playing with stepper motors on the cheap...
rjo_
Posts: 1,825
Hi guys,
Two questions.
Background &question 1:
I've done my due diligence on this. Parallax has a fabulous source document on stepper motors...http://www.parallax.com/Portals/0/Downloads/docs/prod/motors/Stepper_Motor_27964.pdf
The description is so clear, I think just about anyone (including me) could easily follow it. The document discusses using a specific Darlington array(ULN2003), which is readily available, but NOT from Parallax and NOT from RadioShack...
So, I was rummaging through RadioShack's parts to see what was available, which could possibly be used to drive a stepper motor and the only thing I came up with was a reed relay part number 275-232, which is a normally open 5V device. I hooked it up to a flash trigger and used a Prop pin with nothing else in the circuit and it worked[noparse]:)[/noparse] So, I know that the Prop can drive the reed relay.
I realize this isn't the usual way to do this... but for my own peculiar reasons, I am interested in seeing what I can accomplish with these little relays... is there a problem with hooking up four of these reed relays to drive one of Parallax's 12V stepper motors, using a stable 12V external supply? I realize it won't work as well as a normal implementation... but will it hurt my Prop?
Background&question 2:
Any time you put two components into a circuit... beginning students sometimes have problems understanding the operative logic. From this perspective... it would be extremely useful to have a stepper motor, which could be directly driven by the voltage and current available on the Propeller's pins. There must be a source for some tiny stepper motors such as this, but Google won't show it to me... any ideas?
Thanks,
Rich
Post Edited (rjo_) : 2/1/2008 4:27:17 AM GMT
Two questions.
Background &question 1:
I've done my due diligence on this. Parallax has a fabulous source document on stepper motors...http://www.parallax.com/Portals/0/Downloads/docs/prod/motors/Stepper_Motor_27964.pdf
The description is so clear, I think just about anyone (including me) could easily follow it. The document discusses using a specific Darlington array(ULN2003), which is readily available, but NOT from Parallax and NOT from RadioShack...
So, I was rummaging through RadioShack's parts to see what was available, which could possibly be used to drive a stepper motor and the only thing I came up with was a reed relay part number 275-232, which is a normally open 5V device. I hooked it up to a flash trigger and used a Prop pin with nothing else in the circuit and it worked[noparse]:)[/noparse] So, I know that the Prop can drive the reed relay.
I realize this isn't the usual way to do this... but for my own peculiar reasons, I am interested in seeing what I can accomplish with these little relays... is there a problem with hooking up four of these reed relays to drive one of Parallax's 12V stepper motors, using a stable 12V external supply? I realize it won't work as well as a normal implementation... but will it hurt my Prop?
Background&question 2:
Any time you put two components into a circuit... beginning students sometimes have problems understanding the operative logic. From this perspective... it would be extremely useful to have a stepper motor, which could be directly driven by the voltage and current available on the Propeller's pins. There must be a source for some tiny stepper motors such as this, but Google won't show it to me... any ideas?
Thanks,
Rich
Post Edited (rjo_) : 2/1/2008 4:27:17 AM GMT
Comments
Not sure where you find a stepper motor small enough..
You also got issues of back emf etc etc .. I would not suggest the tiniest stepper ...
Use leds to indicate step sequencing ( 4 leds or so) to show simple UNIPOLAR stepping sequences
That would be alot safer...
cheers Ron
Steven
Regards
Gerry
Thanks guys.
Have a look here. Can't be much cheaper than that for interfacing to a low current stepper... Link to stepper too!
http://www.parallax.com/Store/Components/IntegratedCircuits/InterfacingChips/tabid/613/CategoryID/78/List/0/SortField/0/Level/a/ProductID/211/Default.aspx
Fusing the relay sounds like fun to me...I was planning to run everything real... real slow, with short pulses, but I sure am glad to find the right part.
Many thanks.
I'm still looking for a really tiny stepping motor that fits the specs of a prop pin.
http://www.allegromicro.com/en/Products/Part_Numbers/3984/3984.pdf
...and it's not that expensive...
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=620-1084-ND
If I order a part here and a part there the only ones making money are FedEx.
They are build for 5V and i am sure they will work on 3.3V ether.
The disadvantage will be; they are to be driven with a bipolar driver.
But have a look on the schematic below:
this i working just wonderful with a old stepper motor recycled from a ancient HD!
Saluti Joerg
The ULM2803A Darlington array from Parallax would be your best choice. But you can also use discrete transistors
from Radio Shack to drive the windings. A 15-pack of 2N2222s will run you less than $3.00, and you'll have 11 left
over for other procjects.. With four protection diodes and some base resistors, you could drive a unipolar stepper
with currents in the 100 - 400mA range at 5V (12 - 50-ohm coil).
-Phil
Joerg,
I love breaking things apart... but I am still looking for a source on these. If anyone comes across a viable source, I'd appreciate it.
et al
This is a pure exercise for me...
I'm trying to find ways to get 8th graders interested in the Prop... so the simpler the better. BUT I'm also trying to get as complete an understanding as I can.
I'll take full advantage of all of the advice and work through each level of complexity.
Thanks again,
Rich
When i have been teaching students (growing engineer's they have been around 20-25 years old)
i noticed that breadboard and/or experimental stuff created always a lot of trouble (mostly because
of the lack of attention) and the experiments did not have the effect desired. At a certain point i have
created a simple development system for micro controller units. I named it HC(S)08 system because
(obviously) it was for Freescale MCU's. Now it has become UMDL (Universal Microprocessor Development Lab)
containing modules for Propeller Chips and PIC's. The idea is to have an environment with known hardware modules.
So you do not need to build always new interface cables nor do you feel like a EVB (Evaluation Bord) collector!!!
Under Motion you will find SM-UNI a very simple interface for unipolar stepper motors.
You will find it here www.systech-gmbh.ch -> UMDL -> MOTION
Saluti Joerg
I agree completely with you. For younger people, I don't like solder either.
for a translated page :
http://64.233.179.104/translate_c?hl=en&u=http://www.systech-gmbh.ch/indexUMDL-d.html&prev=/search?q=http://www.systech-gmbh.ch/&hl=en&client=safari&rls=en
I really like this: http://www.systech-gmbh.ch/imagesUMDL/PROPELLER/p8x32a-d40.JPG...
when it come to young students... the cosmetic appearance is important and this looks fabulous.
Rich
only for curiosity: What did you translate? (Google says: can not translate English to English!)
Joerg
Everything appeared in German on my end... I use Safari on a Mac...so that might have something to do with it.
Rich
You CAN run Parallax steppers using 4 reed relays, 4 LEDS and a 12V RadioShack wall wart. 12 hours and no smoke yet.
Because the relays have a mechanical component, the maximum velocity is around 120 RPMs...
I know that sounds pretty slow... but with a wheel diameter of 6 feet that is almost 25 miles per hour[noparse]:)[/noparse]