Asked
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Hey All,
I wanted to demonstrate the current handle capabilities of the EZ-B and at the same time doing a small test. Here's a quick video I made of Six with 18 servos, I know a few of you asked a long time ago if Six could run with 18 servos, the answer is Yes!
Six with 18 Servos Video
I also wanted to demonstrate the large in rush current demand that Heavy Duty servos can have and how it might effect your power supply or battery pack so I made another quick video :
In-rush current example Video
I have another answer to an ultimate question of life, the universe, and everything else;....................... 42.
@Ant. Amps are what your going to need to know because that's current. Current is made up of electrons and they are what do the work. Current is kinda like water in a pipe. The force pushing the water in the pipe would be the voltage and the current (amps) would be the water in the pipe. The third part of this is resistance and that would come into play with the type and size of wire your using. Simply put; the smaller and less conductive the wire the more resistance you have or the harder it is for the electrons to rush through the wire. Think about what happens when you try to force way to much water though to small of a pipe. In wire that's too small the electrons will keep squeezing through the wire, starving the load and causing heat and maybe melting the wire. This is also the principle of how a burner on an electric stove works.
Anyway, you need to really need to first know how many amps your load (servos in this case) will pull so you can match your power supply and wire size to it. Not every multimeter can measure amps. I had to buy one that does at Menards. You simply place the meter on the proper Amp reading setting and put the two leads in line somewhere between the positive battery post and the positive load (servo) connection. There are lots of Youtube vids out there showing how to do this.
The meter itself must have a selection for measuring Amps not milliamps
j
I just bought a Uni-T UT61E and it's awesome....
It really does concern me that very few will do things the right way. What use is a robot that's had thousands of man hours spent on building it if it doesn't work or if the wiring melts inside?
I have expressed concerns about the power (is the battery capable? is the wiring big enough? etc.) in the past on some projects but it's generally been brushed aside. I don't like to say I told you so or be Mr. Know-It-All but, well I did tell a few of you.
@Ant, you need to set the meter to DC amps (DCA) and connect it inline between the battery and the connector that currently attaches to the positive on the battery.
I've said it before, I'll say it again, design and calculations for everything is more important than anything else. If you want your robot to work you need to carefully think about what will power it, what will be powered but most important (and something that's not been touched on) what size the wiring needs to be.
No offence is meant to anyone by this and I'd much rather be saying "Wow, that turned out awesome and works well" than saying "you need to change your power supply and replace the cable that was smoking".
1) Dave Schulpius. Wow, awesome analogy using the water pipe to describe volts, amps, and resistance. I am going to use that in the future...
2) A clamp on ammeter can measure the amperage without the power going through the multi-meter so it is possible to get a less expensive one that wouldn't be able to handle the current itself to measure very high amp circuits. See http://en.wikipedia.org/wiki/Current_clamp
I have a pretty cheap radio-shack meter, but it has a clamp on attachment and can measure hundreds of amps (not that we should need to measure that high on a robot, but still....).
Alan
Alan
For the 18 servo test I was using our 7.4VDC 1300mAh LiPo battery and was powering all the servos through the v4. Something to note: the servos cannot effect the regulated supply of the EZ-Bv4 and cause the EZ-B to reset unless the entire power supply browns out.
Something that I forgot to mention was that inside the robot we have a wiring harness that has low gauge wire and a deans connector that are designed for high current delivery from the battery to the EZ-Bv4 and then to the Servos. It looks like this:
The micro deans adapter board is the same one as in the Power base (minus the 2.1mm barrel jack) and can be modified to use for your robot's wiring harness if needed.
From what I can find on those servos, they can pull 2500mA on startup and on stall. 13 x 2.5A = 32.5A (probably more if running above 6v)
Max continuous discharge may be more than 20x1.3A (26A) if all servos are under a full load. Inrush/Burst should be OK at 30x1.3A (39A) though.
Chris