How do I calculate the speed/torque of a servo with a new voltage?
In my case from 3kg @ 4.8V up to 8.4V
Speed is
Maybe some other things good to knwo could be put up here
Calculating
Moderators: BeligerAnt, petec, administrator
Something is inversly proportional when something increases the other decreases.
So S1*V1=S2*V2
S1= Quoted Speed
V1= Origional Voltage (4.8)
S2= New Speed
V2= New Voltage.
However you have not given the origional speed of teh servo so I cannot calculate but I will assume a speed of 0.13 for arguments sake.
S1= 0.13sec/60degrees
V1= 4.8v
S2= to be calculated
V1= 8.4v
S1*V1=S2*V2
0.13*4.8= S2*8.4
0.624=s2*8.4
S2= 0.624/8.4
S2=0.074sec/60degrees
As for torque Torque is proportional to Amps but lets assume that when the VOltage increases that the amps increase proportionaly aswell.
T1/V1=T2/V2
T1= Origional Torque
V1= Origional Voltage
T2= New TOrque
V2= New Voltage
SO for yours we have
T1= 3kg/cm
V1= 4.8v
T2= To be calculated
V2= 8.4v
T1/V1=T2/V2
3/4.8=T2/8.4
0.625=T2/8.4
T2=0.625*8.4
T2=5.25Kg/cm
I hope that helps you.
Although in practice you will probably not see these exact figures.
So S1*V1=S2*V2
S1= Quoted Speed
V1= Origional Voltage (4.8)
S2= New Speed
V2= New Voltage.
However you have not given the origional speed of teh servo so I cannot calculate but I will assume a speed of 0.13 for arguments sake.
S1= 0.13sec/60degrees
V1= 4.8v
S2= to be calculated
V1= 8.4v
S1*V1=S2*V2
0.13*4.8= S2*8.4
0.624=s2*8.4
S2= 0.624/8.4
S2=0.074sec/60degrees
As for torque Torque is proportional to Amps but lets assume that when the VOltage increases that the amps increase proportionaly aswell.
T1/V1=T2/V2
T1= Origional Torque
V1= Origional Voltage
T2= New TOrque
V2= New Voltage
SO for yours we have
T1= 3kg/cm
V1= 4.8v
T2= To be calculated
V2= 8.4v
T1/V1=T2/V2
3/4.8=T2/8.4
0.625=T2/8.4
T2=0.625*8.4
T2=5.25Kg/cm
I hope that helps you.
Although in practice you will probably not see these exact figures.
- BeligerAnt
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Ian's figures appear correct, but some of the terminology is a bit misleading.
DC motors have a constant relationship between speed and voltage:
speed / voltage = K (rpm/volt)
So speed = K * voltage
If you know the speed at a given voltage you can calculate K and then calculate the speed at any voltage.
Note this is speed, what most servo manufacturers specify is time per 60 degrees. (That is the misleading bit)
Now 0.1s / 60 deg is the same as 0.6s / 360 degrees
So the speed is 1 revolution per 0.6s, or 100rpm
Assuming 4.8V we get K = 100 / 4.8 = 20.83 rpm/volt
Thus at 8.4V we get 8.4 * 20.83 = 175rpm
For a servo specified as T secs / 60 deg @ 4.8V, run at V volts, we end up with a short-cut formula of:
S (rpm) = ( 2.083 * V ) / T
One thing to remember is that power is proportional to voltage squared, so if you double the voltage you quadruple the power. A fraction of this power is dissipated in the motor, so the motor is now trying to dissipate 4 times as much power (as heat) as it was designed to do. Beware of overheating motors as they lead to burnt-out windings and scrapped motors!
DC motors have a constant relationship between speed and voltage:
speed / voltage = K (rpm/volt)
So speed = K * voltage
If you know the speed at a given voltage you can calculate K and then calculate the speed at any voltage.
Note this is speed, what most servo manufacturers specify is time per 60 degrees. (That is the misleading bit)
Now 0.1s / 60 deg is the same as 0.6s / 360 degrees
So the speed is 1 revolution per 0.6s, or 100rpm
Assuming 4.8V we get K = 100 / 4.8 = 20.83 rpm/volt
Thus at 8.4V we get 8.4 * 20.83 = 175rpm
For a servo specified as T secs / 60 deg @ 4.8V, run at V volts, we end up with a short-cut formula of:
S (rpm) = ( 2.083 * V ) / T
One thing to remember is that power is proportional to voltage squared, so if you double the voltage you quadruple the power. A fraction of this power is dissipated in the motor, so the motor is now trying to dissipate 4 times as much power (as heat) as it was designed to do. Beware of overheating motors as they lead to burnt-out windings and scrapped motors!
Gary, Team BeligerAnt