[NSRCA-discussion] berg 7 channel Rx

[Bob Richards]

I think the pulse frame rate will increase the holding torque, when the servo is close to its commanded position, but may not increase the absolute torque if the servo is designed for a 50Hz frame rate (ie: the duty cycle has reached 100%). This is true for non-digital servos, the digital servos increase the frame rate internally and should not tell the difference between 50Hz and 100Hz frame rates from the receivers.
   
  For the life of me, I can't see how increasing the frame rate from the transmitter can affect "resolution" in the normal definition. That is a function of the internal electronics of the transmitter, and the designed deadband of the servo. A frame rate increase might appear to have better resolution at the servo, but this would simply be due to the increased holding torque which will allow the servo to do a better job of moving to a commanded position. The commanded position would still be the same, the servo will just be commanded to go there more often. :-)
   
  My Futaba 9Z radio is 1024. That is the maximum number of positions the servo can possibly be commanded to move to. OTOH, my Futaba 4 channel Conquest radio is analog, which means it has INFINITE resolution.
   
  One thing I remember about my old Ace Micropro radio, you could program how many channels to output. This was good if you were only using 4 channels in, lets say, a pylon plane. The frame rate was determined by the number and duration of each channel (nominal 1.5ms each) and the frame reset pulse length. If you did not bother to transmit channels 5 through 8, you saved an average of 6ms (as much as 8ms) in the frame rate. That means your jerk of the elevator stick to go around the pylon would happen quicker.
   
  I just received my Castle Creation USB programmer, I will play with it when I get a chance. This "frame rate" thing has me interested. I suspect it will help with the micro servos I'm using in my small electrics. I may have to rig up an experimental test fixture.....  :-)
   
  Bob R.
  

John Pavlick <jpavlick at idseng.com> wrote:
  Sure. The time integration creates the effect of higher output power. The
maximum torque IS a function of the mechanical limitations of the servo but
the effective output power (torque) is dependant on the signal applied over
time. No torque is generated when the servo is not supplied with a pulse. By
increasing the rate at which the servo receives pulses, power will be
generated more frequently. The resolution will not increase at a higher
pulse rate, however because the original servo pulse is generated at a 50Hz
frame rate in the Tx encoder. You are simply applying this pulse twice per
frame at the 100Hz rate. To double the resolution you would need to double
the original frame rate to 100Hz. That is generated by the transmitter, not
the receiver. Think about it. Oops, it looks like I need another beer...

John Pavlick
http://www.idseng.com


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