battery automatic connection to load circuit

Thread Starter

artmaster547

Joined Jan 6, 2016
409
Hi all

I wondered if you could help with a circuit I am developing I have a battery connection that is connected and disconnected via a FET (12V, 5A). It is normally disconnected, only when a load is connected to the battery will the FET connect, I want to make this connection automatic does anyone have any ideas what kind of circuit I could use to develop this? I do have access to microcontrollers and other circuits any help would be appreciated.

Kind Regards

Art
 

AlbertHall

Joined Jun 4, 2014
12,345
So the load is connected (or not connected) direct to the battery. Then there is also a connection from the battery via a FET switch which feeds power to something unspecified. The FET switch should be on if the load is connected to the battery.

Is that right?

If so, how to detect if the load is connected? By the current it draws (need to specify the minimum current that should trip the switch, and the maximum current that the current measurement system would have to handle), or is there some other means to detect load connection?
 

Thread Starter

artmaster547

Joined Jan 6, 2016
409
So the load is connected (or not connected) direct to the battery. Then there is also a connection from the battery via a FET switch which feeds power to something unspecified. The FET switch should be on if the load is connected to the battery.

Is that right?

If so, how to detect if the load is connected? By the current it draws (need to specify the minimum current that should trip the switch, and the maximum current that the current measurement system would have to handle), or is there some other means to detect load connection?
So the connection will be: positive connection of battery to source of FET then the drain of the FET goes to the outside world the negative of the battery goes to the outside world, there will be current sensors on board, the FET will be OFF though so no current flow to the outside world, and I guess 0V across drain of FET and negative of battery. The behaviour I want to capture via some sort of circuit is when a load is put across the drain of the FET and negative of the battery the circuit is able to detect the presence of a load and then turn the FET ON, is this something that is possible without intervention via buttons/switches?
 

AlbertHall

Joined Jun 4, 2014
12,345
OK but then I don't see the point of the FET switch.

With the FET switch:
1. If there is no load then the switch is off.
2. If there is a load then the switch is on and the load is connected to the battery.

Without the FET switch:
1. If there is no load then nothing is connected to the battery.
2. If a load is connected it receives power from the battery.
 

spinnaker

Joined Oct 29, 2009
7,830
So the connection will be: positive connection of battery to source of FET then the drain of the FET goes to the outside world the negative of the battery goes to the outside world, there will be current sensors on board, the FET will be OFF though so no current flow to the outside world, and I guess 0V across drain of FET and negative of battery. The behaviour I want to capture via some sort of circuit is when a load is put across the drain of the FET and negative of the battery the circuit is able to detect the presence of a load and then turn the FET ON, is this something that is possible without intervention via buttons/switches?

Post a schematic of your idea. It is always a lot easier to see it rather then try to read a description.
 

Reloadron

Joined Jan 15, 2015
7,501
OK but then I don't see the point of the FET switch.
You have what I call a Catch 22. You will only have current flow when the FET, MOSFET or even call it a switch is On and want to detect a load (current flow) to turn on your switch device.

That would be my read and yes, a drawing of what you have in mind would be nice. Now if you are plugging and unplugging a load and want your switch device to only be on when the load is attached or plugged in that can be done but with things hardwired as you describe I don't see this working or know of a way to make it work.

Ron
 
Top