Hi all.
I have spent days going over all the old posts regarding this controller, but there are some things that I still do not understand.
As I can’t contact Mark Kelly, I am hoping that the DIY Community may assist.
I built the actual controller about 1 year ago, and it appears to be functioning correctly, with good range in voltages.
I need to retrofit this into an Oracle Delphi turntable, whose motor died some time ago. As the Maxon Motors are quite expensive, and to limit the amount of retro fit work to the TT, I want to be absolutely sure that it should work OK.
From my readings, it would appear that the controller is meant for driving platters by the rim, using a 12mm pulley (or there abouts).
This equates to a ratio of some 1 : 25, which is above the minimum 1:24 stipulated by Mark. I can only assume that this is a torque issue, as the Maxom 48V motors are only being run at a fraction of their rated voltage.
The issue with the Oracle, is that the platter is driven by a bottom recess being 152.5mm, and a pulley diameter of 13.5mm.
Under these conditions, I have a ratio of only 152.5 /13.5 = 11.29. My understanding is that this is no good.
I can get a new pully machined for me, say 8mm, which would give me a ratio of 152.5 / 8 = 19.06.
My first question – Is this OK?
Now considering that the motor of choice back then was a Maxon 110191 with a speed constant of 127 rpm / v, this equates to a drive voltage for 33.3 and 45 of 4.99v and 6.75v respectively
(33.3 x 19.06) / 127 = 4.99v.
My second question: are these voltages OK, both for the motor controller, and for the motor itself ?
I believe that I may be better off with a more powerful motor, and a lower rpm / v, such as the Maxon RE Max 29, 15W, which has a speed constant of 102 rpm / v.
This would equate to a 33.3 and 45 drive voltage of 6.22v and 8.39v respectively.
My third question, Is this a better option in my circumstances? I.e higher power and voltage to counteract the diminished ratio.
Looking forward to your responses.
Kind Regards
George.
I have spent days going over all the old posts regarding this controller, but there are some things that I still do not understand.
As I can’t contact Mark Kelly, I am hoping that the DIY Community may assist.
I built the actual controller about 1 year ago, and it appears to be functioning correctly, with good range in voltages.
I need to retrofit this into an Oracle Delphi turntable, whose motor died some time ago. As the Maxon Motors are quite expensive, and to limit the amount of retro fit work to the TT, I want to be absolutely sure that it should work OK.
From my readings, it would appear that the controller is meant for driving platters by the rim, using a 12mm pulley (or there abouts).
This equates to a ratio of some 1 : 25, which is above the minimum 1:24 stipulated by Mark. I can only assume that this is a torque issue, as the Maxom 48V motors are only being run at a fraction of their rated voltage.
The issue with the Oracle, is that the platter is driven by a bottom recess being 152.5mm, and a pulley diameter of 13.5mm.
Under these conditions, I have a ratio of only 152.5 /13.5 = 11.29. My understanding is that this is no good.
I can get a new pully machined for me, say 8mm, which would give me a ratio of 152.5 / 8 = 19.06.
My first question – Is this OK?
Now considering that the motor of choice back then was a Maxon 110191 with a speed constant of 127 rpm / v, this equates to a drive voltage for 33.3 and 45 of 4.99v and 6.75v respectively
(33.3 x 19.06) / 127 = 4.99v.
My second question: are these voltages OK, both for the motor controller, and for the motor itself ?
I believe that I may be better off with a more powerful motor, and a lower rpm / v, such as the Maxon RE Max 29, 15W, which has a speed constant of 102 rpm / v.
This would equate to a 33.3 and 45 drive voltage of 6.22v and 8.39v respectively.
My third question, Is this a better option in my circumstances? I.e higher power and voltage to counteract the diminished ratio.
Looking forward to your responses.
Kind Regards
George.
The pulley ratio shouldn't matter as long as the motor is capable of providing the corresponding speed to spin the platter at the correct rate. I assume the voltage is adjustable on the controller and as long as you remain within the motor's operating parameters for voltage & power, it should be OK.
Of greater concern should be the motor's winding resistance. Mark's controllers used current compensation for constant speed control and this is a function of the motor's winding resistance: For constant speed under load, the power supply's negative output impedance must equal the motor's DC winding resistance. It may be adjustable in the controller, but the range may be limited to fine tuning or use with a limited number of motors. If the neg resistance of the supply is less than the winding resistance, the motor will slow under load; if greater than the winding resistance, the motor will increase in speed under load and possibly be unstable.
Of greater concern should be the motor's winding resistance. Mark's controllers used current compensation for constant speed control and this is a function of the motor's winding resistance: For constant speed under load, the power supply's negative output impedance must equal the motor's DC winding resistance. It may be adjustable in the controller, but the range may be limited to fine tuning or use with a limited number of motors. If the neg resistance of the supply is less than the winding resistance, the motor will slow under load; if greater than the winding resistance, the motor will increase in speed under load and possibly be unstable.
Hi Pyramid
Thank you very much for your response, and my apologies for my delay in responding. (was not well over the past few days)
Thanks for bringing to my attention the issue of current compensation. I re-visited the documentation, and there is a procedure that must be followed for correct current compensation and balancing the resistance.
However, I am still concerned that there are limitations within the actual design that limit the usage of this design with certain types of motors.
This is where I am really hoping that someone could chime in, that has experience with this design.!!!
The other issue that I still looking for clarity on is the pulley ratio, which noted by MK cannot be greater than 1:24. Perhaps this ratio was unique to the Maxon 110191.
As always, any advice by other members will be greatly appreciated.
Kind regards
George.
PS: I have attached some pics of the actual motor controller ready built and ready to go.
Thank you very much for your response, and my apologies for my delay in responding. (was not well over the past few days)
Thanks for bringing to my attention the issue of current compensation. I re-visited the documentation, and there is a procedure that must be followed for correct current compensation and balancing the resistance.
However, I am still concerned that there are limitations within the actual design that limit the usage of this design with certain types of motors.
This is where I am really hoping that someone could chime in, that has experience with this design.!!!
The other issue that I still looking for clarity on is the pulley ratio, which noted by MK cannot be greater than 1:24. Perhaps this ratio was unique to the Maxon 110191.
As always, any advice by other members will be greatly appreciated.
Kind regards
George.
PS: I have attached some pics of the actual motor controller ready built and ready to go.
Attachments
Hi I have an un-used board available should anyone be interested. $60 + postage. Cheers
Hi Buddy.
Have not heard from you.
Have also sent you PM
Is it still for sale??
Regards
G.
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