Signal wire load
10-31-2013, 05:23 AM
#1
Thread Starter
Signal wire load
Hi,
I'm looking at making up extension cables for a 2m biplane - quite a lot of cable , servos in the tail ,each wing x 2 etc.
I will be making some 4 core lengths - to supply servo pairs , eg two elevator servos.
I am just wondering how much current travels in the signal wires ??.
If it is very little I should be ok with a lighter wire for the signal only.
Thanks.
Brian
I'm looking at making up extension cables for a 2m biplane - quite a lot of cable , servos in the tail ,each wing x 2 etc.
I will be making some 4 core lengths - to supply servo pairs , eg two elevator servos.
I am just wondering how much current travels in the signal wires ??.
If it is very little I should be ok with a lighter wire for the signal only.
Thanks.
Brian
11-05-2013, 04:27 PM
#2
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It may depend on the receiver you are using, but I believe the signal wire Vpp is actually not full swing of the supply lines. I've read somewhere it is actually 0 to 3.3.v or possibly only 0 to 2.6v although I've never scoped it myself. So in other words, you have less headroom on the signal line and may want to keep it the same gauge as the pwr and gnd. Granted the signal wire will not carry much current but you don't want any signal degradation. People have added "amplifiers".. (in the industry it is actually known as a level shifter but perhaps they are both level shifting and providing a repeater function for slew rate control, who knows). Hopefully Futaba can officially comment on the levels w.r.t each receiver system.
Last edited by dbsonic; 11-05-2013 at 04:35 PM.
11-06-2013, 06:16 AM
#3
Thread Starter
Hi,
Thanks.
I get the point re head room.
Though I will have a lot (relatively speaking) of cable, the longest run is 1.2m.
I would have thought that if the current involved in the signal is really low there would be little or no appreciable voltage drop - am I wrong ??
Brian
Thanks.
I get the point re head room.
Though I will have a lot (relatively speaking) of cable, the longest run is 1.2m.
I would have thought that if the current involved in the signal is really low there would be little or no appreciable voltage drop - am I wrong ??
Brian
11-06-2013, 07:57 AM
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You are correct. That's Kirchoffs.
But there are a whole gamut of other things to consider.. like signal integrity. and how many connectors.
weak signal drive is much more susceptible to crosstalk. Its called the victim net.
Anyways, best solution for running long routes is good servo leads with as few connectors as possible. I'd say 20gauge for each of pwr/gnd/signal and twisted .
that way you get a little shielding running them together. Actually HobbyKing sells some really nice twisted servo wire that I like if you make your own leads.
But there are a whole gamut of other things to consider.. like signal integrity. and how many connectors.
weak signal drive is much more susceptible to crosstalk. Its called the victim net.
Anyways, best solution for running long routes is good servo leads with as few connectors as possible. I'd say 20gauge for each of pwr/gnd/signal and twisted .
that way you get a little shielding running them together. Actually HobbyKing sells some really nice twisted servo wire that I like if you make your own leads.
