Hi,
I’ve finished my Hexy, verified the cabling two times and I’ve the same failure.
As moving forward with PoMoCo, (or another movement) the robot seems to move, but shakes a lot and then crashes.
Video here : youtu.be/gI8z3Lo_gu4
I’ve removed bluetooth and sonic range for debugging.
4x new 1.5 AA Bat
Win 7 with python 2.7.3. Latest firmware & PoMoCo.
Anybody can help ?
Regards
Nicolas
That looks like a power issue. Switch over to the 5-battery pack and be sure to use a fresh set of batteries.
Also, elsewhere on this forum, ArcBotics highly recommended the Powerex 2700mAh Rechargeable Batteries
I purchased three packs so I can get two full development debugging sessions.
All that said, my Hexy is very shaky, so there’s plenty of debugging to be done.
Ok, just asking.
What’s the difference between hexy now, and the video that was posted showing it moving and walking? It seems like there’s been regression in the progress of hexy, I honestly was at least expecting to be able to get it to walk without having to go through ‘debugging’. More complex movements and dancing I would understand, but it seems like there are issues even with it just not jerking, let alone moving well.
Aside from the obvious, that the video shows a prototype unit.
I was curious myself and have been doing a little research on the matter and here are my findings:
I’m basing my conclusions mostly on close inspection of the unit featured in the Kickstarter video and subsequently covered on this Engadget article.
Design:
There are a few mostly minor differences in the Hexy design, nothing that I would consider an issue.
Servos:
In a previous post, I noted the prototype uses Hextronik XHT900 servos whose dimensions look to be a dead-match for the Tower Pros.
In this post, roboalchemist confirms the fit but notes that the servos included in the kit are custom-made and include more durable gears.
In other words, the servos are, for all intents, the same.
Servo Controller Board:
This is where the big difference lies…
As the following images (courtesy of Engadget) show, the controller board on the prototype is not an Arctronics Servotor32 board, but rather a Lynxmotion SSC-32 controller.
This board is pretty tried-and-true and used in plenty of other Hexapod robots, usually in conjunction with a separate board (eg. BotBoarduino, Arduino Mega, etc.) to handle the Inverse Kinematics and “talk” to a remote controller, such as a PS2 game controller.
For reference, here’s another view of the SSC-32:
I suspect that the poor performance we’re seeing is due to the Arduino-based firmware on the board. This firmware looks pretty basic at the moment and may not be as efficient as it could be.
I don’t think this is any reason for alarm and am hopeful that the next few firmware updates will help alleviate the bigger issues. According to a separate forum post, the first of these updates is slated for a Christmas-time release,
I’ve tested with 5x new 1.5 bat, but it’s the same.
I think the Servotor32 is the source of problem.
I’ve tested the 1.4 firmware => nothing works
1.3 firwmare => same problem
I’ve the latest Servotor32 rev 9 with “Tower Pro SG92R” micro servos.
http://www.towerpro.com.tw/viewitem1.asp?sn=737&area=50&cat=159
https://www.dropbox.com/s/k6fuuskx5ppljaf/SG92R_micro_servo.jpg
I think the battery are abnormally hot 
Those are the correct servos that ship with the kits.
As for the batteries getting hot… That sounds normal, but I don’t have much knowledge in that area.
Hey Nicolas,
It looks like your hexy is actually working well, its just running of batteries near the end. The ‘crash’ is the current dipping low enough that the motor board inside each servo starts to fail, and thus has each motor go its position extreme, which creates the ‘crumpling spider’ effect. 98% of the time this caused by low battery current, either from your batteries just plain being drained or by using alkalines. This happens much faster using alkaline batteries, which tend not to have a very high current output. A battery tester won’t pick this up, because they measure voltage, not battery current output. NiCad and NiMH batteries work much better at providing the necessary current output, but will still get warm. Not all AA’s are created equally. 
This seems to be one of the most common problems people have, and we’ll be making this recommendation in the guides we’re writing right now (trying to get them done before tomorrow!).
The slowness is a result of the computer commands being sent too slowly. I increased the rate at which the commands are sent in the new software being posted before Christmas morning.
I’ll post of a video of it moving later.
w00t!
Many thanks you all for the answers.
How much milliamps does servo input need ?
They can use up to 800mA a servo at full stall. Its pretty unlikely that you’d draw that on all servos at the same time, though.
800 mA * 18 servos /1000 * 30% = 4.32 A
Ok, a 5V/4A DC will do the trick.
@nliaudat: That’s a classic ‘out of battery’ curl-up. What kind of batteries are you using? Are they freshly charged?
I use 5x new Energizer AA-LR6 Alkaline
Ok,
I’ve tested with a 7V 2A external power supply.
Hexy still shaking, but is no more “dying” …
7v is on the high side of what we’d recommend, and is really the upper range of what won’t damage the servos immediately. The issue at play is the drained alkaline. Even an alkaline battery that is considered ‘half drained’ is still drained to the point where it cannot provide enough current, even if the voltage is sufficient. The wiki page on powering hexy covers this pretty comprehensively:
github.com/ArcBotics/Hexy/wiki/Powering-Hexy
Ok, I’ll buy NiCad bat.
Is it possible that the shaking observed in last video (7V 2A DC) is due to 50Hz from 220V ?
Another question :
Is it possible to have the PinOut of the servotor32 including EchoTriger ?
I’ve tested the following code found in forum which don’t work :
#include "Ultrasonic.h"
#define TRIGGER_PIN 17
#define ECHO_PIN 11
Ultrasonic ultrasonic(TRIGGER_PIN, ECHO_PIN);
I would like to rewrite the firmware using pinMode() to be more comprehensive for basic arduino users like me.
Perhaps to be compatible with Cellbot android GUI adding simple ascii commands like F (forward), B (backward), L (left), R (right), S (stop), D (demo)
Details on :
cellbots.googlecode.com/svn/bran … ellBot.pde
play.google.com/store/apps/deta … m.cellbots can connect to hexy bluetooth as is.
Regards
My strange movement is when hexy walks forward he turns left while moving forward. Is there a way to fix this? I this post a video tomorrow.
Thanks
Walker
My battery got so hot that it melted the plastic battery casing. I am using 4 AA rechargeable batteries. Battery life seems to be about 5 minutes. In addition to this I cannot get the bluetooth working. I can make maybe one or two commands and then the connection is lost. I can’t attach an image for some reason, but my 4 battery holster is shot. Please help.