Sabertooth with Hpx F?

peterwaller · Post by **peterwaller** » Tue Aug 17, 2010 6:49 pm

It should be pointed out that you are overunning a 6v servo if you are using 2 lithium cells 8.4 v. This is likely to reduce the life expectancy of the servo but people seem to get away with it. I would not do it on three cells.

philippos · Post by **philippos** » Tue Aug 17, 2010 7:55 pm

i am using a 2 cell 7,4V, but isn't the hpx f servo fine at 7,4?

Shakey · Post by **Shakey** » Tue Aug 17, 2010 8:08 pm

daliad100 wrote:Both ways work because both have a 0v wire, hence, only one wire needs to be moved.

Why the seperate regulator? I can't see much point in it because you get full battery voltage through the servo meaning more weapon power without it.

We'll last time I accidentally ran a fully charged 2 cell lipo through a servo the circuit blew inside

and since it doesn't take too much weight I would prefer to keep one on. Also the flipper can flip things around the 450gram mark as it is.

peterwaller · Post by **peterwaller** » Wed Aug 18, 2010 7:43 am

There is always confusion with cell voltages because they don't quote them at the maximum voltage. Lithium Polymer batteries are charged until they reach 4.2 volts per cell ie 8.4 for two cells.
Most servo's are only rated at 6v lets assume the servo takes 1 A then that is 6*1=6 watts. If we increase the voltage to 8.4 v then the servo now takes 8.4 / 6 = 1.4A so 1.4 * 8.4 = 11.6 watts. You now have almost twice the power dissipated in the servo. If all the components are rated at 8.4volts the servo is likely to work but under stalled out conditions you are much more likley to burn out a servo.

philippos · Post by **philippos** » Wed Aug 18, 2010 12:21 pm

ok, looks like im going to play it safe and buy a voltage regulator...

daliad100 · Post by **daliad100** » Mon Aug 23, 2010 9:34 am

How much voltage can the motor in the servo take? I have a cunning plan to piggyback a higher voltage h bridge off of the servo and hook the motor in the servo to the h bridge. This way the servo electronics can run on the 5v regulated supply that the reciever uses and not explode while the motor runs on a 3s lipo (could possibly go higher) for an ?ber flipper.

I know it can be done in such a way that it behaves like an ordinary servo, I just want to know if it's worth the effort and won't destroy the motor every flip.

joey_picus · Post by **joey_picus** » Mon Aug 23, 2010 10:50 am

I think Scott's had the same idea as you, talking to him about it would probably bear fruit...having disassembled a few servos before I can't see why it wouldn't take 11.1v really, the actual motor is the same size and shape as the ones used in Sanyo-type gearmotors which people regularly run from 3 or 4 cells with no problems.

daliad100 · Post by **daliad100** » Mon Aug 23, 2010 11:13 am

Mwa ha ha ha...

Now all I have to do is fit all of this in weight and decide on whether to keep the front hingedness of stack error with a potentially epic flipper or go with some other mechanism.

andrea.taras · Post by **andrea.taras** » Mon Aug 23, 2010 8:16 pm

Hello everyone. I'm new to this forum so I take the chance to introduce myself: I'm Andrea and I'm a 20 yo student from south Italy (so please forgive me if my english is not perfect, I'll do my best, I swear!

).
So, back to the main subject:
I'd like to know if anyone tried using the Sabertooth 2x5 board alongside a Hitec HS-82 MG servo and if you encountered some problems.
I am currently working on a new pusher/flipper project (a looong term project that I'll only be able to finish around Christmas) and I had already planned to use a Sabertooth 2X5 with a 7.2V NiMh battery pack, two micro motors and an Hitec HS-82 MG servo until I read this topic...
Any advice?
Thanks!!

joey_picus · Post by **joey_picus** » Mon Aug 23, 2010 8:48 pm

Hi Andrea, welcome to the forum

I use a HS82-MG myself in Jigsaw as a replacement for a HPXF in the old version (which didn't like the flipper jamming up and shredded itself

) and the level of power in the servos seems to be similar, given that the torque and speed figures are in the same region for both servos I would guess - although I'd get a second opinion since I'm not what anyone would describe as an expert - that if a HPXF will cause problems then there's a good chance the HS82MG might as well.
If you ran the servo directly from the battery voltage (instead of from the BEC supply to the reciever) you might get around that though, assuming your pack's up to providing the current for two motors and the servo all at once?