How to power up the Servotor32 in the Hexy?

Hexy Questions, Problems and Suggestions
#1

Hi,

I believe the Hexy is properly centered and mostly correctly assembled(waiting official instructions on where to put the servotor32 and the battery pack!), but in the meanwhile, I’m using the 5 battery pack with Alkalines(5 x 1.5V = 7.5V, but the multimeter says 6.8V) on the barrel jack labelled “servos”, since I assume that is what is providing the power for the hungry servos.

What I’m seeing is the red LED(status LED, I presume) blink 2x then the servos jolt then stop… after about 10 seconds, the LED blinks again and the servo jolts a little, and it repeats.

After looking at the Servotor32 source code, I am assuming what is happening is that the Servotor32 is rebooting. So I connected the USB cable to my MBA, and surely, the hexy seems to be doing better - it’s still erratic, but the movement part is longer, and I don’t see the LED blink every 10 seconds. However, when I click on “Belly Flop” in PoMoCo, it’s still sluggish and suffering.

My questions are;
[ol][]What are the power requirements for Servotor32 board?[/]
[]If I let the Servotor32 get power from my MBA + 6.8V from the battery pack, the hexy will lock up after curling upwards, tips pointing in a clocwise fashion(even the ultra sensor turns right) and I hear a buzzing sound. I finally stopped when I felt the battery pack and it was heating up! [/][/ol]

Any help would be appreciated!

Thanks in advance!

#2

I recommend strongly not using 5xAA alkalines. The 5 pack is meant for rechargables, which have a lower voltage. Too high a voltage, and you can damage the servos. 4 should do the trick just fine.

1.) 4xAA batteries. NiMH rechargeables are preferred, as they provide more current, and don’t die as fast as a result.
2.) The curling is a sign of dead batteries. I’d try putting 4 fresh AA’s in. It eats through batteries pretty quickly (which is why they heat up).

#3

Ah.

Thanks for the info - so I’ll try putting in 4 fresh batteries and connect that to the servos barrel jack.

for the time being, how about if I were to connect to a switchable voltage power adapter? The PCB says 4.8 - 7V, which voltage should I set it to?

Thanks and hope you guys are safe from Sandy!

#4

I’d start low and tun it up. try 5v first, that should run fine. Make sure your supply has enough current though, Hexy pulls ~5amps or more when running full walk.

Sandy’s not too horrible right now. We’re hunkered down at HQ, getting boards made. :wink:

#5

Cool… I’ll tinker with Hexy later today(thanks Sandy!).

Just to cover all ground - USB will provide the necessary 5V (500mA) for the logic board, and start with 5V for servos, right?

Do you guys have an IRC or some type of chat rooms to discuss Hexy setup, possibly mutations/upgrades?

Thanks

#6

USB provides logic power, and an external 5v source should provide power for the servos. The board is designed in such a way though that as long as the voltage is high enough on any of the inputs (USB, logic power or even servo power), the logic is powered.

No chatrooms yet. We like keeping things in the forums for now, so as to build up a nice publicly-available archive that people can browse through. If it gets popular enough, we’ll add a chat.

#7

That’s good to know. I should really learn to read PCB boards, then I wouldn’t bother with the simple questions :stuck_out_tongue:

As you can probably tell, I’m very excited about the Hexy and like many others, have tons of ideas on application and expansions of this platform. The way I see it, the day can’t come fast enough that we get a fully functional community up and running! :wink:

#8

[quote=“roboalchemist”]I’d start low and tun it up. try 5v first, that should run fine. Make sure your supply has enough current though, Hexy pulls ~5amps or more when running full walk.

Sandy’s not too horrible right now. We’re hunkered down at HQ, getting boards made. :wink:[/quote]

I’m noticing something odd - when I power it up with 4xAA batteries, the hexy tries to curl… so I tried connecting it via Serial Monitor in Arduino and pressed C to center all limbs. What I noticed is that;

RF (servos on pins, 24,25,26),
RB (servos on pins, 16,17,18)
LM (servos on pins, 11,10,9)

straighten out to the centered position(I centered all motors using pin 0 during reassembly)

the remaining 3 legs contort into weird shapes. I find it odd that only 3 legs seem to work, the rest seems to be affected by power drain??

As a test, I powered down the hexy and swapped pins betwen RM and RB, and when I powered up, connected via Serial Monitor and sent “C”, RF and RM straightened out, but not RB - this tells me that most likely the servos are not damaged and that the legs curling/contorting is not due to the motors not being centered.

I swapped batteries with fresh Alkaines and still got the same effect.

I’ve been locked in due to Sandy… but if I’m going out to buy batteries, even the NiMHs, any recommendations on specific battery? I’m not too knowledgeable when it comes to batteries, so apologies for any really simple questions.

I’m thinking of maybe taking the 5V leads from a computer PSU - seems to be easiest way to get 5V with > 1A… but it sounds like an another project and I’m anxious to get the Hexy up and running as quickly as possible, so I would appreciate if you can tell me what brand type batteries you use :stuck_out_tongue:

Thanks

#9

As ridiculous as they look, these are the best batteries we’ve found. We have dozens for when we go to tradeshows:
amazon.com/Powerex-2700mAh-R … 2700mah+aa

Its very odd that only some of the legs are curling. That definitely means its not a battery issue. Can you try and isolate which pins numbers seem to not work for you? Try using C and plugging a servo into each pin, seeing if some of the pins are bad or not. We 100% test all the servo output pins, and all pins are on the same power supply, so its off that this would happen. Try updating the firmware, I’m posting a new update today.

#10

[quote=“roboalchemist”]As ridiculous as they look, these are the best batteries we’ve found. We have dozens for when we go to tradeshows:
amazon.com/Powerex-2700mAh-R … 2700mah+aa

Its very odd that only some of the legs are curling. That definitely means its not a battery issue. Can you try and isolate which pins numbers seem to not work for you? Try using C and plugging a servo into each pin, seeing if some of the pins are bad or not. We 100% test all the servo output pins, and all pins are on the same power supply, so its off that this would happen. Try updating the firmware, I’m posting a new update today.[/quote]

Just to be clear, the servos are hot swappable? I was told in the past to not do that, lest it might damage the motor/controller(granted this was more so with stepper motors, but I thought it also applied to the servos?)

I will definitely test that. At the moment, it’s the pins not listed above that seem to be faulty… but the motors themselves seem fine(especially when plugged into a “working set” of pins.

#11

[quote=“roboalchemist”]As ridiculous as they look, these are the best batteries we’ve found. We have dozens for when we go to tradeshows:
amazon.com/Powerex-2700mAh-R … 2700mah+aa

Its very odd that only some of the legs are curling. That definitely means its not a battery issue. Can you try and isolate which pins numbers seem to not work for you? Try using C and plugging a servo into each pin, seeing if some of the pins are bad or not. We 100% test all the servo output pins, and all pins are on the same power supply, so its off that this would happen. Try updating the firmware, I’m posting a new update today.[/quote]

So I downloaded Servotor32 1.5 and now all the legs center when I type C! There are a few minor jitters, but but they are straight, not severely contorted!

That fixes this issue, thanks for all your help!

And I’ll be ordering those batteries - do they have a special recharger for them?

Regarding batteries…

you are recommending batteries with 2700mAh; what would happen if I were to get something like this, 5V 3000mAh, although the output is 1A max?

#12

Glad to hear that fixed it! Makes those long hours this weekend feel worth it. :wink:

Any AA charger should do. we use this really fancy one, because we do lots of analysis of batteries (we’re figuring out the best sources to re-sell batteries), but this would be just fine, though, and way cheaper:

That iPower battery pack wouldn’t be enough to power it. Its actually a 3.7v battery with a converter to 5v. The converter can only handle 1A, and not faire well under the power draw from all those servos.

I’m thinking we should start looking into selling AC power adapters. We have a couple around here, but not a large supply.

#13

I am very impressed and thankful for your work in checking in those fixes(I’m sure others are too!)

Hmm. After some thinking - I want to come up with a better power solution. So I think I’ll hold off on batteries for the time being… especially if I can get the hexy fully functional at the cost of going through the AA alkaines I have at the moment. I noticed some problems with the PoMoCo… which I’ll post later(it’s 3:40AM here :neutral_face:)

[quote=“roboalchemist”]
I’m thinking we should start looking into selling AC power adapters. We have a couple around here, but not a large supply.[/quote]

This is a great idea. It sorta makes me re-think the converting an old PC PSU into a power supply… maybe like a giant umbilical cord for the hexy?

Ultimately, I think a critical mod is to have a docking station that the hexy can either be plugged into to recharge, or even better, one that the hexy can walk over to itself to charge, like the Roomba vacuum machines.

Keep up the good work!

#14

How do you have an hex if they are not ready yet?

#15

I bought it at MakerFaire.

#16

[quote=“roboalchemist”]I’d start low and tun it up. try 5v first, that should run fine. Make sure your supply has enough current though, Hexy pulls ~5amps or more when running full walk.

Sandy’s not too horrible right now. We’re hunkered down at HQ, getting boards made. :wink:[/quote]

I had a thought - how about if I got 2 of these and connected them in parallel?

hobbypartz.com/98p-5000-4-8v … -pack.html

That should get me 4.8V at about 10000mAh(not sure if I’m doing the math correctly)? Also +750g in weight?

#17

Tying batteries in parallel is not exactly recommended, but it works in a pinch.

I’ve successfully carried ~ 1lb on the robot with smooth walking. The more weight, the more wear on the servos, though, so be careful not to add too much.