Let's look at it this way at whats been tried so far with actual servo movement...

We've gone from bench power, no movement at all. Then on to the D cell batteries, a bit of movement. So the next step in using a LiPo or nimh will yeald excellent results with a fully moving servo. like I said, I'd put money on it.

Bazinga. I think we resolved it (at least it worked )

I separated power supplies for the EZ and the servo with 6 volts going to the servo, 6 volts to the EZ and a common ground between the two I seem to have full control with no drop in connection, and no jerky motion.

Huzzah! Second martini for everyone cool

Daniel

@mulberry.

Nice job. At least you got it working now and you now know it was a power issue as I thought, and not the servo being faulty.

@Daniel, I'm glad you got this worked out. I knew it was a power issue. Hope out private discussions helped a little.

Dave

@Richard, There's nothing wrong with using a bench power supply if it can supply enough amps to provide the servo's power hunger. In fact it if it's large enough I would argue that it's a better and more stable source then any battery.

Also when supplying power to a large servo or motor I will always advise bypassing the EZB and run a separate power circuit to the motor. Why use the EZB as a power conduit and risk power starving it when the large motor starts sucking the juice? @Daniel, Remember that Amps and Volts are two different things.

The trick when either using a bench power supply or a battery is to make sure it will supply enough amps for your needs. Make sure you give your self enough overhead for any amperage inrush as the motor powers up.

@Dave ... I didn't say there was anything wrong with a bench power supply in general. All I was saying is the one that Mulberry was using didn't look like it was putting out enough juice... Minimum bench supply for revolution bots I would say is 20Amp... For my inMoov I would use a minimum of 50amp supply....

What I was trying to do was reduce or minimize all the variables that could have been causing his issues... In a sense get the everything down to the lowest common denominator (an ezb, the servo in question and a good battery).... Then work up from there.... If you have a million other things, wires, other servos, sensors and different power sources, etc hanging off the project it would be that much more difficult to trace the problem.....

Just to note, the only reason why I suggested "putting the bench supply aside for a moment" was to do some back to basics troubleshooting using a tried and tested method which a lot of us have used, of testing servos using a battery. Mulberry mentioned that he has an adjustable bench power supply which I why I suggested using a higher amperage, but it looks like this supply didn't have an option to change this. Even though I didn't know at first what batteries Mulberry had, D cell batteries were used which although not sufficient to power a servo, it did yeald some results which is what we were looking for.

Bench supply produced no servo movement... D cell batteries produced, although erratic, some servo movement = power supply issue which I suspected and mentioned early on.

As myself and Richard mentioned, LiPo or nimh batteries are excellent, especially when powering servos, and advised that these little bad boys should be used. In the confusion I said earlier that a common ground wouldn't be needed as this was on the assumption that the servo was connected directly to the EZ-B (signal, Vcc, Ground), but did mention, along with Rich that a common ground would be needed if powering the servo from a separate source which has now been done with good results.

As Dave had correctly said, using a bench power supply is really a great option for testing which was never in dispute, and it really needs to be supplying 20 amps at least, especially for testing/using a servo or multiple servos. Remember the old adage regarding touching the third rail on a train track. "It's not the volts that will kill you, it's the amps", which gives an idea how important amps are when powering power hungry devices. I don't have bench supply myself, just LiPo batteries, but I'm seriously considering getting myself one as they are a good investment and great addition to a workshop and robot building. I just need to save up some beer tokens to get me one. A multimeter is always handy to have around as well.

As well as helping Mulberry, again I'm glad you finally got some good results, hopefully this info will help someone else who comes across this thread facing similar issues.

Yes guys, great troubleshooting advice you gave. It's like an art form and is sometimes hard to understand and actually do successfully. You really have to have a good understanding of how what your working on really works at the basic level and what effects it. Just like Richard says, it's best to remove everything except what your having trouble with if possible. Take it down to the lowest level. Sectionalize.

When I started working with motors and servos I was very amazed at how many amps the bigger ones pulled and how big of a power supply was needed to run several of them (even running several smaller motors). Up to then I had extensive experience with power distribution but not a lot with application. I knew how to build the circuit and supply the power but less about matching it to the devices needing it. That's where Application and Electrical Engineers come in handy. Robotics and building a big robot like B9 has helped close this loop for me. Also help from good people like the ones on this forum has made all the difference in my education and success(es).

Electricity is very hard to understand and there's a lot of it that is still unknown about it. It's very unpredictable sometimes but can be tamed and channeled if handled properly. It has a lot of the same characteristics of water. It's very lazy and will follow the path of least resistance (sometimes that's through a human body). Like water you also have to give it a conduit big enough to flow through that is leak free. Then when you get to to what you want to turn, like water, you have to have enough of it to do the work.