Starting a motor at full load

I wish to comment on the question and answer about a 3-phase motor controller on page 123 of the August 2006 issue. I suspect the lift pump is of the constant delivery type. This means that for each revolution of the pump there will be a fixed volume displaced.

When one of these pumps is started there could be maximum pressure in the discharge pipe. There is probably a non-return valve in the foot valve and another downstream of the pump. If this is the case, the pump motor will have to exert full load or whatever margin is left in the design to start it, accelerate the rotating parts and move the media in the pipe.

Forget about the soft starter for a moment. The soft starter is to protect the supply side, not the motor; ie, if there is too much current drawn on starting, the voltage will drop and cause a lot of dropout problems.

Most people do not understand how induction motors really work. Full load torque is not developed until the motor is almost up to full speed. The starting torque will be considerably less. Even to obtain this reduced torque at starting requires around five or six times FULL LOAD current. A soft starter only reduces the current; it will not help the starting of the drive at all.

If the scenario above is correct, I suggest putting a relief valve in to allow start-up. This is just a valve which returns the water back to the sump. If automatic start is required, the valve would need to be automated.

If the pump is a centrifugal type, there is a fair chance the soft start will be OK. I suggest that your reader observes the ammeter on start-up rather than look at waveforms. The ammeter will probably show average current in spite of the distorted waveform during the start. Also make sure that all the three phase currents are similar.

The starter design might limit the current during the run-up. If it does and the motor does not get up to speed in a reasonable time, say 20s, I would suspect that the current is not great enough to provide sufficient torque to overcome inertia and system resistance. If this is the case, try closing the outlet valve. The motor will have an easier time, as it only has to accelerate the pump. If this fails, an autotransformer will probably solve the problem but they are expensive.

On the subject of re-using equipment from junk, Hoover front-loading washing machines have a nice little speed controller on the spin/wash motor. The motor has a pulse generator feeding back into one of those chips used in switchmode power supplies.

Jeff Jones,
via email.

Plugpacks could be supply option I note the letter by Ross Herbert in the October 2006 Mailbag section headed "Plugpacks Are Undesirable". I agree with all the issues raised by the writer and the attached comments. May I offer a suggestion on this issue? If projects were designed with the option of using either a built-in mains power supply or a separate plugpack supply, all of the concerns mentioned should be reasonably met. I expect this would require that projects would need to be designed and tested with a built-in mains supply, while the article would describe the steps needed for incorporating either of the two supply types. I guess the power transformer, fuseholder, on-off switch, mains wiring, and cable anchoring, etc would be the main constructional and safety areas of difference between the two supply types. Having the two power supply options should also address the legalities and responsibilities relating to safety. This way, inexperienced constructors should build the plugpack version, while experienced constructors would be able to choose the type appropriate to their needs. In fact, as a majority of projects use DC-output-only supplies, then an option is for the entire rectifier/filter/regulator stage to be made common to both supply types. This does, of course, presume that suitable AC plugpacks would be available; designing for DC plugpacks may add some complexity where ± rails, etc are needed. Still, the idea is there. Further, there is also the option of using single-chip DC-DC voltage converters. Graeme Dennes, via email.

Moon landing conspiracy rebuttals

I could not agree more with your editorial in the October 2006 issue. It might almost be OK if the "fake moon landings" were introduced as a classroom exercise in examining what it means to "know" that an historical event took place. There is a particularly good web site at www.clavius.org which has rebuttals to all of the specious claims of the conspiracy theorists.

Note that many of the "doubters" are Americans themselves. One of the most outrageous books written on the subject is "NASA Mooned America" by Ralph Rene, written in 1992 (his "The Last Skeptic of Science" is, if anything, even more ridiculous).

With the rise of the internet this nonsense is spread wider and faster than ever.

Bill Hanna,
Alice Springs, NT.

Hacking your DVD player is not illegal

I am writing in reply to the letter from John Tingle in the October 2006 issue. In his letter, John talks about DVD region codes and how farcical they are. I have to agree with everything John talks about but I want to point out that there is a website devoted purely to finding out how to circumvent the region-encoding that is embedded into most DVD players currently on the retail market.

Before I list the website’s address, I have to say that "hacking" your DVD player is not illegal - I was informed of this during a phone conversation with the Trading Standards Office in Brisbane. Have a look around the site and you will see that a large majority of manufacturers actually list the codes for their DVD players and they list them voluntarily, along with the procedures required to change or reset the codes.

I also cannot understand why manufacturers still undertake measures to prevent piracy. As far as I know, every type and method of piracy protection that has been implemented by a manufacturer or supplier has been circumvented. We all know that there are a lot of people who have a lot of time on their hands and that these people like nothing more than a challenge.

Please do not get the wrong impression; I am not a pirate, nor do I agree with piracy. In fact, as a systems analyst, I deal with piracy everyday.

When I am called upon to fix a problem, the culprit is usually a piece of software that has been installed to circumvent system or software security, or it is a piece of pirated software installed by a user.

Most hackers also include some form of malware into their hacks. A large number of Trojan and Zombie infections are caused by "hacked" games being downloaded off the Internet and installed onto the office network or home PC.

To make you DVD player region-free, have a look at:

www.dvdregionhacks.com

www.ottmarliebert.com

www.dvdremotehack.com

www.dvdownunder.com.au

You can search these sites to locate your player and take the appropriate action.

As a footnote, I am assured by the various suppliers I have asked that this DOES NOT invalidate the warranty. However, making a mistake during the hacking procedure may render the player inoperative.

Treat these procedures as you would a BIOS update on your PC. If you have any doubts about what you are doing, don’t do it. The responsibility for mistakes or a damaged DVD player is entirely your own.

Dave Sargent,
via email.

Thomas Edison was not a genius

I must take issue with Kevin Poulter’s articles on Edison. While they were a good read, to say that he was a genius is just plain wrong. Edison was an ideas man. He got an idea and then, through sheer hard work and experimentation, brought it to fruition.

For true electrical genius, there is only one man to turn to: Nikola Tesla.

Les Glover,
Earlwood, NSW.

Computer TV card problems With regard to the "Computer TV Card Problems" topic on page 106 of the October 2006 issue, the problems that T. B. has in burning PAL DVDs from captured off-air broadcasts are probably a specific limitation in the software he has tried. PAL DVDs are encoded at 720 x 576 resolution, so input video files of any other resolution must be resized/resampled to that resolution. The software T. B. has tried must be incapable of performing that video resizing function. I have just tested Nero Vision Express 3 and it is capable of resizing high-definition (high-resolution) video files down to PAL DVD resolution as part of the DVD burning process. My copy came bundled with a Pioneer DVD-RW drive as part of Nero OEM suite 6. However, note that converting high-definition video content to PAL DVD will result in a significant loss of resolution (detail). If you have a high-definition television, it would be better to write the MPEG2 file to a data DVD for playback by a PC, or perhaps by a device like the Zensonic Z500 High Definition Network DVD Media Player (www.zensonic.com). This would retain the high-definition aspect of the video. Regarding delays between audio and video, I tried many different (unsuccessful) methods to overcome this problem until finding "VideoReDo". VideoReDo’s main task is editing MPEG files which it does without recompressing the video file - this results in fast performance without adding any further compression artifacts. A 14-day free trial is offered at www.videoredo.com Any mention of recording off-air broadcasts should be tempered by a mention of Australian Copyright Law at: wikipedia.org Andrew Woods, Centre for Marine Science & Technology, Curtin University of Technology, Perth, WA.

Home theatre projector is very satisfying

I would like to thank you for all that information on home-theatre video projectors in the August 2006 issue.

I have been interested in setting up a home-theatre system for some time but was put off by the cost of the projectors. I did not know whether the cheaper ones would be good enough and you can’t tell until you set them up. However, a few weeks ago, Officeworks advertised an Acer PH110 for $799.00 and according to your article, it should do a reasonable job. So I bought one.

We did not want a special room for it, so we set it up in such a way that the room looked like a normal lounge-room except when we put the projector on. All we have to do is shift a few vases.

The projector is about four metres from the wall (screen), giving a picture 2.4 metres wide. We sit about 4.5 metres from the screen. The only giveaways are the surround sound speakers and the projector mounted upside down from the ceiling. The cost? Just under $1600. We are both really pleased with the results.

I hope that this will encourage other readers to have a go.

R. A. Groves,
Tin Can Bay, Qld.

Cheap DVD players are amazing value

Back in January 2005, Leo Simpson wrote an editorial on the perils of cheap consumer audio/electronic gear. While he was quite right for the most part, there is a vastly different situation for items such as DVD players.

I have found that, as a rule, the more you pay for a player, the less formats it is likely to play. So, although a Japanese brand-name unit might play DVDs and VCDs quite OK, don’t expect it to deal with non-standard things or maybe even burned DVD disks.

The most spectacular example of this sort of thing was a small, unpretentious DVD player I purchased recently from Dick Smith Powerhouse for $38. At this price, one would be content with almost any performance level, so long as it plays the basic things. But amazingly, this one plays virtually anything you put into it. Besides DVD, VCD, SVCD, etc, it also plays virtually any MPEG file, MP3 (well, they all do, don’t they?), WMA, DIVX and XVID (AVI format). This capability is not mentioned anywhere in the documentation.

This thing was such good value that I bought three of them, against the day when the optical drive eventually fails, whereupon I will merely place one of the backups into service. I got three of these for less than the cheapest brand-name unit which wouldn’t even approach the performance.

Richard Belanger,
Gosford, NSW.

Teaching about the American moon shots

As a science teacher of some 33 years, I read the October 2006 editorial with great interest. I teach HSC physics and I have followed the development of space exploration since the very first Vostok and Mercury missions. While I have not come across any science teacher who would teach such nonsense, I do encounter students who have been convinced that the moonshots never happened. The power of the media!

When this happens, I bring in books on the subject that basically prove that, if indeed this thing was a hoax, then it must have been the longest and most expensive and elaborate hoax in the history of humankind. I recommend "Apollo: The Epic Journey To The Moon", by David West Reynolds (Tehabi Books Inc, 2002). This is a full-colour history of the equipment and missions.

Once my students see this, they realise that it was real. I also explain that the VAB (Vertical Assembly Building) still exists and is used to refurbish shuttles, while the crawler transporter that was used to move the Saturn V moon rocket to the pad is still used to transport shuttles.

Other notable books are: The Apollo NASA Mission Reports (Apogee Books, www.egpublishing.com) and "A Man On The Moon" by Andrew Chaikin (Penguin Books, 1994).

I had the great pleasure of visiting the National Air and Space Museum in Washington DC last year and the sense of awe I got from standing next to the Apollo 11 command module and Dave Scott’s (Commander, Apollo 15) moon suit were incredible. I wish I could take my students on such an excursion!

If, as the Editor states, some science teachers are indeed pushing this garbage, then perhaps his last sentence would be justified. Thank you for a great magazine.

George Green,
Physics teacher,
Wollongong NSW.

PIC Programmer caused computer restart problem

A while ago, I bought a serial PIC programming kit from Dick Smith Electronics and it’s been a dream to work with. But after I started to leave it plugged into my computer, my computer started to do a very annoying thing: every time I shut it down, it would restart and it would only stop if I held the power button down. I looked at my power management settings under BIOS and then I saw the setting that was causing the problem. Under Wake Events -> LPT/COM, it was set to LPT/COM, so if there was any event on either the parallel or serial port ports, the computer would start up. I turned off the Wake on LPT/COM and there were no more problems.

What I think happens is that the serial port constantly powers the MAX232 chip and when the computer powers down, the MAX232 chip has a little heart attack and manages to trigger the POWER UP event on my computer via the serial port. I am not sure of a hardware fix but for those with Power Management or similar on their computers, they should insure that Wake on LPT/COM is set to NONE to avoid these problems.

Max Bainrot,
via email.

DVD zoning :the explanation With reference to the letter from John Tingle in the October 2006 issue, the reason we can buy zone-free DVD players in Australia is due to a unique High Court decision. All DVD hardware manufacturers were coerced into signing an agreement with the software suppliers (the US-based movie industry) to only sell region coded players in each zone. The reason for the regional coding was to enable the movie industry to restrict DVD sales until after a movie had been released in each market (perhaps also to be able to set prices differently in each market). Consumer hardware (unlike many computer drives) has always had the facility to be modified to allow all zones. When the movie cartel discovered this practice - they filed suits in each affected zone’s countries to have this practice declared illegal. In Australia, however, the High Court held that zoning was an illegal restriction on every Australian’s right to enjoy movies they bought outside Australia. The example cited was people returning from overseas holiday travel with DVDs bought while on their trip, although the argument could as easily be applied to mail order - an "expectation of enjoyment" would be there as well. Thus although all Zone 4 players are manufactured marked with the zones, the manufacturers are still required to do so. Indeed, elsewhere in Zone 4 they only play that code. In Australia, all players sold today are zone-free and usually the distributor makes the change before shipping units to the retailer. If you own an early player, it can still be modified to play all zones, usually by something simple, like changing the remote or by just entering a code. Some early players required a wiring change. I have an RCA, my earliest DVD player which required that kind of treatment; it was bought before the ruling. The dealer made the modification for $200 - worth it to me, since I already had an extensive collection of movies from several zones. It is all perfectly legal. Bear Stanley, Atherton, Qld.

Caution needed with reformed electrolytic capacitors

Over many years in industry I have seen sufficient "near misses" with electrolytic capacitors to have gained a healthy respect for their destructive capabilities under fault conditions. All electrolytics lose their anodic film after extended periods of disuse or storage and I agree with Rodney Champness in his article (in the October 2006 issue of SILICON CHIP) that this film can be restored by "reforming" the capacitor by the application of the appropriate voltage via a low constant-current source.

However after an electrolytic is reformed in this way it is not a foregone conclusion that it is safe to use, particularly if it is of the age of most components found in vintage radios. The ESR could still be high enough to cause over-heating when there is significant ripple current in the circuit where the capacitor is fitted and this is where the trouble can start.

As an example, I was asked to overhaul a 1960s guitar amplifier for a young friend who was a fan of "valve sound". The unit was in quite good condition and appeared to work well, with minimal work required on my part. I was cautious about the three multiple electrolytics fitted since they were over 40 years old and even though they reformed OK and had acceptable ESR, etc, I advised the owner that they should be replaced. Since the capacitors were not standard types and had to be ordered, the owner elected to use the amplifier and return it to me when the new components arrived.

A couple of weeks later I received a phone call to say that the amplifier had "blown up". On examination, one of the electrolytics had exploded. Its metal case had shot backwards out of its metal clamp, passed (fortunately) between the output valves, bent flat a projecting 3.5mm bolt and embedded itself in one corner of the case. Meanwhile the capacitor’s insides had been evenly distributed over the chassis and the inside the cabinet.

On this occasion, the only human damage was the owner’s loss of composure at the time. However if the amplifier had not been in a fully enclosed cabinet or somebody’s face had been near the offending component when it exploded, the results could have been much worse.

Incidents like this convinced me a long time ago that the only good electrolytic is a new one from a reliable manufacturer! New, unused electrolytics that have been stored for a couple of years can often be re-formed and used safely but any of the old brown, grey or blue Ducons should be retired to the "round bin".

Warwick Woods,
Historical Radio Society (Aust).