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### Topic: Battery arrangement and splitting current for a DPST switch (Read 1 time)previous topic - next topic

#### jezuz

##### Mar 25, 2011, 04:53 am
Two separate questions, would be grateful for some help. Not HW, this is for a robot.

1) given the arrangement pictured above, would the 4 cells (the lines) be in parallel? I'm pretty sure they are I'd rather not make a mistake.

2) Are the current ratings of multiple pole switches given per pole (switch junction, or whatever) or for the whole switch? Mechanically the poles are seperated, and electrically intended for separate circuits, so it would make sense that each pole gets its own rating (or all of them have the same rating listed). In the case that this is true, could I do what is pictured above and have the positive leads from the cells run separately thru the two poles of a DPST switch, then connecting them later in the circuit, thus halving the current passing thru each pole of the switch?

#### retrolefty

#1
##### Mar 25, 2011, 05:44 amLast Edit: Mar 25, 2011, 07:21 am by retrolefty Reason: 1
While your circuit is somewhat unusual, (  ) your statements are fundamentally correct, batteries are wired in parallel and switch contact ratings are per contact.

Lefty

#### jezuz

#2
##### Mar 25, 2011, 06:00 am
Quote
While your circuit is somewhat usual

Wait, usual or unusual?

The weird setup comes from having 3s packs arranged along the walls of a box-shaped robot, instead of grouped together in a single pack.

#### GaryP

#3
##### Mar 25, 2011, 01:23 pm
Heh, I don't know why you draw it like that, you have simply two sets of cells in parallel with common ground.

If this is for redundancy, it may have some idea, but without the whole circuit, purpose is unclear.

What is it for?

Cheers,
Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

#### jezuz

#4
##### Mar 25, 2011, 08:53 pm
Quote
What is it for?

The weird setup comes from having 3s packs arranged along the walls of a box-shaped robot, instead of grouped together in a single pack. These mini packs need to be in parallel with each other. The way it works out, the packs end up forming the shape drawn above.

#### GaryP

#5
##### Mar 25, 2011, 09:09 pm
Don't understand....

Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

#### keeper63@cox.net

#6
##### Mar 25, 2011, 09:48 pm

Quote
What is it for?

The weird setup comes from having 3s packs arranged along the walls of a box-shaped robot, instead of grouped together in a single pack. These mini packs need to be in parallel with each other. The way it works out, the packs end up forming the shape drawn above.

This is the thing: A schematic is a logical representation of a physical layout; what you see in a schematic does not have to match (and usually can't!) the physical layout of the circuit itself. For instance, take a look at the schematic for the Arduino, and compare it to the physical PCB - I can guarantee you nothing is in the same place as it is on a schematic.

This doesn't only apply to circuits, either - any schematic diagram (process diagrams, flow charts, etc) is typically representing a logical layout (generally in a manner that makes the intent/usage/operation of the device/system/process clearer to a human) of what could be a very complex physical layout (you want to see complex - look into industrial plant process controls and systems, like that used for refineries, assembly lines, etc; even the schematics for such a system are pretty dense, but they certainly don't represent the physical layout of the plant).

Your "schematic", as drawn, actually does the opposite of what a schematic should do; namely depicting how the system as a whole works in a clear fashion. If you illustrated an entire robot system in this manner, it would quickly become nearly impossible to figure out and follow.

Not that it hasn't been tried in the past, though; pick up really old "popular electronics" magazines from about 1950 or older, and you'll see a ton of articles on radio chassis wiring illustrated with physical wiring layout and assembly diagrams (sometimes with a real schematic, sometimes not!). I will grant in some of these cases it was likely important to lay out some of the items carefully, and show how to wire them, because they were using point-to-point wiring/soldering techniques (PCBs weren't on the scene yet), and if you wired things in the wrong order, you might not be able to solder something else because another component or holder was in the way...

I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

#### jezuz

#7
##### Mar 25, 2011, 09:52 pm
Perhaps I didn't make it clear, but in my first post the reason I asked question (1) wasn't because I don't know what cells in parallel looked like, I wanted to know if this setup, specifically as I had drawn it, was really the same as drawing four cells in parallel. That's the only reason why the schematic is not standard.

#### GaryP

#8
##### Mar 26, 2011, 07:11 amLast Edit: Mar 26, 2011, 02:43 pm by GaryP Reason: 1
I think I got the picture now. Those switches are working in parallel too? They are not drawn to be in the same package, sametime action. If it is so, then that switch is, when pressed, connecting all four batteries in to parallel and supplying power to your circuit.

In the picture, you have two separate switches  pictures, and both can be closing the circuit, to power up your device, but with only half of the power capacity. Maybe there is a reason for that too?

Cheers,
Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

#### jezuz

#9
##### Mar 26, 2011, 02:20 pm
Yeah, that one was my bad, should have drawn a box around the two switches or something. But yes, its a single DPST package.

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