I suspect the problem is that you are drawing your 12v signal from the
wrong battery. Basically, you need to make sure that all circuits use
the same "ground". Specifically, suppose you have two 12V batteries, A
& B, connected in series as your main 24v power supply. Let's assume
that the negative terminal of the A battery is your 24v Ground and the
positive terminal of the B battery is your +24V. In that case, you
should tap all 12v signals using the "A" battery, not the "B" battery.
Otherwise, the ground for the 12V systems will be 12v higher than the
ground for the 24v systems. Many ESCs connect their input and output
grounds together, thereby causing a dead-short if you tap 12v from the B
battery.
I strongly recommend that people use completely separate batteries for
their electronics and controllers, leaving the main batteries to drive
heavy loads, like motors and solenoids. That not only protects you
against system wiring problems, but it also keeps the electrical noises
and heavy current pulses caused by power hungry motors away from your
sensitive electronics.
Case in point, one of my C6C customers was using the C6C to drive a big
robot. Worked fine most of the time, but it sometimes caused problems.
After asking about his circuits he told me about a BEC he had
installed to "make things simpler". I recommended a separate battery to
eliminate electrical problems caused by the motors drawing down the
voltage in the main batteries. He swore that the BEC would prevent such
problems. I told him that the common ground had no protection and
therefore he had no protection at all from electrical disturbances of
all kinds. He said he thought it was something else. Two months later
he wrote saying that he finally tried the separate battery and it worked
perfectly ever since.
Frank P.
On 4/2/2011 9:37 AM, Rusty Bates wrote:
Hello all,
I installed a Sabertooth 2x25 a few weeks ago. The unit appears to do
fine other than a few jerks from the motors on occasion, I believe it
may be radio interference. I'm using a FM ground Freq radio purchased
just for this unit. I still need to tie in some caps to the motors and
make sure the radio antenna is installed correctly so at this point
I'm not really concerned about it.
But and a very big but here, I ran into something the other day that
gave me pause.
Although the Sabertooth has a BEC, I have been using the battery pack
that came along with the radio to power the receiver. This setup is
fine and I've experienced no issues other than mentioned above.
The next step was to install my sound unit (a home brewed unit using a
few PICAXE chips and 2 Vmusic sound modules) into the tank, again
using the battery supplied for the receiver. The unit has a 12 volt
regulated power supply included and uses a simple Y connector for the
radio signal. I've used this unit with success in my past setup using
Joe Sommers ESC. I tested the unit without applying power to the ESC.
The unit worked fine!
But then I decided to apply power to the Sabertooth and run the tank.
It took about 3 seconds before the negative wire leading to the sound
unit began smoking. Lucky for me no damage occurred to the receiver or
ESC. I figured I wired something wrong, but upon inspection decided
every thing was as I have had before in a past setup.
I then removed the sound unit from the system and decided to install
my home brewed BEC circuit (A simple 12 volt regulator circuit
supplying 4.5 volts) into the receiver. Once again I tied the power
supply to one battery for a 12 volt source. Power up the ESC and
watched smoke as the NEG wire to started to sizzle. Again no damage
to the either receiver or ESC. I tested both units wired as before
with the original receiver battery and then with the on board BEC and
the ESC and REC seem to operate thankfully.
I use two 12 volt batteries for a 24 volt system. I'm about 95% sure
that in the past I simply tied the power supply (12 volt input) for
the sound unit to one battery. Not sure why I didn't just power the
sound control unit with 24 volts as the 12 volt regulator will accept
up to 35 volts. Be that as it may, I'm still pretty sure it was only
supplied 12 volts.
Now I know from building the sound control and even a smoke control
unit that the entire circuit has to share a common ground or else the
PICAXE chip will not work correctly with the radio signal. But this
has burning up of the negative wire has me spooked. And yes before I
go any further I plan on installing a control fuse in the negative
side to help prevent any further damage.
So I guess one of my biggest questions is could the circuit being
fried is due my hooking up only side of the battery set to the sound
unit? Could the ESC cause this short of shorting?
Any help, thoughts would be greatly welcome!
Rusty
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