Need Help!- NEED HELP with uln2003 stepper controller

[Dude22]

I am going to be using a uln2003 to as a controller for a stepper motor, interfaced through a computers parallel port, here is a like to the website that I am using for instructions: Easy To Build Stepper Controller from Recycled Materials | colvins.ca the circuit layout can be found here:

http://www.instructables.com/files/d...M4W.MEDIUM.jpg

This system can be used in place of an expensive stepper controller, the only problem is that the chip will only support up to 500ma, any more then this and the chip blows up.

My question is, would it be possible (possibly using ideal diodes) to supply the chip with a low amperage power supply and to supply the motors with a higher amperage using a separate power supply. Any words of wisdom or ideas would be great!!!

Thanks,
Joshua

[doorknob]

Originally Posted by Dude22 My question is, would it be possible (possibly using ideal diodes) to supply the chip with a low amperage power supply and to supply the motors with a higher amperage using a separate power supply. Any words of wisdom or ideas would be great!!!

If I am understanding your question correctly, then I believe that the answer is "no".

The current flowing through each motor winding also must flow through the corresponding output transistor. There is no "chip" output current supply that is separate from the motor winding current.

The ULN2003 datasheet at http://www.datasheetcatalog.org/data.../489337_DS.pdf does allude to the possibility of paralleling two (or more) of the transistors in the package to handle a higher output current. You do have to observe the maximum device dissipation rating, though. There are three unused transistors in the package, but that is not quite enough to double-up on each output.

Alternatively, you could drive some higher-current output transistors from the ULN2003 outputs, but if you're going to go to the trouble of adding supplemental output transistors, then you might as well not even use the ULN2003 to begin with, and simply use discrete darlington transistors that are rated to handle a higher current to drive the motor windings (don't forget the diodes to handle the back emf).

[Dude22]

Originally Posted by doorknob If I am understanding your question correctly, then I believe that the answer is "no". The current flowing through each motor winding also must flow through the corresponding output transistor. There is no "chip" output current supply that is separate from the motor winding current. The ULN2003 datasheet at http://www.datasheetcatalog.org/data.../489337_DS.pdf does allude to the possibility of paralleling two (or more) of the transistors in the package to handle a higher output current. You do have to observe the maximum device dissipation rating, though. There are three unused transistors in the package, but that is not quite enough to double-up on each output. Alternatively, you could drive some higher-current output transistors from the ULN2003 outputs, but if you're going to go to the trouble of adding supplemental output transistors, then you might as well not even use the ULN2003 to begin with, and simply use discrete darlington transistors that are rated to handle a higher current to drive the motor windings (don't forget the diodes to handle the back emf).

I am interested in what you mentioned about paralleling, does that mean stacking the chips and soldering the corresponding tabs of the chip to each other???

[doorknob]

While I believe that you could stack one directly on top of another and solder the corresponding pins together, that would be, if you will excuse the expression, a pretty ugly way to do it.

The downside to doing it that way would be that if one of them were defective, you would probably have to replace both of them together, and also you would probably have to derate the allowable power dissipation per IC package if they were directly adjacent to one another, because the package cooling would suffer by stacking them tightly together.

A better way to do it would probably be to have the two chips side by side with jumper wires or pc board circuit traces connecting the like pins. As an alternative, you could possibly solder together the corresponding input and output pins of adjacent drivers within a single package (but since there are only 7 drivers in the IC package you wouldn't have enough to double up on all 4 in a single package, and anyways the two-chip solution would probably be better able to dissipate additional power if that were a concern).

[john_100]

Hi Dude22 ,

have you had a look at the ULN2803 octal darlington transistor array ?

with 8 transistors inside , one IC you could switch upto a 1A motor current

what is the motor voltage and current you need to control ?


John

[Dude22]

Thanks for the link, it looks like those chips would work although it is cheaper to use 2 uln2003's as they are about 30 cents each.

PS: I tried paralelling them and it worked GREAT!!!

[djnexxus]

Hey guy's I'd like to ask what program you are using to run the cnc using the 2003 circuit? can Mach3 be configured to use it?

[Dude22]

Originally Posted by djnexxus Hey guy's I'd like to ask what program you are using to run the cnc using the 2003 circuit? can Mach3 be configured to use it?

I use TURBO CNC, here is the link: DAK Engineering - TurboCNC Download I heighly recomend it (and it is FREE!!!) It runs in dos and despite what is says on the website it REQUIRES that it be run in a Windows 98 machiene in Ms Dos Mode. Here is a link to another website that will help you getting TURBO CNC set up with the uln2003: Easy To Build Stepper Controller from Recycled Materials | colvins.ca I would heighly recomend paralelling the uln2003's atlease one time. One chip by it self can take 50 volts at 500 mA 2 chips paralelled can take 100 volts at 1000ma and so on. The voltage isnt that important because 50 volts is MORE then enough but the amperage increace is vital when you are running from any "normal" power supply as if you break the limet of the chip then it will start smoking..... NOT GOOD If you have any questions please feel free to ask!!!