View Full Version : POWER SUPPLY HELP

06-02-2007, 08:24 PM
we have made a robo wich hs got 8 servos .it ws seen dat almost 3amp.is reqd in total 4 all dese motors,we used a transformer ratin 15v 3 amp for servos .bt dis 3 amp transformer is not supplying d reqd current for servo.wen i use 2 powersupplies servos r not wrkin properly (due 2 interference).pls help us with a supply wich can supply d reqd cuurent.

06-03-2007, 12:40 AM
Can you translate that into ENGLISH??? :wink:

06-03-2007, 05:52 PM
are u talking abt RC Servos ?? i dont think they can handle voltage upto 15V. secondly try connecting a large value electrolytic capacitor across the power supply terminals. cos the power supplies u get in the market arent filtered well enough and there mebbe AC interference (50Hz) similar to time period for refreshing the servo...this is seen to cause problems

06-03-2007, 09:17 PM
sorry friend for using broken words.servos requre only 6v.we have used a 7806 to convert 15v to 6v.let me try a higher voltage rating capacitor as suggested in the prevoius post.i doubt whether the transformers available in market are giving 3 ampere.if there are any more suggestions please inform me.sorry once again for using broken words.anyway thsnks for your replies.

06-03-2007, 10:16 PM
now now now...the 78xx series regulators have a current rating of only 1Amp
so you wont be able to drive all motors through that... what u could do is try using 2-3 of it in parallel.

06-04-2007, 01:15 AM
Thanks Roshith!
Servos do'nt come with Cruising /Peak current specs. All specs are given are no-load current. They are notorious for hogging current. Almost all of them will draw greater than 2 A each under load conditions. They will draw more than 5 A during the first part of their switching. The ratings are difficult to state in the data sheets due to the unknown load conditions. What is important is the Peak current drawn by the motors. You cant measure this easily.

Further, the current through the Servo is not continuous, due to the PWM nature of the drive. This is why it draws huge current and delivers surprising amounts of torque , for its size!!! :roll:

There are no supplies in the market that can beat a battery for driving Servos. It is useless to use AC converted/derived DC for these.
Your servos will misbehave with Mains derived power since the fast switching PWM requires current in a hurry. The transformer cannot supply this current demand and will drop its voltage. This will move the RC timing ref. voltage haywire.

Nothing less than a NiCd pack can drive the Servos efficiently!!!
The pack wont last long with Servos , so dont bother with costly stuff. NiMh are good but expensive.
Never use a AC mains derived source for them

Good luck!!

:?: 8 of them?? 3A is JUST NOT enough!!

06-04-2007, 07:03 AM
better go for smps(old one)

Bibin John

06-04-2007, 11:46 AM
like yogi said , go for a SMPS.
They are the Cheapest source of high current , good quality power.

06-05-2007, 11:10 PM
i thank all of you for giving me so much information.

09-06-2007, 01:33 AM
use cheap Lead acid battery like Sunca (6 volts) it can delver huge power