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Old Mar 07, 2011, 11:28 AM
firefly_joe is offline
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how to boost servo signal through long wire?


Does anyone know if there is something that I can use to boost a servo signal from the receiver through a large amount of wire (maybe 50ft or more)?

I haven't tried it yet but I'm pretty sure the servo signal is going to be pretty weak.
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Old Mar 07, 2011, 11:39 AM
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No need (I think). There are two components here: the 5-6v power circuit, and the PWM signal (white wire on most servos). The signal line only involves tiny current flow, so there won't be much in the way of voltage drop on that line... and the servo doesn't respond to a voltage signal anyway, but to the pulse widths.
If you do have an issue here, try some heavier gage wire.

For power, you might want a local power source... a 4.8 - 6v batterywired into the red/black leads. Keep a common ground wire back to the source, and delete the +5v red wire in the long run, you'll be fine.
Old Mar 07, 2011, 11:58 AM
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Firefly joe
I have to ask, what are you building that will have a 50’ wire from the receiver to the servo? That is going to be one “really big model”.
Mike
Old Mar 07, 2011, 12:00 PM
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sounds promising! I am more than likely going to to have a battery pack at the other end of the line, so you are saying if I connect the servo's +/- to the secondary pack and then the signal wire only connects to the receiver I should be good?
Old Mar 07, 2011, 12:08 PM
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@Mike, I'd like to be able to drop a mini sub off my barge, long term plans but just thinking ahead now
Old Mar 07, 2011, 12:34 PM
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Quote:
Originally Posted by firefly_joe View Post
sounds promising! I am more than likely going to to have a battery pack at the other end of the line, so you are saying if I connect the servo's +/- to the secondary pack and then the signal wire only connects to the receiver I should be good?
And a common ground wire, the signal needs a reference. So, black and white wires on the long run, black and red wires to the local battery.
Old Mar 07, 2011, 01:09 PM
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awesome thanks!
Old Mar 07, 2011, 07:05 PM
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50 feet


I would test the project before assuming it will work. The capacitance of the parallel signal and ground wire is considerable and with the associated inductance the system becomes a transmission line exercise. The clean square wave pulses from the RX will probably become "rounded" with extended rise and fall times. The device on the far end may still respond correctly - but I would definitely test the system first!

John WA3ETD
Old Mar 08, 2011, 01:57 AM
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Quote:
Originally Posted by firefly_joe View Post
@Mike, I'd like to be able to drop a mini sub off my barge, long term plans but just thinking ahead now
How big of a mini sub will this be? 50' of servo wire will be pretty draggy through the water.
Last edited by Aerominded; Mar 08, 2011 at 02:03 AM.
Old Mar 08, 2011, 02:02 AM
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If your going to have the battery in the sub, better off having the RX in there as well, and just transmit the RF town a thin Coax from the Tx, I have a drawing posted in the ROV forum with a simple circuit to allow video signal up the same coax

I will watch this space

Nick


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