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Standard servo on 7.2V?

Standard servo on 7.2V?

Old 08-25-2004, 03:44 AM
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Originally posted by Tommi Makkinen
...im planning to try this hotwire thing on an old sanwa sx servo... im a few bucks away from getting a futaba 9550 but i need a fast servo to tide me over until i get my proper servo......
hey tmak, please let me know how this turns out i want to try it on my 3003 but i have no idea how to wire the servo. i have a phobia when modifying servos (burned a 9402 once )
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Old 08-25-2004, 04:31 AM
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Originally posted by marvi
i want to try it on my 3003 but i have no idea how to wire the servo.
It's very easy. Pick up a 10 uH ("microHenry") miniature choke from an electronics store. Unplug your servo from the receiver and remove the red wire from the plug. Solder the red wire to one end of the choke. Solder the other end of the choke to Battery+. I did this on my ESC, but you can tap in anywhere between your ESC and your battery. Put the servo plug (minus red wire) back into your receiver, and you're all set.
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Old 08-25-2004, 08:11 AM
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Bandini: thanks for the info

does the choke have any polarity (like a capacitor or diode)? also, after soldering the choke, how should i secure the choke on the servo wires? do i have to CA it to prevent it from flying off or will zip ties do? sorry, but i dont know what a choke looks like ill try to find one next time im at the electronics shop
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Old 08-25-2004, 08:36 AM
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I don't understand... shouldn't you take the negative wire and solder it to the battery's negative tab?
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Old 08-25-2004, 02:46 PM
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marvi: the choke has no polarity. The one I use is 3 mm in diameter and 7 mm long, with a single wire going through it. It looks just like a small resistor. A piece of shrink tubing to prevent any exposed wire is a good idea, but it doesn't really need securing.

Super Steve: no, the negative servo wire stays in the receiver.
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Old 08-25-2004, 03:17 PM
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this is extremely easy. for a non permanent trial, just pull out the +ive servo lead from your connector, and hold it to your battery +ive. now play with the steering. faster? you betcha.

if you need an even better comparison between the two, with it still in the connector, cut a small patch of the sheath back in the +ive servo lead. use a jumper from the battery +ive over to the bare section. turn your radio on. your servo will now operate on 6.0 if the jumper is off, and 7.2 if you make contact with it. notice a difference? i hope so.

that's it in a nutshell. the inductor is just a noise filter and is not always necessary. it has no polarity, and you wire it in series using the +ive servo lead. done.
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Old 08-25-2004, 08:40 PM
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ok, ill try that thanks again. right now, my mounted servos are an S3003 and S3004 that could use a bit more power

since the choke is not entirely necessary, ill just put one in when it glitches, right?
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Old 08-26-2004, 08:34 AM
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Originally posted by marvi
hey tmak, please let me know how this turns out i want to try it on my 3003 but i have no idea how to wire the servo. i have a phobia when modifying servos (burned a 9402 once )
will do. ill show you a document i downloaded when we meet. its got all you need to hotwire the servo...

howd you burn the 9402? isnt that fast already?
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Old 08-26-2004, 10:21 AM
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Originally posted by Super Steve
I don't understand... shouldn't you take the negative wire and solder it to the battery's negative tab?
No. The negative wire already grounds to the battery through the reciever which grounds to the esc which ground to the battery. I believe the signal for the servo alternates between the signal wire and the negative wire and if you ran the negative wire it would tell the server to go full speed in one direction. I could be mistaken on this though.
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Old 08-26-2004, 06:26 PM
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Originally posted by Tommi Makkinen
will do. ill show you a document i downloaded when we meet. its got all you need to hotwire the servo...
howd you burn the 9402? isnt that fast already?
ok, see you this weekend actually, seaball & bandini's last posts were very helpful and ill test the servo this afternoon when i have time. re. the burned 9402, totally different story i think i extended the wires or something (simple matter of splicing and soldering) that turned into a not-so-simple sparking and burning
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Old 08-28-2004, 08:02 AM
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Cool it worked!

i just finished soldering the red servo lead to the battery's positive post and indeed, the servo was visually faster i didnt get to run the car (its 11pm now ) but ill know tomorrow if it glitches. if it does, i hope ill find a 10uf choke to fix the problem. thanks, guys, for your helpful posts
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