On Fri, Oct 22, 2010 at 11:43 AM, vasile surducan <[email protected]>wrote:
> > > On Fri, Oct 22, 2010 at 10:56 AM, vasile surducan <[email protected]>wrote: > >> >> >> On Fri, Oct 22, 2010 at 10:06 AM, Sebastien Lelong < >> [email protected]> wrote: >> >>> Hi Vasile, >>> >>> 2010/10/22 vasile surducan <[email protected]> >>> >>> Hi Seb, >>>> >>>> Looks to me that you have understand well that different DC motors will >>>> give you different EMF values: >>>> >>>> http://sirloon.net/loonaweb/sirblog/experimenting-back-emf-motion-feedback >>>> <http://sirloon.net/loonaweb/sirblog/experimenting-back-emf-motion-feedback>So, >>>> that's it, a poor method using an analog feedback, if you want universal >>>> solutions seems to me you have to switch on digital feedback, which as far >>>> I >>>> know can't be EMF. >>>> >>> >>> Do you mean something like encoded wheels ? bemf is really nice to have >>> because it's not invasive, you can control any DC motors without modifying >>> the structure (which is great when hacking RC toys) >>> >>> >>>> You can't do it without modifying dividers. >>>> >>> >>> Is electronic that limited ?? C'mon, there should be a trick ! >>> >> >> Variable gain amplifier. It modifying dividers in software keeping the ADC >> resolution constant. Still a s**t... >> :) >> >> > There is another way: when read EMF the motor acts as a generator. > Loading it with a variable resistive load (switched digitally using some > transistors) will decrease the EMF level as you wish. However that will > brake the motor as well, as high as the load becomes lower. Probably with 2 > loads you can use two different DC motors. > Do you intend to manufacture some kits? > Ok, thats the best ideea: an active load (programmable constant current source) driven by the 16 level internal reference voltage, switched on the motor coil only when back EMF is read. > > >> Vasile >> >> >> >>> >>> >>> Cheers, >>> Seb >>> >>> >>>> Vasile >>>> >>>> On Fri, Oct 22, 2010 at 7:57 AM, Sebastien Lelong < >>>> [email protected]> wrote: >>>> >>>>> Hi guys, hardware guys, >>>>> >>>>> >>>>> Years ago, I built a DC motor control board, with back-emf sensor: >>>>> http://sirbot.org/sirbot-modules/dc-motor-controller-board/ >>>>> >>>>> This board (and firmware) generates proper PWM signals to control 2 DC >>>>> motors, and in the mean time, collect data about produced back-emf >>>>> voltage, >>>>> using ADC. There's no such power control of DC motors (which was actually >>>>> done using RC tank transistors themselves), it's just about signaling. >>>>> >>>>> Using this board, there's a warning I'd like to get rid of today. It >>>>> says "This board uses ADC (Analog-to-Digital-Conversion) to evaluate >>>>> motor's >>>>> speed. Voltages produced by motors are often far greater than those ADC >>>>> can >>>>> handle. There are voltage dividers on this board which keep those in >>>>> correct >>>>> range. These voltage dividers are designed so voltage produced by motors >>>>> can >>>>> be up to max 12V. If your DC motors produce more than 12V, you'll need to >>>>> adjust voltage dividers' values or you will damage this board. You've been >>>>> warned !!!" >>>>> >>>>> That is, if I'm using 24V DC motors, voltage coming to ADC will be too >>>>> great and could damage the PIC (or worse, I could get wrong data). On the >>>>> other side, using 5V DC motors, I'll obtain a narrow spectrum of values, >>>>> as >>>>> it's always divided by 2 (a little more). >>>>> >>>>> How can I perform a voltage normalization ? Whatever the incoming >>>>> voltage produced by DC motors, I'd like it to be proportionally mapped to >>>>> [0,5V]. I'd like this be dynamic (I don't want to unsolder/solder some >>>>> resistors each time I plug a new DC motors). >>>>> >>>>> Please explain to me with very simple words :) >>>>> >>>>> >>>>> TIA >>>>> Cheers, >>>>> Seb >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "jallib" group. >>>>> To post to this group, send email to [email protected]. >>>>> To unsubscribe from this group, send email to >>>>> [email protected]<jallib%[email protected]> >>>>> . >>>>> For more options, visit this group at >>>>> http://groups.google.com/group/jallib?hl=en. >>>>> >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "jallib" group. >>>> To post to this group, send email to [email protected]. >>>> To unsubscribe from this group, send email to >>>> [email protected]<jallib%[email protected]> >>>> . >>>> For more options, visit this group at >>>> http://groups.google.com/group/jallib?hl=en. >>>> >>> >>> >>> >>> -- >>> Sébastien Lelong >>> http://www.sirloon.net >>> http://sirbot.org >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "jallib" group. >>> To post to this group, send email to [email protected]. >>> To unsubscribe from this group, send email to >>> [email protected]<jallib%[email protected]> >>> . >>> For more options, visit this group at >>> http://groups.google.com/group/jallib?hl=en. >>> >> >> > -- You received this message because you are subscribed to the Google Groups "jallib" group. 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