Servo Interface & Power Boards + types of Arduino

[Jon McCoy]

Hi,

I've noticed a few posts and pictures on the InMoov site showing custom-build boards for interfacing with servos and distributing power.

Before I saw those, I planned on using these: http://www.makerbase.co.uk/products/io-expansion-shield-v5-for-arduino

Just wondering whether people are building boards for a specific reason or just in absence of having anything like that above? These boards have dedicated power for the servos, so provide the split power distribution, plus they already have the pins broken out on nice 3-pin headers for quick connection to servos.

The above is for the UNO/Leo, but there is a MEGA version available. That said, my plan was to use a UNO/Leo for each arm and a UNO/LEO or MEGA for the head/torso. With an IO expansion shield on each, I only need simple power terminals for the control supply and servo supplies. There are terminal shields available with screw/spring terminals, which will make hooking sensors up a bit easier (or you can crimp 0.1" connectors on the wires and use the expansion shields).

Regards

Jon

[Drew Rogge]

Looks interesting. One thing I'd look out for is that it says:

Servos can be powered using a dedicated 5V terminal, making it easier to work with multiple servos or actuators.

I'd be sure you could run your servos at 6V. The big arm servos need all the help they can get.

Drew

[gael langevin]

Like Drew says, you will need the 6V other wise InMoov will be too slow.

Ideally would be to power up the big HS805BB servos at 7.2V to get full speed available.

These big servos drain a lot of current, at peak it goes up to 3Amps per servos, so make sure that board can stand that

When I started the project I had never used a Arduino and I was not sure how servos would be connected to it, that is the reason I later created the power board, but if you have a better solution, go ahead.

Concerning your choice for boards, if I would start my robot today, I would go for 2 Mega instead of 1 Uno and 1 Mega, like I did.

I may change configuration at some point. That will depend on the requirement for the legs.

If you plan to use MRL, 2 Mega will be fine and you will be able to just run the same script as every body building InMoov. We are trying to get them standard, that way they can share all the same infos and programming.
Think of all the USB ports you already need, personnally I would try to save them up :)

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[Jon McCoy]

On Monday, February 10, 2014 3:56:43 PM UTC, Drew Rogge wrote:

Looks interesting. One thing I'd look out for is that it says: 

Servos can be powered using a dedicated 5V terminal, making it easier to work with multiple servos or actuators. 

I'd be sure you could run your servos at 6V. The big arm servos need all the help they can get. 

Drew 

I've got one already, I'll check the schematics and the board traces, but I think from memory that the DC rail for the servos is completely isolated (again, from memory I'm sure there's a jumper that hooks that power input to the Arduino, allowing you to separate the power). My plan is to drive the majority of servos at the 'ideal' rating, so somewhere between 6-7.2v.

On Monday, February 10, 2014 5:44:32 PM UTC, gael langevin wrote:

Like Drew says, you will need the 6V other wise InMoov will be too slow.

Ideally would be to power up the big HS805BB servos at 7.2V to get full speed available.

These big servos drain a lot of current, at peak it goes up to 3Amps per servos, so make sure that board can stand that

When I started the project I had never used a Arduino and I was not sure how servos would be connected to it, that is the reason I later created the power board, but if you have a better solution, go ahead.

Concerning your choice for boards, if I would start my robot today, I would go for 2 Mega instead of 1 Uno and 1 Mega, like I did.

I may change configuration at some point. That will depend on the requirement for the legs.

If you plan to use MRL, 2 Mega will be fine and you will be able to just run the same script as every body building InMoov. We are trying to get them standard, that way they can share all the same infos and programming.
Think of all the USB ports you already need, personnally I would try to save them up :)

With 2x Mega, how would you allocate the IO (I'm guessing that the additional servo outputs would be for the torso)? My concern was the process speed when dealing with multiple inputs (ie finger sensors) and with PWM outputs. I know the Uno can get a little stuttery with too many servos, I'm guessing the Mega is similar, but able to handle a few more.

But you're right regarding the USB. I had actually considered using RS485 serial between all of the boards, but will be simpler to use just USB - and fewer of them! I've not bought my Arudino for this project yet, so I'll go for the Mega :) With the new higher speed version now, I'll aim for that too.

On a slight side note, how powerful of a computer is needed for MRL to power InMoov? I'm looking for an embedded or µATX board I can fit inside the torso!

Thanks all 

[gael langevin]

Most of my test and videos are done on Windows XP with a Pentium4, Memory 2gb.

Nice isn't it?

InMoov2.0 requires a bit more processing apparently but it still works with the old PC.

I'm thinking of the Odroid board to get everything running without a PC.

You are correct if you plan to set sensors in both hands you will need more A0 pins.

here is the default pin connection hardware:
http://www.inmoov.fr/default-hardware-map/

[Jon McCoy]

Gael, how have you connected the finger sensors to the Mega?

For the servos and Mega's, what power supply would you recommend? I'm counting 30A for the larger servos alone...

J

[Vasily Denegin]

Hello Everybody.

I am completing my first arm+bicep. I found that instead of using a plain Arduino there is a new absolutely great board for 12 euro “SunFounder PCA9685 16 Channel 12 Bit PWM Servo Driver for Arduino”.

It is a clone of Adafruit’s same board (25 euro).
It can control up to 16 servos, enough for all Arm servos.

It has a form-factor of Arduino Nano and can fit into the forearm directly. So the entire wiring from the Arm would be 5 wires only (VCC, V+, GND, SCL, SDA).

I have tested it and it works with big motors MG995 Tower Pro (13 kg/sm).

You can find it on Amazon, with the Prime delivery I got it in 2 days.

http://www.amazon.de/SunFounder-PCA9685-Channel-Arduino-Raspberry/dp/B014KTSMLA?ie=UTF8&ref_=pe_386171_134044401_TE_dp_1

Regards, Vasily.
Vienna, Austria

[gael langevin]

Jon,

The Nervo Board has all the connections ready for the finger sensors and you have still another header connector free to add what ever sensor you want to in ject into your InMoov. Since we are using two Arduino Mega with two Nervo boards, that gives a lot of connectors to add sensors as long as your sensors can be connected through A0 pins.

Vasily,

I had bought three years ago some 16 channel PWM boards from Adafruit to drive all the fingers and the arms but according to Greg (MyRobotLab Creator) we wouldn't be able to handle the speed and ramping of each servos using those boards. I think there has been some progress recently done about that and some of the MRL developpers might give you better information about this.

Gael Langevin

Creator of InMoov

InMoov Robot

@inmoov

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