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Member postings for SillyOldDuffer

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

Thread: Arduino Uno Programming Assistance Request
21/01/2018 12:03:15
Posted by James Alford on 21/01/2018 11:15:58:

An irritating update.

I updated my Uno board and libraries following the prompts that came up when plugged it in this morning.

Now, on all versions of my programme, I get an error message on compiling saying:

error: no matching function for call to 'DS3231::DS3231(const uint8_t&, const uint8_t&'

DS3231 rtc(SDA, SCL);

The emoji is not my addition. I have no idea what has happened, but now need to try and unpick what is causing it..................

James.

Edited By James Alford on 21/01/2018 11:17:25

Have a look at the definitions of SDA and SCL. Should be something like:

const uint8_t SDA = 11;

rather than, say, the very similar:

int SDA = 11;

The compiler is complaining because one or both of the SDA and SCL type definitions don't match what the RTC library is expecting. Presumably the RTC library specification was tightened by the last update.

The other way of fixing it is with a cast. eg:

DS3231 rtc( (const uint8_t) SDA, (const uint8_t) SCL);

The first method is the more correct - everything matches. The second method tells the compiler "I know the definition of SDA isn't quite right and I know what it should be, stop moaning".

Dave

20/01/2018 10:06:24

I'm finding your questions and the answers fruitful James! For instance, I didn't know of the AccellStepper library, thanks Marcus!

Despite the attractions of steppers, my inclination would be to ring bells with solenoids as you propose. It might pay to strike the bell via a spring loaded arm : something like a piano key mechanism perhaps. Before leaping in to that complexity I'd experiment with a simple ON/OFF solenoid that directly hits the bell when activated. If it sounds OK, it is OK. If not, think again.

An interesting challenge in this sort of project is deciding what's best done by the Arduino, and what's best done externally. It's fairly obvious that using an Arduino and RTC to keep time eliminates a mass of difficult mechanical clockmaking. It's not so obvious where best to manage something like the acceleration of a striker. It could be done with an Arduino, but my feeling is a simple mechanism would produce better results from less effort.

It's all part of the learning curve. Don't be discouraged by difficulties - it may be painful at the time but overcoming them is pure gold in terms of gaining experience. At this stage I wouldn't worry too much about saving power. Get the thing working first and then refine it.

Dave

Thread: New Granite Surface Plate
19/01/2018 20:37:31
Posted by jimmy b on 19/01/2018 19:01:01:

My new plate came with no marks to indicate how it was supported for calibration.

It was shipped in a box....

Jim

I wouldn't worry about it - I believe only high grade plates (ie better than needed for tool-room use) are so marked. You might be more concerned to know that tables made to support surface plates cost roughly twice as much as the plates themselves. Levelling, stiffness and so forth matter when you're serious about flatness.

Steve's point : 'With reference to the fact this is a model engineering forum it is important to note that the effect of not using 3 points on small granite plates and with small components may be of little consequence' is well made. I use a bit of kitchen worktop and occasionally put a sheet of glass on top as a treat. It's my Bodge Standard Surface Plate. You may well need better, and I'm sure your boxed granite is a considerable improvement!

Dave

Thread: CE Mark - real and fake
19/01/2018 16:27:05

If the CE Mark is meaningless, then what's the alternative? I hope no-one thinks it's the BS Kitemark; they were and are still being counterfeited in exactly the same way. Fuses for example.

Dave

Thread: Newton Tesla Electric Drives
19/01/2018 15:54:15
Posted by Jim Greenhill on 18/01/2018 20:30:49:

Okay I understand, next question, if find could only buy one would you upgrade lathe or mill,

Jim

I guess in theory it would be more value on a mill because they don't have a whacking great chuck helping to smooth out the motor by acting as a flywheel, also I find fine speed control on a mill a tad more helpful than it is on a lathe.

I prefer experiment to theory. Have a look at the smoothness of test cuts made by both machines. If you can see evidence of vibration on the test-pieces, upgrade the one that produced the poorest results.

You wouldn't go far wrong by upgrading the machine that gets used most often.

Dave

Thread: Arduino Uno Programming Assistance Request
19/01/2018 15:12:40

Posted by James Alford on 19/01/2018 07:38:18:

...

I am now looking to see whether I can incorporate PWM into this code so that I can give the solenoids that the pins will drive a soft start, rather than coming on with a bang: I also hope that it will reduce overall power consumption.

...

Is there any way that I can put this "soft start" code into a routine on its own and then replace pulseLength_ms in the line t.pulse( LED_PIN, pulseLength_ms, LOW ); with a call to this sub-routine?

...

I hope someone else will have a crack at this: I think James has set another hard exam question!

Here's a program that 'sort of' does what James wants.

<code>

#include <Event.h>
#include <Timer.h>

 

class jaTimer : public Timer
{
  public:
    int8_t pwmRamp( uint8_t pin, unsigned long period, uint8_t startingValue, int repeatCount = 1 )
    {
      int8_t i = findFreeEventIndex();
      if (i == NO_TIMER_AVAILABLE) return NO_TIMER_AVAILABLE;
    
      _events[i].eventType = EVENT_OSCILLATE;
      _events[i].pin = pin;
      _events[i].period = period;
      _events[i].pinState = startingValue;
      if (  _events[i].pinState )
      {
        for (uint8_t count=100; count<250; count+=50 )
        {
          analogWrite(pin, count);
          delayMicroseconds( 60000 );
          
        }
        analogWrite(pin, 255);
      }
      else analogWrite(pin, 0);
      
      _events[i].repeatCount = repeatCount * 2; // full cycles not transitions
      _events[i].lastEventTime = millis();
      _events[i].count = 0;
      return i;
    }
};

jaTimer t;
const char pwmOutputPin = 2;
unsigned long previousTime = millis();

void setup() {
  pinMode( pwmOutputPin, OUTPUT );
}

void loop() {
  t.update();

  if ( millis() - previousTime > 4000 )
  {
    // A 1000ms ramped pulse once every 4000ms
 
    t.pwmRamp( pwmOutputPin, 1000, HIGH );
  }
}

 

</code>

In it, I have derived a new class (called jaTimer) from the Timer class that James is already using. The derived class does everything that Timer does and has a new function called pwmRamp(). It behaves exactly like pulse() except an internal loop takes a PWM pin up from 0 to 255 in 4 steps with a delay between each step.

We have a problem Houston!

Firstly, I'm not convinced my new code is quite right.

Secondly Arduino PWM is based on a 500Hz square wave, meaning that an analogWrite() change isn't meaningful unless it lasts at least 2mS. Actually my experiments seem to show that PWM takes rather longer than that to settle.

Thirdly because changing the PWM value too quickly generates confused outputs that aren't very ramp-like, it will be necessary to play with both the number of steps in the ramp up and the inter-step delay to get the effect James wants.

Fourthly, if the ramp takes too long to output in total, it will mess up the timing of the main pulse.

In short I think the code I've written can be made to work but it's far from friendly. It may be necessary to find an alternative, for example:

  • Using external faster PWM to control the solenoids.
  • Using a digital output to charge an RC combination that uses the solenoid driving transistor as a fast rheostat rather than a switch. (Wastes power and the transistor might overheat.)
  • Firing the solenoid at full speed (this is easy) and using some form of mechanical linkage to slow down the strike.

Can anyone suggest a simple way of achieving James' goal, either in code, or with electronics (ideally with an off-the-shelf module), or mechanically?

Dave

Edited By SillyOldDuffer on 19/01/2018 15:13:08

Thread: CE Mark - real and fake
18/01/2018 21:59:37

Posted by Phil Whitley on 18/01/2018 18:56:33:.

...

Standards have gone through the floor, as has quality of manufacture. Pity the youngsters who think they are spending their hard earned on the peak of modern technology!

Or pity the old chaps who believe that!

Easily tested Phil. Proceed tomorrow to Argos disguised as a youngster and buy an X-box. Note how much it costs as a percentage of your income and work out what you could have bought for the equivalent in 1967. Now take it apart in your garage and write a list of everything in the machine that's poorly made. Take particular note of anything that doesn't work. (Probably zero.) Next identify all the parts that you cannot make in your workshop; that will be almost all of it. Also, note the many parts that could not have been made anywhere in the world, even an advanced research facility, 20 years ago.

I think what's going on is value engineering. In the past, because materials were poorly understood, it was common for things to be heavily built from the best available materials. Over-engineered and correspondingly expensive, they lasted well. Not value for money though and most of it long since scrap. Modern kit is much more lightly built. It is engineered down to a price, usually very effectively for its intended working life. Of course cheap tat is still being made. Rubbish has always sold to the unwary and it still is. 'Caveat Emptor' said the Romans.

I suggest a new car or a TV set is far more representative of modern industry than cheap electrical parts. Old cars have plenty of character, but they rust, pollute, need lots of maintenance, are heavy, unsafe and low mpg. Modern cars are more refined in every way and they're relatively cheaper too. Morris Marina or Vauxhall Corsa, you tell me which is better?

Dave

Thread: Cross slide improvement for a 9 X 20 lathe
18/01/2018 20:21:57

I noticed that the last photo in the group on this amazon page is provided so customers can tell the difference between a Genuine Brand Huanyang Inverter and a 'Cheap Copy Inverter'.

This is a good sign. Stage 1 of a developing industrial economy is 'anything goes'. Stage 2 is the realisation that quality and reputation matter. It's the point at which selling junk costs an economy more money than it brings in. I wonder how many Chinese industrialists are fed up with the cowboys and are busy lobbying in China for tight copyright law and stiff penalties?

Stage 3 is the realisation that knocking out manufactured goods in clouds of pollution isn't particularly profitable. There are better ways to make a living, like high technology.

Dave

Thread: Newton Tesla Electric Drives
18/01/2018 18:42:22
Posted by Jim Greenhill on 18/01/2018 14:50:40:

Hi I have been reading about vfd on a number of posts/ forums, I can see the attraction for speed control, but what I don’t understand is the reasons to change motor to three phase, and why doing so reduceds the noise. Why not put speed control on single phase motor

Jim

A single phase motor works a little like it's kicking a can down the road - one power feed pulsing 50 times a second. It's a useful compromise for smallish motors in a domestic situation.

A three phase motor has three power feeds each off-set from the others by 1/3rd of a cycle. The windings are arranged to create a smoothly rotating magnetic field. Speed control is achieved by varying the frequency of the supply. Altogether 3-phase motors are a much better solution apart from needing a 3-phase supply to run one. These days, that's much easier and cheaper than it used to be - a VFD,

You can speed-control a single-phase motor but it's done by increasing the can-kicking effect. Even noisier and the motor loses lots of power and torque. Not a good idea.

Dave

Thread: Spot the fake
16/01/2018 20:57:02
Posted by Dave Halford on 16/01/2018 20:36:53:

The Cannon are fibre glass so some of it is fake.

And all the wood has been replaced at least once.

The Rocket displayed in the Science Museum is not as it ran at Rainhill. Note the angle of the cylinders in the Wikipedia photo of the original:

Compared with the replica which has them in the original configuration:

The original is less realistic than the replica. Truth is they're both wrong and they're both right. Confusing or what?

Dave

 

Edited By SillyOldDuffer on 16/01/2018 20:58:46

Thread: Lift-span Bridge
16/01/2018 20:35:34

Most impressive Peter. Have you thought that your construction photos could be part of the museum display? The original bridge is interesting, your model bridge will be interesting and so is how you made it.

Dave

Thread: Spot the fake
16/01/2018 20:25:23

Is HMS Victory in Portsmouth Dockyard an original, a replica or a fake?

The Ship of Theseus paradox is an old one. It applies to you and me - apparently cells are replaced so quickly in the human body that in 6 months 98% of the atoms will be new . Scary!

Dave

Edited By SillyOldDuffer on 16/01/2018 20:26:07

Thread: Ten Useful Things
16/01/2018 20:00:09
  1. Ice cold workshop full of rejects
  2. Armchair
  3. Nothing on telly
  4. Router and paid up Internet connection
  5. Laptop
  6. Browser
  7. Forum Account
  8. Bottle of Beer
  9. Bottle opener
  10. At least one keyboard trained finger

Dave

Thread: Cameras or Dishes?
16/01/2018 19:46:19
Posted by Michael Gilligan on 16/01/2018 15:37:46:
Posted by Neil Wyatt on 16/01/2018 12:47:02:

...

...

My little bit of pedandtry ...

MichaelG.

Pedandtry? Now you're teasing us!

smiley

Dave

Thread: "It" comes to life again
14/01/2018 14:52:07
Posted by Dean da Silva on 13/01/2018 07:48:50:
Posted by Frances IoM on 12/01/2018 15:33:35:
...

I have never ... seen a British locomotive up close and personal.

To me they have more beauty, elegance and character than their American counterparts by a large margin.
...

 

The reasons for that elegance lie in history of railways in Britain.

Firstly the country is densely populated. For perhaps two hundred years before the Stockton and Darlington Railway opened many areas of the UK were criss-crossed by Wagonways, Dramways and Tramways. They were used to shift clay, iron-ore, coal and limestone from mines and quarries to ironworks, potteries, sea-ports or the canal system. There was much slaughter resulting from running unfenced industrial transport through towns and villages. When public railways opened they were obliged to fence the tracks.

Secondly, land is expensive. This meant there were strong financial reasons to minimise the gauge, in this sense the maximum width of the carriages. Tunnels, bridges and curves all conspired to limit the width and height of a train. Also, to attract rich passengers, they put considerable effort into stations - they had platforms and roofs. Fat trains not welcome.

The effect of this is that British engines tend to have all their ugly gubbins hidden away on the inside. At the same time fenced off lines remove the need for British engines to have a bell, headlamp, and cow-catcher. All this leads to a clean good-looking exterior where the designer can indulge his aesthetic talents. It also leads to high maintenance costs - everything is hard to get at.

In the USA and many other countries, land was cheap and there was less concern about mowing down livestock or civilians. Stations didn't have platforms. Having more gauge space made it possible to put the works on the outside of engines making them easier to maintain. On the downside lack of fencing meant the driver needed a headlamp, and a bell, and a cow-catcher to prevent collisions damaging the train.

This is Death Avenue, New York. Here the locomotive has been covered to stop it scaring the horses and a horseman rides in front warning people to get out of the way.

Health and Safety gone mad!

Dave

Edited By SillyOldDuffer on 14/01/2018 14:52:36

Thread: Things must be getting tight for the scammers.
12/01/2018 17:20:49
Posted by Gordon W on 12/01/2018 16:00:15:

I find it best only to reply to messages sent by beautiful women.

I'm a beautiful woman Gordon. Please send me cash. You can trust me - no way I'm an overweight elderly male in urgent need of a bath. Don't believe what my parole officer says either; fake news all of it.

smiley

Edited By SillyOldDuffer on 12/01/2018 17:21:13

12/01/2018 14:02:51
Posted by Neil Wyatt on 12/01/2018 12:33:37:

Dearie, dearie me, some folks must either live very sheltered lives or have incredibly effective spam filters.

...

More likely they are just plain lucky!

My email address was leaked by a friend who forwarded a 'share this joke with all your friends' email. When he sent it to me and others, he also unknowingly sent a blind copy back to the originator that revealed all our email addresses. Since then I've been getting spam from multiple sources. My friend thought he was doing me a favour.

Spam loaded with personal detail is much more dangerous than the unfocussed 'UNITED NATIONS owes you money' type. You're much more likely to fall for spam where they have your name, address, bank, occupation, and other 'private' details right. So it pays not to leak information on the internet if you can avoid it and to assume until proved otherwise that unexpected emails and texts are fakes. For example, ask yourself why someone would choose you to forward an amusing email to your friends and family. Are they spreading goodwill or up to no good?

Dave

Thread: Drill bits for brass?
12/01/2018 13:24:06
Posted by Michael-w on 12/01/2018 11:24:45:

Brass is just awful stuff in general to machine,

I don't know why people don't prefer copper or bronze in that regard, the swarf is a lot easier to clean up.

Michael W

That's intriguing - Brass is my favourite metal because it machines so well! I agree the swarf is a pain. Apart from that I wonder if Michael and I are using different alloys?

In my experience as a junior machinist Bronze and mild-steel are OK. Leaded mild-steel is good. Copper tends to tear rather than cut, avoid. Aluminium can be sticky, Cast Iron sometimes has a skin harder than a file and is filthy. Many (not all) Stainless Steels work-harden, and some steels are gritty or otherwise obnoxious when you cut them.

I've read that Magnesium alloys machine best of all, but are no fun if it catches fire!

Does anyone else have favourite or hated metals and if so why?

Dave

Thread: Need advise please
08/01/2018 20:00:26

Says it's a CL500 in the post's sub-title. Sorry I don't know that one but someone will.

Welcome Wayne,

Thread: Elidir - 3 inch scale Hunslet
08/01/2018 16:16:21

Gorgeous!

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