PDA

View Full Version : Phoenix Pre-Build Questions



SilverVenom
06-01-2008, 05:12 PM
Hey everyone, I'm excited to say that I have decided to construct my own Phoenix based hexapod. :happy: I stumbled across Zenta's design a while back when it was still underway and thought it was one of the neatest things I had ever seen. Since then I've been toying with the idea and have not until now been willing/able to commit the resources and necessary time to the project. But I'm finally giving in. :veryhappy:

I just had a few questions about several of the required parts and was hoping that some of you that have experience with the design would be able to comment. My parts list stands as:

1x Phoenix hexapod body (Lynxmotion)
2x 4200mAh 6V batteries
1x Bot Board II (Lynxmotion)
1x BASIC Atom Pro Processor
6x HS-475HB Servos
12x HS-645MG Servos
+ All required brackets

Now come the questions. :veryhappy: How about HS-805BB servos? They are larger, but does anyone know if they could be made to work and where to find brackets that would still work with the Phoenix body? I would love to upgrade the max load capacity - who knows what might find its way onto this thing. :confused: Initially I will just be using a wired serial connection to get the bot working, but down the road I would be interested in adding wireless capabilities - does anyone have any experience or suggestions? I've used ZigBee devices before, but not on anything like this.

Thanks in advance for all the help!
- Peter H.

tom_chang79
06-01-2008, 05:27 PM
Why the HS805BB? You can go all-out and use something like the Hobbico CS-170 or the HS5955TG (if you can find those cheap and at the same price as the CS-170s).

Hell, if money is not an issue, go all-out and do HSR5990TGs all around! It can handle up to 7.2V so you can even do a 6-cell for it!

One word of advice, I had a hell of a time trying to cram all the batteries and circuits into the Phoenix, as the chassis is very limited in space. Check out my pics hosted on this site if you want to get an idea what I did to cram all that stuff in. I don't know what kind of "4200mAH" 6V batteries you are using (sub-C based, AA-cell based, etc.), but I know for a fact that you cannot cram in sub-C cells into chassis cavity. You can barely fit an AA-cell pack. I was even thinking of doing a AAA-cell pack in the future to get it to be slightly smaller to fit into the cavity better. But for now, my hump-pack 5 AA-Cell scheme seems to work good.

At 4200mAH, I'm assuming these are 5 sub-C cells?

SilverVenom
06-01-2008, 09:55 PM
Hey, thanks for the quick reply. I was checking that model servo out just because it was only a few dollars more than the HS-645 but gave 3x the torque. I'll defiantly be sure to check out those servos you mentioned, however I'd prefer to keep my voltages to 6V. As for the battery type I was looking at: It can be found here (http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2425).

Thanks for the help,
- Peter H.

Alex
06-01-2008, 10:29 PM
yeah, the 805's probably aren't a good route to go. In addition to everything Tom had already mentioned, the SES bracket system (lynxmotion servo brackets) don't fit to the 805's, so you'll have to build your own custom bracket system for them. Unless of course there are other brackets you had in mind. I'm curious though... Have you or anyone seen any bracket system for these larger servos before?

LinuxGuy
06-01-2008, 10:36 PM
yeah, the 805's probably aren't a good route to go. In addition to everything Tom had already mentioned, the SES bracket system don't fit to the 805's, so you'll have to build your own custom bracket system for them. Has anyone seen any bracket system for these larger servos before?
Lynxmotion is starting to come out with new brackets for the larger servos now. They already have the short "C" bracket (ASB-202), long "C" bracket (ASB-203) and the MultiPurpose bracket (ASB-201) available. :veryhappy: All of them are available in black and brushed. I've already created 3D models for the ASB-201 and ASB-202. Now I need to do the ASB-203.

8-Dale

Alex
06-01-2008, 10:39 PM
awesome! I'd like to see more robots built out of these servos. They're nice and beefy, plus with their enormous size, we're looking at MUCH larger robots:D

LinuxGuy
06-01-2008, 10:45 PM
awesome! I'd like to see more robots built out of these servos. They're nice and beefy, plus with their enormous size, we're looking at MUCH larger robots:D
One fellow over on the Lynxmotion forums built a hexapod using larger servos, but he fabricated his own brackets.

8-Dale

tom_chang79
06-02-2008, 01:25 AM
Hey, thanks for the quick reply. I was checking that model servo out just because it was only a few dollars more than the HS-645 but gave 3x the torque. I'll defiantly be sure to check out those servos you mentioned, however I'd prefer to keep my voltages to 6V. As for the battery type I was looking at: It can be found here (http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2425).

Thanks for the help,
- Peter H.


Oh my, these cells are monsters in capacity! Puts my cells (2500mAH) to shame! I bought these 2500mAH Energizer that I soldered into packs:

http://forums.trossenrobotics.com/gallery/files/1/5/6/5/img_2136.jpg

AVOID THESE if you can. I seriously regret buying these cells. These cells suck really bad. They are rated at 2500mAH but I have yet to charge up to this capacity.

My 3300mAH sub-C packs for my R/Cs report charges of 3400-3600mAH. These Energizers charge to about 2000mAH and then trips my peak charger (delta peaks shows up).

Hmm, if those cells are what they are rated at, then I say go for those. But remember, longer run-time deserves consideration for stronger servos for a constant payload. You don't want to run a bot too long if the servos are slowly and slowly heating up to a destructive condition. Conversely, you'd want a long runtime if the servo's heat tapers off and stay well below destructive operating point.

I believe Jim at Lynxmotion mentioned that the CH3-R can be ran continuously with the 645s. The Phoenix, being lighter, should have no problem running through the full charge of a 4200mAH pack...

But always error on the side of precaution when running it. If the servos are hot to the touch outside, where the heat is already transferring through an insulator the plastic case, shut your bot off to be on the safe side!

Zenta
06-02-2008, 03:37 AM
Now come the questions. :veryhappy: How about HS-805BB servos? They are larger, but does anyone know if they could be made to work and where to find brackets that would still work with the Phoenix body? I would love to upgrade the max load capacity - who knows what might find its way onto this thing. :confused: Initially I will just be using a wired serial connection to get the bot working, but down the road I would be interested in adding wireless capabilities - does anyone have any experience or suggestions? I've used ZigBee devices before, but not on anything like this.

Hi Peter,
When designing Phoenix I tried to keep low weight in mind. In one of my movies I did a little payloadtest with 2,5 kg! just for fun;) So I think the servos are strong enough for adding 1 kg of payload extra, but where are you gonna put the extra weight? The body are very small and the leg design (hard axis load on servos) does not allow very heavy loads. A larger body and a different leg design (like the CH3R or Matt Denton's B.F hexapod v5) allow much higher payloads.

But I can see the advantage of using stronger servos (like the 5990) on the femur joint to allow the legs to stretch out much further (pardon my bad english here).

I'm guessing you also need the SSC32 servo controller (couldn't see it on your list);)

Good luck with your Phoenix!
BTW: What color did you choose?

-Zenta

SilverVenom
06-02-2008, 07:55 AM
Hey, thanks for all the replies! I found the larger brackets on the lyxmotion site, but am not sure if I should upgrade to the 805s now...The main reason I was looking at that particular model of servo was because of the huge ammount of torque they offer for such little cost. ~$40 for 805s vs ~$35 for the 645s. Nearly 3x the power for a minimal increase in cost. Other servos that were mentioned on this thread as alternatives cost much more than the 805s. If the cost is too much above the 645s, then I don't believe that the upgrade could be justified.

@Alex: Do you know when the larger brackets that would fit the 805s will be available?

@tom_chang79: Thanks for the info about the batteries - I was considering mounting the batteries on top of the device if they couldn't fit into the body, or perhaps getting larger standoffs?

@Zenta: Thanks for the input! I've seen your video of your load test, and was surprised by the ammount of weight you could pile on. Still an upgrade in servos could make a load such as 1Kg easier, and less of a strain on the components. Many options to weigh... Also the "Bot Board II" includes a servo controller. :) As for color I was looking at black since some of my electronic components will be red - the contrast should be nice. However the red was also appealing.

Thanks agian,
- Peter H.

tom_chang79
06-02-2008, 09:37 AM
I suggested an add-on deck to Jim, he's considering it, but nothing in the works yet. It would be nice to have an add-on deck that's slightly smaller in scale to the chassis, and also something that would go over the electronics, so that an extra servo and batteries can be added on top of the deck.

Adrenalynn
06-02-2008, 11:48 AM
If you project the deck and trace it, larger or smaller scaled, you could trivially send it out to be laser-cut from lexan or acrylic, right?

Sienna
06-02-2008, 12:00 PM
If anyone wants a phoenix deck, contact me, and I will cad something up that will mate with the holes.

(provided you don't want anything too intricate now :P)

Otherwise beg Jim to put the models up on the SES Model Page!

Alex
06-02-2008, 05:42 PM
Did Jim have those larger brackets for sale on his site? If not, then I don't know when they'll be available, sorry:(

Regardless though. Unless you're looking to build a much larger robot, then I would just stick with standard sized servos. Much less of a headache.

SilverVenom
06-03-2008, 03:14 PM
Hey, sorry for the delayed reply guys. Jim did not have the type of brackets that would fit the 805 servos, however he did have a few others that would fit other "large type" servos.
As for extra space, adding an extra deck could potentially be the way to go. There are a few shops around my area that could replicate/scale the deck that ships with the phoenix kit itself. Are the CAD models of Phoenix available anywhere on the net or on a personal request basis? If so then I could customize the designs to fit my exact needs... Perhaps I am too hopeful. :o

Just a few more questions. If for example I have my servo controller, such as the SSC-32 or Bot Board II, and then I have several pressure senors and/or range finders, if I wanted to to an embedded solution, what prototyping board would you recommend? SAM7? Arduino? Something else? Can I simply mate the servo controller board through a TTL Serial connection to one of the development boards or is there a better way to manage that without using an external computer, except for deving of course?

Thanks for all the help,
- Peter H.

LinuxGuy
06-03-2008, 03:35 PM
Did Jim have those larger brackets for sale on his site? If not, then I don't know when they'll be available, sorry:(
Lynxmotion has them for sale right now.

8-Dale

SilverVenom
06-03-2008, 05:11 PM
Thanks for the update. :) But I think I'll heed the advice given to me in this thread and stick to the Hitech 645MG servos. Thanks anyways though - good to know they are there for future projects. :) In addition, will I still be okay using Hitech 475 servos for the coxa?

LinuxGuy
06-03-2008, 06:04 PM
In addition, will I still be okay using Hitech 475 servos for the coxa?
You will be doing yourself a favor by sticking to HS-645MG servos all parts of the legs. The HS-475HB has a plastic spline, and the HS-645MG has a metal spline (all metal gears). That's a big difference in strength, not to mention torque. If at some point you want to step up to a digital servo, all you need to do is replace the electronics in the HS-645MG servos, which are just like the HS-5645MG except for the electronics.

8-Dale

SilverVenom
06-03-2008, 06:22 PM
Thanks robotguy, that helps narrow things down, but my wallet hurts thinking about it. ;-) Any word on CAD files for the Phoenix? :-D

mdenton
06-03-2008, 06:30 PM
One fellow over on the Lynxmotion forums built a hexapod using larger servos, but he fabricated his own brackets.

8-Dale

I started a larger hexapod design: http://forums.trossenrobotics.com/showthread.php?t=1587

This was intended for edducational use, I may do a large scale kit... one day :)

Matt.

tom_chang79
06-03-2008, 08:54 PM
Wait for Sienna to get online, I believe she was the one who did the CAD work for LM's Phoenix kit...

You can buy blank sheets of lexan and go that way. As for your other question, the SSC-32 is a serially driven device, so you can either drive it through the DB9 with an rs-232 logic level or drive it straight into the RX pin which is next to the DB9 connector on the SSC-32... The RX and TX pins are coming/going straight from the Atmega, so you feed it a TTL/CMOS logic level signals. When mating the BotBoard with the SSC-32, the TTL/CMOS to TTL/CMOS serial is the recommended mating. Any processors with a serial port that can do the minimum baud rate of the SSC-32 can talk to it.

As for which embedded solution to go with, I can't be sure which one to tell you since I have no experience with any of those. However, I recently read in botmag about the Propeller chip, and I have to say, it's very impressive chip, and seems like a perfect chip for Real-Time embedded solutions. The chip I saw was a dip-package through-hole, I wonder if they offer a surface mount package with a dev board... I do have experience (and currently use) the Atom Pro. It is a wonderfully simple chip with a great SDK and support. I also have experience with the Z80-based systems that Rabbit puts out. Unfortunately, their dev board was too big and clunky for use with the chassis of my bots. That's how I opted for the Atom Pro with the miniABB(or botboard II for the latest). miniABB and BBII is probably one of the most compact board out there...

There's a also a all-in-one kinda of a solution from bot developer that I saw in the last bot mag. But I don't think they have any products to sell yet...

SilverVenom
06-04-2008, 03:59 PM
Thanks a lot for the info Tom, it helps a lot with understanding the process. :) But my problem is that I am stuck with how to fit all my sensory data + servo control together - especially since I plan on eventually making the whole solution embedded. :/

For example:
18 servos for motion
1-2 servos for controlling a DIY laser range finder/environment mapper
1 TTL connection for a laser (mainly the one featured on trossen's homepage)
2-6 analog sources for pressure senors on the feet
+ who knows what else. :P

In addition - if this is going to be a 100% embedded solution, how will input from a CMOS camera for the range finder be able to attached to the whole mix? The algorithms required have a relatively hefty processing power requirement in terms of micro controllers that is. Can this realistically be done as an embedded solution? I don't want wind up stuck somewhere down the line - 1/2 complete only realizing that embedded isn't going to work for me.

Thanks again :)
- Peter H.

Adrenalynn
06-04-2008, 04:43 PM
I'll chime in on the ranger. Simple laser ranging is trivial mathematically/from a pure MIPS/FLOPS perspective. Even an arduino could compute the range faster than your camera can sample the data.

Sienna
06-04-2008, 07:07 PM
The problem is how to get the Camera data into a format that the cpu can understand?

As for the models, yes, I did them. You will need to beg Beth or Jim Frye for them, as they are really his copyright, and I don't feel right distributing them.

SilverVenom
06-04-2008, 07:50 PM
The problem is how to get the Camera data into a format that the cpu can understand?

As for the models, yes, I did them. You will need to beg Beth or Jim Frye for them, as they are really his copyright, and I don't feel right distributing them.

Totally understandable. :D I'll send a PM off their way. And you have hit the nail on the head - Is there any way to interface the two without getting a full blown miniATX computer onboard? Otherwise I will be forced to redesign some of the project goals... :(

@Adrenalynn: I know the trigonometry is a trivial task - however the algorithm to isolate the brightest pixel or other derivation of the same basic idea does take a much larger chunk of memory & processing power - and that is what I'm worried about on an embedded system.

As a general question about the Bot Board II / Atom Pro combination - I know the specs state that is has 4 analog / digital inputs, but does this mean I could connect for instance the pressure senors directly to the board? Or do I need to find another board, then make the two separate board play nice together?

Thanks again for all the help. :D
- Peter H.

Adrenalynn
06-04-2008, 08:31 PM
I did the algos for finding the brightest spot and measuring the angle as well as measuring a line's length and the break-points in a line a few days ago (see the "Lasers Pew Pew" thread). I ran them first on a winders machine, and they profiled so well I tossed 'em over on a tiny SAM7 and it didn't even yawn.

As far as getting them into something the board likes - you're fond of talking about the Blackfin, Sienna - I'm surprised you didn't mention it. Already a fast CPU and camera right on the board.

There's also the CMUCam (http://www.cmucam.org/) - it has enough umph on its embedded sam7 to find faces...

Sienna
06-05-2008, 06:27 AM
I think its Robotguy that is a fan of the Blackfin, not me :P

Honestly, that is what I was thinking of in the future for myself too (because notionally they have all that image capture code)... but with this Hammer at the moment, one embedded system at a time is more then my limit!

LinuxGuy
06-05-2008, 08:28 AM
I think its Robotguy that is a fan of the Blackfin, not me :P
Yes, indeed, I am becoming a fan of the Blackfin. I want to put a SRV-1 Blackfin Controller and Camera Module (http://www.trossenrobotics.com/surveyor-srv-1-blackfin-camera.aspx) on W.A.L.T.E.R. but I have to figure out how to get one mounted on the end of the arm with sensors (Sharp IR (http://www.trossenrobotics.com/sharp-ir-distance-sensor-gp2d120.aspx) and PING (http://www.trossenrobotics.com/parallax-ping-ultrasonic-range-sensor.aspx)) and the Little Gripper (http://www.trossenrobotics.com/store/p/5561-Little-Gripper-Kit-no-servos-.aspx). I may try using one of those 1.3 MP camera modules from Spark Fun.


Honestly, that is what I was thinking of in the future for myself too (because notionally they have all that image capture code)... but with this Hammer at the moment, one embedded system at a time is more then my limit!
I'm back to tinkering with Hammer now! :veryhappy::veryhappy: I'll be completing the wiring of my Honeywell I2C compass (http://www.sparkfun.com/commerce/product_info.php?products_id=7915) module and serial Bluetooth (http://www.sparkfun.com/commerce/product_info.php?products_id=8461) modules and starting to get them working with Hammer.

8-Dale

Adrenalynn
06-05-2008, 02:19 PM
I think I was probably thinking of your recent post in OMG! LASERS! PEW!! PEW!! or whatever it was...


I think its Robotguy that is a fan of the Blackfin, not me :P

Honestly, that is what I was thinking of in the future for myself too (because notionally they have all that image capture code)... but with this Hammer at the moment, one embedded system at a time is more then my limit!

tom_chang79
06-05-2008, 02:43 PM
I want to put a SRV-1 Blackfin Controller and Camera Module (http://www.trossenrobotics.com/surveyor-srv-1-blackfin-camera.aspx) on W.A.L.T.E.R. but I have to figure out how to get one mounted on the end of the arm with sensors (Sharp IR (http://www.trossenrobotics.com/sharp-ir-distance-sensor-gp2d120.aspx) and PING (http://www.trossenrobotics.com/parallax-ping-ultrasonic-range-sensor.aspx)) and the Little Gripper (http://www.trossenrobotics.com/store/p/5561-Little-Gripper-Kit-no-servos-.aspx). I may try using one of those 1.3 MP camera modules from Spark Fun.

Maybe with one of these:

http://www.trossenrobotics.com/store/p/3264-Dual-Scanner-Servo-Arm-Bracket.aspx

http://www.trossenrobotics.com/store/p/Controls/i/is.aspx?path=/images/Pimages/M-2000-TS-016.jpg