maximum stepper motor wires - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: October 28, 2019, 09:08:49 am
content: I am looking at controlling 2 0.5A stepper motors. I could have a single controller PCB but the second pump would be 1 m away. Is 1 m of cables too much?

author: beanflying
author_rank: Super Contributor
timestamp: October 28, 2019, 09:32:02 am
content: What stepper motor/voltage? Nema 17's as an example are fairly low voltage and can be circa 3V with a 12V nominal maximum. If you are running them at low voltage then pump up the wire gauge to minimize the voltage drop.Nema 24's on my CNC Router are running at more like 3m to the Z axis on a 24V supply and plenty of torque (more likely 1A+)

author: Simon
author_rank: Unknown
timestamp: October 28, 2019, 09:39:09 am
content: It's 12V 0.5A with a 24R coil resistance. It's in a vehicle so 13-14V available for overdrive.

author: Simon
author_rank: Unknown
timestamp: October 28, 2019, 09:41:36 am
content: I'm also struggling to find an off the shelf stepper driver that is potted/waterproof.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 28, 2019, 05:35:44 pm
content: That's not much overdrive, I take it this will be slow (single stepping or low RPMs)?Last drive I made was a quad powerSTEP01 driver, that pushed up to 80V into 5V motors -- these were lower resistance and higher power than your motor obviously (a bit smaller than your fist), but the excess voltage is all about speed, and it's consumed by leakage inductance, not necessarily dissipated as power. Under load, the motors used an ampere or two at top speed and voltage.Those had harnesses around a meter long, not much reason to worry about them. It's just additional inductance and resistance, and if you're stepping slowly, and comparing with a 24 ohm coil, it really doesn't matter.As for number of wires, I've seen 8 or 9 wire steppers before, not sure what the extra ones are, never investigated that one -- most are 4 or 6, the difference being a matter of convenience.Tim

author: Simon
author_rank: Unknown
timestamp: October 28, 2019, 08:00:06 pm
content: It's a 48 step motor that will be run at 400rpm. I guess I twist the cables to each coil so that I reduce inductance as much as possible.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 28, 2019, 08:06:42 pm
content: 48 steps per rev. and 400 RPM is 320 steps per second. This is already quite fast and would normally need quite some reserve voltage to overcome the winding inductance. So this would be more something for a 2 V motor using a 14 V supply.From distant memory the maximum speed with close to nominal voltage would be more like 10-50 steps per second with a good ramp and low load.I have an 8 wire stepper (2 phase with 2 separate coils per phase, so it can be used in 2 configurations). I have seen 10 wires with a 5 phase motor - but this is a rare old version.

author: Simon
author_rank: Unknown
timestamp: October 28, 2019, 08:08:58 pm
content: I'll post the spec sheet tomorrow.

author: langwadt
author_rank: Super Contributor
timestamp: October 28, 2019, 09:48:53 pm
content: Quote from: Simon on October 28, 2019, 09:39:09 amit's the wire resistance in relation to the coil resistance so I doubt it is going to make a difference

author: langwadt
author_rank: Super Contributor
timestamp: October 28, 2019, 09:51:50 pm
content: Quote from: T3sl4co1l on October 28, 2019, 05:35:44 pmwith 8 wires you have access to both ends of four coils so it can be configure as unipolar or as bipolar with coils in parallel or series

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 29, 2019, 01:01:57 am
content: Quote from: Simon on October 28, 2019, 08:00:06 pmNo additional effort here will make a measurable difference. Just use harnessed wires or multiconductor cables so it's not loose and blasting EMI everywhere.Quote from: Kleinstein on October 28, 2019, 08:06:42 pmI don't know that it needs that much more voltage. It would still spin on its own, I think; but the available torque will definitely be small, and we are talking a fairly small motor already. (I admittedly don't have much experience with steppers, you may well be spot on.)Probably a good time for OP to mention what kind of load this thing is under...Tim

author: Simon
author_rank: Unknown
timestamp: October 29, 2019, 09:13:20 am
content: This is the motor data sheet. It drives a "rotary diaphragm" pump (a variation on the peristaltic pump).

author: beanflying
author_rank: Super Contributor
timestamp: October 29, 2019, 09:44:45 am
content: Re potted drivers a quick search revealed some options for IP65, 66 and even 67 so maybe use that in your searches. Unless you are stuck for space oversizing the controllers to manage any heat then pot your own.Out of interest as it is what I used to do is this on a chemical metering job? There may even be a better complete option to drop in the hole with less fuss.

author: Simon
author_rank: Unknown
timestamp: October 29, 2019, 09:59:54 am
content: Quote from: beanflying on October 29, 2019, 09:44:45 amNo, condensate water pump for air conditioning. We always need something that self primes, and we don't need masses of flow but don't have much space. We have used actual peristaltic's in the past but these do a bit more flow for the size as this is what they are aimed at rather than metering. They claim that these will deal with sludge unlike diaphragm pumps that have little valves that will get jammed open with crap and stop the thing functioning.

author: Simon
author_rank: Unknown
timestamp: October 29, 2019, 10:04:58 am
content: I did find a driver, but they are like £25 (it is used on peristaltic pumps we have used in the past). As I am using 2 pumps I could make a single driver PCB for both for the price of one and incorporate all the air conditioning controls. When you look at all the electromechanical bits used in air conditioning you can replace the lot with one single electronic controller. The problem is getting my boss to not look at it as the price of a PCB assembly versus one of the cheap electromechanical items but to be willing to make the jump and change everything to electronic at which point I have the budget for a PCB design.

author: beanflying
author_rank: Super Contributor
timestamp: October 29, 2019, 10:09:26 am
content: At that size take sludge handling with a grain of salt. A nutating type of diaphram pump will only have small clearances internally. They were always very niche and Peristaltics were the common non valved option.I used to work for the importers of this companyhttps://fluidmetering.com/that would see you with a valveless option and the ceramics should stand up well to anything abrasive also they will self prime reasonably.The other type of pump for a quick and dirty option is the Jabsco or Johnson Flexible impeller pump. Typically these will have more flow than you need but they self prime well and your muck handling ability will be well up.If it is only for condensate water actual flow rate shouldn't be that critical so look at straight DC (or AC) with an encoder which was more normal rather than muck around with stepper drives.

author: Simon
author_rank: Unknown
timestamp: October 29, 2019, 10:15:48 am
content: The motor comes with the pump but the supplier is too lazy to come up with the complete package including the driver but that works in my favour. The solids will only be what is sucked out of the air and gets through a foam filter.I am doing 200mL/m, do you have any suggestions?

author: beanflying
author_rank: Super Contributor
timestamp: October 29, 2019, 10:29:27 am
content: Are you making or having made the tank too? There is plenty of all in one systems out there.In Oz for tiny flowrates we had used these guys in the pasthttps://littlegiant.com/products/hvac/condensate-removal-pumps/but typically we worked on bigger industrial systems than this sort of gear. The smaller HVAC even then was always stripped to the bone on $ and quality of parts so we tended to avoid it.Skip the FMI I linked above you can't afford it and the Jabsco/Johnson option is way to much flow so skip that one too.

author: Simon
author_rank: Unknown
timestamp: October 29, 2019, 10:38:04 am
content: Yea this has to be cheap. I have an approximate quote of £30 per pump and motor assembly, and they are quite compact. A chip to drive a stepper is £5 so lots of money left over from the £50 we would spend on pre-made drivers to do the complete controller saving money on things like relays and ice stats which increases the budget.