hi dj

i always though it was a perfect to beginning a project .  thanks for the update .

Quote:

Batteries are rated in milliamp per hour. So they can provide X amount of milliamps in an hour. If your battery was 5,000 mAh and you were drawing 1,000mAh continuously, your battery would theoretically last 5 hours. Also, if your robot were drawing 5,000 mAh, then your battery would last 1 hour.

Quote:

BTW, that hexapod is going to be super cool. I made a large one that I named Super Six.

Quote:

Not sure if that Auto Position GAIT will be helpful to your robot configuration or not. You'd have to make sure the servos are connected in the same orientation, but other than that, maybe it'll be helpful.

I'll definitely have a look at it. THX

Yes that will be an awesome bot there!  Also great vid on DJ's super 6! These types of hex bot always scare the smiles out of visitors, I find!xD

The ezrobot ezb v4 will run on as low as 4v from my tests. I’ve actually seen it run off 3.5v about, but that’s just crazy

your 3d render is wild. The lipo battery link I gave you will work wonderful.

once you get the battery trouble out of the way, it’ll be smooth sailing and the robot will be running in no time.

Hello @Knusel,

Quote:

Ok I think I got that part. And I can operate the EZB with 7.4 volts? I always assumed 9V.

Quote:

Also, tweak the sleep() time to give each servo enough time to move into position. It may require one full second (1000 ms) per servo.

There are two things at play here. One is the nature of wall power supplies. Two is the nature of RC servo motors.

Wall Power supplies

Aka power bricks, wall adapters, or wall warts. These power supplies can deliver a constant current of what they are rated for (example 7.5V 3A). They cannot deliver more current than they are rated for. When more current is demanded by the load (for example motors on a robot) the voltage dips to compensate. If the voltage gets too low, the connected robot controller will reset, due to brownout protection.

This is the reason most Robots use batteries. Batteries can deliver the needed current demands from the load. For example, a 5000mAh 25C Lipo battery can supply 125A momentarily if needed (ignoring wire impedance and other physical limitations). The ability to deliver this kind of current burst allows the battery to keep the robot controller from resetting.

Servo Motors

Aka Hobby servos or RC Servos. These servos have 3 conditions that hugely affect the power supply. The conditions are:

Inrush current - Aka starting current. This is the current needed to move the servo from rest to moving. Operating current - Aka running or steady-state current. This is the current consumed by the servo when moving. Current Spikes - Aka current surge. This happens when you switch the directions of a servo without stopping.

Inrush current is stated to be 4 to 6 times the operating current. With EZ-Robot HDD servos I found it to be around 3 times the operating current. EZ-Robot HDD servos have an operating current of ~250mA (+/- 50mA). Let's do some example calculations:

So the inrush current of an EZ-Robot HDD servo is approximately 3 x 250mA = 750mA, 4 servos starting at the exact same time is an inrush of 3000mA (3A).

This demonstrates that if you start moving 4 x HDD servos at the same time a 3A wall power supply can handle it, but once you add a fifth, the power supply voltage will dip and you'll get an EZ-B reset.

If you stager the starting (inrush current) of the servos a 3A supply can operate up to 12 HDD servos simultaneously (250mA x 12 = 3A).

DJ mentioned using a delay of 500mS or 1S between moving servos, but I've found with my testing that you can even go as low as a 1mS delay between the servos as the inrush current doesn't last that long (under 1mS).

Ok, here's the last and likely most important part of this. If you don't allow a servo to reach its intended position before switching directions you will create a huge current spike. I found that I could get an EZ-B to reset with only 2 HDD servos (using a 3A supply) when moving them quickly back and forth.

This type of current spike is over 6 times the operating current and will quickly cause an EZ-B reset (when powered by a 3A supply), not to mention severely diminishing the life of the motor brushes inside your servo. Try not to move your servos in the opposite direction until they have come to rest, this will greatly promote the longevity of your servos, not to mention all brushed DC motors in general.

I hope this helps and increases everyone's knowledge here.

Maybe I should make my own tutorial about this I did all the tests yesterday to make sure everything I was saying was accurate.

Awesome facts there Jer, great job!:D

some good news and some bad news.

The lipos arrived yesterday, (long live amazon) I did the first tests, wrote an init script... it's not perfect yet, but it works now, the EZB doesn't restart and the motors have a lot of power! (see video) VIDEO

That was the good news. The bad ones are that the EZB looks like he is burned out. It just switched itself off, at first I thought the batteries were empty... but it doesn't work with the other power sources either. He also smells a bit burnt. Anyone an idea why this happened? I didn't do anything other than what is shown in the video...

I used this lipos:Link

(the lipos that dj recommended are not available on German Amazon)

and connected them in parallel with this cable, which shouldn't be the problem if I understood it correctly: Link

Quote:

I'm curious where you found the 9V information, 

I still have two EZB's here in my Johnny 5 robot, but of course I don't want to blow them all up now...

The EZ-Robot EZ-B v4 probably has a blown fuse. It is in the base.

You can see the EZ-Robot EZ-B v4 datasheet specifications here: https://www.ez-robot.com/learn-robotics-ezb-smart-robot-controller-and-iotiny-datasheet.html

Even if you connected the two batteries in series, accidentally, it should still be fine because they're only 7.4v each.

There's also an option that one of the traces burned on the EZ-Robot EZ-B v4 if the servo were drawing too much current. I'd check the fuse first, that's the easiest.

However, if you connected the power backward, that will be easily recognizable by examining the inside of the EZ-Robot EZ-B v4.