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Author Topic: powering the HS-322 HD servo  (Read 4262 times)

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Offline benjiTopic starter

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powering the HS-322 HD servo
« on: November 25, 2007, 09:09:44 AM »
Hey folks , i finally got this servos.
they have 3 terminals (power,control,vcc)
do i just connect the power terminal directly to the voltage? without any resistor??????
anyone has worked with this servo before? how much current does it take?
how much current does the control terminal take?
good ol' BeNNy

Offline benjiTopic starter

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Re: powering the HS-322 HD servo
« Reply #1 on: November 25, 2007, 09:51:36 AM »
also i would like to know if this servo is able to turn 180 degrees without modification?
some websites says it only turns 90 degrees without modification,. and i cant find a datasheet for this servo
good ol' BeNNy

Offline cooldog

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Re: powering the HS-322 HD servo
« Reply #2 on: November 25, 2007, 10:05:16 AM »
i don't know about your servos but there are ones that will turn 180 without mod but they can't turn continuasly
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Offline airman00

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Re: powering the HS-322 HD servo
« Reply #3 on: November 25, 2007, 10:15:56 AM »
OK,
I use that servo as a scanning servo for my sonar

I give it 5 volts straight from the voltage regulator and it works fine. As for current it takes less than an amp for sure, as I'm running three servos off the same 1.5 A voltage regulator

Servos are "meant" to work at voltages from 4.8V to 6V , anything higher might damage the servo and it will wear out quicker.

What do you mean by 180 degrees?

From the center point I can turn my servo to 90 degrees on the left and from the center point I can turn it to 90 degrees on the right. Meaning 90 degrees to either side.
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Offline Admin

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Re: powering the HS-322 HD servo
« Reply #4 on: November 25, 2007, 10:37:51 AM »
Quote
do i just connect the power terminal directly to the voltage? without any resistor???

don't use a resistor!

Quote
anyone has worked with this servo before? how much current does it take?

its basically the same as the HS-311 (which has well known specs on google)
You probably won't draw more than half an amp under a normal scenario

Quote
also i would like to know if this servo is able to turn 180 degrees without modification?
some websites says it only turns 90 degrees without modification,. and i cant find a datasheet for this servo

a useful read:
http://www.societyofrobots.com/robotforum/index.php?topic=2379.0
as for the datasheet, go to the manufacturer website :P
http://www.hitecrcd.com/servos/list?category=10

Quote
I give it 5 volts straight from the voltage regulator and it works fine. As for current it takes less than an amp for sure, as I'm running three servos off the same 1.5 A voltage regulator

wha?! noooo don't regulate servo voltage! (unless your batteries are greater than 6V and you need a cheap/fast solution)
you want the servos directly connected to the battery

Offline airman00

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Re: powering the HS-322 HD servo
« Reply #5 on: November 25, 2007, 11:43:26 AM »
wha?! noooo don't regulate servo voltage! (unless your batteries are greater than 6V and you need a cheap/fast solution)
you want the servos directly connected to the battery


Yes, obviously if I have less than 6V batteries Ill power them directly.

My setup on my line following bot ( the newest one with obstacle avoidance and green victim/tape detection ) has 6 AA batteries connected to two 5V 1.5A regulators. One regulator is to the three servos and the other regulator is for the MCU , sensors , and LCD.



But hey, why would I not want to regulate servo voltage?  ( lets say i had batteries that add up to be less than 6V)
What affect would that have on the servo?
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Offline Admin

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Re: powering the HS-322 HD servo
« Reply #6 on: November 25, 2007, 12:24:00 PM »
Quote
But hey, why would I not want to regulate servo voltage?

Its a huge waste of battery power.

So lets say you have your 7.2V regulated to 5V and you need your 1.5A of current.

Wasted power is:
(7.2V-5V)*1.5A = 3.3W

Percentage wise, its
(7.2V-5V)/7.2V = 30.6% of your battery energy wasted to thermal heat
(thats almost 1/3rd!!!)

Speaking of heat, your voltage regulator probably has thermal shutdown, meaning that if it overheats it will throttle down current to your servos - meaning your servos will have lower torque and lower speed.

If you really really need to regulate for servos, get a switching regulator (like 83% efficiency on average).

For example:
http://www.dimensionengineering.com/DE-SWADJ.htm
(but it can only do 1 amp)

Offline bens

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Re: powering the HS-322 HD servo
« Reply #7 on: November 25, 2007, 01:14:57 PM »
how much current does the control terminal take?

Consider the servo control lead to be equivalent to a microcontroller I/O connection.  The current draw will probably be measured in microamps.


And I've got to agree with Admin here.  You want to be passing microamps or milliamps through your linear regulator, not amps (i.e. you don't want to be using a linear regulator to regulate motor/servo voltage).

Offline airman00

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Re: powering the HS-322 HD servo
« Reply #8 on: November 25, 2007, 01:18:31 PM »
So any suggestions what I should do?

I have 6 AA batteries connected to two regulators , how should I change this to eliminate the problems mentioned?

can i get a switching regulator as a free sample somewhere?
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Offline Admin

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Re: powering the HS-322 HD servo
« Reply #9 on: November 25, 2007, 01:30:17 PM »
Why not just use 5AA (for 6V) and ditch the regulators?

Your question (and the fact its been asked several times before) has inspired me to update my servo tutorial:
http://www.societyofrobots.com/actuators_servos.shtml#regulate
 ;D

Offline benjiTopic starter

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Re: powering the HS-322 HD servo
« Reply #10 on: November 25, 2007, 03:24:19 PM »
well as i saied before there is somthin wrong with the datasheet opening over my pc....dunno why,,maybe its not my pc only.
thanks admin for lettin me know its 180 degrees ,,huff,, :) .

the most important q is how much current does the control terminal draws?
why??? because i want to use the same microcontroller pin to control 3 servos or maybe 4
,,can I do this? the micro im using provides 20mA on its pic, would that be enough for 3 or 4 servo control
terminals?
good ol' BeNNy

Offline airman00

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Re: powering the HS-322 HD servo
« Reply #11 on: November 25, 2007, 03:50:47 PM »
Why not just use 5AA (for 6V) and ditch the regulators?

Your question (and the fact its been asked several times before) has inspired me to update my servo tutorial:
http://www.societyofrobots.com/actuators_servos.shtml#regulate
 ;D



Aww, i feel special    :D


You're right ill just use 5AAs , but then how can I regulate the MCU's voltage? Does it matter if its regulated???? ( i mean it would work but isn't regulating it the preffered way.
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Offline bens

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Re: powering the HS-322 HD servo
« Reply #12 on: November 25, 2007, 04:12:52 PM »
Regulated voltage goes to the MCU, unregulated voltage goes to the servos.

Offline benjiTopic starter

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Re: powering the HS-322 HD servo
« Reply #13 on: November 26, 2007, 11:17:30 AM »
Quote
the most important q is how much current does the control terminal draws?

anyone? :-\
good ol' BeNNy

Offline Admin

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Re: powering the HS-322 HD servo
« Reply #14 on: November 26, 2007, 12:23:58 PM »
bens already answered that ;)
http://www.societyofrobots.com/robotforum/index.php?topic=2439.msg16442#msg16442

if you need a more exact answer, it should be in the datasheet . . .

Offline benjiTopic starter

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Re: powering the HS-322 HD servo
« Reply #15 on: November 26, 2007, 01:45:21 PM »
Quote
Consider the servo control lead to be equivalent to a microcontroller I/O connection.  The current draw will probably be measured in microamps.

my micro pin can provide 20 milliamps .
if the servo control just draws micro amps then i would be glad......
it makes a big difference here if it is miliis or micros
good ol' BeNNy

Offline bens

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Re: powering the HS-322 HD servo
« Reply #16 on: November 26, 2007, 03:09:22 PM »
my micro pin can provide 20 milliamps .

I expect this will be more than sufficient, but you'd really need to check the servo datasheet to be sure.

 


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