Absolute Beginner Project.

Using Arduino Project Guidance
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Hi All,

I'm brand new to robotics, never touched it before but my son is doing it at school and I'd like to build one with him.

I actually make a small income from 3D printing and am an instrument tech by trade, so I can fabricate and solder very neatly.

We have made a start on this project:

http://www.thingiverse.com/thing:19170/#remixes

Straight away I didn't like the 3 piece chassis and there was no proper mounting points for the Arduino, so I designed and printed a new chassis (in orange).

All the help I'm after at this stage is how to wire it and some advice on which components to buy.

I have:

An Arduino UNO

A shield of some sort.

2x continuous rotation servo. Springrc Sms Australia | Little Bird Australia

A bunch of 2S lipos I already use on quads, and a balance charger to suit.

Some questions are:

Can I run these 2 servos straight of the UNO? It would be good for my first project, I won't want to add any other servos to this one.

If I need to use a shield, is this one too advanced for this project? I'm happy to buy a simpler one.

Is there a cheaper option for sensors than 2 of these? Parallax Pings Australia | Little Bird Australia
If it has to be these, so be it.

On the front bumper are apparently 3 IR proximity sensors, and he says this:

"The sensors on the bottom are the Adafruit VCNL4000 Proximity IR sensors. Unfortunately, I would avoid using these at all cost. What they didn't make clear is that you can't change the I2C address of these, which means you can only normally run one sensor. Since I have more than one sensor, I had to try and hack it together using an I2C bus switch which lets you run multiple I2C buses. I then got busy, and haven't had a chance to write the code for them, so at the moment my rover is just using the PING ultrasonic sensors."

What would be good IR sensors to get?

Once I've got everything I need ordered, I'm hoping some of you may be able to show me what to connect to where.

I won't even start to get into programming it yet.

Thank you very much in advance to those kind enough to help me out.

This is one of those father/son things, and I'd like to see it finished successfully.

Cheers

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You should be able to run up to a dozen servos from a Uno, but make sure you give them their own power supply.
Allow 1 amp at 5V per servo for ordinary servos, but check the specs for anything out of the ordinary.

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AWOL:
You should be able to run up to a dozen servos from a Uno, but make sure you give them their own power supply.
Allow 1 amp at 5V per servo for ordinary servos, but check the specs for anything out of the ordinary.

Thank you for your reply.

I do have a Turnigy 5V/3A ubec here, but it would be ugly/bulky to fit onto this little machine.

Is there anything that would piggyback straight onto the UNO board?

For the sake of 15-20 bucks, I don't mind a bit of overkill.

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The Arduino 5v pin cannot provide enough current for a servo. It is nothing to do with "piggybacks".

If you have a regulated 5v power supply for the servos you could also power the Arduino from it - assuming it can comfortably meet the needs of the servos with current to spare.

The important thing is not to pass the servo power THROUGH the Arduino board.

...R

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Robin2:
The Arduino 5v pin cannot provide enough current for a servo. It is nothing to do with "piggybacks".

If you have a regulated 5v power supply for the servos you could also power the Arduino from it - assuming it can comfortably meet the needs of the servos with current to spare.

The important thing is not to pass the servo power THROUGH the Arduino board.

...R

Thank you.

What I've been looking at is a motor driver shield by another brand (best not mentioned here?) that has outlets specifically for 2 servos, 2 steppers and 4 dc motors.

It has it's own power connection terminals that I'm guessing removes the problem of running power through the Arduino board.

I do realize this is probably overkill, and that a simple regulated 5v connection to the servo would do the same, it just looks really neat on top of the Arduino where there is actually room for it.

My understanding was that the Arduino could be supplied by anything from around 6-12v via the black plug beside the USB connection, so I was thinking I could connect my Arduino and shield in parallel and supply them both from my 2S lipo.

I am sorry if my questions seem inane, I did mention I knew very little about this. Obviously a lot to get my head around.

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Is there a cheaper option for sensors than 2 of these? Parallax Pings Australia | Little Bird Australia

I do not believed I have ever seen anyone charge more for those. is that for a quantity of 20 units?

http://www.ebay.com.au/itm/371459859858

I used ebay au because that is where you link showed.

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dave-in-nj:
I do not believed I have ever seen anyone charge more for those. is that for a quantity of 20 units?

http://www.ebay.com.au/itm/371459859858

I used ebay au because that is where you link showed.

Thanks for that.

Funny...the same company had a cheap one too, but in Australia (where I am) available for quicker delivery.

I'm wondering what the difference is between this one:

and this one:

But as I need 2 I'm quite sure I'm going to try the cheaper ones.

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robonoob:
Thank you.

What I've been looking at is a motor driver shield by another brand (best not mentioned here?) that has outlets specifically for 2 servos, 2 steppers and 4 dc motors.

do not hesitate to mention any manufacturer or any brand or even generic.
we do ask that you post a link
and if it is a chip, then a data sheet link as well.
your 2S offers 7.2v
a 3S will offer 11 volts.
the basic 5 volt arduino has a klunky voltage regulator that needs power the spec sheet,

between 6 and 20vdc power. clones may not have such a wide range.
your 2S might work fine.
I don't think anyone recommends you get anywhere near 6 v supplies, looking for problems.
and since there is a huge clone market, you cannot expect quality components on clones.
your meaning of piggyback may mean something different.
you can power your project from a 2S, and life is dependent on motor size, current drain from sensors and the arduino and quality and number of power supplies.
to run power to anything that consumes more than about 10mA, you should not feed it power from a pin of any arduino. although one pin can deliver about 20mA, you cannot run all pins at that, the overall load would exceed ratings.
rather use an FET, a 2n7000 is a simple FET that would allow you to turn loads on an off with a very small voltage from a pin, and also allow you to use it to control fading of an LED or motor speed of a DC motor.
a 2n7000 will handle up to about 200mA, an IRL510, one amp, an IRL 520, 3 amps.
the 'L' in IRL means logic, or will work on 5 volts. an IRS520 might need a voltage up to the power supply voltage. not good if you are using 24volts !

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littlebird pricing is funny. I've bought a few things from them. Often they list the same item under a slightly different description with a different price. I think its just an issue with having to handle so many SKUs.

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robonoob:
Thanks for that.

Funny...the same company had a cheap one too, but in Australia (where I am) available for quicker delivery.

I'm wondering what the difference is between this one:

Ultrasonic Ranging Module HC-SR04 (Itead IM120628012) | Little Bird

and this one:

Parallax Pings Australia | Little Bird Australia

But as I need 2 I'm quite sure I'm going to try the cheaper ones.

the difference is some printing and about $50
the cheap ones use a crystal.
the parallax not not have one on the front.
I did not see any notes on why they do not, maybe they use an internal one ?

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bigfatsirion:
littlebird pricing is funny. I've bought a few things from them. Often they list the same item under a slightly different description with a different price. I think its just an issue with having to handle so many SKUs.

I find that others do the same. I think it is due to cost of acquisition. if they get one lot at one price, they list it, if they get a second lot at a different price or different supplier, they use a different SKU to keep track of suppliers and profit.
I don't mind paying more for faster or local, but that price difference is huge. check amazon for the parallax part.

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nice start on your project, I noticed something that is a pet peeve of mine. using threaded rod without any bushing.
I have repaired countless failures with a simple bushing or replacing a full thread rod with a partial threaded one.

BTW, if you drill and tap the nuts for small set screws, you can lock them in place.
others use 2 nuts, or thread sealant. nail polish works for thread sealant.

also, the plastic may wear as it touches the threads. you might consider that if it does, to use a bushing. something as simple as a section of copper pipe if you can get a close size. or a bushing.

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Cheers Dave,

Appreciate your help.

Don't worry about the threaded rod, I've just thrown this together for a look today and there's plenty I don't like about the design. Fabrication is my thing and I can make almost anything on my printers, I'll be looking for improvements along the way.

Here's what I'm thinking of using:

My arduino UNO (V2 I think, I've had it for over a year and never used it) with this motor shield:

As I said I know it's overkill, but it's nice and neat and even has a little prototyping area. It also has 2 servo connections that should (?) power the servos I have purchased:

I'm actually starting to consider 2 of these:

Instead of sonar sensors. I could make a new front bumper with 2 of these angled slightly outwards, as it's really just to stop it bumping into walls.

I could even go with a third pointing downward to warn of drop offs like stairs perhaps?

Will my arduino communicate with several of these?

By "piggyback" I just mean that the shield above stacks straight onto the Arduino. I may have inadvertently used a term that is used differently in robotics.

I like really neat wiring which is soldered with as little connectors as possible. I was considering removing the black power plug from the UNO and soldering in 18AWG silicone wire that I could run to the terminals on the motor shield (both boards in parallel) and on to an XT60 plug for my lipo.

I can do this neatly, and the shield could still be removed from the UNO by undoing the terminal screws on the shield connector.

As it is my first robot and I know nothing about programming, I'd just like to be able to drive around and not bump into walls or drive straight off drops.

I'm sure I'll get into fancier things after that lol.

Cheers again for the patience and advice.

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Getting closer to completion now, and am hoping for some advice on a couple of points.

I'm just designing a hood/bonnet to go over the UNO board, on which I can mount an HC-SR04 sensor and possibly a fan and power switch.

I'm powering this with a 3S lipo. Is a 40mm computer fan over the board advisable? I can fit one easily enough and design all the mounts etc into the bonnet before I print it.

I'm planning to use one or two HC-SR04 sensors for a simple obstacle/wall avoidance (I've never programmed anything like this and want to start simple), and will mount it up on the bonnet at the front.

Is one sensor pointed forward going to be enough, and is it simpler to program than 2? Ie, is it better to have one sensor focusing left and one right, or will the one sensor pointing straight forward be enough for rudimentary automation?

I understand the sensor has a 15 degree spread, and am happy enough with that if it's going to be simpler for a beginner.

If that's just not going to work I'll use 2, but I'm just looking for a very simple model to start with.

I've also gone away from the Adafruit driver board for this one, and will power the 2 servo's with a 3A UBEC. Again, simpler.

Chassis has turned out well. I redesigned the lot, as none of the Thingiverse version fitted or worked well.

Thanks in advance for any help and advice.

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