Stepper Motor not working with Adafruit Motor Shield

Adafruit Ethernet, Motor, Proto, Wave, Datalogger, GPS Shields - etc!

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Hi there,

My project partner and I have been running into lots of issues trying to run our stepper motors with this shield. We have four shields at our disposal. The main problem seems to be too much current being drawn in by the steppers, burning out the H bridges. Let me elaborate:

- for our robot project, we need to run four stepper motors independently, using a AC-DC switching power supply
- we also have a standard lab power supply available for testing, with which we can set the maximum load current and desired voltage output

- we are testing by piggybacking two SN754410's per stepper, which should allow for 2A

- in testing two different shields with the switching DC supply, our H bridges burnt instantly (we were testing a single stepper at a time)
- it seemed as if much more than 2A was going into the stepper, burning the H bridge
- we were unable to get these shields working again, even by replacing the H bridges AND the 74HC595N

- We soldered a fresh shield and ran it purely with the lab power supply (setting at 24V, 1A), and two piggybacked SN754410's to test a single stepper
- test was successful, motor was working, however we observed that as we changed the maximum load current the supply outputs, the stepper would easily take the maximum amount available (we thought it would stop at ~1A as per the datasheet), and set the voltage accordingly
- i.e. I witnessed it taking up to 1.5 A before I stopped testing
- I observed the voltage in the 8-9V region, at 1A, rather than the expected 24V, Why?
- we then tested this working shield setup with the switching DC supply and again, it instantly burnt (H bridge chip lining popped, etc.), obviously taking over 2A

Our problem now is that these shields seem to be dead. We can't seem to get them working simply by replacing the H bridges. It seems like something else is fried. Also, the capacitors seem to be fine, and we've played with swapping the latch chip as well. We've tried making them work with strict current limits via the lab supply and the L293's as well.

The code I ran was the standard "Stepper Test" example found in the AFMotor library folder.

Our goal, if we can get these shields up and running, is to simply load all 4 steppers on the switching supply, therefore any singly stepper will be unable to take in too much current. We might also attempt to limit the current output.

Does anyone have any idea what the issue could be, and if it's possible to get our shields working again?

Please let me know if I can provide more info on anything at all. Thank you for the help!

samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Re: Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Here are a couple pictures of the shield that was initially successful with the lab power supply, but later burnt with the switching DC supply. The corner socket of the latch is messy due to some problems I had desoldering a previous latch.

Image

Image

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by adafruit_support_bill »

There are 9 steppers covered by that data sheet. Which one are you using?

samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Re: Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Hi there,

The stepper we are using goes by the part number "23KM-K066-00V/99V", 4th row in the table on the 2nd page of the data sheet:

Part Number [mm] [deg] [A] [Ohms] [mNm] [g]
23KM-K066-00V/99V 56 ~54 1.8 1 7 900 680


Thanks for the help!

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by adafruit_support_bill »

The data sheet is somewhat misleading. The motor is not designed for straight 24v operation. Your motor is rated at 1A with a 7 ohm coil resistance. Since V=IR, if you feed it straight 24v, it will pull about 3.4A which would quickly toast even a piggy-backed SN754410's. If you read the fine-print on the chart, they are using a "chopper drive" which uses a type of PWM to control the current to the motor.

The easiest solution here would be to switch to a lower voltage power supply (With the ~1.2v drop through the H-bridge, an 8v supply would give you ~6.8v at the motor).

samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Re: Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Ah, that actually explains a lot! Thanks for that information!

We'll try to look into a suitable supply for our project.

Also, do you happen to know why we can't get the shields working again after the H bridges are burnt out? We've replaced the burnt H bridges and even set the current to be limited to 1A just for testing and it still doesn't work at all. It's really strange..

Thank you!

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by adafruit_support_bill »

Not sure what is going on there. I've smoked plenty of H-bridge chips but I have never seen the damage extend beyond the H-bridge.

Is the Arduino it was attached to still functional? The only logic on the shield is the 74HC595 and you say you have replaced that.
I suppose it is possible that you may have blown a trace on the board. Are there any signs of damage on the board itself?

samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Re: Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Hi,

The arduino is still fully functional (we've been using it for other things as well), and we've bought and replaced the 74HC595 as well.

I was looking to see if there was any trace damage but I wasn't able to find anything (see pics I attached earlier). It's really strange that we've had the same issue with 3 of the boards.

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by adafruit_support_bill »

That is strange. :?
Does the green LED light up? Are you getting 5v on the VCC pins of all the chips? (pin 16 of the bridge chips & pin 10 on the latch chip)
Digital pins 3 and 5 appear a bit solder-starved in the photo. But that would affect only M2 and M4 on that board.

samurai7
 
Posts: 6
Joined: Sun Dec 25, 2011 9:25 pm

Re: Stepper Motor not working with Adafruit Motor Shield

Post by samurai7 »

Hi,

We actually have a milestone deadline due this Monday, so we're using super expensive gecko drives right now just to get things working for that milestone. But after that's out of the way, I'm going to bust out the shields again and follow the troubleshooting tips you gave, so I'm really sorry if I don't reply for several days!

Thanks!

Reaper08
 
Posts: 1
Joined: Tue Feb 07, 2012 2:41 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by Reaper08 »

I have run into this same issue. Tried running a stepper with different combos of Arduinos and motor shields with no luck. Any other thoughts? Thanks!

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Stepper Motor not working with Adafruit Motor Shield

Post by adafruit_support_bill »

I have run into this same issue.
You burned up a piggybacked set of SN754410's using motors with 7 ohm coils @24v?
If your issue is different, you might want to start a new thread.

Locked
Please be positive and constructive with your questions and comments.

Return to “Arduino Shields from Adafruit”