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1  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 24, 2011, 06:45:10 pm
5 cm diameter = 2.5 cm radius
so the original motors had something little over 1 / 40 * 9.18 = 0.245 N m

2kg on 10cm (5 cm radius) reel was my overestimate just to have more room, but the new motors I found are 0.5 N m -- double the torque of the old ones.
I plan on using smaller diameter to get the power I need, and there's also an option of upping them to 14V (says the datasheet) that would give out 0.7 N m if it turns out that the original ones were giving out a lot more power because I was really pushing them.

2  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 24, 2011, 04:56:27 pm
I have specific speed goal set. Maybe 100-150 steps/sec would be the minimum speed? Dunno. The previous motors were running at 300 steps/sec smoothly, but they were 12V applied on a 2.4V motor (and then they burned). That was far faster than I ever hoped in the first place. I'll see how much I can get out of these new ones and deal with the issue if they end up being too slow. They should be powerful enough to get the needed speed just by making a little bigger reel for the rope and interleaving them, but if not -- I have a (sort of) datasheet for the new motors with all the possible connection combos suggested so I'll be able to control them more precisely. Hopefully, now I'm a bit more aware of what I'm doing smiley I would sure like to keep the electronics simple, and now it seems like everything could work with only arduino + motorshield (possibly with exchanging L293D for L293 for a bit more current if the former ends up being to weak).
3  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 24, 2011, 05:10:11 am
I found 2 motors that run on 12VDC and have enough torque, 0.6A current per winding, etc. Resistance is 20ohms unipolar so that should do the trick. No regulators or anything will be needed and it might even work fine with the unmodified Adafruit MotorShield which would be great as the original plan was to release the project as Open Source and make it as uncomplicated as possible to replicate.

Thank all for your input.
Keeping my fingers crossed.
4  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 21, 2011, 01:45:16 pm
OK, so the measurements make no sense:

It's 1.4 ohms on each coil end-to-end.
End-to-middle (ground) values are all over: 0.9 and 1.2 on one coil, 1.0 and 1.4 on the other.
My meter is probably very imprecise. Connecting probes together gives me 0.4 ohm on the most precise setting (200 ohm) smiley-sad
I think I need to go by the info I found online and gues they are 1.1 end-to-end. Makes sense with 2.4V.

So, the initial 8.4A impulse calculated by RuggedCircuits seems to be more like 10.9!

Grumpy_Mike: as for switching regulator - seems I'll have to go with that.

So if I put a regulator that can handle 8.4 A (wow, that's a lot) and reduces voltage to motor's needs and if I keep the current flow bellow the H-bridge capacity, I might even be able to make it work? smiley

Is it possible to do parallel switching regulators to get the current I need?
5  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 21, 2011, 05:59:00 am
Yes, it is underpowered for such application.
As I need to get new pair of motors I was calculating with safe numbers of torque needed. The burned motors barely produced enough torque to lift 1kg on a 5cm diameter reel (0.25 N m ?)

I'll measure resistance on the remaining motor's coils later today and post here.

What's the current that the 5 parallel L293D's can provide?
6  Using Arduino / Motors, Mechanics, and Power / Re: nema 23 stepper burned to a crisp on: September 20, 2011, 09:17:56 pm
Thank you, that explains a lot. smiley

The driver board I made spreads L293D's flat and than there's a large heat sink that goes on top of all of them together. When I actually piggy-backed them on the MotorShield the problem with convection that you described occurred. I tried to "redesign" them to be flat on PCB so I can install the heat sink to deal with the heat issues.

I couldn't find the specifications for the motor anywhere. Here's the picture:
(Sorry for the crappy picture.) The label doesn't state the voltage.
MINEBEA Astrosyn 23LM-C355-05 search in google didn't reveal much.

The only info I could find by giving it another shot right now was some Italian forum where it claims to be 2.4-2.6V:

The guy who sold them to me said the are 24V (?!) smiley-razz

Basically, I need a motor that can lift 2kg of load on a reel 10 cm in diameter.
If I calculated right (probably not) I need a motor that has torque of 1 N m (?)
Correct me if I'm wrong, please.

Is the driver I made usable at all for such a purpose (or at all)?
7  Using Arduino / Motors, Mechanics, and Power / nema 23 stepper burned to a crisp on: September 20, 2011, 01:12:26 pm
Hi. There's a saying that there are no stupid question, but this one might break the rule...

I'm working on a project involving 2 steppers. I managed to find 2 used ones, NEMA23, 1.8 deg/step, 2.1A/phase. The guy who sold me opened the back seal to oil them, but they were relatively cheap and I didn't think it could cause any problems.

I've tried using Adafruit MotorShiled to drive them. They requre 2.1A per phase so I ended up piggy-backing 5 x L293D all together (per motor), 5th one was kinda by accident as I was certain that motor label said 2.8A per phase for some reason. I calculated that it would give me a nice 0.6 x 5 = 3.0A per phase and 5A peak. It was overheating and the heat protection was kicking in making motors buzz, so I decided to make my own drivers, basically using the same logic (as I know little about capacitors needed and such), use the same IC as it's the only one I could find in my country, put a heat sink backed with some silver paste on and I ended up with this:

It's the same capacitor scheme as in MotorShield (I believe), without the rest of the stuff as I don't need it. The external computer supply provided for 12V/12A (at least rated as such) and I thought it would be enough even for doublestepping two motors.

It worked nicely for a while, or so I thought. The motors ran nicely for a while, were hot like hell, and then one of them started skipping. I opened it up and realized one of the wires desoldered. I soldered it back in and continue to test.

Today, there was a foul smell and one of the motors (the other one) skipped like crazy. I opened it up, hoping it might be the same problem, but no: it melted inside, one of the coils swollen up, blocking the rotor.

Both incidents happened when playing with interleaved and doublestep signals. Both incidents happened while motors were connected to a big pieces of aluminum used as a heat sinks.

I'm planing on getting 2 new motors this time, but I don't want to burn them too. Can anyone help and explain the current issues I might not be aware? Are the motors getting too much to handle and is that the reason for them dying (duh)? Should I get higher current rated motors, and if so how much?
Will 2.8A/phase ones be ok or will they have the same issue? Is it better to have motor rated more than the driver can provide?

Money's running tight and I need to get the motors ASAP so I have only one chance at this.

Thank you for reading this wall of text and for all your help.
8  Forum 2005-2010 (read only) / Development / positioning on: September 04, 2007, 04:47:44 am

didn't know in which forum to post....

i'm trying to build a project that is going to have several BT arduinos in a room.
one of the main components of this project is exact distance of individual arduinos within a room.
i resarched into it, and, to my knowledge, there are two posible solutions:
1. triangulation/trilateration of a "slow" signal (ultrasound?) with fixed us-mics int the room, each arduino transmitting it's own ID
2. some other magical sensor available for arduino that does the distance calculation and identification of other arduinos... smiley

i kinda hoped that someone had a similar problem here and that she/he can direct me somewhere.

all i could find was Cricket system from MIT, but the whole system costs $2K+, and the Active Bat system that's supposed to be cheaper...
the other way is to build my own system...

the precision i'm seeking is 0.5-1m.

additional question: is there a way of using bluetooth for this task, or is it too fast/imprecise?


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