Need to replace DC gearmotor with a stepper one

[frazelle09]

i've already been using this Granger motor (DAYTON - DC Gearmotor 12VDC Nameplate RPM 17 Max. Torque 30.0 in.-lb. It also lists it as being only 1.4 full load Amps.) for a while with a LED and circuit board to track the sun for our solar parabolic hot water heater project (http://www.appropedia.org/Parabolic_Solar_Hot_Water_Heater), but since the LEDs were getting confused by stray reflections and we were going to use the Raspi B for temp readings, we decided to try and adapt Jay Dosher's (https://github.com/polyideas/Raspbe...r/Software (File System Root)/usr/lib/cgi-bin) program to Python 3.x. We had a bear of a time, since we're not programmers, but we finally got this phase finished - well except for calibrating the IMU sections of the new program. However we decided to set that aside and begin work on the type of motor we'd need, since we were told that our simple Dayton DC gearmotor would not do with our new setup and an IMU.

So we set about looking for a comparable motor to the Granger - and since we're not engineers - we decided that the most important part of the motor setup would be related to how much torque the motors produced. We saw that the Granger apparently produces about 30 in. lbs. and looked up the nearest Nema which apparently produces about 24. However the Nema requires almost double the amps of the Granger (actually it's a Dayton motor) and so, we're asking for help in this forum to figure out which stepper we really need and if our puny L298N H-Bridge will handle it.

Have a great afternoon!

 

[pgib8]

This is probably of no help but why not just try it
You may also be able to use multiple H-Bridges in parallel for more current (they sure do that with audio amplifiers).

 

[frazelle09]

pgib8, thank you very much for your suggestion: "...why not just try it". It's actually not a bad idea - i've already got the parts... i guess the worst that can happen is that i burn out some component on the H-Bridge (hopefully it would be the H-Bridge and not something on the Raspberry Pi B - lol)

Again, thanks for replying and have a great morning!

 

[pgib8]

No problem. Check the datasheet of your h-bridge, it may feature internal protection, including temperature. If it does it shouldn't burn out even if it gets overloaded. If the h-bridge is not powerful enough, look into the possibility of using 2 in parallel or just find a different part that can handle more current. If it gets hot but can otherwise handle the current, you may look into a heatsink. (I did not look up those parts btw.)

 

[Minder]

Although often used as a motor torque or HP size, a motor NEMA size refers to the frame size not the torque, you can have many torques sizes in the same NEMA frame.
Did you include any gearing in your torque calculations?
M.

 

[frazelle09]

"a motor NEMA size refers to the frame sizee" Boy, this is news to me.

Thanks, Minder, for posting. Learning - little by little.
Also, pgib8, thanks for replying as well.

As the the "gearing" question, no i didn't include any. i thought/was hoping that the Nema would "take care" of that - which is why i was looking at torque output from the Nema thinking it would be similar to the Dayton DC gearmotor...

Have a great afternoon!

 

[BobK]

Do you realize that gearing a motor down increases the torque by the same ratio as it decreases the RPM? If you used say, 10:1 gearing on your stepper you would only need 3 in pounds instead of 30.


Bob

 

[frazelle09]

No, Bob, i didn't realize that. Uf - more learning has occured - lol.

Thanks for replying and have a wonderful afternoon!