Your thoughts on my next move (but I have a picture for you!)
Bill Chennault
Posts: 1,198
All--
I have not been posting much. But, I have been building my first platform. Basically, the bearing blocks necessary to hold the axles that support my skid-steer's "traction wheels." All the components are built and I am ready to assemble them into the two, parallel·aluminum frame members. I could use your input on a couple of things before I go much further, though.
I am still confused about how to power this device. It will end up having multiple, dedicated Stamps. Each will control a major subsystem. For example, I will dedicate one Stamp to the gear motor for one track. (Obviously, the Stamps will do pin-to-pin communication.) So, just for vehicle motivation, think three Stamps; one for each track and both of them reporting to a third, decision-making Stamp. I will have a least two more polling sensor inputs. (I realize the machine will be way over-Stamped, but this is ok.)
I have thought of using the BS2 in its OEM packaging. That seems a painless way to accomplish this configuration and it is not too expensive. However, I would really like to use Stamp modules (say, the BS2p24-IC) on that big Jameco breadboard you see in the picture. Ideally, I would power them with a single supply and build the RS2332 connectors necessary for each one to talk to the IDE on the PC.
It would be neat to have a single battery assembly that allowed me to tap it in various places for all the power requirements I will have: 12v for the two gear motors, each of which need to be fused to·blow at something just below their safe limits since the motors will take up to 42 amps,·(up to 25 amps per motor via two HB-25s???), 6 volts (no more!!!) for the EB500, and ???
I could sure use some help figuring this battery situation out and I can supply more information, as required. Eventually, this prototype will evolve into a skid-steer with a wheelbase long enough to allow it to negotiate stairs.
What say you?
--Bill
Parts is parts!
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You are what you write.
I have not been posting much. But, I have been building my first platform. Basically, the bearing blocks necessary to hold the axles that support my skid-steer's "traction wheels." All the components are built and I am ready to assemble them into the two, parallel·aluminum frame members. I could use your input on a couple of things before I go much further, though.
I am still confused about how to power this device. It will end up having multiple, dedicated Stamps. Each will control a major subsystem. For example, I will dedicate one Stamp to the gear motor for one track. (Obviously, the Stamps will do pin-to-pin communication.) So, just for vehicle motivation, think three Stamps; one for each track and both of them reporting to a third, decision-making Stamp. I will have a least two more polling sensor inputs. (I realize the machine will be way over-Stamped, but this is ok.)
I have thought of using the BS2 in its OEM packaging. That seems a painless way to accomplish this configuration and it is not too expensive. However, I would really like to use Stamp modules (say, the BS2p24-IC) on that big Jameco breadboard you see in the picture. Ideally, I would power them with a single supply and build the RS2332 connectors necessary for each one to talk to the IDE on the PC.
It would be neat to have a single battery assembly that allowed me to tap it in various places for all the power requirements I will have: 12v for the two gear motors, each of which need to be fused to·blow at something just below their safe limits since the motors will take up to 42 amps,·(up to 25 amps per motor via two HB-25s???), 6 volts (no more!!!) for the EB500, and ???
I could sure use some help figuring this battery situation out and I can supply more information, as required. Eventually, this prototype will evolve into a skid-steer with a wheelbase long enough to allow it to negotiate stairs.
What say you?
--Bill
Parts is parts!
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You are what you write.
Comments
I would use separate supplies for the stamps and motors because the current draw of the motors could interfere with the stamps supply and cause it to reset.
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agree with D. Faust on separate batteries for control logic and motor drive. voltage regulators will breakdown with those kinds of amps .... quicker then with out the amp spikes.
get a 12 volt battery for the motor, maybe connect a couple of 12v batteries for longer term use, and use a 6v battery for control logic (stamps) still use a voltage regulator, maybe even one voltage regulator for each stamp.
when you talking batteries are you talking the type that you can find in UPS units (gel cell aka lead acid, aka car batteries) or do you just plan on getting a bunch of D size batteries? or some lion battery packs that are used in Remote Control devices?
1. I don't think you need that many stamps... for example, the HB-25 is a "set and forget" controller, so you just need to send it a command once and it will keep doing it over and over and over until you tell it otherwise. It doesn't seem to warrent a Stamp dedicated to serving it's needs.
2. Since you are planning to have multiple Stamps, I would just build the parts you need once. that is, build one voltage regulator circuit, one RS-232 circuit, and one brown-out circuit. What you are then left with is simply the pre-programmed PIC chip, and EEPROM, a resonator, and a few resistors. Refer to this thread for building your own Stamp-Lite... http://forums.parallax.com/forums/pr.aspx?f=21&m=106379
-Martin
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StampPlot - GUI and Plotting Software
Southern Illinois University Carbondale, Electronic Systems Technologies
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A wealth of ideas! Thank you. I knew I would get them!
It seems the consensus is two power supplies, one for the Stamps and one for the motors. (Tie the grounds together?) Two supplies is doubtless cheaper.
I have not decided on batteries. Since this device will be driven by two rather powerful (4935 oz-in, 134 rpm, 4.5 - 12 volt, 1 amp no load, 42 amp stall) gear motors with 128·CPR quadrature·encoders, I can afford some extra weight in the form of batteries. I would appreciate a suggestion for 12 volt gear motor batteries in this application. (I will use a six volt battery pack for the Stamps.)
D Faust, I built the bearing blocks from solid aluminum (which I machined to size), roller bearings, and a BUNCH of OJT! They work perfectly and one of the larger timing belt pulleys will spin well over 30 seconds with just a little shove. Each bearing block has two bearings to support the 10mm shaft. Additionally, I am using thrust bearings between rotating sections and non-rotating sections, such as between the aluminum structure and the timing belt pulleys and between the shaft collars and the bearing blocks. I have a BS2 OEM. I have not fired it up, yet. I believe I will and then just stick with the BS2 OEMs for this project. Thank you for the compliment!
cyplesma, 12 volt motorcycle or garden tractor batteries sound good, but so do UPS batteries. Got a recommendation?
Steve Joblin, you are doubtless 100% correct: I am way over-Stamped! However, I want to gain experience in the "networked" Stamp world and this is a good way to do it. There are other advantages. Programming each Stamp for its dedicated task becomes much easier, as well. Another reason is that it will give me GOBS of I/O for later use after the platform is up and running. (By "networking", I meant more like bit signaling than anything even approaching true networking.) The only other task the Stamps controlling the gear motors will have to perform is to watch the encoders and signal the "master" Stamp when necessary. Thank you very much for the thread! I will devour it.
Martin, I did not consider the most-excellent Propeller because I do not want to mount that learning curve at this time. Doubtless, though, it would be the machine for this application!
--Bill
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You are what you write.
probably start with some smaller 7ah - 12ah batteries they use on scooters or wheel chairs, just beware they can get heavy pretty quick. They are usually gel cells which is a modified lead acid battery. if you go with a motorcycle battery try to use a gel cell one. more mounting options.
this may be a bit much for now but something to think about: (I don't know how long a stamp will last on one of these but I usually test things physically and go with ball park figures then sit down with a formula, mind you some engineers hate that kind of thing)
maybe use a pair of 7.2 v rechargeable paks to power the stamp(s).
run one 7.2v through a voltage regulator to power the stamp(s). With the other 7.2 pak not being used (find a recharge unit that works from a 12vdc supply) keep it on hold/recharge. need to make sure you have a switching circuit for this. ( a stamp with the brown out status checker may do the part of it, just keep in mind there's more to this then meets the eye.
i would keep batteries grounded to each other, mind you there is a web site that can give engineering reasons why you would or would not want to though. personally I would.
most vehicles that use different supplies usually tie all their grounds together
just keep in mind there is no over unity device. 8 )
That is very helpful! Thank you.
I just happen to have two 4200 milli-amp/hour 7.2v battery packs with the charger! Can I use the appropriate voltage regulator to get them down to 6v to feed my EB500 which MUST have no more than six volts? (I've already blown one.)
Thanks.
--Bill
ps The edit is "milli-"! Thank you RLD2004!
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You are what you write.
Post Edited (Bill Chennault) : 9/6/2007 11:08:05 PM GMT
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- Rick
I don't exactly know how to tell you the "size" of my skid steer 'bot. It is about 16" long and 8" wide. The aluminum side frames are 5" tall. So, if you add the ground clearance I have by using the large diameter timing belt pulleys, then from the ground to the top of the structural aluminum side frames the machine is about 6.5" tall.
As can be seen, I will have some room to put "stuff" in the resultant 16" x 8" enclosure created by the side frames. I am allowing 7" for the 6.15" (including a 2.15" shaft that I will cut to size . . . so the OAL of the motor will be shorter). The big Jameco breadboard is 6" wide.
One gear motor will reside in back and drive one side. The other will be in the front and drive the other side. Both will be mounted high between the frames. So, one or two fairly (gee . . . what's that mean?) good sizes batteries would fit well between the motors with the breadboard mounted above them.
How much will it weigh? All structural components and the bearing blocks are made of aluminum. The timing belt pulleys are acetel. The timing belts are made out of timing belt stuff. The bearings are made of steel. There are eight of them, but the total weight is insignificant. The gear motors weigh 12.6 ounces each.
It will be rather heavy. Not bad, though. Those are powerful motors and the real concern is just getting batteries with a sufficient rating to make the thing move for an hour or so.
--Bill
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You are what you write.
check this out, I think you might find them for less. but there are other batteries on this site:
http://www.allelectronics.com/cgi-bin/item/GC-1214/160/12_VOLT_12_AH_RECHARGEABLE_BATTERY_.html
Thanks! I bookmarked that site.
I bet the trickle charger for my Sportster would charge that sucker right up!
--Bill
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You are what you write.
Believe or not, using the Propeller will have a much lower learning curve than trying get BASIC Stamps to coordinate actions while doing thier own tasks. All 8 processors can share the same data making things very easy to coordinate. And if you are already familiar with PBASIC, you can check out the BS2_Functions object for the Propeller to ease your learning curve even more.
Good luck, sounds like fun!
-Martin
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StampPlot - GUI and Plotting Software
Southern Illinois University Carbondale, Electronic Systems Technologies
I am committed to nothing in this project. And, the thing I am building is merely a prototype. The next one will have a wheelbase long enough to navigate stairs.
Both machines are/will be·ideal candidates for the Propeller. I have written a LOT of commercial code in many, many versions of BASIC; PBASIC is a little alien to me, of course, but still somewhat familiar. And, in the beginning, I was an assember programmer. Somehow, making those Stamps blast a bit here and there fascinates me! It must come from my earliest days writing modem code using the 8080 instruction set in binary.
Still, I am going to put the Propeller back on my list of processors for this project, or the ensuing project I mentioned above.
Thank you for the idea.
--Bill
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You are what you write.
The Propeller is so easy in Spin, it's shocking, and having some machine code background you may enjoy Propeller ASM as well!
Enjoy, see you in the Prop Forums!
-Martin
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StampPlot - GUI and Plotting Software
Southern Illinois University Carbondale, Electronic Systems Technologies
Ahhh! Are you the devil? Maybe the Propeller devil? I do not know if I can stand the temptation!!! [noparse]:)[/noparse]
--Bill
ps Then again, you could be the Angel of Deliverance.
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You are what you write.
yes a trickle charger should do a halfway decent job at keeping that battery from going dead in even half sun. Full sun you may have to work the robot or have a switch to disconnect the panel if the battery gets to full.
if you need to know more check otherpower.com
it won't make a dent in your electric bill, but it should keep you from spending more while you use a little more electric (your own) maybe help persuade the other half (if you have one) to allow you to spend more on these kinds of toys. heheheh
I looked at the Propeller when I first joined this forum. But, the Stamp series immediately captured my interest because I have been a BASIC programmer for decades. (However, I started life as an assembler programmer.) I dismissed the Propeller as something I did not want to tackle at the time.
At your urging, I took another look and REALLY examined its features. I had no idea it is so much faster. You are exactly right: It is the ideal processor(s!) for my application. Therefore, I intend to acquire one and base my second machine--which will be much like the first, only with a wheelbase long enough to handle the staircase--around the Propeller.
Thank you for suggesting it. Now, you will have to tolerate my ignorant questions in the Propeller forum.
--Bill
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You are what you write.