Multiple DC Power Supply

[Manchu]

I have twelve 6-9VDC/200-250mA CMOS cameras and have been attempting
to design a power supply for them. The Transformer I am using is
24VAC/100A. Unfortunately, the cameras are extremely sensitive to
power fluctuations above the 9VDC/250mA levels. Does anyone know of
schematics or references I can use to develop this? Any help would be
greatly appreciated.

 

[Guest]

24VAC @ 100A?
That's just a little hot for your application I would think! I read your
last post - how about starting with something like raw 12 to 15VDC (4 to
5A) supply. Feed this to 12 seperate legs each feeding a 9v 3 terminal
regulator (7809 rated 1 amp) which then feeds thru a diode to your camera.
Except you could attach a 6V or maybe better yet a 7.2v nicad or lithium-
Ion battery at the V+ input of your camera as well. I would think a
charging limit resistor would be needed in series with the chargeable
battery or you could do the same with regular batteries if you add another
diode in series with the + battery lead.
This way if your supply fails you have battery backup to take over. This
would be the ideal I would design around if I was you. To get an idea of
what I am talking about, refer to the "steering diode" posters link:
http://ourworld.compuserve.com/homepages/g_knott/elect212.htm

Todd

 

[Manchu]

24VAC @ 100A?
That's just a little hot for your application I would think! I read your
last post - how about starting with something like raw 12 to 15VDC (4 to
5A) supply. Feed this to 12 seperate legs each feeding a 9v 3 terminal
regulator (7809 rated 1 amp) which then feeds thru a diode to your camera.
Except you could attach a 6V or maybe better yet a 7.2v nicad or lithium-
Ion battery at the V+ input of your camera as well. I would think a
charging limit resistor would be needed in series with the chargeable
battery or you could do the same with regular batteries if you add another
diode in series with the + battery lead.
This way if your supply fails you have battery backup to take over. This
would be the ideal I would design around if I was you. To get an idea of
what I am talking about, refer to the "steering diode" posters link:
http://ourworld.compuserve.com/homepages/g_knott/elect212.htm

Todd

Todd Thanks!

This looks like a promising solution. I'll be setting this up this
weekend to see how she works out. I'll let you know.

Bob

 

[DarkMatter]

I have twelve 6-9VDC/200-250mA CMOS cameras and have been attempting
to design a power supply for them. The Transformer I am using is
24VAC/100A. Unfortunately, the cameras are extremely sensitive to
power fluctuations above the 9VDC/250mA levels. Does anyone know of
schematics or references I can use to develop this? Any help would be
greatly appreciated.

Design for the nominal voltage of 7.5 Volts. At a 0.25 amps each at
low line, and 0.20 amps each at high line, the power for twelve at 7.5
volts should be at around 225mA each unit for a total of 2.7 amps at
7.5 volts, or just over 20 Watts.

You could likely take the 5 volt rail of a good stiff 50W switcher
supply, and adjust it to get 7.5 volts out, and easily push into a 20
watt load. Maybe a cap bank on the output to reduce ripple even
further... Or a cap at each camera.

See a military surplus store, or an industrial liquidator.

Better yet, just get on e-bay and buy one. Hell, even a bench
supply will do nicely.

Definitely get a bigger supply than you think you appear to need, as
the cameras like steady, quiet voltage. Headroom is a good thing.

 

[Manchu]

Todd Thanks!

This looks like a promising solution. I'll be setting this up this
weekend to see how she works out. I'll let you know.

Bob

Todd It worked out Great. Thanks for your help. Got another idea from Amnon.

 

[Guest]

So you are making progress? are you using the battery scheme - nicads?
Todd

[email protected] (Manchu) wrote in message
Todd It worked out Great. Thanks for your help. Got another idea from

Amnon.