Author Topic: Beta-DMX Servo Controller Project (See first post for specs and features)  (Read 37029 times)

Offline dlhoppe

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Ok, I've been doing some testing to find out just how much load a 3A power supply can handle before creating brown-outs on the logic pwr bus. What I'm finding is that certain types of servos really pull some current when they move quickly regardless of their torque ratings. For instance, I'm testing with some Hitec HS605MG's that are just absolute power hogs even though they're not outrageously powerful torque-wise. The digitals I'm testing with have twice the torque or more, but have way lower power consumption spikes when moving quickly. So the moral of the story here is that we just can't equate power requirements to torque.

So to get to the point, it's going to be trial and error in terms of figuring out whether you'll need to go with dual power supplies or can live with a single one. If you want a recommendation, I'd say 4 servos is the limit for using the single power supply configuration. Although I can get a brown-out to occur with just 3 HS605MG's by putting the DMX tester in "pulse" mode (toggles all channels full on/full off). 

I'm currently lobbying for a minor change to the PCB design for the single/dual power input option. I'm hoping we can allow for switching between the two with maybe a jumper rather than soldering a diode in one of two places. That will make it much more flexible and allows you to change back and forth between single and dual in an instant. Will keep you posted on that. The other minor change is to feed the Ex/Rx with 6v from the upstream side of the logic pwr bus regulator. That will help raise the tolerance a bit for power dips.

So in summary, using dual power supplies is working flawlessly. The questions only arise when using a single power source for both logic and servos.


Dave
« Last Edit: October 18, 2011, by dlhoppe »

Offline n1ist

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Jumper is now in the artwork...
/mike

Offline dlhoppe

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Jumper is now in the artwork...
/mike

Excellent! Thanks Mike.

So the release revision will include the ability to combine/split the power inputs with a simple jumper. Folks will just have to see what their power requirements are based on the combinations of servos they use. If the load is high enough where power dips cause issues on the logic side of the board, then switch to dual power supplies.

Offline dlhoppe

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BETA TESTERS...PLEASE READ!

Ugh,   Apparently some Rev 1 boards were let out for beta testing. Please do not build the Rev 1 boards. They can be identified as having only "D1" instead of "D1 and D4". It looks like 2 of them are out there.

Please let me know if you have a Rev 1 board and we'll see if we can get you the correct one.

My apologies.....again.
« Last Edit: October 19, 2011, by dlhoppe »

Offline Steve Gase

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Where do I find the version?

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Offline blaha

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Where do I find the version?

Steve is looks like you are good. You can see the D1 and D4 right above the DMX Out.

Offline Steve Gase

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Offline dlhoppe

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Steve,

Thanks for posting your photo. That's an example of the Rev2 board and is the one we're beta-testing.
« Last Edit: October 19, 2011, by dlhoppe »

Offline n1ist

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Another quick way to tell is to look at the power connector.  Rev 1 has a 2-pin connector.  Rev 2 has a 4-pin one.
/mike

Offline jess_her

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OK I'm running, For now I'm using battery's to power my board until I get a better power supply.  The board is running solid with cheep china servos  ;D. The only problem  is when ran by Vixen, at the start  the servos will try to center (4) and cause a brown out and jitter on all four servos. The servo board will shut down and red led will flash. disconnect power and reapply the fault will clear, very cool.
Thanks you Dave and Mike

Jess
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Offline dlhoppe

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OK I'm running, For now I'm using battery's to power my board until I get a better power supply.  The board is running solid with cheep china servos  ;D. The only problem  is when ran by Vixen, at the start  the servos will try to center (4) and cause a brown out and jitter on all four servos. The servo board will shut down and red led will flash. disconnect power and reapply the fault will clear, very cool.
Thanks you Dave and Mike

Jess

I'd say your batteries aren't able to deliver the current you need. Although I think you mentioned you had a hefty power supply that might work. Let us know how that goes.

Offline dlhoppe

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FYI,

This power supply showed up at my door today:

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I was just playing around with it and I must say it's got some real balls. Handles my HS605MG power hogs very nicely. I'm running 8 servos all in constant motion on single power supply input and it doesn't even appear to be breaking a sweat.

I'll report on the other one when it arrives.

Offline jess_her

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Well yep I used some batteries, had to see it work! But what I found out was when the power drooped causing servo jitter, compounding the problem and the servo controller went into fault mode.
So I had an old 5V 15A adjustable power supply turned it all the way up (5.8V) never had another problem. Power power power don't skimp <fp.
« Last Edit: October 21, 2011, by jess_her »
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Offline holland lights

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Way it sounds, you need atleast a 3 amp supply to work right.

Offline dlhoppe

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Way it sounds, you need atleast a 3 amp supply to work right.

Depends on the number of servos and load. However, I wouldn't invest in a weak one up front because you'd possibly outgrow it down the road.

Hopefully everyone will keep their eyes open for a good deal on a 6VDC power supply with ample power. I have a regulated 2.5A switching supply coming that is reasonable in cost ($11.99). I'll see how it compares to the 3A ($18.92) I just got. I'll let you know.

Remember also that wiring has something to do with it. The smaller the gauge, the less current it can deliver. You can have a good power supply and cripple it with tiny gauge wire leads. Then there's battery performance. Some batteries are suited for higher current applications and some aren't. Just make sure you do some research (google is your friend) before investing.
« Last Edit: October 21, 2011, by dlhoppe »