Adding external power source

Will be possible to use an external power source like a larger (and a lot more capable) battery instead of the 5 AA batteries?

I’d also be interested in this, as during development I can see myself getting through batteries at a rate of knots.

What are the power requirements of the Hexy (standard kit)? I can guess at the 6V output, but I think I saw somewhere on another post that the peak current requirement was 5A. That suddenly makes for a reasonably hefty power supply (e.g. not a repurposed phone charger), although a desktop PC PSU might get close, albeit at 5V. Are the battery solutions really up for providing that much current?

I’d guess that most of the people on here should be sufficiently confident to wire up a power supply through some sort of connector to the Hexy kit.

We’re trying to find an AC power supply that we can resell. We have a couple around the lab for our own development, but those are hand-wired DC supplies usually used inside other hardware. Trying to find something you could just plug into the power jack in a Servotor32.

I hope you find it soon, I would like to order an hexy but I wont pay double delivery cost :mrgreen:

My excitement is really growing, so even without a shipping confirmation I have rummaged around the internet and found this little gem:

Mean Well GS40A05-P1J, 5V 5A AC-DC Adapter (available in the UK and US) for about £27/ $37 each.

Interface is a 2.1mm inner-pin diameter, so you should be able to find a compatible socket from pretty well any electronics hardware store. Only thing that I have noticed with a quick search is that quite a lot of the compatible connectors are not rated to take 5 amps continuous. This one should fit the bill for the UK shoppers.

Difficulty in this recommendation is that I don’t know what the interface to the Hexy electronics looks like, might be that there’s a more sensible way to connect this supply to it, or perhaps a more suitable basic supply.

Arcbotics gurus: what’s the power connector specified on the Servotor32 board?

This looks like that one should work, but of course without testing it ourselves first we can’t give a guarantee.

Servotor32 has two 2.1mm plugs, one for servo power and logic, and one dedicated for logic (just in case the servo voltage starts to dip too low with all the servo load). The board auto-switches supply sources for logic between power and logic, logic and USB to whichever is the highest.

Just to give an update, we have several suppliers shipping sample units to test with. We’ll include this one as well. Cheap power bricks are notorious for outputting really crappy, noisy electricity, letting through damaging electrical surges and just plain being unsafe (i.e. catching on fire). We’ve got multiple of each on the way, and will be torture-testing them until they break. We want to make really sure we’re shipping quality, especially when it comes to power supplies. It’ll take us some time, but we feel its better than just shipping whatever we can get cheapest from China.

Got mine yesterday and have it assembled with just a few minor issues.

One of the H’s for a leg didn’t have a clean cut, but it was a quick slice with the exacto to fix it. The other issue is one of the body side supports was off by almost 2 mm. I had to sand down the tabs where it fits into the top and bottom of the body and I had to sand one side of the servotor tray. If I didn’t know any better I’d say that it was almost enlarged by 1%. But the sanding worked and it is all together.

Power is another issue, I was able to power it using the 5 AA pack while assembling, and while running the pomoco I can move a single servo at a time, but more than that and it doesn’t have enough power.

I tried using one of my RC NiCad packs that had 4000mah and should’ve been able to provide enough current but it didn’t work either.

I’ve pulled a bunch of AA’s from my 1/24th scale tanks and making sure they have a nice solid charge on them and give that a try.

Not sure what I’ll do if that doesn’t work, while running it off a External plugged PS will work, it kind of defeats the purpose of having Bluetooth and a hex that walks around.

Anyone else care to share what they’ve ended up using that’s been successful?

Ok, kind of stumped here.

Can’t get it to work with either the NimH AA’s or a 2 amp wall supply. Won’t even center the servos when I plug it in.

Anyone have any suggestions on what to try next?

Where do you have it plugged in? Are you sure its in the servo power supply port, and not just the logic port?

It’s plugged in to the servo power port when looking at the board with the USB on the left and power plugs on the right it’s in the top one.

Ok, I guess the servotor has pretty stiff power requirements if you don’t have a pack plugged in to power the board and are running it from USB. I switched to a more powerful USB port and now I can at least connect.

Still can’t get more than one or two servos to run at one time. I’ve tried using a NiCad pack, a 2s Lipo, a wall supply with 2 amps, and a new set of nimh rechargeables.

NiCad doesn’t work at all
2s Lipo the servos move intermittently, like every other second, but they aren’t moving the full range, they just jerk back and forth when the move and that’s it.
With the wall supply the servos jitter like crazy, and they move a little bit more towards what’s expected. But if I have just a single servo turned on I can move it manually fine. It will also move to zero position.

What is the power requirements for the servotor both for the logic, and for the config for hexy using 18 servos? Is it possible to run it with a 3s pack?

The only thing I can think of to try next is to get a ubec and hook it up and see how it does.

So has anyone gotten their hexy to walk with any kind of portable power?

Ok, did some more troubleshooting this morning and this is where I am at now.

  1. The hexy itself apparently all the servos are shot, I have to go through all of them but so far the ten I tested on various legs are not working.
  2. I figured out #1 above by plugging the servos into my other servotor that I can get some of my personal servos to work with. With a known good servo that’s operable by pomoco I plug in the servo on the hexy and try to move it and nothing happens while the original servo still works.
  3. The servotor on the hexy itself appears to not be working any more. I unplugged all the mounted servos and plugged in two known good servos that I was using on my external servotor and they do not work.
  4. The servotor is extremely sensitive to power. When I had the external board plugged in to the USB if I plugged or unplugged the servo power it would usually cause it to hang ie no servos would work. Even resetting it wouldn’t always get it to start working, eventually after several resets and plugging unplugging the USB it would start responding. No amount of resetting/power manipulation on the servotor would get it to function.

So at this point I’m going to order a set of servos to replace the ones on the hexy, and before I rebuild it I’m going to get everything hooked up on the bench and working.

2s lipos are not recommended. 3s lipos are HIGHLY not recommended, and could immediately kill all of your servos instantly. They’re just not designed for that much voltage. This is indicated by the voltage limit printed onto the board (4.8v-7v). The logic power supply is only rated up to 10v, although I don’t recommended anything beyond 9v. A 3s lipo at 11.1v would probably fry said regulator.

This make me thing I should start placing a shunt zener on the next board version, as it seems people think about doing this.

The servotor is powered off of whatever power supply is plugged into it. USB, servo plug and logic plug all power it, if one or more of them are plugged in at any point. It automatically selects the one with the highest voltage.

If you want to completely power cycle it, you thus need to either unplug it completely or press the reset button in the middle of the board.

HXT900’s work, although there are different versions of those on the internet. We use the higher-grade black carbon servos. The white plastic ones tend to snap the gear teeth too easily. We also sell replacements in the store:
arcbotics.com/store

I’m not going to use the lipos directly to the board, I’ll be using a ubec just like I do in my RC vehicles that output either 5v or 6v depending on how they get set.

Right now I’m just rather frustrated that its not even close to what is shown on the videos. I wouldn’t have expected it to have this many issues.

Yes, the zeners would be a good idea in any case, just to protect the board.

What is the current requirement for the logic side of the board. I can’t imagine it being very different than a standard arduino.

Will the hxt900’s have enough torque? They are rated for about half of the 92’s?

I do like the frame design and I’ve started a print of another one so I will have two to experiment with.

On the subject of adding an external power supply it think what is needed is:

  • a 5A (at least) 5V supply
  • 6 feet of cable to enable some freedom to roam
  • 5V of clean supply at the end of the cable

Can someone confirm the total power supply needs for 18 active/moving servos.

John

We’re currently using a 5a/5v power supply from mouser, and it seems to have plenty of power. To be honest, its the best we’ve seen hexy operating outside of a high-power bench supply! This isn’t an official endorsement, just some information on the progress of our external power supply search.

I’ve found this one http://www.powerpayless.com/replace-netgear-pwr-023-002-power-adapter-for-network-device.html searching for a Netgear switch. Maybe it could be included in your tests ?

I haven’t received my Hexy yet, so I’ll wait for a recommandation being made before buying a Power Supply. But, though I should share my findings :slight_smile:

That also looks like it would work. I imagine I would trust netgear to ship a reasonable product :wink:

I used a ubec rated for 5 amps with a 3s1p 2200 mah lipo and still had it be twitchy and not able to lift itself up when it tilts. My next thing was to parallel two of them for 10 amp max draw but I only recently got my laptop back from service so haven’t tried it yet. I am in the same camp as the poster above. I am disappointed in the performance of these servos but they are cheap and replacing them with anything better would be another $200+.

Indeed, one has to come at this with eyes wide-open, Hexy offers a great, affordable and simple intro hexapod robotics. The servos are indeed a bit of an issue, but they’re easy to repair and cheap to replace. I’ve been learning a lot from this experience ranging from working with the hardware to the intricacies of inverse-kinematics and beyond. From this perspective, it’s well-worth the price tag.

Eventually I’ll explore upgrading the Hexy with bigger servos and perhaps a different servo controller board. I just found out a friend of mine has easy access to a CNC router and might be able to get me access to a laser cutter, so I should be able to manufacture custom leg parts to better fit different servos. But first I want to see how far I can push the limits on the out-of-the-box Hexy.