[SCzEngrgGroup]

I have a project I'm doing (a small bench-top automated distributor testing machine) for which I need a really cheap stepper driver and power supply. There was a nice, really cheap A3977 board (about $25) I've used in the past, but the guy that made it is no longer selling them. So, does anyone know of another very low cost board out there? Specs are modest - 30V/2A is plenty.

Also, anyone have a source for a very cheap power supply for the above? The best I've found so far is buying a transformer for about $25 from Digikey, and putting my own rectifier/cap on it.

I'd like both the stepper driver and power supply to have reliable sources (i.e. - not surplus parts that may notr be available 6 months from now)., as I'll probably be building a small quantity of these over time.

Regards,
Ray L.

[cadmonkey]

For the P.S. you could probably get by with cheap PC power supplies converted for on-off use (get the right connector and you can handle the conversion as a snap on so replacement would be a swap of a shelf unit not modifying one each time). They can be had rather cheaply in quantity, and a basic off brand would most likely be reliable enough for the purpose. Is 30V 2A the required for the speed and torque you need? Or could you drop down to a 16 or 24v doorbell transformer - hundreds of sources for those and should be much cheaper than the xfmr you list above.

Sorry I can't give any help on the driver, I'd probably get some help designing my own (since you don't sound like it needs a lot of features and you're environment won't be too taxing it wouldn't need a lot of the protection circuitry) and source everything back through you.

Just spitballing. HTH

Greg

[SCzEngrgGroup]

For the P.S. you could probably get by with cheap PC power supplies converted for on-off use (get the right connector and you can handle the conversion as a snap on so replacement would be a swap of a shelf unit not modifying one each time). They can be had rather cheaply in quantity, and a basic off brand would most likely be reliable enough for the purpose. Is 30V 2A the required for the speed and torque you need? Or could you drop down to a 16 or 24v doorbell transformer - hundreds of sources for those and should be much cheaper than the xfmr you list above.

Sorry I can't give any help on the driver, I'd probably get some help designing my own (since you don't sound like it needs a lot of features and you're environment won't be too taxing it wouldn't need a lot of the protection circuitry) and source everything back through you.

Just spitballing. HTH

Greg

A doorbell transformer is a good idea - hadn't thought of that. I did find a promising driver:

http://cgi.ebay.com/Stepper-Motor-Sp...1%7C240%3A1318

Can't beat the price. If I thought there would be any volume on this, I'd go ahead to do a PCB, but right now, I *really* don't want to go to that bother.

Regards,
Ray L.

[TOTALLYRC]

For what you are looking to do that driver might just be the ticket. If you need 2 amps dc and that driver will take 9 volts as a minumum, you could look at either a small battery trickle charger or find a supplier of wall warts, 2 amps and around 12v should be cheap. I have a bunch in my parts bin wating for projects, but since you might be doing this in a little volume and don't want to have different parts each time, a suplus vendor might be out of the question.

This is nice but I don't know what really cheap means in terms of actuall price.

http://www.12vadapters.com/adapter/p.../2-amp-2a.html

Mike

[SCzEngrgGroup]

For what you are looking to do that driver might just be the ticket. If you need 2 amps dc and that driver will take 9 volts as a minumum, you could look at either a small battery trickle charger or find a supplier of wall warts, 2 amps and around 12v should be cheap. I have a bunch in my parts bin wating for projects, but since you might be doing this in a little volume and don't want to have different parts each time, a suplus vendor might be out of the question.

This is nice but I don't know what really cheap means in terms of actuall price.

http://www.12vadapters.com/adapter/p.../2-amp-2a.html

Mike

Mike,

I'm sure 12V won't cut it. I need to get up to at least 1000 RPM, preferably 2000 RPM, so it's gonna need some voltage.

Regards,
Ray L.

[Teyber12]

any power supplies here useful? (24v)
http://www.allelectronics.com/make-a...upplies/1.html

[dertsap]

http://cgi.ebay.com/Stepper-Motor-Sp...1%7C240%3A1318

Can't beat the price. If I thought there would be any volume on this, I'd go ahead to do a PCB, but right now, I *really* don't want to go to that bother.

.

i don't think thats a chopper driver so you will need to connect power resistors to your motors if your going to run high voltage , if you add up the cost of high wattage resistors , heatsinks and probably fans then it won't be such a great deal , and the performance won't be near what you will get with a decent chopper

[SCzEngrgGroup]

i don't think thats a chopper driver so you will need to connect power resistors to your motors if your going to run high voltage , if you add up the cost of high wattage resistors , heatsinks and probably fans then it won't be such a great deal , and the performance won't be near what you will get with a decent chopper

What makes you think that? It does micro-stepping, and it appears to use the National stepper driver chip, which is a chopper.

Regards,
Ray L.

[dertsap]

it say on the ad "Voltage (stepper motor): 9-40VDC " which leads me to believe they are saying to match the voltage to the motor , its a cheap driver probably using cheap parts , if its not a chopper and you put high voltage to your motors then you will smoke your motors
i have a non chopper unipolar driver for experimentation use and the only way to up the voltage is to add resistors
look here or do a search thru the forum about the difference in drivers http://www.cnczone.com/forums/showthread.php?t=11139

[SCzEngrgGroup]

it say on the ad "Voltage (stepper motor): 9-40VDC " which leads me to believe they are saying to match the voltage to the motor , its a cheap driver probably using cheap parts , if its not a chopper and you put high voltage to your motors then you will smoke your motors
i have a non chopper unipolar driver for experimentation use and the only way to up the voltage is to add resistors
look here or do a search thru the forum about the difference in drivers http://www.cnczone.com/forums/showthread.php?t=11139

The voltage spec is simply stating the allowable motor power supply voltage range, to avoid exceeding the rating on the H-Bridge chip. 40V/2A is a respectable rating for a small driver like this.

If it was not a chopper, it WOULD have large power resistors to limit motor current, regardless of what motor you were using. The resistors are required to limit the surge current which can damage the drive FETs. It does not have any power resistors (see the picture of the driver wired directly to a NEMA23 motor). Resistive current limiting is used only on the cheapest unipolsr drivers. Since this works only in bipolar (4-wire) configuration, it pretty much has to be a chopper - I've haven't seen a non-chopper bipolar stepper driver in ages.

My guess is this is some version of the PICStep controller, since it has a PIC processor chip on it, and an SGS-Thomson chip that looks like either an integrated stepper driver or at least an H-Bridge. There is no question in my nmind that it IS a PWM driver.

Regards,
Ray L.

[dertsap]

Resistive current limiting is used only on the cheapest unipolsr drivers. Since this works only in bipolar (4-wire) configuration, it pretty much has to be a chopper - I've haven't seen a non-chopper bipolar stepper driver in ages.


.[/QUOTE]

in addition to the unipolar board i have a bipolar driver in my workshop that needs power resistors if i use voltage above the start voltage rating of the motor , so they are out there .
If your confident that it is a chopper then its going to be a good deal but if i was to buy it i would make sure it was a chopper

this guy sells the same thing http://cgi.ebay.com/Stepper-Motor-Co...1%7C240%3A1318

it also says Functions And Features:
1. Matching motors: 6 wires or 4 wires stepper motor, 2-phase, amperage<2A, voltage: DC3V-DC40V.
2. Need two power supplies: 5VDC for the board; 3-40VDC for stepper motor (corresponding to your motor votage).


cheers
Curt

[dertsap]

out of curiousity i ask the seller if it was a chopper this was his reply "This controller apply IC driver L298, not chopper driver."

[SCzEngrgGroup]

out of curiousity i ask the seller if it was a chopper this was his reply "This controller apply IC driver L298, not chopper driver."

The L298 is nothing but a dual H-Bridge, so the fact that it uses the L298 tells us nothing about whether it's a chopper or not. If it's not a chopper, it would have to use power resistors, and it doesn't. Like I said, I'm pretty sure it's basically a PICStep, using the PIC to do the PWM.

Regards,
Ray L.

[dertsap]

i have often seen those drivers on ebay and thats what caused me to email them and ask some questions , it would be a great deal if they were choppers , i'd buy some
but if the guy selling it says its not a chopper , i have to take his word for it
i asked virtual villiage the same question and they said they have no other information than what is in the ad

when you use power resistors they are connected between the driver and the motor , they are not on the driver or you would be stuck using a specified amperage with a specified voltage , the resistor is dependant upon the amperage of the motor and the voltage being applyed , i have a multitude of power resistors , so that with those drivers i can apply a wide range of voltage depending upon which motor i want to power up or which power supply i want to use

you meantioned that it does microstepping , i'm not sure what would have given you that impression , it says nothing about microstepping or am i missing something ?

cheers

[sansbury]

A couple of thoughts.

First, trying to achieve these kind of low prices in low volumes can be a bit of a fool's errand, at least in my experience. If you want to make money on low prices you need relatively high volume. Otherwise it is better to focus on providing very high quality service at a fair price.

Second, is it possible to rethink your assumptions? I think of a stepper motor as a "premium" device in the sense that it permits extremely precise control, for which you pay in complexity (and cost). Do you need all that precision? Maybe you could spin the distributor with an ordinary 12V motor and use a cheap rotary encoder to determine shaft position. If all you're trying to do is spin the distributor and check where the contacts are closing, a stepper might be overkill.

[SCzEngrgGroup]

A couple of thoughts.

First, trying to achieve these kind of low prices in low volumes can be a bit of a fool's errand, at least in my experience. If you want to make money on low prices you need relatively high volume. Otherwise it is better to focus on providing very high quality service at a fair price.

Second, is it possible to rethink your assumptions? I think of a stepper motor as a "premium" device in the sense that it permits extremely precise control, for which you pay in complexity (and cost). Do you need all that precision? Maybe you could spin the distributor with an ordinary 12V motor and use a cheap rotary encoder to determine shaft position. If all you're trying to do is spin the distributor and check where the contacts are closing, a stepper might be overkill.

Perhaps, but small stepper motors and simple drivers are cheap (it doesn't need to be very big), and they give me absolute control over both position and speed, without the need for any encoder, or even an index pulse, as I always *know* what position the motor is in, and how fast it's going. My *only* connection to the (very small and simple) test stand is the one wire to the points/trigger.

A DC motor would still require some kind of controller (minimally some PWM source and an H-bridge - pretty much just like a stepper controller), and would cost as much as a cheap stepper controller. The motor also would likely cost nearly what a small stepper would. Then I'd have to add an encoder, which would likely make the whole thing more expensive, not less.

Regards,
Ray L.