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  #41  
Old 26-05-2020, 10:48 AM
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Quote:
Originally Posted by alval View Post
.... I thread away from the chuck. Same set up except tool is upside down and you run the lathe in reverse..... Speed is then not an issue and most things cut better with a bit of speed.
Al
Yep, I was thinking about this method if they send the wrong controller again.
But, since the machine is new and sort of under warranty, I will insist on full functionality as advertised.. Anything else may be considered as improvement (the seller actually offered to pay for cost of repairs),

I sort of enjoy solving problems like those and at the end of the day I will know what I have.
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  #42  
Old 29-05-2020, 05:10 PM
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Daniel Reardon's post (Astrophysicist with magnets in nose) gave me an idea - how to firmly attach dial bracket to lathe bed, for precision readout of tool position... and to be easily removable at the same time. I used 8mm Neodymium magnets (I found them in some old faulty toys, and until now I kept them on kitchen fridge door... I think this application is much more useful.
Picture is self-explanatory...
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  #43  
Old 29-05-2020, 10:26 PM
alval (Alan)
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Yeah neodymium magnets are great for quick attachment of all sorts. Might I suggest a bit of tape over the magnets as they attract lots of swarf and chips, when you need to pull off the tape and the magnets are clean, put on some fresh one for next time. They are a pain to pull chips off of but really handy.
Al
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  #44  
Old 30-05-2020, 04:50 AM
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Quote:
Originally Posted by alval View Post
Yeah neodymium magnets are great for quick attachment of all sorts. Might I suggest a bit of tape over the magnets as they attract lots of swarf and chips, when you need to pull off the tape and the magnets are clean, put on some fresh one for next time. They are a pain to pull chips off of but really handy.
Al
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  #45  
Old 31-05-2020, 05:52 PM
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Angry

Today, after 1 w waiting, I received the parcel (from China via DHL).
But.. instead of new, correct motor control module or new processor (as I hoped we agreed after many messages), I found the potentiometer in the box (not that I wasn't expected something un-expected after what was going on previously).

I will have to give negative feedback to this seller..

They really, really don't know what they are selling (and neither manufacturer know what they are doing.. or they think I am stupid. Which is probably true because I was too patient with them).


Anyway.. not a big deal really (machine works), but this is not the way how to treat customers.
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  #46  
Old Yesterday, 11:01 AM
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Since the issue with seller isn't going anywhere, I decided to modify existing controller by replacing original processor with AtTiny85.
The following "sketch" (arduinian for "source code") does the trick:

****const byte pwmPin = 0;
const byte analogInPin = A2;
// MS_TIMER_TICK_EVERY_X_CYCLES in arduino-1.0x/hardware/digispark/cores/tiny/wiring.c is set to 8
// resulting in PWM frequency 4kHz (default is 64, f(pwm)= ~500Hz)

void setup() {
pinMode(pwmPin, OUTPUT);
pinMode(1, OUTPUT);
digitalWrite(1, HIGH);
}

void loop() {
int analogIn = analogRead(analogInPin);
analogIn >>= 2;
analogIn=analogIn/2;
// analogIn = map(analogIn, 0, 1023, 0, 255);
analogWrite(pwmPin, (255-analogIn));
***
I will couple the PWM output to the rest of controller electronics with opto-isolator, which will give me the option of using GRBL for spindle speed control in the future.


EDIT: I had to rewrite the code posted earlier because PWM output is supposed to be inverted. I also added enable output, the same functionality was on Holtek HT66F018 processor, probably to prevent activation of high voltage output during processor startup.

Last edited by bojan; Today at 03:10 PM.
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  #47  
Old Today, 10:45 AM
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This is how $2 Digispark ATTINY85 board fits onto existing controller PCB without any modification. I may solder the chip directly on board later, but it's mounted perfectly OK as it is now.
I also reverse-engineered the controller circuit to some extent..
HT66F018 (faulty now) is full-blown 8-bit processor, but it's only function here is generation of PWM from pot position (exactly what Attiny85 with my program from previous post does).. and nothing else.

Overload protection is facilitated by separate Opamp and comparator IC's, signal from this circuit disables PWM externally in separate wired-OR circuit.. Maybe they used here processor from, say, vacuum cleaner power regulator to save the effort of designing more sophisticated firmware? This would explain my troubles with minimum head speed....

Anyway, it seems I will have exactly the same functionality after this modification is finished, except I will have the desired lower speed.
And another controller board as spare :-)
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  #48  
Old Today, 01:30 PM
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The motor controller works on bench, as expected
It is ready now for test in the machine.
If all goes well after tweaking speed, I will need to figure out how to get rid of 5 sec delay (used by bootloader) so the main code starts immediately after power-up.
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Last edited by bojan; Today at 03:08 PM.
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  #49  
Old Today, 05:33 PM
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This is turning into an expensive DYI. For the money you've paid the seller should ship you a new one. I wouldn't modify it.
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  #50  
Old Today, 05:59 PM
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Quote:
Originally Posted by multiweb View Post
This is turning into an expensive DYI. For the money you've paid the seller should ship you a new one. I wouldn't modify it.
Well.. no....
Seller send me already the wrong items anyway, I think they are helpless here as well. They are just sellers..
The new machine may have numerous other problems, I found heaps of videos about them.. and I didn't want to pay 3x or 4x more for professional machine. If I found something second hand I would have gone for it, but, I was not that lucky.

Then...
First, what else to do in isolation?

Second, it is only my time that is really spent here, plus couple of bucks for additional electronics (which I already had in my drawers doing nothing), and a bit more for bearings ($5 each, some of them I also had in my stash).
And, this story may be useful for someone. Like, what to do in similar situation, or what not to do to get into situation .
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