View Full Version : servo help

01-25-2008, 05:51 PM
hi all
i bought VTS-08A servo motors from vegakitindia. I am using 8051 for the control signal. The control signal is perfect, but the servo is not running. Instead its giving jerks immediately when power is switched on. The control signal i am using is high for 1-2ms and low for 20ms. I am using a DC power supply for the testing. It showed an overload initially but was moving to one extreme for any control signal. When I increase the current, the overload is gone but the motor does not work:(. Please help me guys.

01-25-2008, 11:10 PM
1)check the signal with a CRO.
2)If you get the signal right, check the connections.
3)If you get the connections right, check the batterie.
4)If the batteries are good, the servo is gone.
5)to know if your batteries are god, mention the type of batteried you are using, here.

01-25-2008, 11:21 PM
The Vegakit VTS-XXX are absolute junk.
Better not buy them till they standardise their Servos.

01-29-2008, 07:34 PM
Thnx a lot for the replies:)....but i still have one more doubt....Can i take the control signal directly from the microcontroller or shud i have some extra circuitry????

as for now i am just using a regulated DC power supply....so i guess the servo is gone.....

01-29-2008, 09:06 PM
Using a DC regulated power supply doesnt mean the servos are gone. Check the current rating of the supply. I do not recommend their use..
Always use batteries to power 1-5 servos.

my question is, did you exactly follow all the steps i suggested ??

01-29-2008, 09:15 PM
I am also having same problem with same motor

I dont have CRO at my disposal so i checked pwm at the simulator at my computer before burning the code on atmega16 it was ok.

I am using a ac to dc adaptor

connections are ok

and i am also using direct dc supply widout any extra circuitory


I used this link for avr code and took Portb1 as output

01-29-2008, 09:26 PM
Ac - DC adaptor has very LOW current capability.

use normal AA batteries (if you are low on budjet - or buy nicd or nimh or even SLA) - 4 of them give you 6V - 4.8V

Your computer simulator may NOT give you the correct read out. Generating signals for servo is a bit tricky- or you have to do a bit of trial and error.

what problem are you having?? are you having at least a jitter??
or nothing at all??

01-29-2008, 09:33 PM
yes...i followed them in the same order....the control signal is perfect on the CRO...i checked the connections too...no problem with tht either....the servo is taking 500mA....

01-29-2008, 09:38 PM
the first servo i used for testing is just giving jerks when i switch on the supply....with the same arrangement, i tested another new servo of the same kind.....it did rotate in different directions for 1ms and 2ms signals....it was rotating to the extreme ends and getting stuck there....

the pulses i am sending are continuous with around 15ms low and 1-2ms high....do i need to send any fixed number and not a continuous one???[/img]

01-29-2008, 09:57 PM
You have to send continuous signals.

If its taking 500mA, and not rotating, not even a hum, no holding...


time to hack it. Open it up, if the motor is fine, u can use it as a good continuous rotation servo...

or else.. handicrafts. :wink:

01-29-2008, 10:07 PM
wat about the control signal?????can i give it directly from the microcontroller??? I saw one guy use some fast recovery diodes...is it required???

01-30-2008, 06:12 PM
well i can feel sumthng vibrating inside but that vibration can be felt only with vcc given and no control signal

02-25-2008, 02:13 PM
guyz even i hav same prob wit vts-08a servo(i need 4 servo 2 control robotic arm for ma project )... as someone mentioned its bcos ,that vts servo are not standerdzied......where i can get standard servo like hitech or futaba servo motors in india..????

02-25-2008, 03:05 PM

02-26-2008, 01:02 AM
The VTS-0XXx from Vegakit is junk!! :evil: They're ripping off students with a local substandard servo.
I have 13 good 'vibrators' out of the 15 bought servos (over the counter @ Gala, Mumbai).
I endorse Allbits' advise , as i have done the same....a glorified gear motor for 800 bucks!! ....and they don't provide any specs/details of it.

03-04-2008, 06:12 PM
hey I finally got my hand on a oscilloscope i checked my signal

when i give it a signal of about 4.5ms high in 20ms pwm

it gives a rotation of somewat 100 degrees(its a 180 degree servo)

which makes me feel that instead of 1-2ms high period it has a diff high period for position control

ne idea??? of any such motors which have a diff pwm requirements

ps: i applied same pwm to futabaa s 3001 it gives full 180 degree rotation

03-04-2008, 08:17 PM
Whats the brand of the 4-5ms servo?

04-04-2008, 08:09 PM
hello friendz... as i told i hav vts-08a servo ... can i modify t atleast 4 continuos rotation .. ? n how?plz reply..

04-06-2008, 12:50 AM
just take a look at my VTS-08B post , ull get all ur answers

05-22-2008, 05:19 PM
thankz guyz 4 ur help .. i bought hitech servo and is working ... then i found the problem wit vts servo also just need 4 provide the power supply wit proper current rating;;;