ServoTest: SG90; MG90S; SG92R; DS238MG. Which one is truly digital?
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- Опубліковано 22 лют 2018
- All servos have been driven by arduino nano signal pin connected to D9
by a simple 20ms pwm signal with constant duty cycle 5% - 1000us
program can be downloaded from here
drive.google.com/file/d/1Cs5r...
Oscilloscope (powered from 230Vac mains isolated transformer 1:1) was connected via probe directly to servo's motor
RC Servo Analog vs Digital Demonstration
• RC Servo Analog vs Dig...
More theory
www.rchelicopterfun.com/rc-se...
Tower Pro SG90
0:25
Tower Pro SG90S
0:54
Tower Pro SG92R
1:19
Corona DS238MG
1:54
Results
1:58
drive.google.com/file/d/1kStM...
Tested servos:
1. Tower Pro SG90
Weight: 9g
Dimension: 23×12.2x29mm
Stall torque: 1.8kg/cm(4.8v)
Gear type: POM gear set
Operating speed: 0.12 sec/60degree(4.8v)
Operating voltage: 4.8v
Temperature range: 0℃_ 55℃
Dead band width: 1us
Power Supply: Through External Adapter
servo wire length: 25 cm
Servo Plug: JR (Fits JR and Futaba)
www.towerpro.com.tw/product/sg...
Bought from ebay.com a year ago
2.Tower Pro SG90S
Weight: 13.4g
Dimension: 22.8×12.2×28.5mm
Stall torque: 1.8kg/cm (4.8V); 2.2kg/cm (6.6V)
Operating speed: 0.10sec/60degree (4.8V); 0.08sec/60degree (6.0V)
Operating voltage: 4.8V~ 6.6V
Temperature range: 0℃_ 55℃
Dead band width: 1us
Power Supply: Through External Adapter
servo wire length: 25 cm
Servo Plug: JR (Fits JR and Futaba)
servo arms &screws included and fit with Futaba servo arm
It’s universal “S” type connector that fits most receivers, including Futaba, JR, Hitec ,GWS, Cirrus, Blue Bird, Blue Arrow, Corona, Berg, Spektrum.
CE &RoHS approved
www.towerpro.com.tw/product/mg...
Bought from gearbest.com (a couple of months ago)
3.Tower Pro SG92R
Weight: 9g
Dimension: 23×12.2x27mm
Stall torque: 2.5kg /cm(4.8v)
Gear type: POM with carbon fiber
Operating speed: 0.1sec /60degree (4.8v)
Operating voltage: 4.8v
Temperature range: 0℃_ 55℃
Dead band width:1us
servo wire length: 25 cm
Servo Plug: JR (Fits JR and Futaba)
servo arms &screws included and fit with Futaba servo arm
It’s universal “S” type connector that fits most receivers, including Futaba, JR, Hitec ,GWS, Cirrus, Blue Bird, Blue Arrow, Corona, Berg, Spektrum.
CE &RoHS approved
www.towerpro.com.tw/product/sg...
Bought from bangood.com (a couple of days ago)
4. Corona DS238MG
Model: DS238MG
Operating Voltage: 4.8V / 6.0V
Operating Current: 300mA / 400mA
Operating Speed: 0.15sec.60º/ 0.14sec.60º
Stall Torque: 4kg.cm / 4.6kg.cm
Size: 29X13X30mm
Weight: 22g
Dead Band: ≤3uSec
Operating Travel: 40º/one side pulse traveling 400us
Potentiometer: 3 slider/Direct Drive
Ball bearing: MR106
Gear: Metal
Connector wire: 215mm
Operating Temperature Range: -20c ~ +60c
Spline count: 25
hobbyking.com/en_us/corona-ds...
Bought from hobbyking.com (2 years ago)
Question:
What does make TowerPro servos digital? - Наука та технологія
Good work
Awesome test
Great work thanks
Thankyou.
What do these numbers mean?
Well the only truly digital servo is DS238MG.
50Hz is refresh rate for SG90; MG90S; SG92R;
DS238MG should be able to handle 250Hz. (5x faster than servos above)
amd the sg92r is advertised as digital... what's the benefot of digital over analog?
@@SladkaPritomnost
@@daslolo
digital is faster but more EM noisy
digital servo could just mean it drived inside by a digital component (vs analog comparator). It's do not tell anything about PWM frequency.
Hi, digital servos have usually motor driven much faster than analog ones. (higher than 50hz (usually 200-400Hz that's why they can achieve faster responses, and jitters due to power spikes if not proper filtered (e.g. ferrite bead)), I measured signal that drives the motor.
To me (all tested Tower Pro) are practically analog with maybe some more digital processing but internal motor is not driven the same way as digital ones.
It's misleading to say they are digital.
yeah. I agree with you. It's misleading. I'll carefully paid attention when I'll buy new ones. Maybe it's due to the size of the 9g servo. Does real digital servo at 9g size exist ?
The size should not be a problem, EMAX ES9251 should be digital 2.5g (plastic) really tiny servo. (I haven't tested it yet.)
Maybe I will give it a try one day :) The nice thing about digital servos is that they can be faster driven by flight controller e.g. iNAV (allows servo refresh rate up to 333Hz) and get much faster responses, theoretically a simple servo gimbal (stabilization) should be possible :) 50Hz ones won't handle that speed and will burn...
Digital is input part, not the pwm signal to motor. You can drive servo in 2 modes. Why do you test output signal ? Output signal form is not strictly related to input board.
Output is what matters the most :)
Input was constant in all cases. True digital has faster update rate regardless of 50Hz input drive.
@@SladkaPritomnost I don't think so. If you have 60hz in input... yeah you have 60 cycle of refresh positioning per second. If you connect a 100Hz servo to a 333hz controller you burn it cause it cannot stand up that refresh rate. You CAN have fast motor drive square signal. Digital is the converter in input and for var resistor reading for axle position. Pwm is a pulse signal, does not tell the type of signal.
@@davidemarchi6366
DS238MG is the only true digital servo and you can drive it by 250Hz PWM signal (5x faster than 50Hz), the rest of "digital" servos in the test will burn (at anything higher than 50Hz).
Digital input convertor doesn't make servo digital. That's a tricky labeling by manufacturers.
www.rchelicopterfun.com/rc-servos.html
@@SladkaPritomnost ya, I understand. It will be interesting if you apply a 100hz, then 200, 300hz signal to "fake digital" and watch what's happen. I never see a clear datasheet of towerpro & C with real frequency written. Someone on a forum said that towerpro replied to him by email that servos are ok for 100hz .
Analog take 50hz input and apply a 50hz motor control, so...I if apply 100hz input, they control motor at 100hz frequency ? Can you test this?
The motor of mg90d is very fast, but I suspect that control electronic cannot manage over frequency. Digital is very relative in this case XD
pwm is a digital mode for driving motor, but in this way EVERY servo is digital... but this is not true.
We will wait your tests! thanks
@@davidemarchi6366 I only did testing with 50Hz pwm. I wouldnt drive any of tested towerpro servos with 100Hz pwm or above. Only the Corona's one should be capable of 250Hz pwm.
I sent email to: customerservice.towerpro@gmail.com
Would you define what makes MG90S and SG92R servo digital?
I've checked driving of the motor within each servo and there is no difference between analog and digital driving.
ua-cam.com/video/EHraKAqjDCc/v-deo.html
Standard digital servo is driven much faster though.
---------------
Answer:
"If you purchased from us. MG90S is usint metal gear instead and Both of them are Digital Servos. "
My reply:
The servos were bought from bangood.com and gearbest.com
I'm surprised that servo motor is driven by 50Hz (I expected higher driving frequency),
I've tested these servos:
- SG90 - analog servo - 50Hz driving
- MG90S - digital servo - 50Hz driving
- SG92R - digital servo - 50Hz driving
What does make digital servo if driving frequency is the same as for analog (50Hz)?
Can you please check with your engineers if your digital servos are driven by 50Hz?
(NO ANSWER)
Any update on this? great test
Hi,
nope, I got no reply from TowerPro after my reply
SG92R you fake. Apparently for this, it was not digital. Almost all sold in the shops SG90 SG92 fake. Compare with the photo on the manufacturer's website.
Well at least I sent an email to towerpro for explanation what makes their servo digital and if they can provide refresh rate of these servos, but as for today I've got no reply.
Apart from digital issue, my SG92R centeres pretty well, much better than SG90 I like it.