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polarity of servo wires

change polarity

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neil howard-pritchard30/11/2020 14:46:45
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1625 forum posts
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is it possible to change the polarity of one servo so that it turns in the opposite direction when linked to a "Y" harness.

reason i ask is i have two servos at the stern of my Tyne class lifeboat operating the two trim tabs that keep the boat level when sailing.

the servos have only one direction of travel for the tabs and that is a 45 degree downwards movement to lower the tabs.

the starboard one works fine, but the port servo, with exactly same directional movement of the axis, when turned around to port in the cradle, lifts the tab, this making it inoperable without major surgery to the cradle.

last night i took the one that operated in the wrong direction and joined it to the one that works correctly and joined black to red and red to black........but this stopped both from working through the receiver.

the only way i can do it is by switching polarity of the one turning in wrong direction via my transmitter, but that means using two channels of the tx and rx, which i don't want to do.........am confused enough as it is, lol.

any help gratefully appreciated.

img_7316.jpg

ashley needham30/11/2020 15:37:59
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6920 forum posts
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Get a servo reverser? Easy option?...

Ashley

Colin Bishop30/11/2020 15:42:52
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4756 forum posts
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Servo reverser:

**LINK**

Colin

Dave Milbourn30/11/2020 16:24:18
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4025 forum posts
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Neil

NEVER EVER try to change the rotation of a servo by swapping the red and black wires. Inside that gizmo is an amplifier and logic circuit which depends on the correct polarity for its operation. Get that wrong and you will kill it. Colin and Ashley have the answer for less than a fiver.

Dave M

neil howard-pritchard30/11/2020 16:55:05
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1625 forum posts
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i thought i would get a rollocking off you dave...... you know my skills and abundant knowledge of electrickery, lol

and always thank you for doing so mate...

and thanks Colin and Ashley..........Someone on facebook pointed these things out to me as i didn't know they existed, so have ordered two and a few Y harnesss too, hope they do the trick.

cheers to you all. just charging the batteries now on a few radio sets for me to play with..........something i haven't done for a long while.......but quite surprised that they all still have some charge in the batteries.

Malcolm Frary01/12/2020 09:34:44
943 forum posts

I have heard tell of servos that do have reversed logic, at a price. It is also possible to create one by taking the servo apart, reversing the motor connections AND transposing the two outer connections to the pot. The servo reverser is by far the simplest and cheapest option, and the most likely to work.

neil howard-pritchard01/12/2020 13:05:56
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1625 forum posts
1059 photos

Cheers Malcolm........some on their way as we speak.

Tim Cooper01/12/2020 14:06:29
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394 forum posts
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Neil

I had a similar situation on my Graupner Bernhard Gruben model. Two servos work together to lift and lower the stern gate for launching the small rescue boat. In this case the two servos were set up on either side of the hull , and with the servo arm on the right of the servo, when looking toward the bow. This meant that the servos operated together from one channel with a y lead.

Tim

Robert Foreman 101/12/2020 20:00:56
2 forum posts

You can reverse an analogue servo, but you will need a small soldering iron.

After taking the case to pieces:

1) swap over the two wires attached to the motor

2) locate the potentiometer usually connected to the output shaft. This will have 3 wires attached, swap over the two outer wires

Job done !

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