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### Topic: Power source for project motors regulators amps and volts  (Read 628 times)previous topic - next topic

#### hert

##### Jul 12, 2019, 04:37 am
Hi, This is My first post and I'm hoping to get some really good feed back. I am working on a really cool project and am having trouble with the power supply. I have done soooooooo much research and have found nothing for what I need.

I am using 8 (380) kg.cm servo motors -High Torque Servo 380kg.cm Steel Gear for Robot Mechanical Arm 12-24V US-. I am trying to find a battery and circuit that will work. It states that each motor has a no load of 500mA and requires 12 to 24 volts. I think I want 24 volts because I want to lift as much weight as possible. Do I need a regulator or resistors? I think this means that I need a battery with at least 4,000 mA and 192 volts. But the volts total doesn't seem right. I plan on adding more to the project later on so I want a battery with more mA. But will that then burn out the motors if there is too much? Do I need resistors there for now? These are just a few of my question but I would be great if someone could answer them. LINKS WOULD BE AMAZONG!!! Anything will help.

Parameters:
- Working voltage: DC12-24V
- Maximum torque(actual measurement): 380kg.cm(24V) ;1764N.cm(24V) ;90kg.cm(12V) ;882N.cm(12V)
- Angular velocity: 0.5s/60degree, when 24V;1.0s/60degree, when 12V
- Rotation angle: 330 degree MAX. (0-360 degree, adjustable)
- Input mode: PWMIN is PWM signal; ADIN is analog voltage signal(potentiometer)
- Pulse signal input range: 0.5ms-2.5ms for all "multi channal controller", 1ms-2ms for drone remote controller, SCM program, Arduino, etc.
- Voltage signal input range: 0-5V
- Control accuracy: 0.32 degree
- Weight: 530g
- Gear material" Steel
- Size: 95.5*60.5*102.6mm
- Application: Robot, mechanical arm, other high torque control area
- Power input: DC12-24V
- Motor output: 12-24V

#### slipstick

#1
##### Jul 12, 2019, 10:46 am
No-load current is not really useful. What you need to allow for is the stall/starting current which is MUCH HIGHER, I'd guess at least 4-5A per servo! Can you post a link to the specification/datasheet of that device. The information may be in there somewhere. But you're probably going to need a battery to supply something like 24V @ 40A or more.

Also you connect servos in parallel. So a set of 8 will need 8 x the current that one takes but still at the original voltage.

Resistors have nothing to do with it and if you were thinking that you need 8 x current AND 8 x voltage then I'm afraid you have a lot more research on electrical basics still to do.

Steve

#### hert

#2
##### Jul 12, 2019, 03:52 pm
Thank You Slip stick, I do have one more question and that is if say all the motors need 40 amps in total and I want to add to it and also have other components on top of would I need to add a few extra mA to 40 amps? Also would this burn out the servos if they have too much current going through them or do they have some leeway or possible only draw what they need? Should I do one battery for the servos and one for everything else?

This is all the specs they have on the order info:

High Torque Servo DC12V 24V 380kg.cm Steel Gear for Robot Mechanical Arm

Function
- Potentiometer control, remote control
- CW and CCW  switching, AD&PWM switching,pulse width 1-2ms&0.5-2.5ms
- Compatible with Futaba, JR, SANWA, Hitec,etc.

Parameters:
- Working voltage: DC12-24V
- Maximum torque(actual measurement): 380kg.cm(24V) ;1764N.cm(24V) ;90kg.cm(12V) ;882N.cm(12V)
- Angular velocity: 0.5s/60degree, when 24V;1.0s/60degree, when 12V
- Rotation angle: 330 degree MAX. (0-360 degree, adjustable)
- Input mode: PWMIN is PWM signal; ADIN is analog voltage signal(potentiometer)
- Pulse signal input range: 0.5ms-2.5ms for all "multi channal controller", 1ms-2ms for drone remote controller, SCM program, Arduino, etc.
- Voltage signal input range: 0-5V
- Control accuracy: 0.32 degree
- Weight: 530g
- Gear material" Steel
- Size: 95.5*60.5*102.6mm
- Application: Robot, mechanical arm, other high torque control area
- Power input: DC12-24V
- Motor output: 12-24V

Package list:
- 1 x Servo

Much appreciated

#### JCA79B

#3
##### Jul 12, 2019, 04:35 pmLast Edit: Jul 12, 2019, 04:40 pm by JCA79B
380kg/cm = 37.3 Nm, for a 530g servo? Impossible! Are you sure that's not 38.0? Post a link to the seller's webpage.

#4

#### shimidan

#5
##### Jul 13, 2019, 01:01 pmLast Edit: Jul 13, 2019, 01:01 pm by shimidan
As an amateur, i tell you some notes: Volt must be as same as the consumer (for one consumer). More volt may damage it. But amp should be more or at least as same as the consumer. More current has no adverse effect.
For multi-consumers, you should convert them to ONE consumer (parallel or ...).

#### JCA79B

#6
##### Jul 13, 2019, 03:48 pm
What is the current when the servo is putting out 380 kg/cm torque? It will be MUCH higher than 500mA.

#### slipstick

#7
##### Jul 13, 2019, 04:34 pmLast Edit: Jul 13, 2019, 04:35 pm by slipstick
https://www.ebay.com/itm/12V-24V-380KG-CM-Ultra-high-power-High-torque-Servos-Driver-Full-Metal-Robot-/171811325577 is an advert for an almost identical "servo" but with more detail. That says max current is 5A +/-0.2A which was roughly my first guess.

Of course it still needs to be measured for the OP's version...if the servo ever actually delivers the stated torque.

Steve

#### hert

#8
##### Jul 13, 2019, 05:06 pm
I am trying to find the actual current because it does make a lot of sense that it is not 500 mA. From there what is the equation to find the exact current I need for the motor I am working on If it is lifting its full potential. My plan for the project is to be lifting almost the full weight but I am adding a few more amps to the final amperage of the 8 motors for additions later on.

#### Paul_KD7HB

#9
##### Jul 14, 2019, 01:35 am
I am trying to find the actual current because it does make a lot of sense that it is not 500 mA. From there what is the equation to find the exact current I need for the motor I am working on If it is lifting its full potential. My plan for the project is to be lifting almost the full weight but I am adding a few more amps to the final amperage of the 8 motors for additions later on.
One more equation for your project is to determine if the moving weight will be held against gravity and the servo motor stalled and holding that position. If holding or if the moving takes a long time you need to have a way to dissipate the heat generated in the servo motor.

Paul

#### hert

#10
##### Jul 14, 2019, 01:39 am
I have calculated the lifting and holding torque of the servos.

#### hert

#11
##### Jul 14, 2019, 01:50 am
Does anyone have any suggestions on how to release the heat from the servos if the have reached there limit on lift? Do I need resistors?

#### Paul_KD7HB

#12
##### Jul 15, 2019, 05:58 pm
Does anyone have any suggestions on how to release the heat from the servos if the have reached there limit on lift? Do I need resistors?

Why do you have a fixation on "resistors" to solve every problem?

You have never shown a drawing of your project. If you want to lift a weight and hold it you need an industrial designed servo that is designed to dissipate the heat in the motor. OR you need to design a different moving and holding mechanism.

Paul

#### MarkT

#13
##### Jul 16, 2019, 11:00 pm
Repeat ten times till you remember:

torque is not a ratio
torque is not a ratio.....

The units are newton metres, or Nm, ie the _product_ of a force and a distance, not a ratio...

You'll get into all manner of confusion if you get this wrong!!!  And always convert to sensible units
before doing calculations, kg-cm is bad, kgf-cm is better, but Nm is the proper unit and works with
all the useful formulae such as
P = wT
T = L dw/dt

P is power in watts
w is angular velocity (should be lower case omega, can't find it on my keyboard!) units radians/second
T is torque (should be uppercase tau)
L is angular momentum, units kg m^2

(Actually torque it can be thought of as a ratio, but in that case its a ratio of _energy_ to _angle_, joules per radian