1 Continuous MCPWM at a time

[barneyfrance]

fwd values : 0, 1, 3, 7, 15, 31, 63, 62, 60, 56, 48, 32
reverse values : 0, 32, 48, 60, 62, 63, 62, 60, 56, 48, 32

I have 2 truth tables with switches to turn on/off for these values.
Now i have a pot and a switch start/stop and a switch fwd/reverse..
Now we should not be able to change the sequence commutation if the pot is not 0 so I did a little code like this :

Direction VAR bit
direction = 0

Main:

        encoderstate1 = PORTA
        
        GoSub GetADC
        
        If ADRESH = 0 Then 'value of the pot stored in ADRESH
            If ADRESL = 0 Then ''value of the pot stored in ADRESH
                direction = PORTE.1 'switch for direction
            EndIf
        EndIf

if encoderstate = 0  then
'switches turn ON/OFF
elseif encoderstate = 1 then 
'switches turn on OFF
elseif encoderstate = 3 then 
..... etc
endif

goto main

I'm getting desesperate to put all this together with my switches
and my reverse sequence with if then. ifelse isn't working properly (need to have oldstate stored like you told me, Olson no ?)

[HenrikOlsson]

I'm sorry, I can't keep up with you here.

Did the Select-case version not work? Is that the reason why you're now using IF and ELSEIF? And did keeping track of the previous state thru the OldState variable not work? Or why did you skip that.

If I got the sequence wrong did you try to correct it and see if the aproach I took would work or not or did you just abandon that idea because I had the reverese sequence wrong?

If the only thing controling the sequence of the commutation is the desired direction then there's no reason to keep track of the previous state because then it doesn't matter.

/Henrik.

[barneyfrance]

hello, no I did try your great ideas, the case work for the forward direction but as my elseif code the case code for the forward does not work because the second half of the commutation is the same as the previous one. So in that case I think I need to have the old case. I will keep trying experiments, thank you for your time and ideas

[barneyfrance]

Do you have a good software for schematics ??

[HenrikOlsson]

Hi,
Personally I use EAGLE from CADSoft, other popular packages are DipTrace and KiCAD but there are many many other in various priceranges. TARGET, OrCAD, Protel, DesignSpark, EDWIN, AutoTrax are a couple that springs to mind.

[barneyfrance]

thanks eagle seems pretty nice, we have orCAD at the university but I really don't like it...
I'm gonna try this eagle thing

[barneyfrance]

you're right lol... I'm sorry that you've waisted your time with me, I also figured this out yesterday :s I waisted my time too.
My last problem is to be able to switch frequency only if my pot = 0 (duty cycle = 0) so that the motor won't stall..
Any ideas ?

[barneyfrance]

The only problem i'm now having is with my reverse sequence...
I tried with select case and oldstate and it does not work I don't know why

If the only thing controling the sequence of the commutation is the desired direction then there's no reason to keep track of the previous state because then it doesn't matter.

Yep that's what I thought so for the reverse sequence I tried something like this :
If encoderstate = 62 Then
'switches ON/off
endif
IF encoderstate = 63 Then
'switchesON/off
endif
IF encoderstate = 62 Then
'switches on/off
endif


The probem is that the switches (for a same encoder state (62)) should not be the same. When I tried the above code, it is kind of like it's doing the both If..Endif at the same time which is not good.
Any more ideas ?, there's gotta be a way...
Thank you in advance..

[HenrikOlsson]

Hi,
No, I'm sorry, I've misunderstood this. You need to keep track of the old state since 62 are on both sides of 63 there's no way for a simple IF-THEN to determine if the if next commutation "step" should be that equaling encoderstate 60 or 63.

In the forward direction that is not a problem since the same value isn't on both sides of any other value but in reverse it is so you'll have to keep track of the previous state as well.

I must admit though that I still don't understand how this thing work. Let's say the motor is turning forward and then stops at "step" 7, ie EncoderState is 7. It now reverses direction, what is the next expected encoderstate? I don't see 7 in the expected sequence when moving in reverse but it has to be there since, no?

I can't see how the actual numbers can change depending on the direction of rotation. I would guess that if going forward gives you this sequence:

0, 1, 3, 7, 15, 31, 63, 62, 60, 56, 48, 32

the reverse sequence would be:

32, 48, 56, 60, 62, 63, 31, 15, 7, 3, 1, 0

But you're saying it's not. Can you explain, show a diagram or a photo of how this thing works. How can the sensors give out the value 7 in one direction but not in the other? I mean, at that specific rotation angle some sensors are activated and others are not giving the binary value of 7, I can't see how it can be different depending on in which direction the shaft got there.

I'm clearly missing something here but untill I understand how this thing really works there's no use in trying to come up with a solution.

/Henrik.