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Author Topic: Loads of different amps connected to single battery  (Read 381 times)

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Offline ignatius_gimTopic starter

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Loads of different amps connected to single battery
« on: February 18, 2014, 07:06:07 AM »
So, I've never really wired a whole robot before, but I am attempting that now. I've gotten everything together, but I was wondering if it is okay to connect to loads of uneven amp values to the same battery dirrectly.  I have a 7A 12V lead acid battery, an arduino and a hefty Victor Motor controller attached to a 2A motor. I am distributing the power normally through a T connection with the wires.

Thanks for your help.

Offline waltr

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Re: Loads of different amps connected to single battery
« Reply #1 on: February 18, 2014, 09:58:48 AM »
Yes. Think of it this way: each component on a PCB draws a different amount of current but they all use the common V+ connection to the Voltage regulator and battery.

Now for a subtle detail.
Motors tend to draw lots of current compared to the processor board. Motors are also very noisy electrically. For both of these reasons it is best to connect the power wires to feed to motor control circuit (H-bridge) directly to the battery. The processor board would then also go to the battery. This is called a "star" connection.

Offline ignatius_gimTopic starter

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Re: Loads of different amps connected to single battery
« Reply #2 on: February 18, 2014, 05:09:11 PM »
So, let me get this straight, I wire the H-Bridge directly to the battery not through a T-arrangement of wires with a single connection to the battery?  Do you have a schematic?

Offline jwatte

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Re: Loads of different amps connected to single battery
« Reply #3 on: February 18, 2014, 06:33:26 PM »
"to the battery" is also a somewhat nonsensical concept, because there are single conductors within the battery, from the cells to the connectors. So there will be a T- or Y-style split at some point for sure.
The main idea is to make sure that:
1) H-bridge is wired to battery using sufficiently thick wiring all the way
2) digital electronics are not on the "direct path" between the battery and the controller

Easiest is to make a Y split right at the battery connector, with a thinner cable going to digital electronics, and a thicker cable going to H-bridge.
There are other options. For example, you can wire thick cables to the H-bridge, and then use thin cables from H-bridge input to digital electronics. This is slightly less ideal, though.
In any case, you probably want to clean up the microcontroller input with a 10-100 uH inductor and a 100-1000 uF capacitor before the actual entry to the MCU.

Offline waltr

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Re: Loads of different amps connected to single battery
« Reply #4 on: February 18, 2014, 08:03:39 PM »
Here is a some info on the star connection:
http://www.maxbotix.com/articles/067.htm

 


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