Ok, seeing as how I should be getting my servos Monday, I scrapped my little 4 servo bot, in favor of my tripod.
The tripod will have the following servos installed:
6x 5990TG
3x 5645MG
For power, I have the following lying around and available:
2x 7.2V 3Ah 6 cell NiMH (old, but they still work kinda sorta)
1x 4.8V 600mAh 4 cell NiCd (again, old )
2x 11.1V 900mAh 3S LiPo
9V batteries
I also have 1 DE SportBEC if needed
How would you all recommend I power and wire the bot? (and if I really should be looking at other power items that I will need to buy, I can consider that too, but that would be less optimal, as I am broke for a little bit )
I agree. I use 1700mAh 2cell Li-Po’s for most of my robotic servos. With a 6V switching regulator. They are great. So light and small for their capacity.
I have an Ultimate BEC, which is for aircarft. It can handle 40V but output is only 3-5 amps. Jim’s 6V regulator is better for robots (10 amps continuous):
Let me know how those work out Zenta! The price / claimed spec ratio seems a little off, my head is screaming “Warning”!
For me in general, I am going to shy away from any linear regulator. I plan to use at least 3S, if not 4S LiPos, because I want the same LiPo to be usable with my 12V motors. Linear BECs would burn up at those voltages.
For the moment, I am still looking at just ordering one or two more DE BECs, because I know their customer service rocks.
I’m on vacation for the time. But I’ll give you feedback of how they act. The linear BEC’s I used for Oxyopus worked ok, but they does only support 2S LiPo’s. And they get a bit hot. But I didn’t like the dimensions, they were a bit large.
I hooked up my SportBEC today for the first time! Right now I am running off one of the old 7.2V NiMH packs. Despite the fact that the BEC is rated at 9V min, it seems to have no problems. Of course, the NiMHs do measure about 8.5V off the charger, but hey, I am not complaining.
I am very impressed with this BEC. Rock solid 5.99V open circuit, only going down to 5.98V when I was trying to push against one of my 5645s. Now I know for sure I won’t be going with those other brands, who people measure having +/-0.35V around their target voltage.
It is a low current (3.5A). But they certify that all of their BECs can be paralleled for more current. None of the other manufacturers of the switching BECs do that that I could find.
I asked them if they had any plans for a large BEC like that, they said no So, if anyone wanted to make one…
Hi,
I’ve not measured it, but my simple (consists of 5 x AA cells) 2700 mAh 6v NiMh pack lasts for about (guessing) 15 minuttes of walking/moving. To be more exact I’ve to do a real test. But I don’t think Phoenix’s current draw is much different from Lynxmotion’s other 3DOF hexapods, so maybe someone have done a real test?
I have one of the Turnigy swiching regulators zenta mentioned.
It’s been great so far. And good luck finding any others rated so high for a reasonable price. Worst case is it fails eventually and you have to get a new one… at least you’re not using it in an aircraft.
Any switching regulator should be able to be wired in parallel provided it is the same type and set at the same voltage, but you can never guarentee than one isn’t working a lot harder than the other.
Each of the two LiPos that I had on hand weigh 80g each. So, 160g battery weight at the moment.
The DE SportBEC weighs 13g. So, three of them weigh 36g.
So, even with three voltage regulators, I am only looking at under 200g, which is still an 80g savings over the 7.2V battery alone, upon which you still need to add at least one of Jim’s 11g regulators.
So, yes, still a weight savings, even if not as much as it could be.
Kroony, any chance you can do some voltage measurements, both open circuit and under load? I am curious how accurate they are. Thanks!
Seriously though, LiPos are a huge advantage over NiMH because of the weight-to-capacity ratio is so much lower (or capacity-to-weight higher, whichever way you look at it).
I just took some readings for you.
No load was 5.82V
Loaded with 5 servos(HS-475) as far as I dared push them it went down to 5.74V
Then I connected one of my old helicopter motors to it and tried to load it as much as possible (burned a hole in my wood development platform ). It went down to 5.55V at about 8A. I measured the current afterwards with the same multimeter, so they may not be the most accurate results, but they’re pretty close.
So it dropped less than 0.3V at its continuous rated 8A. Not bad for the price.
Personally, I am running two 5xAA 2500mAH packs in my CH3-R.
It is using 18 H645MGs… One pack for the electronics/control and one pack just for the servos (VL and VS respectively).
Even with the pack being 2500mAH cells, the hexapod lasts about 20 minutes or so. But you can definitely see when the cells dump…
A 5xSub-C with 4800mAH capacity would last much much longer, but I figured the battery dumping is a great safety precaution to let the servo rest and never get too warm.
I’m not carrying too much payload, just an SSC-32, ABB, and two packs…
)
So, if anyone wanted to make one… 
). It went down to 5.55V at about 8A. I measured the current afterwards with the same multimeter, so they may not be the most accurate results, but they’re pretty close.