Hi there,

I hope some can give me some tips.. I have a very simply circuit in =
which I have a PIC
12CE673 which
drives a standard servo as used in RC-models.

The servo (Hitec HS-81) is a small servo like used in gliders/electric =
helicopters (micro
servo).

Basically the circuit consists of a 7805 voltage regulator which powers =
the 12CE673 and
the servo.
The servo pulse is 1,8 ms for about half-a-second and the 1,2 ms for =
about 3 seconds after
which it
loops back to the first step. (For the books:  the signal is about 50 =
hz, 20 ms pause +
pulse signal)

When this setup is left for some days to for some days , the servo is =
killed after some
time en gets quite hot.
On inspection of the servo you can see that the electronics has been =
'killed'.
Because Hitec has put some kind of glue on the electronic parts I can't =
measure anything..
:-(

Not only the Hitec servo's are killed, but a servo from another brand =
also gets killed...

I have also tried an old standard size servo and this seems to keep =
working.

My question: Can someone maybe think of some reason why the servo's are =
killed after some
time.?
Sometimes the Hitec servo's keep working for 5 days, but sometimes it is =
over in a few
hours.

My power supply is stable and the 7805 isn't getting too hot. (in other =
words: I know for
sure that the
power supply is giving a stable 5,0 volt all the time..)

I can only think that there can be something wrong with the signal or =
maybe I need to add
a resistor
between the servo and PIC..??

Does someone maybe have some detailed information how the electronics in =
a servo works.?
I know the basic setup (small motor - gear box - potentio meter with =
feedback from the
gearbox), but
how is the electronics working/triggered.

Any opinions are greatly appreciated.. Already killed 6 servo's.... and =
they are not
cheap..:-(

With kind regards,
David Bouw

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