Telescope drive motors that don't...

[mister_e]

Is there any exact motor Model we can refer to?

i found this PDF for those interested in Stepper Motor Basics
http://www.solarbotics.net/library/p...f/motorbas.pdf

Turning the problem in many ways... i'm still thinking of unsufficient current AND/OR voltage at the driver output. I would suggest you to use a higher voltage source, and connect the driver before the voltage regulator. If you have any variable voltage power supply that would be nice. This bring mvs_sarma's suggestion to the front. Make sense, there's probably some voltage loss at the output.

Why the previous driver circuit worked... well hard to tell, no schematic or pic of it (with some part# of the transistor/Mosfet)? Any coils or else fancy stuff on it?

[Archangel]

Turning the problem in many ways... i'm still thinking of unsufficient current AND/OR voltage at the driver output. . . .

Hi Steve, that was where I was going by asking if the enable pins were held high, as I do not understand the assembler . . . I think those ports should not be pulsed . . .JS

[mister_e]

i just had a look at L293D... there's an interesting voltage drop.. typical Vs-1.2 to Vs-1.8 v... ok ok @0.6A... but... could this be enough to lost most torque... i would think.

Probably the original design used MOSFETs, so the voltage loss was reduced to a minimum. Pure guess here.

[mister_e]

There's still some Sound-Card based Free software you could used... it's still better than nothing. Be carefull with signal amplitude and it should give you some pointers.

I already used VA (Visual analyser)
http://hacca.altervista.org/

[Dodgy Geezer]

Wow! A free oscilloscope! Thank you, Mister-e! Now I must find an old sound-card....

"Probably the original design used MOSFETs, so the voltage loss was reduced to a minimum..." - I thought I was actually building the original design. You will clearly see +6v on the original circuit diagram. But I am now inclined to think you are right, and this circuit does not actually work as specified...

[mister_e]

Well it has to work as expected with HIS OWN step motor... but how many different model is there in the world?

You can now buy a sound card under 20$ here... 1/10 of almost any decent used scope.

When i talked about the original design, i meant your previous one... not the one you found and post here.

[Dodgy Geezer]

"...but how many different model is there in the world...?"

He is using a standard chinese clock-drive for an EQ4/5 scope - so am I. I was expecting our motors to be identical....

"You can now buy a sound card under 20$ here.."

I have some separate sound cards already - I was assuming that you plugged the probes into the game port on them. But now I have downloaded VA, I see there is no info about where to connect the probes to at all. Do you connect the probe to the 'microphone-in'? If so, I can connect it to the built-in sound card on the motherboard of the system I am using. It is odd that there seems to be no information about this vital point...?

"When i talked about the original design, i meant your previous one.."

Sorry - I misunderstood. In fact, I still have the original handcontroller. My problem is not that it was broken, but that it drove the motors at the correct speed for an EQ4/5 mount (1/10 rpm) and I wanted to use it for an EQ3-2 mount (1/11 rmp). Those are the final speeds - there is a gear train of approx 200:1 between the scope and the stepper. The original controller used an Amtel micro, directly driving an array of 8 transistors. They could well be MOSFETs.

[mister_e]

you plug your probe to in Line in, make sure you set your Soundcard Mixer properly as well.

In VA, Click on Settings>> In/Out Device to confirm your setings.


Trent, i can't tell, it worked for me awhile back, not sure about the current one...

EDIT seems that I had the same version... doesn't seems to bug here.

[T.Jackson]

There's still some Sound-Card based Free software you could used... it's still better than nothing. Be carefull with signal amplitude and it should give you some pointers.

I already used VA (Visual analyser)
http://hacca.altervista.org/

That GUI is real buggy on my machine.

[Dodgy Geezer]

Mister-e '..Is there any exact motor Model we can refer to?..'

There are no markings on the motors. The original controller used a 6v battery pack, and the coil resistance is 18ohm. A similar looking motor is the BPM42 from Astrosyn, but that is specified as 12v.

Joe S. - thanks for joining the party! i would be happy to rewrite the code in Basic if that would help, but I think the code is working. I programmed the PIC on a Vellerman 8048 unit, which has a limited test function (6 leds and 4 switches), and the test showed the leds all lighting up at the right times. I have also run the code on a couple of software simulators, and it does what it says it does - holds the specified pins high.

What I cannot simulate is what the L293D is doing (no oscilloscope ). In other circuits I see the possibility of varying the current passed to the stepper, but I don't think you can on the L293D. How does the chip know how much current to pass the stepper?

The Lini Stepper is very interesting, and I would buy one like a shot - if it supported Bipolar steppers like I have on the telescope. Unfortunately, the telescope hardware is fixed. I was wondering about getting one of these - http://www.jafmotion.co.uk/motordrives.htm

[Archangel]

Mister-e '..Is there any exact motor Model we can refer to?..'

There are no markings on the motors. The original controller used a 6v battery pack, and the coil resistance is 18ohm. A similar looking motor is the BPM42 from Astrosyn, but that is specified as 12v.

Joe S. - thanks for joining the party! i would be happy to rewrite the code in Basic if that would help, but I think the code is working. I programmed the PIC on a Vellerman 8048 unit, which has a limited test function (6 leds and 4 switches), and the test showed the leds all lighting up at the right times. I have also run the code on a couple of software simulators, and it does what it says it does - holds the specified pins high.

What I cannot simulate is what the L293D is doing (no oscilloscope ). In other circuits I see the possibility of varying the current passed to the stepper, but I don't think you can on the L293D. How does the chip know how much current to pass the stepper?

The Lini Stepper is very interesting, and I would buy one like a shot - if it supported Bipolar steppers like I have on the telescope. Unfortunately, the telescope hardware is fixed. I was wondering about getting one of these - http://www.jafmotion.co.uk/motordrives.htm

I wasn't asking you to rewrite anything, Your reference to the website incurred me to think you found this code rather than wrote it, my appologies! My statement stands as is, I do not understand your code, so I do not know that it did that, I was simply suggesting a possible area to search.
Regards
JS

[mister_e]

ASM looks way harder than it is actually.

Let's see few common expressions

MOVLW .10
MOVWF PORTA
It's nothing else than PORTA = 10
<hr>
BTFSC PORTA.1
GOTO $-1

Could be translated as

WHILE PORTA.1=1 : WEND

OR

TestPORTABit1:
IF PORTA.1=0 then GOTO DoSomething
Goto TestPORTABit1
DoSomething:
<hr>
MOVF PORTA
MOVWF MyVar

would be MyVar=PORTA
<hr>
INCF MyVar,F

MyVar=MyVar + 1
<hr>
nothing really hard to learn... but yeah... could be a bit hard to follow/understand a little bit when you begin. 18Fs and DsPIC assembler is way easier to code, but you have more Mnemonics to learn.