I want to build my own switch

[sbudz]

I have electrical and electronics from my days in the navy 62-66. so I
know something about this, but not much.

I want to build a 'box' that will allow me to connect my solar panel
(12-18v) and also a ac/dc adapter 12v to my low voltage solar power
pump that I use in my backyard fountain.

right now the solar panel doesnt work in the shade or cloudy days. so
at times I use the 12 volt ac/dc adapter.

what I want to build is a device that will allow me to connect both
the solar panel and ac/dc adapter to it, and be able to use the unit
(solar panel or ac/dc adapter) to the pump,
and send the low voltage to a resistor or whatever.

right now I have disconnect wires every time I want to use the other
device.

 

[Skenny]

sbudz wrote:

I have electrical and electronics from my days in the navy 62-66. so I
know something about this, but not much.

I want to build a 'box' that will allow me to connect my solar panel
(12-18v) and also a ac/dc adapter 12v to my low voltage solar power
pump that I use in my backyard fountain.

right now the solar panel doesnt work in the shade or cloudy days. so
at times I use the 12 volt ac/dc adapter.

what I want to build is a device that will allow me to connect both
the solar panel and ac/dc adapter to it, and be able to use the unit
(solar panel or ac/dc adapter) to the pump,
and send the low voltage to a resistor or whatever.

right now I have disconnect wires every time I want to use the other
device.

Wouldnt a relay do this?

Have the solar panel turn on a relay at a certain voltage, then have the
relay disconnect the pump from the solar panel and connect to the adapter.
You could use a transitor switched by a zener diode when the solar volts
reaches 12, then turn off at below 12. The transistor would turn on the
relay.
Or to save solar power, have the relay powered by the ac/dc adapter, but
the relay controlled with the transistor, by the solar panel.

 

[Stephen J. Rush]

On Wed, 25 Jul 2007 16:22:34 -0700, sbudz wrote:

I want to build a 'box' that will allow me to connect my solar panel
(12-18v) and also a ac/dc adapter 12v to my low voltage solar power
pump that I use in my backyard fountain.

right now the solar panel doesnt work in the shade or cloudy days. so
at times I use the 12 volt ac/dc adapter.

Couldn't you just connect both sources to the pump, through diodes?

 

[sbudz]

On Jul 25, 8:54 pm, "Stephen J. Rush" <sjr...@comcast.net> wrote:

On Wed, 25 Jul 2007 16:22:34 -0700, sbudz wrote:
I want to build a 'box' that will allow me to connect my solar panel
(12-18v) and also a ac/dc adapter 12v to my low voltage solar power
pump that I use in my backyard fountain.

right now the solar panel doesnt work in the shade or cloudy days. so
at times I use the 12 volt ac/dc adapter.

Couldn't you just connect both sources to the pump, through diodes?

any chance I can get some kind of schematic to get an idea of what I
can do?
looks like my navy E/E schools weren't enough.
thanks

 

[Stephen J. Rush]

On Thu, 26 Jul 2007 10:40:02 -0700, sbudz wrote:

On Jul 25, 8:54 pm, "Stephen J. Rush" <sjr...@comcast.net> wrote:
On Wed, 25 Jul 2007 16:22:34 -0700, sbudz wrote:
I want to build a 'box' that will allow me to connect my solar panel
(12-18v) and also a ac/dc adapter 12v to my low voltage solar power
pump that I use in my backyard fountain.

right now the solar panel doesnt work in the shade or cloudy days. so
at times I use the 12 volt ac/dc adapter.

Couldn't you just connect both sources to the pump, through diodes?

any chance I can get some kind of schematic to get an idea of what I
can do?
looks like my navy E/E schools weren't enough.
thanks

This is so simple that it doesn't really need a diagram.
Connect the cathodes of two silicon rectifiers (current rating to suit
the motor) to the positive lead of the motor.
Connect the positive lead from the solar panel to one rectifier anode and
the AC adapter to the other anode.
Connect all three negative leads together.

Whenever the voltage from the solar panel is higher than that of the AC
adapter, the solar panel will supply all of the motor current. When the
solar panel's output drops, the AC adapter will take over.

If the rectifiers are rated at more than 3 amps, they will probably be
in stud-mount packages that look like short bolts, designed to mount on
a heat sink. You can use a piece of aluminum plate or angle stock. The
mounting stud is usually connected to the rectifier cathode, so you can
mount both on one heat sink, just make sure it's insulated from the
negative side of the circuit.