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January 9, 2006
Principal Embedded Systems Engineer
Logic Product Development
Schmalz Haus LLC
Product ROB-11876 |
It sounds like your motors are compatible - however you won’t be able to get anywhere near the fully rated torque out of them with the BED. That may or may not be a big issue depending on exactly how you’re using them. The 2.8A means 2.8A/phase.
Have you measured the maximum HIGH voltage on the STEP and DIR pins from your PLC? If they are over 5V, then they may have damaged the BED. Your resistors should have prevented that problem, but measuring it (without the BED in place) would be a good double check.
if you disconnect your motor from the BED and then power up the BED, do you still see the same LED pattern?
You may have damaged the board, or it may have been defective. Have you contacted SparkFun?
Cheese - you have good points. The resistors for Vref should be tweaked to give a better range. The notes on the schematic should be changed and amended to better explain how adjusting the pot controls the current. There are a lot of subtleties to this though that can’t really be completely explained on the schematic and are, unfortunately, left up to the user to understand. For example, just because you set the pot at 1.5A doesn’t mean you’re going to get 1.5A/phase. It also depends on the inductance and resistance of the motor coil, as well as the input voltage to the BED. It will never be more than 1.5A if you set it there, but it may be less.
SparkFun has begin using Github to manage design files (which is totally awesome) and I will work on updating the schematic at the very least to better explain. Thanks for the suggestion.
Product WIG-10025 |
Depending on what you need in CNC, yes it is. It does not natively process G-code, and it only has 2 axis of stepper outputs. However, it does have eight RC servo outputs, and both the Egg-Bot and Water Color Bot products use this board in a 2.5D type CNC configuration where the ½ Z axis is done with the RC servo.
You need to run the UBW Driver Installer v2.0 : driver Give that a try and let me know if it doesn’t help.
The existing driver is signed and works just fine under Windows 8 and 8.1 (both 32 and 64 bit). Try running the UBW Driver Installer v2.0 from the Egg-Bot site : driver and see if that allows you to use the EBB. That’s the latest driver installer that we have.
Product ROB-11876 |
about 3 months ago
I’m really sorry to hear you had problems with the BED. It sounds like it’s best that you try other boards to see if you can get your system to work. Many people have constructed CNC systems using BEDs with no problems in the past- I’m very confident in the design itself. These little Allegro chips are quite sturdy. But because of the big powers involved, it is easy to make an innocent mistakes that can cause damage to the driver.
The resistor change was due to the need for reducing the power and voltage lost across the sense resistor. The smaller that sense resistor value, the more power goes into the motor, and the better we can make the microsteps at a lower input voltage. You are correct - if you crank the pot up high it will try to tell the driver to use more current than it’s able to dissipate. What happens in this situation is simply thermal limiting - the driver chip rapidly cycles on and off, which will keep it’s die temp down, and will produce a chattering or stuttering of the motor. This protects the driver chip. So you can’t hurt the driver by turning the pot up too much. Note that the actual max current you can get will depend on your input voltage, current pot setting, motor coil winding and inductance and ability to remove heat from the board. So some people max out at 1.5A, and some max out at 2.4V or above.
It could be. Do the Q13) checks on http://www.schmalzhaus.com/EasyDriver/index.html and see if you have any errors there. That should help you determine if you have a bad driver chip or not.
I have seen a couple of people with this problem in the past. Sometimes it’s a problem with their Arduino code (check your DIR pin with a volt meter or scope to make sure it’s going all the way high and low) or grounding between the various pieces of the system.
No public wish lists :(