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Old 08-04-2004, 06:58 AM   #1
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Default Standard servo on 7.2V?

I wonder if it's possible to hook up a standard servo straight to the battery and run it on 7.2V?

I know I need to get a better servo eventually, but would this work as a temporary solution, or would I immediately fry the servo? It's a cheap standard Hitec servo. Not sure about the number.

My ESC (GM V4R) only has a 5V BEC. Should only look at getting a new 7.2V servo, or is it possible to run 6V servos straight off the battery? I believe I read that someone did this with a Futaba S9550.
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Old 08-04-2004, 07:39 AM   #2
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It's called "hotwiring".

There is a chance that the servo will fry - but it doesn't always happen.

It may be a cheap way to a faster servo - but it's never going to be as fast or accurate as a more expensive servo.

Personally, I'd stick to the standard voltage, and keep saving for a quality servo, rather than waste money on replacing a cooked standard servo if the hotwiring goes wrong.
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Old 08-04-2004, 09:44 AM   #3
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i do it with all of my 9550's. it's seemingly more susceptable to noise, but using the inductor that ko propo supplies with their fet servos helps that. it also seems sensitive to where in the +ive line you tap into.

i have not had any adverse effects over the course of 10 months running weekly to twice a week. while the servo motor is going to wear faster with higher voltage applied, i am satisfied with what i've already acheived in the 10 months. i would be surprised if i do burn one up.

mind you, i am not proposing this as a solution to spending the big $. the 9550 is already top of the line. i love it for what it is, but i have struggled with the semi-slow transit time that it has at 6.0v. with cars getting less and less tollerant of larger electronics, the 9550 is a great weapon to have. i don't think it would be my first choice if i had to run it on 6 volts, though.

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Old 08-04-2004, 10:10 AM   #4
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where do you guys connect the positive lead?do you remove the + wire on the servoplug and connect it to the + battery?
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Old 08-04-2004, 02:26 PM   #5
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Quote:
Originally posted by wothrottle
where do you guys connect the positive lead?do you remove the + wire on the servoplug and connect it to the + battery?
Basically, yes. It's easier if you pick up a KO-style blue wire, which has a tiny gold pin connector in the middle of it.
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Old 08-05-2004, 02:41 AM   #6
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Quote:
Originally posted by seaball
it's seemingly more susceptable to noise, but using the inductor that ko propo supplies with their fet servos helps that.
Can you get the KO inductor separately, or do you know any specs? I believe the inductance is 4.7 mH, but there are several different types of inductors to choose from. What does the KO look like?

Quote:
it also seems sensitive to where in the +ive line you tap into.
I was planning on using the batt+ terminal on my ESC. Did you get better results somewhere else?

sosidge: I appreciate your advice, and you're probably right. I'm half thinking of trying this anyway, though. I have the money to get a quality servo if it does go wrong, so I won't spend any more money on standard servos.

Did anyone here already try this, and fail?
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Old 08-05-2004, 05:38 AM   #7
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It might also be worth considering getting an ESC with 6 volt BEC - that gives you a wider choise of servoes, instead of limit to KO 7,2 volt types.

But personally, I find it's a good investment to get a high quality servo - it'll serve you well in the long run, it can be taken to the next car and the next car...

And a good servo is the difference of being able to counter steer in a chicane or not, if something unforeseen suddenly happen...
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Old 08-05-2004, 07:34 AM   #8
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Quote:
it also seems sensitive to where in the +ive line you tap into.
my best results are straight from the battery positive. the later down the line i go, the more noise it get. it's a pretty setup to just tap off of the +ive post on the esc, but it was noisier for me. i can't offer any kind of logical explanation as it's all a common conductor, but maybe it is just too close the the esc and that is where the noise comes in.
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Old 08-05-2004, 08:45 AM   #9
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o.k.Connect the pos servo wire direct to + bat and remove the + servo wire from the servo connector going in the receiver.Is this right so long?
then connect a conductor in the line,or isnīt it needed?If,which conductor specs?
Cheers,
Ludwig
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Old 08-05-2004, 09:13 AM   #10
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Quote:
o.k.Connect the pos servo wire direct to + bat and remove the + servo wire from the servo connector going in the receiver
yup. just pull the + from the harness and solder it to the battery. i am running one car that way, and the other does have an inductor in the + line for added noise protection. it does not appear to always be necessary to use one for clean signals.
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Old 08-09-2004, 11:58 PM   #11
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that sounds good,my servo is noticably faster-but,someone told me that the esc wonīt hold that,I donīt understand why ,did you guys ever had problems?

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Old 08-10-2004, 02:37 AM   #12
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I've done it too with 3003's... and it's worth it. however, if you're racing it, you can be sure the servo will blow up when you're leading the A... As long as it doesn't fry (mine hadn't so far, still I replaced it with a "real" servo for accuracy), it's still rather constant.

later
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Old 08-24-2004, 07:33 AM   #13
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I hotwired my dirt cheap Hitec HS-311 servo yesterday.

First I tried simply soldering the wire to the ESC, but the interference at full speed was terrible. I put a 10uH miniature choke between the ESC and the wire, and that took care of it.

My servo is now faster, stronger, and works perfectly. The choke cost less than a dollar, and the job took about a minute. Not a bad deal, eh?
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Old 08-24-2004, 09:45 AM   #14
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bandini,

whats a choke? can you elaborate a bit? is it a capacitor?

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...

thanks in advance...
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Old 08-24-2004, 10:50 AM   #15
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it's not a capacitor, it is an inductor. radio shack has a few, but specialty electronics stores will have more values of which to choose.
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