Robot BN42 Version 4 - Schematic Diagram Help

"De gustibus non est disputandum"

I think the circuit is OK.

I would try to put the circuit on a single page. I think it would be easier to understand.

Also, the circuit naturally divides into subsections, i.e., the motor subcircuit repeats. So, I'd build each motor and test it separately, adding new motors as you go. You'd keep your focus on fewer connections.

I don't know the motors, so I didn't realize the encoders were powered separately. That bothers me. There are 3 power supplies here, the motors, the encoders, and something for the UNO.

Good luck!

@greendragon

At a glance it appears ok and you have used the interrupt pins as required for reading the encoders. I assume you have a source for this project? My robots only use two motors with hall encoders salvaged from vacuum cleaner robots. My source when I first joined this forum was from Bill's tutorial except the motors  used hall encoders.

Part of the wiring is in the code itself to set up the pins as required.

Hi @greendragon,

 I assume by "Manual Rest Breaker" you meant to type Reset, not Rest, and you are actually referring to a circuit breaker which maybe reset manually after it has tripped.

Whilst such devices can often be manually 'tripped', it is normally considered bad practice to use circuit breakers as 'regular' On/Off switches, because their contact structures etc. are not usually designed for the repetitive arcing that will occur if an appreciable current is flowing or will start flowing, when it is used regularly as On/Off switch.

In addition, ensure that the breaker device you select can actually break the short circuit current that may result if a short circuit occurs close the battery. Li-ion batteries tend to be able to deliver a very high current, which could 'instantly' weld the contacts of an inadequate breaker together, preventing it from performing its essential safety function when you most need it.  

I am sorry if this sounds a bit 'nit-picking', but I am concerned for your safety.

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I am not clear how the Arduino is powered ... When there are sensors, microcontrollers, motor controllers, etc, which are connected together, care is needed to ensure that they are all powered up at the same time, which is tricky if they have different power sources. The concern is when one part is powered up, say a sensor that is feeding its output to a controller, but the controller is not powered up. Under these conditions, for many common circuit designs, it is possible to inject a current into the controller, possibly causing latch up, which will prevent it functionally until the whole system is power cycled, and sometimes damaging it. 

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I would also suggest you carefully draw out your earth connection topology.  I am not suggesting there are obvious mistakes in your diagram, but ensuring the high current loops do not inject noise into the more sensitive parts of the circuit will help to prevent problems.

Good luck with your project. Best wishes, Dave

@davee 

"I assume by "Manual Rest Breaker" you meant to type Reset, not Rest, and you are actually referring to a circuit breaker which maybe reset manually after it has tripped."

This is correct Just a simple typo sorry about that. I was hoping someone would comment about the breaker as I was unsure if I should use it as a switch or not, and so I am just going to add a on/off switch as well. 

Thanks for that suggestion.

In answer to your question about power to the arduino mega I am unsure about what to do here. I hate the idea of having three or more separate power systems, but I also don't like the idea of building some kind of power distribution system, and using the 12 volt 20 Amp battery as the only power source. Note: I plan on using a Lithium iron phosphate battery, and so I do not have to worry about the thing overheating, and burning the entire neighborhood down.

what would you suggest? Anyone is welcome to answer this as well.

Posted by: @greendragon

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In answer to your question about power to the arduino mega I am unsure about what to do

Why not power the encoders from the UNO via the 5V pin? Then you would just need a separate power supply for the UNO. That makes more sense to me.

@robotbuilder 

"I assume you have a source for this project? My robots only use two motors with hall encoders salvaged from vacuum cleaner robots. My source when I first joined this forum was from Bill's tutorial except the motors  used hall encoders."

I am unsure what you mean by source?

If you are referring to where to get the motors that's not a problem as I already have them. 

If you are referring to where are you getting your ideas and information from? I have been researching the subject at length from Bill's videos to other youtube video to articles online. 

The reason I am wanting 4 motors is simple - one for each of the four wheel's. Oh and the reason I don't scale back to 2 motors is that my robot when finished will weigh about 25 lbs. I have been in contact with the manufacturer of the motors and have been assured that 4 motors will move 25 lbs no problem. 

Now here is my question - should I connect 2 motors together, and then hook them to the motor driver as one side like left or right, or should I keep all 4 seprate? 

Posted by: @greendragon

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I am unsure what you mean by source?

I think he means project source code, i.e. the Arduino sketch.

@tfmccarthy 

"I think he means project source code, i.e. the Arduino sketch."

Yea I'm not getting into the actual programing code till later as I want to get the design finished first.

Hi @greendragon,

  I think I would use the main battery, with  one or more voltage regulators, and include some low current fuses, say around 1A or less, to feed the regulators, as appropriate, for the low power demands, But it is your choice. 

Remember that for almost all 'everyday' power distribution applications, including houses, etc., the fuses/circuit breakers are primarily intended to stop the wiring causing a fire. So design your wiring imagining that a short circuit could occur at any point ... and that all of the wiring from the source to each possible point should be able to cope with the maximum current that the breaker or fuse will pass for an appreciable time.

LFP batteries are safer than some of the other Li-ion types, but they are not immune from catastrophic failure. They store a lot of energy, and under duress, like a short circuit, are likely to be very hazardous.

We don't generally consider (car) lead-acid batteries to be a major hazard, but even they have caused serious injury and even death as they exploded, when shorted out with a stray spanner, or similar. So please take care. 

Best wishes, and good luck, Dave

Posted by: @davee

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I think I would use the main battery, with  one or more voltage regulators

Yes, I like this idea. Single power source; hefty battery.

Unless I'm mistaken, if you power the encoders from the UNO you only need a single voltage regulator.

@greendragon 

robotbuilder wrote:
"I assume you have a source for this project?

greendragon wrote:
I am unsure what you mean by source?

Much easier if you are duplicating or modifying an actual source project like those Bill has provided as a starting point which includes hardware and associated code. I see you have done that so I wondered are you using any particular project as a starting point?

Now here is my question - should I connect 2 motors together, and then hook them to the motor driver as one side like left or right, or should I keep all 4 separate?

Depends on the type of wheels (omni wheels need independent control) and the amount of control you want. For your basic four motorized wheels I would combine the left wheels together and the right wheels together and drive it like tank wheels for simplicity. I have no experience using four motors.

I am personally much more interested in the software side of a robot.