristol spline TorqSet, Triwing and Hi-Torq.

Robert G8RPI.

Edited By Robert Atkinson 2 on 05/07/2019 19:33:22

Thread: Phone charger
02/07/2019 07:24:13

Are they original Apple chargers or aftermarket items? Both the charger(s) and the Lead(s)?

How old are they and what condition are they in?


It sounds like a glitch in the communications between charger and device. For a full fast charger there is "intelligence" in the device, lead (lightning) and charger. Unplugging resets the electronics in the charger and lead.

The spark you are seeing is from the EMI filter capacitor. While shorting it should not cause damage it would be better to just leave them unplugged for 5 minutes.

Robert G8RPI.

Thread: Using a lathe
01/07/2019 12:52:05

SOD raises a good one " lack of imagination" this seem very prevalent these days. I deal with failure analysis and environmental / performance testing as part of my day job. Few engineers seem to be able to imagine what might go wrong or the consequences of the failure,. Some of it is down to experience, but they don't seem to be taught what my wife (an educator from the USA) calls "critical thinking". Many just accept any old rubbish on the net or even data/specification sheet. If a tolerance /rating/ performance figure isn't on the data sheet it's probably because it's not very good. A classic and repeated, electrical one is the metal clad "25 Watt" resistor which is only rated at about 7W unless it's on a foot square aluminium sheet or similar heatsink and even then gets to over 100 degrees C.

Curiosity starts at an early age and I think it's wrong to restrict it due to mis-placed safety worries.

It's also not just schools that restrict use of machine tools. As an "office worker" My employer says I can't use even a pillar drill because I don't have the correct "skill code" and enforces it by locking up the tools. This is despite being a qualified engineer (OK avionics, but the formal training did include machine tools) and using a fully equipped prototype machine shop at my previous employer.

Robert G8RPI.

 

Edited By Robert Atkinson 2 on 01/07/2019 12:53:17

Thread: Mini Lathe - turning 6" long, 1.5" dia AL
30/06/2019 20:59:01

At 300mm between centres and a MT2 tailstock on the SC2 there should be no problem turning 6" between a chuck and centre. lots of choice in MT2 centres. why don't you think you can do it?

Thread: Do you need one of these in your life?
27/06/2019 07:29:53

Nothing new there. Lots of variations on this out there. Mostly for bigger magnets. This one is quite nice

**LINK**

Thread: Gents impulse clock
17/06/2019 07:31:40
Posted by Michael Gilligan on 16/06/2019 22:30:02:

Posted by Robert Atkinson 2 on 16/06/2019 21:47:44:

... run it from a 10MHz OCXO and a optocoupler obscured every pendulum swing and it will send the time of every swing to a PC via the serial port.

Robert G8RPI.

.

I think that's where we are probably on different interpretations, Robert

... I anticipate needing to use several measuring points; being more interested in the perturbations within a swing than in its overall duration

MichaelG.

that's more of a challenge as to how you capture the data without affecting the pendulum. A high frame rate camera and software would be one option. A more interesting one would be line CCD or diode array sensor like those used in document scanners sensing the shadow of the pendulum rod. This would give better resolution, easily 1024 positions, and require less processing. The sensor and lens from a flat bed scanner would probably work as is. Disconnect the sensor from the mechanical drive (initially leave that is as is for home and end sensors) and just try the scanning software. The image should be a sine wave.

I just realised I made a mistake on the OCXO accuracy. 31.5 seconds per year is 1x10^-6 if it all went out in the same direction at the beginning of the year. A more typical 1x10^-9 average is 0.03 seconds in a year.

Robert G8RPI.

16/06/2019 21:50:11

Deleted

 

 

Edited By Robert Atkinson 2 on 16/06/2019 21:50:34

16/06/2019 21:47:44

Michael and I are interested in the behaviour of individual pendulum swings where averaging hides useful detail. The easiest way (I think) is to compare the test pendulum with a much more accurate clock, and the more accurate the better.

With a pendulum clock, tens of microseconds are interesting, and picosecond resolution would be even more revealing. It's a bit like measuring length: to measure a thou accurately, you need an instrument that can get close to tenths.

Looking closely at the timing of a pendulum shows clock faults, for example I think I can detect the difference between a pendulum swinging true and one following an ellipse. On my test rig an elliptical swing has more jitter, I'm not sure why. I suspect it's due to a combination of the impulse being misplaced relative to the bob, torsion in the rod, and maybe bending at the pivot.

Dave

The PICTIC I linked to (corrupted by smiley) "http://www.ko4bb.com/doku2015/doku.php?id=precision_timingictic" Google KO4BB (O not zero) pictic to find it

is ideal for what you want. run it from a 10MHz OCXO and a optocoupler obscured every pendulum swing and it will send the time of every swing to a PC via the serial port.

Robert G8RPI.

16/06/2019 15:31:05

For a lowcost time interval counter with logging on a pc for checking clocks etc see

http://www.ko4bb.com/doku2015/doku.php?id=precision_timingictic

Robert G8RPI

16/06/2019 15:27:06
Posted by Michael Gilligan on 15/06/2019 22:25:54:
Posted by Robert Atkinson 2 on 15/06/2019 19:24:05:

For clock setting you don't need a full GPSDO. Just get ... etc.

.

With the greatest respect, Robert

[and a man with 5 GPSDO's, 4 Rubidium atomic frequency standards, HP 5370B etc. surely deserves that]

My interest is more to do with studying the stability of a pendulum than setting its rate

and I would have more confidence in my results if the crystal oscillator was 'disciplined'

Please feel free to put me right [publicly or privately] if I have this wrong ... I am a mere dabbler.

MichaelG.

Any decent OCXO will be accurate to 1 part per million in a year (<1x10^6, HP's 10811A is more than 10 times better than that) so that's 31 seconds in a year worst case. Over shorter time scales eg days it's typically a thousand times better so 0.001 seconds per day. How good do you need?

Robert G8RPI.

Thread: sulphuric acid
16/06/2019 14:49:19
Posted by pgk pgk on 16/06/2019 11:55:21:
Posted by SillyOldDuffer on 16/06/2019 09:42:37:

In the UK we have a regulation requiring dog owners to bag and remove the animal's poo. Lots of dogs doing their business in the streets and children's playparks. Apart from the slimy distress caused by standing in it, dog poo spreads unpleasant diseases, notably Toxicaria. Bagging and sending to land-fill fixes the problem. Why then do so many dog owners carefully hang the bagged mess in the nearest hedge or tree, thus adding plastic and an offensive eye-sore to the problem?

Dave

Fisrly I have to say that i agree with the unpleasantness of dog waste on streets and parks and the commonsense and health utility of worming pets but I do get on my high-horse when news media and people overblow the human health risks. The actual incidence of visceral larval migrans diagnosed Enland and Wales is very low. While it can afect brains and other organs the only paperwok on-line I could find currently is for the more? common ocular form here

This shows about 12 cases per year out of our 60mill population and indeed mostly in adults. A previous study i found back in the 80's on neurological cases was around 6-7. I did some back-of-fag-packet sums on it back then and if anything the risks of going to the vet to buy the worm tablets from the viewpoint of motor accidents and other hazards is actually higher (yes I realise if folk didn't go buy the tablets then human incidence would be higher )

I had a long discussion with my local health authority and environmental health folk while I was in Practice and the subject of dog faeces was media highlighted... they did claim to carry out regular checks on dog worm burdens in parks and playgrounds and finally reluctantly conceded they had never turned up viable infective material in the soil (which is not the same as saying it's not there).

I'm all for prevention and monitoring but I do get angry when stuff is blown out of proportion and magnified by social media. the classic 'If we only prevent one case' argument when there could be hugely greater benefits to mankind with resources elsewhere.

The same type of nonsense happens with the UK approach to water backflow prevention. Businesses have to comply with all sorts of legislation but there's no legislation covering households with babies in nappies, geriatrics at home or the many folk on home immunosupprresive drugs, antibiotics and chemo - which in total blows away the numbers in a few clinics. At the same time they wouldn't allow a simple mains ingress backflow solution as used e.g Australia. I'd hate to guess what proportion of domestic houses Uk still have an open water tank in the loft...

I agree totally. Of the dozen or so cases it's probable that most are from own dogs. We get lots of complaints about dog mess in the village newsletter but few about the bottles, glassses and drink cans (cans get shredded by the councel mowers into razor sharp pieces). I reguarly pick up bottles and cans on the greens and playing fields. Septicemia kills hundreds in the UK every year so a cut while playing is potentially much more dangerous than dog mess. I am biased, I had septicemia from a cut in a park as a child and am a dog owner and ouy dog has had to have vet visits twice due to a cut paw.

Robert G8RPI.

Thread: Gents impulse clock
15/06/2019 19:24:05

For clock setting you don't need a full GPSDO. Just get a Oven Controlled Crystal Oscillator (OCXO) or Temperature Compensated Crystal Oscillator (TCXO) with adjust ment and set it occasionally aginst a GPS. This is easy if you have an oscilloscope. Trigger the 'scope from the GPS 1PPS output (e.g.) put it on channel one) and monitor the output of the oscillator on one channel. The trace of the oscillator will drift across the screen. adjust it for minimum drift and it will be accurate to fractions of parts per million. you can then put the GPS away for 6 months. or more. This assumes it was already within 1Hz of nominal frequency.

Lots of OCXOs and TCXOs on ebay.

Robert G8RPI. (time nut, 5 GPSDO's, 4 Rubidium atomic frequency standards, HP 5370B etc).

14/06/2019 22:02:39
Posted by Michael Gilligan on 13/06/2019 16:51:09:
Posted by Frances IoM on 13/06/2019 16:24:11:
why not just extract the mechanism from a radio controlled clock or even the many GPS rcvrs that push out the time accurate to microseconds!

.

Which reminds me of a round tuit ... I have most of the parts to build something like this:

**LINK**

http://www.jrmiller.demon.co.uk/projects/freqstd/frqstd.htm

MichaelG.

You don't need the extra oscillator and phase locking for a master clock, just a divide by 30 on the 1pps output (an a flipflop to reverse the polarity every other pulse for a Gents. If you want to build a Miller style GPSDO you need one of the Jupiter receivers with a 10kHz output. I've got a couple if you are stuck. Andy G4JNT has some good info too.

Robert G8RPI.

14/06/2019 21:54:40

Yes, that is a master clock. Nice find.

Robert G8RPI.

Thread: Rover V8 drilling valve guides
14/06/2019 07:22:46

TR7? Surely it's a TR8 or haven't you told your insurers and the DVLA? devil

Robert G8RPI.

Thread: High performance Torx bits
12/06/2019 20:41:16

+1 for Wiha or stop your local Snap-On van.

Robert G8RPI.

Thread: Chinese speed controller
12/06/2019 13:38:22

A 12V (or better 24V e.g. truck) brushed DC motor like a wiper motor and a PWM controller would probably be a good opton for light work on a Pultra at higher speeds. PWM controllers are available on ebay and are cheaper than variacs and inherently safer being low voltage.

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