Author Topic: 12 or 24 VDC system  (Read 1453 times)

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Offline heycatmanTopic starter

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12 or 24 VDC system
« on: January 11, 2011, 11:12:57 PM »
I'm a robot noob but have experience with fabricating and programing. Wanted to build a 3 wheeled robot (2 wheels in front 1 rear wheel that rotates freely). The load would have a camera mounted on a turret. I was looking at something a bit heavier to accommodate some power it doesn't have to be small or light. What my in experience needs help with is.......

What type of electrical system to put into this thing. I like the idea of a 12vdc car type battery powering two 12vdc electric motors one motor for the right side one for the left if that makes sense. I thought perhaps I could get a deep cycle battery for this. The only thing is what type of electrical motors to look for? Then I though if I could find 24VDC deep cycle batteries and corresponding motors that would be even better but then of course I'm stuck in the same situation. The appeal to a 12VDC car battery is that I can easily replace, repair, accessorize pretty easily. I just don't know where to start though. I'm totally good with starting from scratch cause my building ability is excellent but don't want to purchase motors to find out they don't have enough torque and don't want to purchase batteries to find out I need a different system to run the motors.

Offline photomark

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Re: 12 or 24 VDC system
« Reply #1 on: January 12, 2011, 01:38:52 AM »
This is probably best asked in the electrical section but hey who am I to judge .

12 or 24 ? you could use both . two car battery's in series will give you the 24 volts witch would be better for the drive system where there is heavy current draw.

The 12 volt systems can just be wired from either of the battery's as needed   

Offline waltr

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Re: 12 or 24 VDC system
« Reply #2 on: January 12, 2011, 10:21:55 AM »
Your basic ideas are sound and are commonly used. There are pros and cons to the 12V vs 24V system as you have already thought. Another item to think about:
Weight- more batteries are heaver which then require stronger (larger) motors which require more batteries.... This becomes a trade-off no matter on what you decide.
If you keep weight and the motor power constant: At 12V the current draw will be double the current draw from 24V. This affects the wire sizes and the choice of motor driver circuits and the resistive losses. If you really need large motors than a higher voltage can be a good thing (the new electric autos use several hundred volts to keep the currents low).

Did you read through all of the tutorials and articles found under the "Robot Tutorials" above. These will answer many of your questions so that you will then have newer and better questions.

Good luck and have fun.

Offline Soeren

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Re: 12 or 24 VDC system
« Reply #3 on: January 12, 2011, 12:30:57 PM »

[...] I was looking at something a bit heavier to accommodate some power it doesn't have to be small or light.
First things first.
You need to decide on the (total loaded) weight and wheel size before you select motors.
Whether you go 12V or 24V, the same capacity should be the same weight.

And yes, you need a deep cycle battery - golf cart type, marine type or similar.

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline darknrgy

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Re: 12 or 24 VDC system
« Reply #4 on: January 13, 2011, 12:38:09 AM »
12V vs 24V came down to availability for me. In general I noticed that most motor controllers could handle up to 24V. In general it seemed that price was correlated with amp draw, so it made sense to try and use 24V motors because that would mean half the price for the same power (for the controller). However, once I figured out what I actually needed in terms of power and gearing, I started searching for motors and found that what was available was 12V motors. The 24V gear motors available were generally much more power than I needed.

So Soeren has it right. Either way I had to start with figuring out how much power I needed, which came down to brushing up on physics.

I chose a Li-Poly battery on ebay for about twice the price of a sealed lead acid equivalent and 1/5th the weight. That's right, 1/5th. That could dramatically change the weight of your robot.

Edit: And possibly explode!


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