newbie dunce :-)

[phe259]

hi all and congrats on an awesome forum

been tinkering with making a desktop cnc machine for around a year now i scrounged a few printer motors small unipolar 5 wire motors then set about building a circuit to handle the 3 motors i used the uln2803a chip from a link i found on line got it working without to much trouble link it to my old 486 laptop through the printer port downloaded turbocnc and wallah all was well.

the motors i had were not man enough for a cnc machine so i ordered 2 23d-6103h from these (http://www.distel.co.uk/asps/details1.asp?ID=TS13)

they arrived yesterday i worked out the wireing as follows black - white-common
red 1 white/red 2 green 3 and white/green 4 i hooked the motors up the turned a few times then the circuit board released that mysteriouse blue smoke
that cant be captured and returned.

electronics is my weakest point but i am building this machine for as little as pos.

i assume the circuit i built is not man enough for these motors

can anybody suggest a circuit that is cheap to build the speed of the machine is not an issue this time round as its just an experiment into cnc

thanks in advance

regards paul

sorry all in my haste i have put this in the wrong place could some kind soul please move it to the right one

[ynneb]

The guy who owns this page http://pminmo.com/ is also a member here. There has been many who have made his circuits. Phil also is the sort of guy who will help you if you have troubles. I hope this helps, and welcome to the forum.

i hooked the motors up the turned a few times then the circuit board released that mysteriouse blue smoke
that cant be captured and returned.

BTW, this is a no smoking area

[phe259]

cheers for that
does anybody now if i can connect uln2803 chips together to get 2amp output?

[pminmo]

phe295,
You really don't want to use multiple 2083's, not that it's not technically feasable, but it would take 3 chips, and your running them at max package power dissipation. Look at the discrete board, 7051, and L297uni on my website. While the discrete board is the simplest, and will run your motor it has the least to offer in future capability.

[phe259]

hi all

can somebody tell me why my circuits failed i need to learn from my mistakes i can make most things out of metal but electronics goes over my head a bit as i said in my first post i spent a couple of weeks researching and building a simple unipolar motor drive using the uln2803a chips and got the system running perfect using turbocnc
but when i got the new motors nema type 23d's 3v 2amps the website igot them from stipulated upto 2 amps me being a complete electronics dunce thought that being upto 2 amps my experimental circuit would power them or could it just be the case that i had the wiring wrong on the motors being used parts they came with no specs
as i have mentioned before the speed of the machine is not a major concern at this stage just want to make a prototype cnc machine in the hopes of building a second machine out of aly using the first machine and pos using gecko drivers.

i now that the above is prob a stupid question to those in the know but i need to learn its driving me up the wall at the mo

pminmo do you do your circuits in kit form if so would you be prepared to post to the uk

[jeffs555]

ULN2803a is only good for 1/2 amp. Also, what power supply voltage are you using, and what are you doing to limit the current? You can parallel several sections of a ULN2803a to get higher current.

[phe259]

thanks for the reply jeffs555 the power supply is from an old pc using the 5volt side i gor the setup from the attachment below but sub the uln2803a as my local maplins dont stock the uln2003 built and run as is with the zena diode and worked fine with my test printer motors is there a way of limiting the amp the motor needs just to get things running again??

thanks for your time

[pminmo]

phe259,
No not really, I'm not really in the business. Just had the boards made to help the hobbiest.

[phe259]

phe259,
No not really, I'm not really in the business. Just had the boards made to help the hobbiest.

cool thats good work your doing maybe as i get more involved i will be able to make contributions like that

thanks for the reply

[jeffs555]

You should be glad your drivers blew out, you could have blown out your motors. Any time your power supply voltage is higher than the rated motor voltage, you need power resistors in series with your motor wires.(unless you use a chopper drive) Read the section in red in this document from Pminmo's site. http://www.pminmo.com/discrete/hvdata.pdf

To get the best performance from stepper motors, you normally want the power supply to be many times the rated motor voltage. For your 3 volt motors, you would ideally want a supply of at least 24 volts. With these higher voltages, it is extremely important to either use a chopper drive set to the proper current, or use correctly calculated series resistors.

Jeff