Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: johnv on August 03, 2018, 10:42:21 pm

Title: Servos
Post by: johnv on August 03, 2018, 10:42:21 pm

Hi why do servos twitch got two servos in a y lead and thay twitch .Unplug one all ok need to get to servos working and how do you stop twitching cheers John V

Title: Re: Servos
Post by: Andyn on August 03, 2018, 11:09:41 pm

Analogue servos can pick up interference they won't filter out through the signal wire in a Y lead.

Title: Re: Servos
Post by: johnv on August 03, 2018, 11:24:22 pm

Hi cheers for your reply what do I need to work two servos together off the one channel tried y lead but that twitch just need to stop twitching cheers John V

Title: Re: Servos
Post by: chas on August 03, 2018, 11:35:32 pm

What is your power supply to the receiver? Sometimes this is relevant. I have no problems using a y lead, and there shouldn't be a problem, although so called digital servos do have a reputation for twitching.

Title: Re: Servos
Post by: johnv on August 03, 2018, 11:42:28 pm

Hi it's two 7.2 battery to speed controller cheers John V

Title: Re: Servos
Post by: Andyn on August 04, 2018, 12:22:30 am

Are you using a computer radio? if so, you'll want to have the servos in different channels and mix them together

Title: Re: Servos
Post by: johnv on August 04, 2018, 07:38:12 am

Hi Andy it's a five channel Saturn cheers John V

Title: Re: Servos
Post by: malcolmfrary on August 04, 2018, 08:51:53 am

Servos twitch because the supply voltage isn't stable enough under load.  Two on the same lead is not a problem provided that the lead can pass the current needed without changing the voltage.  Servo positioning relies on comparing one voltage with another, one is got from the supply, the other from the control signal.  If the load of two motors causes the supply voltage to shift even a fraction, that will be the start of the servo going to a new position.  When it gets there, the load changes and away it goes again.  If the supply into the receiver is borderline inadequate, the bit of the receiver that creates the timing pulses could also be affected.
A work-around is to add a 0.47μF capacitor across the red and black of each servo lead to slow down the voltage changes.

Title: Re: Servos
Post by: johnv on August 04, 2018, 09:13:12 am

Hi cheers for that will a V tail mixer help cheers John V

Title: Re: Servos
Post by: chas on August 04, 2018, 04:12:36 pm

Hi again Jonny, Malcolm's advice is very sound, and I'm sure the voltage is the source of your problem. A quick easy thing to try is to change the receiver power supply from the bec in the speed control, and use a separate battery pack.
   Try this at first with the speed controler(s) unplugged from the receiver. If all works OK, come back here for more advice BEFORE plugging in the speed controllers. You may need to make a little modification before plugging them back in.
Chas

Title: Re: Servos
Post by: johnv on August 04, 2018, 05:52:37 pm

Hi cheers for help good idea I will have ago tomorrow cheers John V