Powering a 5V and a 9V circuit from one 9V battery -- isolation help?

[[email protected]]

For size/weight reasons, I'm hoping to use a single 9V battery plus
mic2950 5V regulator to power a mini video camera (9V) and some RC
servos (5V). Unfortunately, every time the servos move, there's a burst
of interference on the video signal. There's no interference when the
camera and the servos are powered by separate batteries.
The circuit is simple: 9V battery, mic2950, camera, and RC stuff, just
wired together the obvious way. I tried adding a capacitor between
output and ground of the regulator, but that didn't have any effect.
Is there any way to eliminate the interference?
Or, is there a 5 or 6V power source that's smaller than 4AA cells, or
an alternate 9V battery that's smaller than the usual?
Thanks for your attention.


Michael

 

[Phil Allison]

** Hotmail & GG !

Double whammy .....

For size/weight reasons, I'm hoping to use a single 9V battery plus
mic2950 5V regulator to power a mini video camera (9V) and some RC
servos (5V).

** What sort of servos draw under 150mA ?

The servo load current is hammering the battery and causing the noise.

Using the 5 volt reg has no effect on this.

Unfortunately, every time the servos move, there's a burst
of interference on the video signal. There's no interference when the
camera and the servos are powered by separate batteries.
The circuit is simple: 9V battery, mic2950, camera, and RC stuff, just
wired together the obvious way. I tried adding a capacitor between
output and ground of the regulator, but that didn't have any effect.
Is there any way to eliminate the interference?

** Yeah - use as decent 9 volt battery and a decent reg IC.

Or, is there a 5 or 6V power source that's smaller than 4AA cells,

** Yep, 4 or 5 AAA cells, Ni-Cd or NiMH

The very low internal resistance will make a BIG improvement.



....... Phil

 

[[email protected]]

For size/weight reasons, I'm hoping to use a single 9V battery plus
mic2950 5V regulator to power a mini video camera (9V) and some RC
servos (5V). Unfortunately, every time the servos move, there's a burst
of interference on the video signal. There's no interference when the
camera and the servos are powered by separate batteries.
The circuit is simple: 9V battery, mic2950, camera, and RC stuff, just
wired together the obvious way. I tried adding a capacitor between
output and ground of the regulator, but that didn't have any effect.
Is there any way to eliminate the interference?
Or, is there a 5 or 6V power source that's smaller than 4AA cells, or
an alternate 9V battery that's smaller than the usual?
Thanks for your attention.


Michael

It's tried-and-true solution to have separate power supplies for the
motors and the control circuitry. Your system has already demonstrated
that it works well this way, so if you go with the flow, you can
optimize the batteries for each subsystem. Your control circuit and
video might be able to get by with a couple of lightweight lithium
cells @ 3 volts each. Meanwhile, your servo motors could run on some
sort of rechargeable cells because that's where the bulk of your power
is being consumed. This also allows you to maintain full control and
video even when the servo motor batteries are getting low.

 

[Luhan]

For size/weight reasons, I'm hoping to use a single 9V battery plus
mic2950 5V regulator to power a mini video camera (9V) and some RC
servos (5V). Unfortunately, every time the servos move, there's a burst
of interference on the video signal. There's no interference when the
camera and the servos are powered by separate batteries.
The circuit is simple: 9V battery, mic2950, camera, and RC stuff, just
wired together the obvious way. I tried adding a capacitor between
output and ground of the regulator, but that didn't have any effect.
Is there any way to eliminate the interference?
Or, is there a 5 or 6V power source that's smaller than 4AA cells, or
an alternate 9V battery that's smaller than the usual?
Thanks for your attention.


Michael

I've done this before without any problems. The camera was 12 volts
and the servos were powered from a 7805 regulator with about 100uf on
both the input and output. You dont need a fancy low-dropout regulator
for this application.

Also, watch out for any common ground connections, run both bach to the
battery seperately. Or, try physically moving the servos away from the
camera to see if the coupling is inductive from the motor coils.

Good luck,
Luhan

 

[[email protected]]

Thanks all for the rapid and helpful responses! On a Sunday morning, no
less.

 

[[email protected]]

** Hotmail & GG !

Double whammy .....

Hmmm. Is there something I can add to become a triple threat?

 

[James Waldby]

Hmmm. Is there something I can add to become a triple threat?

Sure,
3. Top-post,
4. Add a big ascii-graphics sig,
5. Don't quote the posts you reply to,
6. Use 733t spelling (l33t speak),
7. Tell the old guard they're newbies,
etc, etc.
-jiw

 

[[email protected]]

Thanks!

 

[Rich Grise]

Hmmm. Is there something I can add to become a triple threat?

Yeah - keep feeding the troll. ;-)

Good Luck!
Rich