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### Author Topic: Help Needed with Power Management of Maze Solver  (Read 1384 times)

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#### h3lios

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##### Help Needed with Power Management of Maze Solver
« on: October 12, 2010, 10:36:09 PM »
Hi everyone,

I am a student assigned to create a line maze solving robot and since i am new at this, i am in dire need for some guidance. i have already gone through most tutorials available on the website, however, i am left with some questions.

i am using 2 - 7.2VDC motors for running my robot. going through the tutorial i read that before connecting any battery to motors or to the microprocessor, a power regulating circuit is required. so...

1. first of all, do i need a seperate 7VDV battery pack for each motor? i think if i try to split the current from 1 pack to 2 motors, the current draw to each motor will be halved which would decrease my torque output, which is not good. am i right?

2. if i use a seperate 7v battery for each motor, how do i make a power regulator circuit for each one? i have no idea how to come up with the circuitry for it so help would be appreciated?

3. i also need to power up my microelectronics, which means that i need a seperate battery pack for them?? can i just use the battery output from one of the motors for powering the microelectronics?...i dont think my microcontroller draws more than 450 mA so the torque output of that one motor should not be affected too much......

again, i am new to this and i might be totally on the wrong track/.....can someone tell me whats the most optimal way of going about powering 2 motors and a mictrocontroller....also, can someone give me a list of all kinds of circuits i need for my robot (e.g. h-bridges, power regulator etc.).....thnx!!!!!

#### Soeren

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #1 on: October 13, 2010, 02:06:28 PM »
Hi,

1. first of all, do i need a seperate 7VDV battery pack for each motor? i think if i try to split the current from 1 pack to 2 motors, the current draw to each motor will be halved which would decrease my torque output, which is not good. am i right?
No, the current draw will be the same, but the runtime will be about half of course.

2. if i use a seperate 7v battery for each motor, how do i make a power regulator circuit for each one? i have no idea how to come up with the circuitry for it so help would be appreciated?
Same way as with one battery.

3. i also need to power up my microelectronics, which means that i need a seperate battery pack for them?? can i just use the battery output from one of the motors for powering the microelectronics?...i dont think my microcontroller draws more than 450 mA so the torque output of that one motor should not be affected too much......
Just use a single motor battery (or both in parallel if needs be) and then run that through an LDO regulator for getting the 5V to your electronics.

[...] can someone give me a list of all kinds of circuits i need for my robot (e.g. h-bridges, power regulator etc.).....thnx!!!!!
Just look in any decent tutorial.
Regards,
Søren

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

#### h3lios

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #2 on: October 13, 2010, 07:05:11 PM »
Thanks for your response...yes immediately after i posted that thread i realized my mistake in the first question....

anyways, i have decided that i am using 2 -7.2VDV motors and a microprocessor that uses 5V. I am going to use a single 9V battery for each motor and and and a 9V battery for the microprocessor. So I am going to place 3 - 9V batteries in parallel and connect them to a power regulating circuit and connect the circuit to my 2 H-bridges (each of which connects to a motor), AND the microprocessor. How would I go about creating such a circuit (i.e. what is the schematic of the circuit and what components does it have)?

Again, i appreciate your help.

#### Soeren

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #3 on: October 13, 2010, 07:31:29 PM »
Hi,

anyways, i have decided that i am using 2 -7.2VDV motors and a microprocessor that uses 5V. I am going to use a single 9V battery for each motor and and and a 9V battery for the microprocessor. So I am going to place 3 - 9V batteries in parallel and connect them to a power regulating circuit and connect the circuit to my 2 H-bridges (each of which connects to a motor), AND the microprocessor. How would I go about creating such a circuit (i.e. what is the schematic of the circuit and what components does it have)?
If you by "9V batteries" are referring to PP3's (the box shaped so called "transistor batteries", you won't get anywhere, as the motors would drain them in no time, perhaps not even being able to move at all (depends on the particular motors of course, but words like "torque" and "9V PP3" doesn't mix well).

Upgrade your power source first and then follow one of the tutorials on the net about the connections - no point in others spending time repeating such stuff.
When you stumble over a problem, go ahead and ask, but don't expect to be spoon fed every step of the way.
Regards,
Søren

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

#### h3lios

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #4 on: October 13, 2010, 08:46:42 PM »
again...thnx again for ur guidance. dispite what you may think, i have gone over plenty tutorials and articles on this matter. every page i go on, some dude uses random capatitance values and etc for his regulator circuit and they dont say anything about why or how they arrive at the circuit. and since i am a little tight on project time, i thought it might be helpful hitting the forums and having someone who has years of experience, to explain to me some basics in layman's terms. i beleive this circuit here: http://That.Homepage.dk/PDF/24V+5V_PSU.pdf was refered by you regarding a similar topic. however, AGAIN i do understand where all the numbers and capacitance/resistance values and stuff like that come from.

#### cyberfish

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #5 on: October 13, 2010, 09:03:59 PM »
If you look into the regulator IC's datasheet, it will tell you what capacitance they recommend/require, as well as the capacitor type for more picky (LDO) regulators. Just follow the manufacturers' advice.

#### Soeren

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #6 on: October 13, 2010, 10:25:54 PM »
Hi,

[...] every page i go on, some dude uses random capatitance values
I don't think randomness is a parameter of the designs, rather it's in the eye of the beholder.

[...] and etc for his regulator circuit and they dont say anything about why or how they arrive at the circuit.
Do you need the circuit or someone teaching you engineering?

[...] and since i am a little tight on project time, i thought it might be helpful hitting the forums and having someone who has years of experience, to explain to me some basics in layman's terms.
You obviously don't realize what you're asking for.
Electronics engineering cannot be explained in a few sentences in laymans terms on an internet forum. Either you take the time to learn it the right way, or you accept the functionality of circuits found by, or given to, you and view them as modules/black boxes that does this or that.

i beleive this circuit here: http://That.Homepage.dk/PDF/24V+5V_PSU.pdf was refered by you regarding a similar topic. however, AGAIN i do understand where all the numbers and capacitance/resistance values and stuff like that come from.
I think you meant "AGAIN i do not understand [...]", or it doesn't make sense.
Actually, that is a rather small circuit, but I don't see why you feel a need to understand it in detail (unless you're going to pretend it's your own work in a school report or similar), as that will only steal away time that you claim to be lacking of. Just use the circuits you need, as long as they do what they're supposed to, who cares?

You know, my girlfriend get's at least as much joy as me from watching a flick on the boob tube, even if she hasn't got the first clue as to how the pictures reach the screen.
Regards,
Søren

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

#### h3lios

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #7 on: October 14, 2010, 04:21:51 PM »
1. i dont copy info from the net without giving credit to the person/website who's information im using.

2. i need to understand the circuit: i) for my own curosity, but if your dont have the time to explain it, you dont have to. ii) because im not using the exact same voltage source (im using 7.2 V instead of 24V) and i want to find out if i have to change the resistance/capacitance values in the circuit.

#### Soeren

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##### Re: Help Needed with Power Management of Maze Solver
« Reply #8 on: October 15, 2010, 09:37:16 PM »
2. i need to understand the circuit: i) for my own curosity, but if your dont have the time to explain it, you dont have to.
I know.

ii) because im not using the exact same voltage source (im using 7.2 V instead of 24V) and i want to find out if i have to change the resistance/capacitance values in the circuit.
For 7.2V...
R3 should be 1k
C1 could be lowered to a 16V or 25V type (but there's no need to do that).
The reason that C1 is a higher in value than in most other circuits is that it does double duty, acting as part of the LC filter made by L1 and C1.

IC1 could be any LDO with 5V out that can handle the current needed.

R1, R2 and K1 is only used for measuring the battery voltage by an A/D-C input on the controller. R1 and R2 is a voltage divider to get the voltage into the 0..5V range.
Since I don't know what chemistry your battery is, I cannot tell you what division rate you need to use a 5V (or 3.3V) A/D-C fully, but I gather you have no use for this part of the circuit, so you could just leave out the connector K1 and these two resistors.
Regards,
Søren

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

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